diff --git a/.gitignore b/.gitignore
index ec605697..5a81439f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,11 +6,12 @@ hs_err_pid*
 
 ## Intellij
 out/
-lib/
+/lib/
 .idea/*
 !.idea/runConfigurations*
 !.idea/inspectionProfiles*
 !.idea/codeStyles*
+!.idea/dictionaries*
 *.ipr
 *.iws
 *.iml
@@ -33,7 +34,8 @@ local.properties
 
 ## NetBeans
 **/nbproject/private/
-build/
+/build/
+/app/build/
 nbbuild/
 dist/
 nbdist/
@@ -50,6 +52,3 @@ gradle-app.setting
 
 ## Android
 gen/
-
-## Prebuilt
-Backup.apk
diff --git a/.idea/codeStyles/Project.xml b/.idea/codeStyles/Project.xml
index 35a40e4e..427a78f6 100644
--- a/.idea/codeStyles/Project.xml
+++ b/.idea/codeStyles/Project.xml
@@ -4,15 +4,6 @@
       <option name="PACKAGES_TO_USE_STAR_IMPORTS">
         <value />
       </option>
-      <option name="PACKAGES_IMPORT_LAYOUT">
-        <value>
-          <package name="" alias="false" withSubpackages="true" />
-          <package name="java" alias="false" withSubpackages="true" />
-          <package name="javax" alias="false" withSubpackages="true" />
-          <package name="kotlin" alias="false" withSubpackages="true" />
-          <package name="" alias="true" withSubpackages="true" />
-        </value>
-      </option>
       <option name="NAME_COUNT_TO_USE_STAR_IMPORT" value="2147483647" />
       <option name="NAME_COUNT_TO_USE_STAR_IMPORT_FOR_MEMBERS" value="2147483647" />
       <option name="CODE_STYLE_DEFAULTS" value="KOTLIN_OFFICIAL" />
diff --git a/.idea/dictionaries/user.xml b/.idea/dictionaries/user.xml
new file mode 100644
index 00000000..131779fd
--- /dev/null
+++ b/.idea/dictionaries/user.xml
@@ -0,0 +1,14 @@
+<component name="ProjectDictionaryState">
+  <dictionary name="user">
+    <words>
+      <w>apk</w>
+      <w>chunker</w>
+      <w>ejectable</w>
+      <w>hasher</w>
+      <w>hkdf</w>
+      <w>restorable</w>
+      <w>seedvault</w>
+      <w>snowden</w>
+    </words>
+  </dictionary>
+</component>
\ No newline at end of file
diff --git a/.idea/runConfigurations.xml b/.idea/runConfigurations.xml
index 7f68460d..e497da99 100644
--- a/.idea/runConfigurations.xml
+++ b/.idea/runConfigurations.xml
@@ -3,6 +3,7 @@
   <component name="RunConfigurationProducerService">
     <option name="ignoredProducers">
       <set>
+        <option value="com.android.tools.idea.compose.preview.runconfiguration.ComposePreviewRunConfigurationProducer" />
         <option value="org.jetbrains.plugins.gradle.execution.test.runner.AllInPackageGradleConfigurationProducer" />
         <option value="org.jetbrains.plugins.gradle.execution.test.runner.TestClassGradleConfigurationProducer" />
         <option value="org.jetbrains.plugins.gradle.execution.test.runner.TestMethodGradleConfigurationProducer" />
diff --git a/.idea/runConfigurations/All_unit_tests.xml b/.idea/runConfigurations/All_unit_tests.xml
new file mode 100644
index 00000000..8136a9a1
--- /dev/null
+++ b/.idea/runConfigurations/All_unit_tests.xml
@@ -0,0 +1,8 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="All unit tests" type="CompoundRunConfigurationType">
+    <toRun name="Unit tests: storage/lib" type="AndroidJUnit" />
+    <toRun name="Unit tests: app" type="AndroidJUnit" />
+    <toRun name="Unit tests: contactsbackup" type="AndroidJUnit" />
+    <method v="2" />
+  </configuration>
+</component>
\ No newline at end of file
diff --git a/.idea/runConfigurations/Instrumentation_Tests.xml b/.idea/runConfigurations/Instrumentation_tests__app.xml
similarity index 93%
rename from .idea/runConfigurations/Instrumentation_Tests.xml
rename to .idea/runConfigurations/Instrumentation_tests__app.xml
index 60200c14..9bc639a6 100644
--- a/.idea/runConfigurations/Instrumentation_Tests.xml
+++ b/.idea/runConfigurations/Instrumentation_tests__app.xml
@@ -1,5 +1,5 @@
 <component name="ProjectRunConfigurationManager">
-  <configuration default="false" name="Instrumentation Tests" type="AndroidTestRunConfigurationType" factoryName="Android Instrumented Tests" singleton="true">
+  <configuration default="false" name="Instrumentation tests: app" type="AndroidTestRunConfigurationType" factoryName="Android Instrumented Tests" singleton="true">
     <module name="seedvault.app" />
     <option name="TESTING_TYPE" value="0" />
     <option name="METHOD_NAME" value="" />
diff --git a/.idea/runConfigurations/Unit_Tests.xml b/.idea/runConfigurations/Unit_tests__app.xml
similarity index 85%
rename from .idea/runConfigurations/Unit_Tests.xml
rename to .idea/runConfigurations/Unit_tests__app.xml
index 0a2becf3..9d0f07f9 100644
--- a/.idea/runConfigurations/Unit_Tests.xml
+++ b/.idea/runConfigurations/Unit_tests__app.xml
@@ -1,5 +1,5 @@
 <component name="ProjectRunConfigurationManager">
-  <configuration default="false" name="Unit Tests" type="AndroidJUnit" factoryName="Android JUnit">
+  <configuration default="false" name="Unit tests: app" type="AndroidJUnit" factoryName="Android JUnit">
     <module name="seedvault.app" />
     <useClassPathOnly />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="true" />
diff --git a/.idea/runConfigurations/Unit_tests__contactsbackup.xml b/.idea/runConfigurations/Unit_tests__contactsbackup.xml
new file mode 100644
index 00000000..cb836a4e
--- /dev/null
+++ b/.idea/runConfigurations/Unit_tests__contactsbackup.xml
@@ -0,0 +1,15 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="Unit tests: contactsbackup" type="AndroidJUnit" factoryName="Android JUnit">
+    <module name="seedvault.contactsbackup" />
+    <useClassPathOnly />
+    <option name="MAIN_CLASS_NAME" value="" />
+    <option name="METHOD_NAME" value="" />
+    <option name="TEST_OBJECT" value="directory" />
+    <option name="PARAMETERS" value="" />
+    <option name="WORKING_DIRECTORY" value="$MODULE_DIR$" />
+    <dir value="$PROJECT_DIR$/contactsbackup/src/test/java" />
+    <method v="2">
+      <option name="Android.Gradle.BeforeRunTask" enabled="true" />
+    </method>
+  </configuration>
+</component>
\ No newline at end of file
diff --git a/.idea/runConfigurations/Unit_tests__storage_lib.xml b/.idea/runConfigurations/Unit_tests__storage_lib.xml
new file mode 100644
index 00000000..55889f74
--- /dev/null
+++ b/.idea/runConfigurations/Unit_tests__storage_lib.xml
@@ -0,0 +1,15 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="Unit tests: storage/lib" type="AndroidJUnit" factoryName="Android JUnit">
+    <module name="seedvault.storage.lib" />
+    <useClassPathOnly />
+    <option name="MAIN_CLASS_NAME" value="" />
+    <option name="METHOD_NAME" value="" />
+    <option name="TEST_OBJECT" value="directory" />
+    <option name="PARAMETERS" value="" />
+    <option name="WORKING_DIRECTORY" value="$MODULE_DIR$" />
+    <dir value="$PROJECT_DIR$/storage/lib/src/test/java" />
+    <method v="2">
+      <option name="Android.Gradle.BeforeRunTask" enabled="true" />
+    </method>
+  </configuration>
+</component>
\ No newline at end of file
diff --git a/.idea/runConfigurations/seedvault_storage_lib__assembleRelease_.xml b/.idea/runConfigurations/seedvault_storage_lib__assembleRelease_.xml
new file mode 100644
index 00000000..397b0409
--- /dev/null
+++ b/.idea/runConfigurations/seedvault_storage_lib__assembleRelease_.xml
@@ -0,0 +1,21 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="seedvault:storage:lib [assembleRelease]" type="GradleRunConfiguration" factoryName="Gradle">
+    <ExternalSystemSettings>
+      <option name="executionName" />
+      <option name="externalProjectPath" value="$PROJECT_DIR$/storage/lib" />
+      <option name="externalSystemIdString" value="GRADLE" />
+      <option name="scriptParameters" value="" />
+      <option name="taskDescriptions">
+        <list />
+      </option>
+      <option name="taskNames">
+        <list>
+          <option value="assembleRelease" />
+        </list>
+      </option>
+      <option name="vmOptions" value="" />
+    </ExternalSystemSettings>
+    <GradleScriptDebugEnabled>true</GradleScriptDebugEnabled>
+    <method v="2" />
+  </configuration>
+</component>
\ No newline at end of file
diff --git a/Android.bp b/Android.bp
index 258391b7..5664d6d1 100644
--- a/Android.bp
+++ b/Android.bp
@@ -31,10 +31,17 @@ android_app {
         "androidx.lifecycle_lifecycle-livedata-ktx",
         "androidx-constraintlayout_constraintlayout",
         "com.google.android.material_material",
+        // storage
+        "seedvault-lib-storage", // did not manage to add this as transitive dependency
+        "seedvault-lib-tink-android",
+        "androidx.room_room-runtime",
+        "libprotobuf-java-lite",
+        // koin
         "seedvault-lib-koin-core", // did not manage to add this as transitive dependency
         "seedvault-lib-koin-android",
         "seedvault-lib-koin-androidx-viewmodel",
-        "seedvault-lib-novacrypto-bip39",
+        // bip39
+        "seedvault-lib-kotlin-bip39",
     ],
     manifest: "app/src/main/AndroidManifest.xml",
 
diff --git a/README.md b/README.md
index 49410804..5e3f347e 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,12 @@
 
 A backup application for the [Android Open Source Project](https://source.android.com/).
 
+## Components
+
+* [Local Contacts Backup](contactsbackup) - an app that backs up local on-device contacts
+* [Storage library](storage) - a library handling efficient backup of files
+* [Seedvault app](app) - the main app where all functionality comes together
+
 ## Features
 - Backup application data to a flash drive.
 - Restore application data from a flash drive.
@@ -30,6 +36,9 @@ It uses the same internal APIs as `adb backup` which is deprecated and thus need
 * `android.permission.WRITE_SECURE_SETTINGS` to change system backup settings and enable call log backup.
 * `android.permission.QUERY_ALL_PACKAGES` to get information about all installed apps for backup.
 * `android.permission.INSTALL_PACKAGES` to re-install apps when restoring from backup.
+* `android.permission.MANAGE_EXTERNAL_STORAGE` to backup and restore files from device storage.
+* `android.permission.ACCESS_MEDIA_LOCATION` to backup original media files e.g. without stripped EXIF metadata.
+* `android.permission.FOREGROUND_SERVICE` to do periodic storage backups without interruption.
 * `android.permission.MANAGE_DOCUMENTS` to retrieve the available storage roots (optional) for better UX.
 
 ## Contributing
diff --git a/app/build.gradle b/app/build.gradle
index 3159d385..fe1a84da 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -16,13 +16,12 @@ def gitDescribe = { ->
 }
 
 android {
-
-    compileSdkVersion 30
-    buildToolsVersion '30.0.2'
+    compileSdkVersion rootProject.ext.compileSdkVersion
+    buildToolsVersion rootProject.ext.buildToolsVersion
 
     defaultConfig {
         minSdkVersion 29 // leave at 29 for robolectric tests
-        targetSdkVersion 30
+        targetSdkVersion rootProject.ext.targetSdkVersion
         versionNameSuffix "-$gitDescribe"
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
         testInstrumentationRunnerArguments disableAnalytics: 'true'
@@ -44,6 +43,7 @@ android {
     }
     kotlinOptions {
         jvmTarget = JavaVersion.VERSION_1_8.toString()
+        languageVersion = "1.3"
     }
     testOptions {
         unitTests.all {
@@ -81,19 +81,75 @@ android {
     buildTypes.debug.signingConfig = signingConfigs.aosp
 }
 
-apply from: '../gradle/dependencies.gradle'
+dependencies {
+    compileOnly rootProject.ext.aosp_libs
 
-ktlint {
-    version = "0.36.0" // https://github.com/pinterest/ktlint/issues/764
-    android = true
-    enableExperimentalRules = false
-    verbose = true
-    disabledRules = [
-            "import-ordering",
-            "no-blank-line-before-rbrace",
-    ]
+    /**
+     * Dependencies in AOSP
+     *
+     * We try to keep the dependencies in sync with what AOSP ships as Seedvault is meant to be built
+     * with the AOSP build system and gradle builds are just for more pleasant development.
+     * Using the AOSP versions in gradle builds allows us to spot issues early on.
+     */
+    implementation rootProject.ext.kotlin_libs.std
+    // These coroutine libraries get upgraded otherwise to versions incompatible with kotlin version
+    implementation rootProject.ext.kotlin_libs.coroutines
+
+    implementation rootProject.ext.std_libs.androidx_core
+    // A newer version gets pulled in with AOSP via core, so we include fragment here explicitly
+    implementation rootProject.ext.std_libs.androidx_fragment
+    implementation rootProject.ext.std_libs.androidx_preference
+    implementation rootProject.ext.std_libs.androidx_lifecycle_viewmodel_ktx
+    implementation rootProject.ext.std_libs.androidx_lifecycle_livedata_ktx
+    implementation rootProject.ext.std_libs.androidx_constraintlayout
+    implementation rootProject.ext.std_libs.androidx_documentfile
+    implementation rootProject.ext.std_libs.com_google_android_material
+
+    /**
+     * Storage Dependencies
+     */
+    implementation project(':storage:lib')
+//    implementation fileTree(include: ['storage.aar'], dir: "${rootProject.rootDir}/storage/lib/libs")
+
+    /**
+     * External Dependencies
+     *
+     * If the dependencies below are updated,
+     * please make sure to update the prebuilt libraries and the Android.bp files
+     * in the top-level `libs` folder to reflect that.
+     * You can copy these libraries from ~/.gradle/caches/modules-2
+     */
+    // later versions than 2.1.1 require newer kotlin version
+    implementation fileTree(include: ['*.jar'], dir: "${rootProject.rootDir}/libs/koin-android")
+    implementation fileTree(include: ['*.aar'], dir: "${rootProject.rootDir}/libs/koin-android")
+
+    implementation fileTree(include: ['kotlin-bip39-1.0.2.jar'], dir: "${rootProject.rootDir}/libs")
+
+    /**
+     * Test Dependencies (do not concern the AOSP build)
+     */
+    lintChecks rootProject.ext.lint_libs.exceptions
+
+    // anything less than 'implementation' fails tests run with gradlew
+    testImplementation rootProject.ext.aosp_libs
+    testImplementation 'androidx.test.ext:junit:1.1.2'
+    testImplementation('org.robolectric:robolectric:4.3.1') { // 4.4 has issue with non-idle Looper
+        // https://github.com/robolectric/robolectric/issues/5245
+        exclude group: "com.google.auto.service", module: "auto-service"
+    }
+    testImplementation "org.junit.jupiter:junit-jupiter-api:$junit5_version"
+    testImplementation "io.mockk:mockk:$mockk_version"
+    testRuntimeOnly "org.junit.jupiter:junit-jupiter-engine:$junit5_version"
+    testRuntimeOnly "org.junit.vintage:junit-vintage-engine:$junit5_version"
+
+    androidTestImplementation 'androidx.test:runner:1.3.0'
+    androidTestImplementation 'androidx.test:rules:1.3.0'
+    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
+    androidTestImplementation "io.mockk:mockk-android:$mockk_version"
 }
 
+apply from: "${rootProject.rootDir}/gradle/ktlint.gradle"
+
 gradle.projectsEvaluated {
     tasks.withType(JavaCompile) {
         if (JavaVersion.current() >= JavaVersion.VERSION_1_9) {
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 02e69e15..c8a8da5e 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -2,8 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     package="com.stevesoltys.seedvault"
-    android:versionCode="30000011"
-    android:versionName="11-1.1">
+    android:versionCode="30000211"
+    android:versionName="11-2.1">
     <!--
     The version code is the targeted SDK_VERSION plus 6 digits for our own version code.
     The version name is the targeted Android version followed by - and our own version name.
@@ -113,5 +113,24 @@
             </intent-filter>
         </receiver>
 
+        <!-- Used to start actual BackupService depending on scheduling criteria -->
+        <service
+            android:name=".storage.StorageBackupJobService"
+            android:exported="false"
+            android:label="BackupJobService"
+            android:permission="android.permission.BIND_JOB_SERVICE" />
+        <!-- Does the actual backup work as a foreground service -->
+        <service
+            android:name=".storage.StorageBackupService"
+            android:exported="false"
+            android:foregroundServiceType="dataSync"
+            android:label="BackupService" />
+        <!-- Does restore as a foreground service -->
+        <service
+            android:name=".storage.StorageRestoreService"
+            android:exported="false"
+            android:foregroundServiceType="dataSync"
+            android:label="RestoreService" />
+
     </application>
 </manifest>
diff --git a/app/src/main/java/com/stevesoltys/seedvault/App.kt b/app/src/main/java/com/stevesoltys/seedvault/App.kt
index a99e08a6..a443b3bc 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/App.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/App.kt
@@ -17,8 +17,10 @@ import com.stevesoltys.seedvault.restore.install.installModule
 import com.stevesoltys.seedvault.settings.AppListRetriever
 import com.stevesoltys.seedvault.settings.SettingsManager
 import com.stevesoltys.seedvault.settings.SettingsViewModel
+import com.stevesoltys.seedvault.storage.storageModule
 import com.stevesoltys.seedvault.transport.backup.backupModule
 import com.stevesoltys.seedvault.transport.restore.restoreModule
+import com.stevesoltys.seedvault.ui.files.FileSelectionViewModel
 import com.stevesoltys.seedvault.ui.notification.BackupNotificationManager
 import com.stevesoltys.seedvault.ui.recoverycode.RecoveryCodeViewModel
 import com.stevesoltys.seedvault.ui.storage.BackupStorageViewModel
@@ -43,11 +45,12 @@ open class App : Application() {
         factory<IBackupManager> { IBackupManager.Stub.asInterface(getService(BACKUP_SERVICE)) }
         factory { AppListRetriever(this@App, get(), get(), get()) }
 
-        viewModel { SettingsViewModel(this@App, get(), get(), get(), get(), get()) }
-        viewModel { RecoveryCodeViewModel(this@App, get(), get(), get()) }
-        viewModel { BackupStorageViewModel(this@App, get(), get(), get()) }
+        viewModel { SettingsViewModel(this@App, get(), get(), get(), get(), get(), get()) }
+        viewModel { RecoveryCodeViewModel(this@App, get(), get(), get(), get(), get()) }
+        viewModel { BackupStorageViewModel(this@App, get(), get(), get(), get()) }
         viewModel { RestoreStorageViewModel(this@App, get(), get()) }
-        viewModel { RestoreViewModel(this@App, get(), get(), get(), get(), get()) }
+        viewModel { RestoreViewModel(this@App, get(), get(), get(), get(), get(), get()) }
+        viewModel { FileSelectionViewModel(this@App, get()) }
     }
 
     override fun onCreate() {
@@ -85,6 +88,7 @@ open class App : Application() {
                 backupModule,
                 restoreModule,
                 installModule,
+                storageModule,
                 appModule
             )
         )
diff --git a/app/src/main/java/com/stevesoltys/seedvault/UsbIntentReceiver.kt b/app/src/main/java/com/stevesoltys/seedvault/UsbIntentReceiver.kt
index c225ac6e..8f175a3f 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/UsbIntentReceiver.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/UsbIntentReceiver.kt
@@ -14,9 +14,12 @@ import android.os.Handler
 import android.os.Looper
 import android.provider.DocumentsContract
 import android.util.Log
+import androidx.core.content.ContextCompat.startForegroundService
 import com.stevesoltys.seedvault.metadata.MetadataManager
 import com.stevesoltys.seedvault.settings.FlashDrive
 import com.stevesoltys.seedvault.settings.SettingsManager
+import com.stevesoltys.seedvault.storage.StorageBackupService
+import com.stevesoltys.seedvault.storage.StorageBackupService.Companion.EXTRA_START_APP_BACKUP
 import com.stevesoltys.seedvault.transport.requestBackup
 import com.stevesoltys.seedvault.ui.storage.AUTHORITY_STORAGE
 import org.koin.core.context.KoinContextHandler.get
@@ -54,9 +57,16 @@ class UsbIntentReceiver : UsbMonitor() {
     }
 
     override fun onStatusChanged(context: Context, action: String, device: UsbDevice) {
-        Thread {
-            requestBackup(context)
-        }.start()
+        if (settingsManager.isStorageBackupEnabled()) {
+            val i = Intent(context, StorageBackupService::class.java)
+            // this starts an app backup afterwards
+            i.putExtra(EXTRA_START_APP_BACKUP, true)
+            startForegroundService(context, i)
+        } else {
+            Thread {
+                requestBackup(context)
+            }.start()
+        }
     }
 
 }
diff --git a/app/src/main/java/com/stevesoltys/seedvault/plugins/saf/DocumentsProviderBackupPlugin.kt b/app/src/main/java/com/stevesoltys/seedvault/plugins/saf/DocumentsProviderBackupPlugin.kt
index 9789b434..c71d4509 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/plugins/saf/DocumentsProviderBackupPlugin.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/plugins/saf/DocumentsProviderBackupPlugin.kt
@@ -44,11 +44,6 @@ internal class DocumentsProviderBackupPlugin(
         storage.currentFullBackupDir ?: throw IOException()
     }
 
-    @Throws(IOException::class)
-    override suspend fun deleteAllBackups() {
-        storage.rootBackupDir?.deleteContents(context)
-    }
-
     @Throws(IOException::class)
     override suspend fun getMetadataOutputStream(): OutputStream {
         val setDir = storage.getSetDir() ?: throw IOException()
diff --git a/app/src/main/java/com/stevesoltys/seedvault/plugins/saf/DocumentsProviderRestorePlugin.kt b/app/src/main/java/com/stevesoltys/seedvault/plugins/saf/DocumentsProviderRestorePlugin.kt
index b1f38fa8..596ee1f4 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/plugins/saf/DocumentsProviderRestorePlugin.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/plugins/saf/DocumentsProviderRestorePlugin.kt
@@ -24,6 +24,9 @@ internal class DocumentsProviderRestorePlugin(
     override val fullRestorePlugin: FullRestorePlugin
 ) : RestorePlugin {
 
+    private val tokenRegex = Regex("([0-9]{13})") // good until the year 2286
+    private val chunkFolderRegex = Regex("[a-f0-9]{2}")
+
     @Throws(IOException::class)
     override suspend fun hasBackup(uri: Uri): Boolean {
         val parent = DocumentFile.fromTreeUri(context, uri) ?: throw AssertionError()
@@ -59,18 +62,21 @@ internal class DocumentsProviderRestorePlugin(
             return backupSets
         }
         for (set in files) {
+            // retrieve name only once as this causes a DB query
+            val name = set.name
+
             // get current token from set or continue to next file/set
-            val token = set.getTokenOrNull() ?: continue
+            val token = set.getTokenOrNull(name) ?: continue
 
             // block until children of set are available
             val metadata = try {
                 set.findFileBlocking(context, FILE_BACKUP_METADATA)
             } catch (e: IOException) {
-                Log.e(TAG, "Error reading metadata file in backup set folder: ${set.name}", e)
+                Log.e(TAG, "Error reading metadata file in backup set folder: $name", e)
                 null
             }
             if (metadata == null) {
-                Log.w(TAG, "Missing metadata file in backup set folder: ${set.name}")
+                Log.w(TAG, "Missing metadata file in backup set folder: $name")
             } else {
                 backupSets.add(BackupSet(token, metadata))
             }
@@ -78,21 +84,29 @@ internal class DocumentsProviderRestorePlugin(
         return backupSets
     }
 
-    private fun DocumentFile.getTokenOrNull(): Long? {
-        if (!isDirectory || name == null) {
-            if (name != FILE_NO_MEDIA) {
+    private fun DocumentFile.getTokenOrNull(name: String?): Long? {
+        val looksLikeToken = name != null && tokenRegex.matches(name)
+        // check for isDirectory only if we already have a valid token (causes DB query)
+        if (!looksLikeToken || !isDirectory) {
+            // only log unexpected output
+            if (name != null && isUnexpectedFile(name)) {
                 Log.w(TAG, "Found invalid backup set folder: $name")
             }
             return null
         }
         return try {
-            name!!.toLong()
+            name?.toLong()
         } catch (e: NumberFormatException) {
-            Log.w(TAG, "Found invalid backup set folder: $name")
-            null
+            throw AssertionError(e)
         }
     }
 
+    private fun isUnexpectedFile(name: String): Boolean {
+        return name != FILE_NO_MEDIA &&
+            !chunkFolderRegex.matches(name) &&
+            !name.endsWith(".SeedSnap")
+    }
+
     @Throws(IOException::class)
     override suspend fun getApkInputStream(
         token: Long,
diff --git a/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreActivity.kt b/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreActivity.kt
index 635d10d7..9b78d7d3 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreActivity.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreActivity.kt
@@ -5,6 +5,8 @@ import androidx.annotation.CallSuper
 import com.stevesoltys.seedvault.R
 import com.stevesoltys.seedvault.restore.DisplayFragment.RESTORE_APPS
 import com.stevesoltys.seedvault.restore.DisplayFragment.RESTORE_BACKUP
+import com.stevesoltys.seedvault.restore.DisplayFragment.RESTORE_FILES
+import com.stevesoltys.seedvault.restore.DisplayFragment.RESTORE_FILES_STARTED
 import com.stevesoltys.seedvault.restore.install.InstallProgressFragment
 import com.stevesoltys.seedvault.ui.LiveEventHandler
 import com.stevesoltys.seedvault.ui.RequireProvisioningActivity
@@ -28,6 +30,8 @@ class RestoreActivity : RequireProvisioningActivity() {
             when (fragment) {
                 RESTORE_APPS -> showFragment(InstallProgressFragment())
                 RESTORE_BACKUP -> showFragment(RestoreProgressFragment())
+                RESTORE_FILES -> showFragment(RestoreFilesFragment())
+                RESTORE_FILES_STARTED -> showFragment(RestoreFilesStartedFragment())
                 else -> throw AssertionError()
             }
         })
diff --git a/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreFilesFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreFilesFragment.kt
new file mode 100644
index 00000000..235ce9ab
--- /dev/null
+++ b/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreFilesFragment.kt
@@ -0,0 +1,66 @@
+package com.stevesoltys.seedvault.restore
+
+import android.app.Activity.RESULT_OK
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.view.ViewStub
+import android.widget.Button
+import android.widget.TextView
+import androidx.fragment.app.Fragment
+import com.stevesoltys.seedvault.R
+import org.calyxos.backup.storage.api.SnapshotItem
+import org.calyxos.backup.storage.ui.restore.SnapshotFragment
+import org.koin.androidx.viewmodel.ext.android.sharedViewModel
+
+internal class RestoreFilesFragment : SnapshotFragment() {
+    override val viewModel: RestoreViewModel by sharedViewModel()
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        val v = super.onCreateView(inflater, container, savedInstanceState)
+
+        val topStub: ViewStub = v.findViewById(R.id.topStub)
+        topStub.layoutResource = R.layout.header_snapshots
+        topStub.inflate()
+
+        val bottomStub: ViewStub = v.findViewById(R.id.bottomStub)
+        bottomStub.layoutResource = R.layout.footer_snapshots
+        val footer = bottomStub.inflate()
+        val skipView: TextView = footer.findViewById(R.id.skipView)
+        skipView.setOnClickListener {
+            requireActivity().apply {
+                setResult(RESULT_OK)
+                finishAfterTransition()
+            }
+        }
+        return v
+    }
+
+    override fun onSnapshotClicked(item: SnapshotItem) {
+        viewModel.startFilesRestore(item)
+    }
+}
+
+internal class RestoreFilesStartedFragment : Fragment() {
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        val v: View = inflater.inflate(R.layout.fragment_restore_files_started, container, false)
+
+        val button: Button = v.findViewById(R.id.button)
+        button.setOnClickListener {
+            requireActivity().apply {
+                setResult(RESULT_OK)
+                finishAfterTransition()
+            }
+        }
+        return v
+    }
+}
diff --git a/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreProgressFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreProgressFragment.kt
index e3b4ce77..adc8ced4 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreProgressFragment.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreProgressFragment.kt
@@ -1,6 +1,5 @@
 package com.stevesoltys.seedvault.restore
 
-import android.app.Activity.RESULT_OK
 import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
@@ -38,7 +37,7 @@ class RestoreProgressFragment : Fragment() {
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
-    ): View? {
+    ): View {
         val v: View = inflater.inflate(R.layout.fragment_restore_progress, container, false)
 
         progressBar = v.findViewById(R.id.progressBar)
@@ -61,8 +60,7 @@ class RestoreProgressFragment : Fragment() {
 
         button.setText(R.string.restore_finished_button)
         button.setOnClickListener {
-            requireActivity().setResult(RESULT_OK)
-            requireActivity().finishAfterTransition()
+            viewModel.onFinishClickedAfterRestoringAppData()
         }
 
         // decryption will fail when the device is locked, so keep the screen on to prevent locking
diff --git a/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreSetFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreSetFragment.kt
index b04a56e6..9cefe48a 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreSetFragment.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreSetFragment.kt
@@ -22,19 +22,19 @@ class RestoreSetFragment : Fragment() {
     private lateinit var listView: RecyclerView
     private lateinit var progressBar: ProgressBar
     private lateinit var errorView: TextView
-    private lateinit var backView: TextView
+    private lateinit var skipView: TextView
 
     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
-    ): View? {
+    ): View {
         val v: View = inflater.inflate(R.layout.fragment_restore_set, container, false)
 
         listView = v.findViewById(R.id.listView)
         progressBar = v.findViewById(R.id.progressBar)
         errorView = v.findViewById(R.id.errorView)
-        backView = v.findViewById(R.id.backView)
+        skipView = v.findViewById(R.id.skipView)
 
         return v
     }
@@ -49,7 +49,9 @@ class RestoreSetFragment : Fragment() {
             onRestoreResultsLoaded(result)
         })
 
-        backView.setOnClickListener { requireActivity().finishAfterTransition() }
+        skipView.setOnClickListener {
+            viewModel.onFinishClickedAfterRestoringAppData()
+        }
     }
 
     override fun onStart() {
diff --git a/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreViewModel.kt b/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreViewModel.kt
index 199de755..2b4e398f 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreViewModel.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/restore/RestoreViewModel.kt
@@ -5,9 +5,11 @@ import android.app.backup.IBackupManager
 import android.app.backup.IRestoreObserver
 import android.app.backup.IRestoreSession
 import android.app.backup.RestoreSet
+import android.content.Intent
 import android.os.RemoteException
 import android.os.UserHandle
 import android.util.Log
+import androidx.annotation.UiThread
 import androidx.annotation.WorkerThread
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
@@ -27,11 +29,14 @@ import com.stevesoltys.seedvault.metadata.PackageState.UNKNOWN_ERROR
 import com.stevesoltys.seedvault.metadata.PackageState.WAS_STOPPED
 import com.stevesoltys.seedvault.restore.DisplayFragment.RESTORE_APPS
 import com.stevesoltys.seedvault.restore.DisplayFragment.RESTORE_BACKUP
+import com.stevesoltys.seedvault.restore.DisplayFragment.RESTORE_FILES
+import com.stevesoltys.seedvault.restore.DisplayFragment.RESTORE_FILES_STARTED
 import com.stevesoltys.seedvault.restore.install.ApkRestore
 import com.stevesoltys.seedvault.restore.install.InstallIntentCreator
 import com.stevesoltys.seedvault.restore.install.InstallResult
 import com.stevesoltys.seedvault.restore.install.isInstalled
 import com.stevesoltys.seedvault.settings.SettingsManager
+import com.stevesoltys.seedvault.storage.StorageRestoreService
 import com.stevesoltys.seedvault.transport.TRANSPORT_ID
 import com.stevesoltys.seedvault.transport.restore.RestoreCoordinator
 import com.stevesoltys.seedvault.ui.AppBackupState
@@ -54,6 +59,11 @@ import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.onCompletion
 import kotlinx.coroutines.flow.onStart
 import kotlinx.coroutines.launch
+import org.calyxos.backup.storage.api.SnapshotItem
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.restore.RestoreService.Companion.EXTRA_TIMESTAMP_START
+import org.calyxos.backup.storage.restore.RestoreService.Companion.EXTRA_USER_ID
+import org.calyxos.backup.storage.ui.restore.SnapshotViewModel
 import java.util.LinkedList
 import kotlin.coroutines.Continuation
 import kotlin.coroutines.resume
@@ -68,8 +78,10 @@ internal class RestoreViewModel(
     private val backupManager: IBackupManager,
     private val restoreCoordinator: RestoreCoordinator,
     private val apkRestore: ApkRestore,
+    storageBackup: StorageBackup,
     private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO
-) : RequireProvisioningViewModel(app, settingsManager, keyManager), RestorableBackupClickListener {
+) : RequireProvisioningViewModel(app, settingsManager, keyManager),
+    RestorableBackupClickListener, SnapshotViewModel {
 
     override val isRestoreOperation = true
 
@@ -110,6 +122,8 @@ internal class RestoreViewModel(
     private val mRestoreBackupResult = MutableLiveData<RestoreBackupResult>()
     internal val restoreBackupResult: LiveData<RestoreBackupResult> get() = mRestoreBackupResult
 
+    override val snapshots = storageBackup.getBackupSnapshots().asLiveData(ioDispatcher)
+
     @Throws(RemoteException::class)
     private fun getOrStartSession(): IRestoreSession {
         val session = this.session
@@ -168,7 +182,7 @@ internal class RestoreViewModel(
             .asLiveData(ioDispatcher)
     }
 
-    internal fun onNextClicked() {
+    internal fun onNextClickedAfterInstallingApps() {
         mDisplayFragment.postEvent(RESTORE_BACKUP)
         val token = mChosenRestorableBackup.value?.token ?: throw AssertionError()
         viewModelScope.launch(ioDispatcher) {
@@ -371,6 +385,20 @@ internal class RestoreViewModel(
 
     }
 
+    @UiThread
+    internal fun onFinishClickedAfterRestoringAppData() {
+        mDisplayFragment.setEvent(RESTORE_FILES)
+    }
+
+    @UiThread
+    internal fun startFilesRestore(item: SnapshotItem) {
+        val i = Intent(app, StorageRestoreService::class.java)
+        i.putExtra(EXTRA_USER_ID, item.storedSnapshot.userId)
+        i.putExtra(EXTRA_TIMESTAMP_START, item.time)
+        app.startForegroundService(i)
+        mDisplayFragment.setEvent(RESTORE_FILES_STARTED)
+    }
+
 }
 
 internal class RestoreSetResult(
@@ -389,4 +417,6 @@ internal class RestoreBackupResult(val errorMsg: String? = null) {
     internal fun hasError(): Boolean = errorMsg != null
 }
 
-internal enum class DisplayFragment { RESTORE_APPS, RESTORE_BACKUP }
+internal enum class DisplayFragment {
+    RESTORE_APPS, RESTORE_BACKUP, RESTORE_FILES, RESTORE_FILES_STARTED
+}
diff --git a/app/src/main/java/com/stevesoltys/seedvault/restore/install/InstallProgressFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/restore/install/InstallProgressFragment.kt
index 9388c7e2..a4c2c813 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/restore/install/InstallProgressFragment.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/restore/install/InstallProgressFragment.kt
@@ -59,7 +59,7 @@ class InstallProgressFragment : Fragment(), InstallItemListener {
             addItemDecoration(DividerItemDecoration(context, VERTICAL))
         }
         button.setText(R.string.restore_next)
-        button.setOnClickListener { viewModel.onNextClicked() }
+        button.setOnClickListener { viewModel.onNextClickedAfterInstallingApps() }
 
         viewModel.chosenRestorableBackup.observe(viewLifecycleOwner, Observer { restorableBackup ->
             backupNameView.text = restorableBackup.name
@@ -76,7 +76,7 @@ class InstallProgressFragment : Fragment(), InstallItemListener {
 
     private fun onInstallResult(installResult: InstallResult) {
         // skip this screen, if there are no apps to install
-        if (installResult.isEmpty) viewModel.onNextClicked()
+        if (installResult.isEmpty) viewModel.onNextClickedAfterInstallingApps()
 
         // if finished, treat all still queued apps as failed and resort/redisplay adapter items
         if (installResult.isFinished) {
diff --git a/app/src/main/java/com/stevesoltys/seedvault/settings/AppStatusFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/settings/AppStatusFragment.kt
index 2f8538cb..ec56126d 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/settings/AppStatusFragment.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/settings/AppStatusFragment.kt
@@ -36,7 +36,7 @@ class AppStatusFragment : Fragment(), AppStatusToggleListener {
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
-    ): View? {
+    ): View {
         setHasOptionsMenu(true)
         val v: View = inflater.inflate(R.layout.fragment_app_status, container, false)
 
diff --git a/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsFragment.kt
index 0aa2f04f..679dd6a6 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsFragment.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsFragment.kt
@@ -5,7 +5,7 @@ import android.content.Intent
 import android.os.Bundle
 import android.os.RemoteException
 import android.provider.Settings
-import android.provider.Settings.Secure.BACKUP_AUTO_RESTORE // ktlint-disable no-unused-imports
+import android.provider.Settings.Secure.BACKUP_AUTO_RESTORE
 import android.util.Log
 import android.view.Menu
 import android.view.MenuInflater
@@ -37,6 +37,8 @@ class SettingsFragment : PreferenceFragmentCompat() {
     private lateinit var apkBackup: TwoStatePreference
     private lateinit var backupLocation: Preference
     private lateinit var backupStatus: Preference
+    private lateinit var backupStorage: TwoStatePreference
+    private lateinit var backupRecoveryCode: Preference
 
     private var menuBackupNow: MenuItem? = null
     private var menuRestore: MenuItem? = null
@@ -101,6 +103,19 @@ class SettingsFragment : PreferenceFragmentCompat() {
             return@OnPreferenceChangeListener false
         }
         backupStatus = findPreference("backup_status")!!
+
+        backupStorage = findPreference("backup_storage")!!
+        backupStorage.onPreferenceChangeListener = OnPreferenceChangeListener { _, newValue ->
+            val disable = !(newValue as Boolean)
+            if (disable) {
+                viewModel.disableStorageBackup()
+                return@OnPreferenceChangeListener true
+            }
+            onEnablingStorageBackup()
+            return@OnPreferenceChangeListener false
+        }
+
+        backupRecoveryCode = findPreference("backup_recovery_code")!!
     }
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
@@ -109,6 +124,11 @@ class SettingsFragment : PreferenceFragmentCompat() {
         viewModel.lastBackupTime.observe(viewLifecycleOwner, Observer { time ->
             setAppBackupStatusSummary(time)
         })
+
+        val backupFiles: Preference = findPreference("backup_files")!!
+        viewModel.filesSummary.observe(viewLifecycleOwner, Observer { summary ->
+            backupFiles.summary = summary
+        })
     }
 
     override fun onStart() {
@@ -189,4 +209,40 @@ class SettingsFragment : PreferenceFragmentCompat() {
         backupStatus.summary = getString(R.string.settings_backup_status_summary, lastBackup)
     }
 
+    private fun onEnablingStorageBackup() {
+        AlertDialog.Builder(requireContext())
+            .setIcon(R.drawable.ic_warning)
+            .setTitle(R.string.settings_backup_storage_dialog_title)
+            .setMessage(R.string.settings_backup_storage_dialog_message)
+            .setPositiveButton(R.string.settings_backup_storage_dialog_ok) { dialog, _ ->
+                if (viewModel.hasMainKey()) {
+                    viewModel.enableStorageBackup()
+                    backupStorage.isChecked = true
+                } else {
+                    showCodeVerificationNeededDialog()
+                }
+                dialog.dismiss()
+            }
+            .setNegativeButton(R.string.settings_backup_apk_dialog_cancel) { dialog, _ ->
+                dialog.dismiss()
+            }
+            .show()
+    }
+
+    private fun showCodeVerificationNeededDialog() {
+        AlertDialog.Builder(requireContext())
+            .setIcon(R.drawable.ic_vpn_key)
+            .setTitle(R.string.settings_backup_storage_code_dialog_title)
+            .setMessage(R.string.settings_backup_storage_code_dialog_message)
+            .setPositiveButton(R.string.settings_backup_storage_code_dialog_ok) { dialog, _ ->
+                val callback = (requireActivity() as OnPreferenceStartFragmentCallback)
+                callback.onPreferenceStartFragment(this, backupRecoveryCode)
+                dialog.dismiss()
+            }
+            .setNegativeButton(R.string.settings_backup_apk_dialog_cancel) { dialog, _ ->
+                dialog.dismiss()
+            }
+            .show()
+    }
+
 }
diff --git a/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsManager.kt b/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsManager.kt
index 0217638d..bb28b149 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsManager.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsManager.kt
@@ -30,6 +30,8 @@ private const val PREF_KEY_FLASH_DRIVE_PRODUCT_ID = "flashDriveProductId"
 
 private const val PREF_KEY_BACKUP_APP_BLACKLIST = "backupAppBlacklist"
 
+private const val PREF_KEY_BACKUP_STORAGE = "backup_storage"
+
 class SettingsManager(private val context: Context) {
 
     private val prefs = permitDiskReads {
@@ -138,6 +140,8 @@ class SettingsManager(private val context: Context) {
 
     fun isBackupEnabled(packageName: String) = !blacklistedApps.contains(packageName)
 
+    fun isStorageBackupEnabled() = prefs.getBoolean(PREF_KEY_BACKUP_STORAGE, false)
+
     @UiThread
     fun onAppBackupStatusChanged(status: AppStatus) {
         if (status.enabled) blacklistedApps.remove(status.packageName)
@@ -171,13 +175,14 @@ data class Storage(
      * but it isn't available right now.
      */
     fun isUnavailableNetwork(context: Context): Boolean {
-        return requiresNetwork && !hasInternet(context)
+        return requiresNetwork && !hasUnmeteredInternet(context)
     }
 
-    private fun hasInternet(context: Context): Boolean {
+    private fun hasUnmeteredInternet(context: Context): Boolean {
         val cm = context.getSystemService(ConnectivityManager::class.java)
+        val isMetered = cm.isActiveNetworkMetered()
         val capabilities = cm.getNetworkCapabilities(cm.activeNetwork) ?: return false
-        return capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
+        return capabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET) && !isMetered
     }
 }
 
diff --git a/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsViewModel.kt b/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsViewModel.kt
index 5f4ee0f9..b8e0e8e5 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsViewModel.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/settings/SettingsViewModel.kt
@@ -1,6 +1,9 @@
 package com.stevesoltys.seedvault.settings
 
 import android.app.Application
+import android.app.job.JobInfo.NETWORK_TYPE_NONE
+import android.app.job.JobInfo.NETWORK_TYPE_UNMETERED
+import android.content.Intent
 import android.database.ContentObserver
 import android.net.ConnectivityManager
 import android.net.Network
@@ -12,6 +15,7 @@ import android.util.Log
 import android.widget.Toast
 import android.widget.Toast.LENGTH_LONG
 import androidx.annotation.UiThread
+import androidx.core.content.ContextCompat.startForegroundService
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.Transformations.switchMap
@@ -22,11 +26,17 @@ import com.stevesoltys.seedvault.R
 import com.stevesoltys.seedvault.crypto.KeyManager
 import com.stevesoltys.seedvault.metadata.MetadataManager
 import com.stevesoltys.seedvault.permitDiskReads
+import com.stevesoltys.seedvault.storage.StorageBackupJobService
+import com.stevesoltys.seedvault.storage.StorageBackupService
+import com.stevesoltys.seedvault.storage.StorageBackupService.Companion.EXTRA_START_APP_BACKUP
 import com.stevesoltys.seedvault.transport.requestBackup
 import com.stevesoltys.seedvault.ui.RequireProvisioningViewModel
 import com.stevesoltys.seedvault.ui.notification.BackupNotificationManager
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.backup.BackupJobService
+import java.util.concurrent.TimeUnit.HOURS
 
 private const val TAG = "SettingsViewModel"
 private const val USER_FULL_DATA_BACKUP_AWARE = "user_full_data_backup_aware"
@@ -37,7 +47,8 @@ internal class SettingsViewModel(
     keyManager: KeyManager,
     private val notificationManager: BackupNotificationManager,
     private val metadataManager: MetadataManager,
-    private val appListRetriever: AppListRetriever
+    private val appListRetriever: AppListRetriever,
+    private val storageBackup: StorageBackup
 ) : RequireProvisioningViewModel(app, settingsManager, keyManager) {
 
     private val contentResolver = app.contentResolver
@@ -59,6 +70,9 @@ internal class SettingsViewModel(
     private val mAppEditMode = MutableLiveData<Boolean>()
     internal val appEditMode: LiveData<Boolean> = mAppEditMode
 
+    private val _filesSummary = MutableLiveData<String>()
+    internal val filesSummary: LiveData<String> = _filesSummary
+
     private val storageObserver = object : ContentObserver(null) {
         override fun onChange(selfChange: Boolean, uris: MutableCollection<Uri>, flags: Int) {
             onStorageLocationChanged()
@@ -89,6 +103,7 @@ internal class SettingsViewModel(
             metadataManager.getLastBackupTime()
         }
         onStorageLocationChanged()
+        loadFilesSummary()
     }
 
     override fun onStorageLocationChanged() {
@@ -116,6 +131,14 @@ internal class SettingsViewModel(
             networkCallback.registered = true
         }
 
+        if (settingsManager.isStorageBackupEnabled()) {
+            // disable storage backup if new storage is on USB
+            if (storage.isUsb) disableStorageBackup()
+            // enable it, just in case the previous storage was on USB,
+            // also to update the network requirement of the new storage
+            else enableStorageBackup()
+        }
+
         viewModelScope.launch(Dispatchers.IO) {
             val canDo = settingsManager.canDoBackupNow()
             mBackupPossible.postValue(canDo)
@@ -134,8 +157,15 @@ internal class SettingsViewModel(
         // maybe replace the check below with one that checks if our transport service is running
         if (notificationManager.hasActiveBackupNotifications()) {
             Toast.makeText(app, R.string.notification_backup_already_running, LENGTH_LONG).show()
-        } else {
-            Thread { requestBackup(app) }.start()
+        } else viewModelScope.launch(Dispatchers.IO) {
+            if (settingsManager.isStorageBackupEnabled()) {
+                val i = Intent(app, StorageBackupService::class.java)
+                // this starts an app backup afterwards
+                i.putExtra(EXTRA_START_APP_BACKUP, true)
+                startForegroundService(app, i)
+            } else {
+                requestBackup(app)
+            }
         }
     }
 
@@ -156,6 +186,14 @@ internal class SettingsViewModel(
         settingsManager.onAppBackupStatusChanged(status)
     }
 
+    @UiThread
+    fun loadFilesSummary() = viewModelScope.launch {
+        val uriSummary = storageBackup.getUriSummaryString()
+        _filesSummary.value = if (uriSummary.isEmpty()) {
+            app.getString(R.string.settings_backup_files_summary)
+        } else uriSummary
+    }
+
     /**
      * Disables AOSP's call log backup
      *
@@ -170,4 +208,25 @@ internal class SettingsViewModel(
         }
     }
 
+    fun hasMainKey(): Boolean {
+        return keyManager.hasMainKey()
+    }
+
+    fun enableStorageBackup() {
+        val storage = settingsManager.getStorage() ?: error("no storage available")
+        if (!storage.isUsb) BackupJobService.scheduleJob(
+            context = app,
+            jobServiceClass = StorageBackupJobService::class.java,
+            periodMillis = HOURS.toMillis(24),
+            networkType = if (storage.requiresNetwork) NETWORK_TYPE_UNMETERED
+            else NETWORK_TYPE_NONE,
+            deviceIdle = false,
+            charging = true
+        )
+    }
+
+    fun disableStorageBackup() {
+        BackupJobService.cancelJob(app)
+    }
+
 }
diff --git a/app/src/main/java/com/stevesoltys/seedvault/storage/SeedvaultStoragePlugin.kt b/app/src/main/java/com/stevesoltys/seedvault/storage/SeedvaultStoragePlugin.kt
new file mode 100644
index 00000000..9f67ca93
--- /dev/null
+++ b/app/src/main/java/com/stevesoltys/seedvault/storage/SeedvaultStoragePlugin.kt
@@ -0,0 +1,20 @@
+package com.stevesoltys.seedvault.storage
+
+import android.content.Context
+import androidx.documentfile.provider.DocumentFile
+import com.stevesoltys.seedvault.crypto.KeyManager
+import com.stevesoltys.seedvault.plugins.saf.DocumentsStorage
+import org.calyxos.backup.storage.plugin.saf.SafStoragePlugin
+import javax.crypto.SecretKey
+
+internal class SeedvaultStoragePlugin(
+    context: Context,
+    private val storage: DocumentsStorage,
+    private val keyManager: KeyManager
+) : SafStoragePlugin(context) {
+    override val root: DocumentFile
+        get() = storage.rootBackupDir ?: error("No storage set")
+
+    override fun getMasterKey(): SecretKey = keyManager.getMainKey()
+    override fun hasMasterKey(): Boolean = keyManager.hasMainKey()
+}
diff --git a/app/src/main/java/com/stevesoltys/seedvault/storage/Services.kt b/app/src/main/java/com/stevesoltys/seedvault/storage/Services.kt
new file mode 100644
index 00000000..1c54beb2
--- /dev/null
+++ b/app/src/main/java/com/stevesoltys/seedvault/storage/Services.kt
@@ -0,0 +1,55 @@
+package com.stevesoltys.seedvault.storage
+
+import android.content.Intent
+import com.stevesoltys.seedvault.transport.requestBackup
+import org.calyxos.backup.storage.api.BackupObserver
+import org.calyxos.backup.storage.api.RestoreObserver
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.backup.BackupJobService
+import org.calyxos.backup.storage.backup.BackupService
+import org.calyxos.backup.storage.backup.NotificationBackupObserver
+import org.calyxos.backup.storage.restore.NotificationRestoreObserver
+import org.calyxos.backup.storage.restore.RestoreService
+import org.koin.android.ext.android.inject
+
+/*
+test and debug with
+
+  adb shell dumpsys jobscheduler |
+  grep -A 23 -B 4 "Service: com.stevesoltys.seedvault/.storage.StorageBackupJobService"
+
+force running with:
+
+  adb shell cmd jobscheduler run -f com.stevesoltys.seedvault 0
+
+ */
+internal class StorageBackupJobService : BackupJobService(StorageBackupService::class.java)
+
+internal class StorageBackupService : BackupService() {
+
+    companion object {
+        internal const val EXTRA_START_APP_BACKUP = "startAppBackup"
+    }
+
+    override val storageBackup: StorageBackup by inject()
+
+    // use lazy delegate because context isn't available during construction time
+    override val backupObserver: BackupObserver by lazy {
+        NotificationBackupObserver(applicationContext)
+    }
+
+    override fun onBackupFinished(intent: Intent, success: Boolean) {
+        if (intent.getBooleanExtra(EXTRA_START_APP_BACKUP, false)) {
+            requestBackup(applicationContext)
+        }
+    }
+}
+
+internal class StorageRestoreService : RestoreService() {
+    override val storageBackup: StorageBackup by inject()
+
+    // use lazy delegate because context isn't available during construction time
+    override val restoreObserver: RestoreObserver by lazy {
+        NotificationRestoreObserver(applicationContext)
+    }
+}
diff --git a/app/src/main/java/com/stevesoltys/seedvault/storage/StorageModule.kt b/app/src/main/java/com/stevesoltys/seedvault/storage/StorageModule.kt
new file mode 100644
index 00000000..68254e88
--- /dev/null
+++ b/app/src/main/java/com/stevesoltys/seedvault/storage/StorageModule.kt
@@ -0,0 +1,10 @@
+package com.stevesoltys.seedvault.storage
+
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.koin.dsl.module
+
+val storageModule = module {
+    single<StoragePlugin> { SeedvaultStoragePlugin(get(), get(), get()) }
+    single { StorageBackup(get(), get()) }
+}
diff --git a/app/src/main/java/com/stevesoltys/seedvault/transport/ConfigurableBackupTransportService.kt b/app/src/main/java/com/stevesoltys/seedvault/transport/ConfigurableBackupTransportService.kt
index 328ff1bd..7ab65f46 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/transport/ConfigurableBackupTransportService.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/transport/ConfigurableBackupTransportService.kt
@@ -2,10 +2,8 @@ package com.stevesoltys.seedvault.transport
 
 import android.app.Service
 import android.app.backup.BackupManager
-import android.app.backup.BackupManager.FLAG_NON_INCREMENTAL_BACKUP // ktlint-disable no-unused-imports
 import android.app.backup.IBackupManager
 import android.content.Context
-import android.content.Context.BACKUP_SERVICE // ktlint-disable no-unused-imports
 import android.content.Intent
 import android.os.IBinder
 import android.os.RemoteException
@@ -55,22 +53,27 @@ class ConfigurableBackupTransportService : Service(), KoinComponent {
 
 @WorkerThread
 fun requestBackup(context: Context) {
-    val packageService: PackageService = get().get()
-    val packages = packageService.eligiblePackages
-    val appTotals = packageService.expectedAppTotals
+    val backupManager: IBackupManager = get().get()
+    if (backupManager.isBackupEnabled) {
+        val packageService: PackageService = get().get()
+        val packages = packageService.eligiblePackages
+        val appTotals = packageService.expectedAppTotals
 
-    val observer = NotificationBackupObserver(context, packages.size, appTotals)
-    val result = try {
-        val backupManager: IBackupManager = get().get()
-        backupManager.requestBackup(packages, observer, BackupMonitor(), 0)
-    } catch (e: RemoteException) {
-        Log.e(TAG, "Error during backup: ", e)
-        val nm: BackupNotificationManager = get().get()
-        nm.onBackupError()
-    }
-    if (result == BackupManager.SUCCESS) {
-        Log.i(TAG, "Backup succeeded ")
+        val result = try {
+            Log.d(TAG, "Backup is enabled, request backup...")
+            val observer = NotificationBackupObserver(context, packages.size, appTotals)
+            backupManager.requestBackup(packages, observer, BackupMonitor(), 0)
+        } catch (e: RemoteException) {
+            Log.e(TAG, "Error during backup: ", e)
+            val nm: BackupNotificationManager = get().get()
+            nm.onBackupError()
+        }
+        if (result == BackupManager.SUCCESS) {
+            Log.i(TAG, "Backup succeeded ")
+        } else {
+            Log.e(TAG, "Backup failed: $result")
+        }
     } else {
-        Log.e(TAG, "Backup failed: $result")
+        Log.i(TAG, "Backup is not enabled")
     }
 }
diff --git a/app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupCoordinator.kt b/app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupCoordinator.kt
index fd4bd5e4..69c4cd8f 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupCoordinator.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupCoordinator.kt
@@ -321,7 +321,7 @@ internal class BackupCoordinator(
             ?: throw AssertionError("Cancelling full backup, but no current package")
         Log.i(
             TAG, "Cancel full backup of ${packageInfo.packageName}" +
-                " because of $state.cancelReason"
+                " because of ${state.cancelReason}"
         )
         onPackageBackupError(packageInfo)
         full.cancelFullBackup()
diff --git a/app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupPlugin.kt b/app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupPlugin.kt
index 5a08a63a..f8672503 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupPlugin.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupPlugin.kt
@@ -25,12 +25,6 @@ interface BackupPlugin {
     @Throws(IOException::class)
     suspend fun initializeDevice()
 
-    /**
-     * Delete all existing [RestoreSet]s from the storage medium.
-     */
-    @Throws(IOException::class)
-    suspend fun deleteAllBackups()
-
     /**
      * Returns an [OutputStream] for writing backup metadata.
      */
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/RequireProvisioningViewModel.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/RequireProvisioningViewModel.kt
index 50952758..68b02eec 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/ui/RequireProvisioningViewModel.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/RequireProvisioningViewModel.kt
@@ -9,7 +9,7 @@ import com.stevesoltys.seedvault.ui.storage.StorageViewModel
 abstract class RequireProvisioningViewModel(
     protected val app: Application,
     protected val settingsManager: SettingsManager,
-    private val keyManager: KeyManager
+    protected val keyManager: KeyManager
 ) : AndroidViewModel(app) {
 
     abstract val isRestoreOperation: Boolean
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/files/FileSelectionFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/files/FileSelectionFragment.kt
new file mode 100644
index 00000000..54099150
--- /dev/null
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/files/FileSelectionFragment.kt
@@ -0,0 +1,32 @@
+package com.stevesoltys.seedvault.ui.files
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import com.stevesoltys.seedvault.R
+import com.stevesoltys.seedvault.settings.SettingsViewModel
+import org.calyxos.backup.storage.ui.backup.BackupContentFragment
+import org.koin.androidx.viewmodel.ext.android.sharedViewModel
+import org.koin.androidx.viewmodel.ext.android.viewModel
+
+class FileSelectionFragment() : BackupContentFragment() {
+
+    override val viewModel by viewModel<FileSelectionViewModel>()
+    private val settingsViewModel by sharedViewModel<SettingsViewModel>()
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        requireActivity().setTitle(R.string.settings_backup_files_title)
+        return super.onCreateView(inflater, container, savedInstanceState)
+    }
+
+    override fun onDestroy() {
+        super.onDestroy()
+        // reload files summary when we navigate away (it might have changed)
+        settingsViewModel.loadFilesSummary()
+    }
+}
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/files/FileSelectionViewModel.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/files/FileSelectionViewModel.kt
new file mode 100644
index 00000000..359c9965
--- /dev/null
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/files/FileSelectionViewModel.kt
@@ -0,0 +1,18 @@
+package com.stevesoltys.seedvault.ui.files
+
+import android.app.Application
+import androidx.lifecycle.viewModelScope
+import kotlinx.coroutines.launch
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.ui.backup.BackupContentViewModel
+
+class FileSelectionViewModel(
+    app: Application,
+    override val storageBackup: StorageBackup
+) : BackupContentViewModel(app) {
+
+    init {
+        viewModelScope.launch { loadContent() }
+    }
+
+}
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeAdapter.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeAdapter.kt
index 606e024b..1003300e 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeAdapter.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeAdapter.kt
@@ -8,7 +8,7 @@ import androidx.recyclerview.widget.RecyclerView
 import androidx.recyclerview.widget.RecyclerView.Adapter
 import com.stevesoltys.seedvault.R
 
-class RecoveryCodeAdapter(private val items: List<CharSequence>) :
+class RecoveryCodeAdapter(private val items: List<CharArray>) :
     Adapter<RecoveryCodeViewHolder>() {
 
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecoveryCodeViewHolder {
@@ -30,9 +30,9 @@ class RecoveryCodeViewHolder(v: View) : RecyclerView.ViewHolder(v) {
     private val num = v.findViewById<TextView>(R.id.num)
     private val word = v.findViewById<TextView>(R.id.word)
 
-    internal fun bind(number: Int, item: CharSequence) {
+    internal fun bind(number: Int, item: CharArray) {
         num.text = number.toString()
-        word.text = item
+        word.text = String(item)
     }
 
 }
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeInputFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeInputFragment.kt
index 94f0b3c3..fdd8c1e2 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeInputFragment.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeInputFragment.kt
@@ -19,15 +19,16 @@ import androidx.activity.result.contract.ActivityResultContracts.StartActivityFo
 import androidx.appcompat.app.AlertDialog
 import androidx.constraintlayout.widget.ConstraintLayout
 import androidx.fragment.app.Fragment
+import cash.z.ecc.android.bip39.Mnemonics
+import cash.z.ecc.android.bip39.Mnemonics.ChecksumException
+import cash.z.ecc.android.bip39.Mnemonics.InvalidWordException
 import com.google.android.material.snackbar.Snackbar
 import com.google.android.material.textfield.TextInputLayout
 import com.stevesoltys.seedvault.R
 import com.stevesoltys.seedvault.isDebugBuild
 import com.stevesoltys.seedvault.ui.LiveEventHandler
-import io.github.novacrypto.bip39.Validation.InvalidChecksumException
-import io.github.novacrypto.bip39.Validation.WordNotFoundException
-import io.github.novacrypto.bip39.wordlists.English
 import org.koin.androidx.viewmodel.ext.android.sharedViewModel
+import java.util.Locale
 
 internal const val ARG_FOR_NEW_CODE = "forVerifyingNewCode"
 
@@ -62,7 +63,7 @@ class RecoveryCodeInputFragment : Fragment() {
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
-    ): View? {
+    ): View {
         val v: View = inflater.inflate(R.layout.fragment_recovery_code_input, container, false)
 
         introText = v.findViewById(R.id.introText)
@@ -93,13 +94,18 @@ class RecoveryCodeInputFragment : Fragment() {
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
 
+        activity?.setTitle(R.string.recovery_code_title)
+
         if (viewModel.isRestore) {
             introText.setText(R.string.recovery_code_input_intro)
             backView.visibility = VISIBLE
             backView.setOnClickListener { requireActivity().finishAfterTransition() }
         }
 
-        val adapter = getAdapter()
+        val adapterLayout = android.R.layout.simple_list_item_1
+        val adapter = ArrayAdapter<String>(requireContext(), adapterLayout).apply {
+            addAll(Mnemonics.getCachedWords(Locale.ENGLISH.language))
+        }
 
         for (i in 0 until WORD_NUM) {
             val wordLayout = getWordLayout(i)
@@ -120,14 +126,6 @@ class RecoveryCodeInputFragment : Fragment() {
         if (forVerifyingNewCode && isDebugBuild() && !viewModel.isRestore) debugPreFill()
     }
 
-    private fun getAdapter(): ArrayAdapter<String> {
-        val adapter = ArrayAdapter<String>(requireContext(), android.R.layout.simple_list_item_1)
-        for (i in 0 until WORD_LIST_SIZE) {
-            adapter.add(English.INSTANCE.getWord(i))
-        }
-        return adapter
-    }
-
     private fun getInput(): List<CharSequence> = ArrayList<String>(WORD_NUM).apply {
         for (i in 0 until WORD_NUM) add(getWordLayout(i).editText!!.text.toString())
     }
@@ -137,10 +135,10 @@ class RecoveryCodeInputFragment : Fragment() {
         if (!allFilledOut(input)) return
         try {
             viewModel.validateAndContinue(input, forVerifyingNewCode)
-        } catch (e: InvalidChecksumException) {
+        } catch (e: ChecksumException) {
             Toast.makeText(context, R.string.recovery_code_error_checksum_word, LENGTH_LONG).show()
-        } catch (e: WordNotFoundException) {
-            showWrongWordError(input, e)
+        } catch (e: InvalidWordException) {
+            showWrongWordError(input)
         }
     }
 
@@ -153,10 +151,11 @@ class RecoveryCodeInputFragment : Fragment() {
         return true
     }
 
-    private fun showWrongWordError(input: List<CharSequence>, e: WordNotFoundException) {
-        val i = input.indexOf(e.word)
+    private fun showWrongWordError(input: List<CharSequence>) {
+        val words = Mnemonics.getCachedWords(Locale.ENGLISH.language)
+        val i = input.indexOfFirst { it !in words }
         if (i == -1) throw AssertionError()
-        val str = getString(R.string.recovery_code_error_invalid_word, e.suggestion1, e.suggestion2)
+        val str = getString(R.string.recovery_code_error_invalid_word)
         showError(i, str)
     }
 
@@ -190,7 +189,7 @@ class RecoveryCodeInputFragment : Fragment() {
 
     private val regenRequest = registerForActivityResult(StartActivityForResult()) {
         if (it.resultCode == RESULT_OK) {
-            viewModel.deleteAllBackup()
+            viewModel.reinitializeBackupLocation()
             parentFragmentManager.popBackStack()
             Snackbar.make(requireView(), R.string.recovery_code_recreated, Snackbar.LENGTH_LONG)
                 .show()
@@ -233,7 +232,7 @@ class RecoveryCodeInputFragment : Fragment() {
     private fun debugPreFill() {
         val words = viewModel.wordList
         for (i in words.indices) {
-            getWordLayout(i).editText!!.setText(words[i])
+            getWordLayout(i).editText!!.setText(String(words[i]))
         }
     }
 
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeOutputFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeOutputFragment.kt
index 35f6af76..d8b3a5ef 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeOutputFragment.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeOutputFragment.kt
@@ -23,7 +23,7 @@ class RecoveryCodeOutputFragment : Fragment() {
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
-    ): View? {
+    ): View {
         val v: View = inflater.inflate(R.layout.fragment_recovery_code_output, container, false)
 
         wordList = v.findViewById(R.id.wordList)
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeViewModel.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeViewModel.kt
index c3069475..3eb3329e 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeViewModel.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/recoverycode/RecoveryCodeViewModel.kt
@@ -1,48 +1,47 @@
 package com.stevesoltys.seedvault.ui.recoverycode
 
+import android.app.backup.IBackupManager
+import android.os.UserHandle
 import android.util.Log
 import androidx.lifecycle.AndroidViewModel
+import cash.z.ecc.android.bip39.Mnemonics
+import cash.z.ecc.android.bip39.Mnemonics.ChecksumException
+import cash.z.ecc.android.bip39.Mnemonics.InvalidWordException
+import cash.z.ecc.android.bip39.Mnemonics.WordCountException
+import cash.z.ecc.android.bip39.toSeed
 import com.stevesoltys.seedvault.App
 import com.stevesoltys.seedvault.crypto.Crypto
 import com.stevesoltys.seedvault.crypto.KeyManager
-import com.stevesoltys.seedvault.transport.backup.BackupPlugin
+import com.stevesoltys.seedvault.transport.TRANSPORT_ID
+import com.stevesoltys.seedvault.transport.backup.BackupCoordinator
 import com.stevesoltys.seedvault.ui.LiveEvent
 import com.stevesoltys.seedvault.ui.MutableLiveEvent
-import io.github.novacrypto.bip39.JavaxPBKDF2WithHmacSHA512
-import io.github.novacrypto.bip39.MnemonicGenerator
-import io.github.novacrypto.bip39.MnemonicValidator
-import io.github.novacrypto.bip39.SeedCalculator
-import io.github.novacrypto.bip39.Validation.InvalidChecksumException
-import io.github.novacrypto.bip39.Validation.InvalidWordCountException
-import io.github.novacrypto.bip39.Validation.UnexpectedWhiteSpaceException
-import io.github.novacrypto.bip39.Validation.WordNotFoundException
-import io.github.novacrypto.bip39.Words
-import io.github.novacrypto.bip39.wordlists.English
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.GlobalScope
 import kotlinx.coroutines.launch
+import org.calyxos.backup.storage.api.StorageBackup
 import java.io.IOException
 import java.security.SecureRandom
-import java.util.ArrayList
 
 internal const val WORD_NUM = 12
-internal const val WORD_LIST_SIZE = 2048
 
-class RecoveryCodeViewModel(
+private val TAG = RecoveryCodeViewModel::class.java.simpleName
+
+internal class RecoveryCodeViewModel(
     app: App,
     private val crypto: Crypto,
     private val keyManager: KeyManager,
-    private val backupPlugin: BackupPlugin
+    private val backupManager: IBackupManager,
+    private val backupCoordinator: BackupCoordinator,
+    private val storageBackup: StorageBackup
 ) : AndroidViewModel(app) {
 
-    internal val wordList: List<CharSequence> by lazy {
-        val items: ArrayList<CharSequence> = ArrayList(WORD_NUM)
-        val entropy = ByteArray(Words.TWELVE.byteLength())
+    internal val wordList: List<CharArray> by lazy {
+        // we use our own entropy to not having to trust the library to use SecureRandom
+        val entropy = ByteArray(Mnemonics.WordCount.COUNT_12.bitLength / 8)
         SecureRandom().nextBytes(entropy)
-        MnemonicGenerator(English.INSTANCE).createMnemonic(entropy) {
-            if (it != " ") items.add(it)
-        }
-        items
+        // create the words from the entropy
+        Mnemonics.MnemonicCode(entropy).words
     }
 
     private val mConfirmButtonClicked = MutableLiveEvent<Boolean>()
@@ -57,17 +56,15 @@ class RecoveryCodeViewModel(
 
     internal var isRestore: Boolean = false
 
-    @Throws(WordNotFoundException::class, InvalidChecksumException::class)
+    @Throws(InvalidWordException::class, ChecksumException::class)
     fun validateAndContinue(input: List<CharSequence>, forVerifyingNewCode: Boolean) {
+        val code = Mnemonics.MnemonicCode(input.toMnemonicChars())
         try {
-            MnemonicValidator.ofWordList(English.INSTANCE).validate(input)
-        } catch (e: UnexpectedWhiteSpaceException) {
-            throw AssertionError(e)
-        } catch (e: InvalidWordCountException) {
+            code.validate()
+        } catch (e: WordCountException) {
             throw AssertionError(e)
         }
-        val mnemonic = input.joinToString(" ")
-        val seed = SeedCalculator(JavaxPBKDF2WithHmacSHA512.INSTANCE).calculateSeed(mnemonic, "")
+        val seed = code.toSeed()
         if (forVerifyingNewCode) {
             keyManager.storeBackupKey(seed)
             keyManager.storeMainKey(seed)
@@ -79,14 +76,38 @@ class RecoveryCodeViewModel(
         }
     }
 
-    fun deleteAllBackup() {
+    /**
+     * Deletes all storage backups for current user and clears the storage backup cache.
+     * Also starts a new app data restore set and initializes it.
+     *
+     * The reason is that old backups won't be readable anymore with the new key.
+     * We can't delete other backups safely, because we can't be sure
+     * that they don't belong to a different device or user.
+     */
+    fun reinitializeBackupLocation() {
+        Log.d(TAG, "Re-initializing backup location...")
         GlobalScope.launch(Dispatchers.IO) {
+            // remove old storage snapshots and clear cache
+            storageBackup.deleteAllSnapshots()
+            storageBackup.clearCache()
             try {
-                backupPlugin.deleteAllBackups()
+                // will also generate a new backup token for the new restore set
+                backupCoordinator.startNewRestoreSet()
+
+                // initialize the new location
+                backupManager.initializeTransportsForUser(
+                    UserHandle.myUserId(),
+                    arrayOf(TRANSPORT_ID),
+                    null
+                )
             } catch (e: IOException) {
-                Log.e("RecoveryCodeViewModel", "Error deleting backups", e)
+                Log.e(TAG, "Error starting new RestoreSet", e)
             }
         }
     }
 
 }
+
+internal fun List<CharSequence>.toMnemonicChars(): CharArray {
+    return joinToString(" ").toCharArray()
+}
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/storage/BackupStorageViewModel.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/storage/BackupStorageViewModel.kt
index 617ab24a..aa8a0bb6 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/ui/storage/BackupStorageViewModel.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/storage/BackupStorageViewModel.kt
@@ -16,6 +16,7 @@ import com.stevesoltys.seedvault.transport.backup.BackupCoordinator
 import com.stevesoltys.seedvault.transport.requestBackup
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
+import org.calyxos.backup.storage.api.StorageBackup
 import java.io.IOException
 
 private val TAG = BackupStorageViewModel::class.java.simpleName
@@ -24,6 +25,7 @@ internal class BackupStorageViewModel(
     private val app: Application,
     private val backupManager: IBackupManager,
     private val backupCoordinator: BackupCoordinator,
+    private val storageBackup: StorageBackup,
     settingsManager: SettingsManager
 ) : StorageViewModel(app, settingsManager) {
 
@@ -32,6 +34,9 @@ internal class BackupStorageViewModel(
     override fun onLocationSet(uri: Uri) {
         val isUsb = saveStorage(uri)
         viewModelScope.launch(Dispatchers.IO) {
+            // remove old storage snapshots and clear cache
+            storageBackup.deleteAllSnapshots()
+            storageBackup.clearCache()
             try {
                 // will also generate a new backup token for the new restore set
                 backupCoordinator.startNewRestoreSet()
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageCheckFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageCheckFragment.kt
index 3c8c60d1..566d03fd 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageCheckFragment.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageCheckFragment.kt
@@ -3,6 +3,7 @@ package com.stevesoltys.seedvault.ui.storage
 import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
+import android.view.View.GONE
 import android.view.View.INVISIBLE
 import android.view.View.VISIBLE
 import android.view.ViewGroup
@@ -37,7 +38,7 @@ class StorageCheckFragment : Fragment() {
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
-    ): View? {
+    ): View {
         val v: View = inflater.inflate(R.layout.fragment_storage_check, container, false)
 
         titleView = v.findViewById(R.id.titleView)
@@ -55,6 +56,7 @@ class StorageCheckFragment : Fragment() {
 
         val errorMsg = requireArguments().getString(ERROR_MSG)
         if (errorMsg != null) {
+            view.findViewById<View>(R.id.patienceView).visibility = GONE
             progressBar.visibility = INVISIBLE
             errorView.text = errorMsg
             errorView.visibility = VISIBLE
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageRootsFragment.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageRootsFragment.kt
index ae872ad1..b50b24de 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageRootsFragment.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageRootsFragment.kt
@@ -83,6 +83,9 @@ internal class StorageRootsFragment : Fragment(), StorageRootClickedListener {
             backView.setOnClickListener { requireActivity().finishAfterTransition() }
         } else {
             warningIcon.visibility = VISIBLE
+            if (viewModel.hasStorageSet) {
+                warningText.setText(R.string.storage_fragment_warning_delete)
+            }
             warningText.visibility = VISIBLE
             divider.visibility = VISIBLE
         }
diff --git a/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageViewModel.kt b/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageViewModel.kt
index 0f12b0f5..f04eaa8d 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageViewModel.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageViewModel.kt
@@ -41,6 +41,8 @@ internal abstract class StorageViewModel(
     private var storageRoot: StorageRoot? = null
 
     internal var isSetupWizard: Boolean = false
+    internal val hasStorageSet: Boolean
+        get() = settingsManager.getStorage() != null
     abstract val isRestoreOperation: Boolean
 
     companion object {
diff --git a/app/src/main/res/drawable/ic_library_add.xml b/app/src/main/res/drawable/ic_library_add.xml
new file mode 100644
index 00000000..35674009
--- /dev/null
+++ b/app/src/main/res/drawable/ic_library_add.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M4,6L2,6v14c0,1.1 0.9,2 2,2h14v-2L4,20L4,6zM20,2L8,2c-1.1,0 -2,0.9 -2,2v12c0,1.1 0.9,2 2,2h12c1.1,0 2,-0.9 2,-2L22,4c0,-1.1 -0.9,-2 -2,-2zM19,11h-4v4h-2v-4L9,11L9,9h4L13,5h2v4h4v2z" />
+</vector>
diff --git a/app/src/main/res/drawable/ic_save_alt.xml b/app/src/main/res/drawable/ic_save_alt.xml
new file mode 100644
index 00000000..c9407604
--- /dev/null
+++ b/app/src/main/res/drawable/ic_save_alt.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M19,12v7L5,19v-7L3,12v7c0,1.1 0.9,2 2,2h14c1.1,0 2,-0.9 2,-2v-7h-2zM13,12.67l2.59,-2.58L17,11.5l-5,5 -5,-5 1.41,-1.41L11,12.67L11,3h2z" />
+</vector>
diff --git a/app/src/main/res/drawable/ic_vpn_key.xml b/app/src/main/res/drawable/ic_vpn_key.xml
index 7b554c94..1374f65f 100644
--- a/app/src/main/res/drawable/ic_vpn_key.xml
+++ b/app/src/main/res/drawable/ic_vpn_key.xml
@@ -1,7 +1,7 @@
 <vector xmlns:android="http://schemas.android.com/apk/res/android"
     android:width="24dp"
     android:height="24dp"
-    android:tint="?attr/colorControlNormal"
+    android:tint="?android:attr/colorControlNormal"
     android:viewportWidth="24"
     android:viewportHeight="24">
     <path
diff --git a/app/src/main/res/layout/footer_snapshots.xml b/app/src/main/res/layout/footer_snapshots.xml
new file mode 100644
index 00000000..d6c75b3b
--- /dev/null
+++ b/app/src/main/res/layout/footer_snapshots.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content">
+
+    <TextView
+        android:id="@+id/skipView"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:background="?android:selectableItemBackground"
+        android:padding="16dp"
+        android:text="@string/restore_storage_skip"
+        android:textColor="?android:colorAccent"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/app/src/main/res/layout/fragment_recovery_code_input.xml b/app/src/main/res/layout/fragment_recovery_code_input.xml
index 911415eb..a8d10d35 100644
--- a/app/src/main/res/layout/fragment_recovery_code_input.xml
+++ b/app/src/main/res/layout/fragment_recovery_code_input.xml
@@ -60,6 +60,7 @@
 
         <Button
             android:id="@+id/doneButton"
+            style="@style/ActionPrimaryButton"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_marginStart="8dp"
@@ -74,7 +75,8 @@
             android:id="@+id/backView"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:layout_margin="16dp"
+            android:background="?android:selectableItemBackground"
+            android:padding="16dp"
             android:text="@string/restore_back"
             android:textColor="?android:colorAccent"
             android:visibility="gone"
diff --git a/app/src/main/res/layout/fragment_recovery_code_output.xml b/app/src/main/res/layout/fragment_recovery_code_output.xml
index 8a84d5bd..54560f51 100644
--- a/app/src/main/res/layout/fragment_recovery_code_output.xml
+++ b/app/src/main/res/layout/fragment_recovery_code_output.xml
@@ -57,19 +57,21 @@
     <androidx.recyclerview.widget.RecyclerView
         android:id="@+id/wordList"
         android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        android:orientation="vertical"
+        android:layout_height="0dp"
+        android:scrollbars="vertical"
         app:layoutManager="androidx.recyclerview.widget.GridLayoutManager"
         app:layout_constraintBottom_toTopOf="@+id/confirmCodeButton"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toBottomOf="@+id/divider"
+        app:layout_constraintVertical_chainStyle="spread_inside"
         app:spanCount="2"
         tools:itemCount="12"
         tools:listitem="@layout/list_item_recovery_code_output" />
 
     <Button
         android:id="@+id/confirmCodeButton"
+        style="@style/ActionPrimaryButton"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginStart="8dp"
@@ -78,6 +80,7 @@
         android:text="@string/recovery_code_confirm_button"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintStart_toStartOf="parent" />
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/wordList" />
 
 </androidx.constraintlayout.widget.ConstraintLayout>
\ No newline at end of file
diff --git a/app/src/main/res/layout/fragment_restore_files_started.xml b/app/src/main/res/layout/fragment_restore_files_started.xml
new file mode 100644
index 00000000..8746717b
--- /dev/null
+++ b/app/src/main/res/layout/fragment_restore_files_started.xml
@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <ImageView
+        android:id="@+id/imageView"
+        android:layout_width="32dp"
+        android:layout_height="32dp"
+        android:layout_margin="16dp"
+        android:tint="?android:colorAccent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        app:srcCompat="@drawable/ic_cloud_restore"
+        tools:ignore="ContentDescription" />
+
+    <TextView
+        android:id="@+id/titleView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:gravity="center"
+        android:text="@string/restore_storage_in_progress_title"
+        android:textSize="24sp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/imageView" />
+
+    <TextView
+        android:id="@+id/infoView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:text="@string/restore_storage_in_progress_info"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/titleView" />
+
+    <Button
+        android:id="@+id/button"
+        style="@style/Widget.AppCompat.Button.Colored"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:text="@string/restore_storage_got_it"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="1.0"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/infoView"
+        app:layout_constraintVertical_bias="1.0" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/app/src/main/res/layout/fragment_restore_progress.xml b/app/src/main/res/layout/fragment_restore_progress.xml
index 4bd34495..c2bd8457 100644
--- a/app/src/main/res/layout/fragment_restore_progress.xml
+++ b/app/src/main/res/layout/fragment_restore_progress.xml
@@ -68,7 +68,7 @@
 
     <Button
         android:id="@+id/button"
-        style="@style/Widget.AppCompat.Button.Colored"
+        style="@style/ActionPrimaryButton"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginStart="16dp"
diff --git a/app/src/main/res/layout/fragment_restore_set.xml b/app/src/main/res/layout/fragment_restore_set.xml
index 2b81c026..eba8d78e 100644
--- a/app/src/main/res/layout/fragment_restore_set.xml
+++ b/app/src/main/res/layout/fragment_restore_set.xml
@@ -36,7 +36,7 @@
         android:layout_marginTop="16dp"
         android:layout_marginEnd="16dp"
         app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
-        app:layout_constraintBottom_toTopOf="@+id/backView"
+        app:layout_constraintBottom_toTopOf="@+id/skipView"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toBottomOf="@+id/titleView"
@@ -47,7 +47,7 @@
         style="?android:progressBarStyleLarge"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        app:layout_constraintBottom_toTopOf="@+id/backView"
+        app:layout_constraintBottom_toTopOf="@+id/skipView"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toBottomOf="@+id/titleView" />
@@ -57,10 +57,10 @@
         android:layout_width="0dp"
         android:layout_height="wrap_content"
         android:layout_margin="16dp"
-        android:textColor="@android:color/holo_red_dark"
+        android:textColor="?android:colorError"
         android:textSize="18sp"
         android:visibility="invisible"
-        app:layout_constraintBottom_toTopOf="@+id/backView"
+        app:layout_constraintBottom_toTopOf="@+id/skipView"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toBottomOf="@+id/titleView"
@@ -68,11 +68,12 @@
         tools:visibility="visible" />
 
     <TextView
-        android:id="@+id/backView"
+        android:id="@+id/skipView"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:layout_margin="16dp"
-        android:text="@string/restore_back"
+        android:background="?android:selectableItemBackground"
+        android:padding="16dp"
+        android:text="@string/restore_skip"
         android:textColor="?android:colorAccent"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
diff --git a/app/src/main/res/layout/fragment_storage_check.xml b/app/src/main/res/layout/fragment_storage_check.xml
index 0694ab16..8965997c 100644
--- a/app/src/main/res/layout/fragment_storage_check.xml
+++ b/app/src/main/res/layout/fragment_storage_check.xml
@@ -29,6 +29,17 @@
         app:layout_constraintTop_toBottomOf="@+id/imageView"
         tools:text="@string/storage_check_fragment_backup_title" />
 
+    <TextView
+        android:id="@+id/patienceView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:gravity="center_horizontal"
+        android:text="@string/storage_check_fragment_patience"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/titleView" />
+
     <ProgressBar
         android:id="@+id/progressBar"
         style="?android:progressBarStyleLarge"
@@ -37,10 +48,10 @@
         android:layout_marginStart="16dp"
         android:layout_marginTop="32dp"
         android:layout_marginEnd="16dp"
-        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintBottom_toTopOf="@+id/backButton"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toBottomOf="@+id/titleView"
+        app:layout_constraintTop_toBottomOf="@+id/patienceView"
         app:layout_constraintVertical_bias="0.0" />
 
     <TextView
@@ -50,20 +61,20 @@
         android:layout_marginStart="16dp"
         android:layout_marginTop="32dp"
         android:layout_marginEnd="16dp"
-        android:textColor="@android:color/holo_red_dark"
+        android:textColor="?android:colorError"
         android:textSize="18sp"
         android:visibility="invisible"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toBottomOf="@+id/titleView"
+        app:layout_constraintTop_toBottomOf="@+id/patienceView"
         app:layout_constraintVertical_bias="0.0"
         tools:text="@string/storage_check_fragment_backup_error"
         tools:visibility="visible" />
 
     <Button
         android:id="@+id/backButton"
-        style="@style/Widget.AppCompat.Button.Colored"
+        style="@style/ActionPrimaryButton"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_margin="16dp"
diff --git a/app/src/main/res/layout/fragment_storage_root.xml b/app/src/main/res/layout/fragment_storage_root.xml
index a6267bb1..3263f5b6 100644
--- a/app/src/main/res/layout/fragment_storage_root.xml
+++ b/app/src/main/res/layout/fragment_storage_root.xml
@@ -22,24 +22,24 @@
         android:layout_width="0dp"
         android:layout_height="wrap_content"
         android:layout_margin="16dp"
+        android:gravity="center"
         android:text="@string/storage_fragment_backup_title"
         android:textSize="24sp"
-        android:gravity="center"
-        tools:text="Choose where to store backup (is a short title, but it can be longer)"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toBottomOf="@+id/imageView" />
+        app:layout_constraintTop_toBottomOf="@+id/imageView"
+        tools:text="Choose where to store backup (is a short title, but it can be longer)" />
 
     <ImageView
         android:id="@+id/warningIcon"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginStart="16dp"
-        android:layout_marginTop="24dp"
         android:src="@drawable/ic_warning"
         android:visibility="gone"
+        app:layout_constraintBottom_toBottomOf="@+id/warningText"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toBottomOf="@+id/titleView"
+        app:layout_constraintTop_toTopOf="@+id/warningText"
         tools:ignore="ContentDescription"
         tools:visibility="visible" />
 
@@ -96,7 +96,8 @@
         android:id="@+id/backView"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:layout_margin="16dp"
+        android:background="?android:selectableItemBackground"
+        android:padding="16dp"
         android:text="@string/restore_back"
         android:textColor="?android:colorAccent"
         android:visibility="gone"
diff --git a/app/src/main/res/layout/header_snapshots.xml b/app/src/main/res/layout/header_snapshots.xml
new file mode 100644
index 00000000..d91bfa44
--- /dev/null
+++ b/app/src/main/res/layout/header_snapshots.xml
@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content">
+
+    <ImageView
+        android:id="@+id/imageView"
+        android:layout_width="32dp"
+        android:layout_height="32dp"
+        android:layout_margin="16dp"
+        android:tint="?android:colorAccent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        app:srcCompat="@drawable/ic_cloud_download"
+        tools:ignore="ContentDescription" />
+
+    <TextView
+        android:id="@+id/titleView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:gravity="center"
+        android:text="@string/restore_storage_choose_snapshot"
+        android:textSize="24sp"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/imageView" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
\ No newline at end of file
diff --git a/app/src/main/res/layout/list_item_recovery_code_output.xml b/app/src/main/res/layout/list_item_recovery_code_output.xml
index fade3223..780f3df7 100644
--- a/app/src/main/res/layout/list_item_recovery_code_output.xml
+++ b/app/src/main/res/layout/list_item_recovery_code_output.xml
@@ -4,7 +4,8 @@
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
-    android:padding="24dp"
+    android:layout_marginTop="24dp"
+    android:layout_marginBottom="24dp"
     tools:showIn="@layout/fragment_recovery_code_output">
 
     <TextView
@@ -25,12 +26,12 @@
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginStart="16dp"
-        android:autoSizeTextType="uniform"
         android:textSize="24sp"
+        app:layout_constrainedWidth="true"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toEndOf="@+id/num"
         app:layout_constraintTop_toTopOf="parent"
-        tools:text="Test1" />
+        tools:text="Test1CanBeLong" />
 
 </androidx.constraintlayout.widget.ConstraintLayout>
\ No newline at end of file
diff --git a/app/src/main/res/values-de/strings.xml b/app/src/main/res/values-de/strings.xml
index bd7b8d08..8cbee9f7 100644
--- a/app/src/main/res/values-de/strings.xml
+++ b/app/src/main/res/values-de/strings.xml
@@ -18,7 +18,7 @@
     <string name="notification_title">Sicherung läuft</string>
     <string name="notification_channel_title">Sicherungsbenachrichtigung</string>
     <string name="recovery_code_error_checksum_word">Ihr Wiederherstellungsschlüssel ist ungültig. Bitte prüfen Sie alle eingegebenen Wörter und versuchen Sie es erneut!</string>
-    <string name="recovery_code_error_invalid_word">Falsches Wort. Meinten Sie %1$s oder %2$s\?</string>
+    <string name="recovery_code_error_invalid_word">Falsches Wort.</string>
     <string name="recovery_code_error_empty_word">Sie vergaßen, dieses Wort einzugeben.</string>
     <string name="recovery_code_input_hint_12">Wort 12</string>
     <string name="recovery_code_input_hint_11">Wort 11</string>
diff --git a/app/src/main/res/values-el/strings.xml b/app/src/main/res/values-el/strings.xml
index 67988b49..c7924e52 100644
--- a/app/src/main/res/values-el/strings.xml
+++ b/app/src/main/res/values-el/strings.xml
@@ -80,7 +80,7 @@
     <string name="notification_title">Εκτελείται δημιουργία αντιγράφων ασφαλείας</string>
     <string name="notification_channel_title">Ειδοποίηση δημιουργίας αντιγράφων ασφαλείας</string>
     <string name="recovery_code_error_checksum_word">Ο κωδικός σας δεν είναι έγκυρος. Ελέγξτε όλες τις λέξεις και δοκιμάστε ξανά!</string>
-    <string name="recovery_code_error_invalid_word">Λάθος λέξη. Εννοείτε %1$s ή %2$s;</string>
+    <string name="recovery_code_error_invalid_word">Λάθος λέξη.</string>
     <string name="recovery_code_error_empty_word">Ξεχάσατε να εισαγάγετε αυτήν τη λέξη.</string>
     <string name="recovery_code_input_hint_12">Λέξη 12</string>
     <string name="recovery_code_input_hint_11">Λέξη 11</string>
diff --git a/app/src/main/res/values-es-rUS/strings.xml b/app/src/main/res/values-es-rUS/strings.xml
index 82a77787..d5735baa 100644
--- a/app/src/main/res/values-es-rUS/strings.xml
+++ b/app/src/main/res/values-es-rUS/strings.xml
@@ -46,7 +46,7 @@
     <string name="notification_success_title">Respaldo terminó</string>
     <string name="notification_title">Ejecución de respaldo</string>
     <string name="recovery_code_error_checksum_word">Tu código no es válido. Por favor revise todas las palabras e intente nuevamente!</string>
-    <string name="recovery_code_error_invalid_word">Palabra equivocada. ¿Quisiste decir %1$s o %2$s\?</string>
+    <string name="recovery_code_error_invalid_word">Palabra equivocada.</string>
     <string name="recovery_code_error_empty_word">Olvidaste ingresar esta palabra.</string>
     <string name="recovery_code_input_hint_12">Palabra 12</string>
     <string name="recovery_code_input_hint_11">Palabra 11</string>
diff --git a/app/src/main/res/values-es/strings.xml b/app/src/main/res/values-es/strings.xml
index d69cef52..a3ec950c 100644
--- a/app/src/main/res/values-es/strings.xml
+++ b/app/src/main/res/values-es/strings.xml
@@ -72,7 +72,7 @@
     <string name="notification_title">Copia de seguridad en ejecución</string>
     <string name="notification_channel_title">Notificación de copia de seguridad</string>
     <string name="recovery_code_error_checksum_word">Su código es inválido. Por favor, compruebe todas las palabras e inténtelo de nuevo!</string>
-    <string name="recovery_code_error_invalid_word">Palabra equivocada. ¿Quisiste decir %1$s o %2$s \?</string>
+    <string name="recovery_code_error_invalid_word">Palabra equivocada.</string>
     <string name="recovery_code_input_intro">Ingrese su código de recuperación de 12 palabras que anotó al configurar las copias de seguridad.</string>
     <string name="recovery_code_confirm_intro">Ingrese su código de recuperación de 12 palabras para asegurarse de que funcionará cuando lo necesite.</string>
     <string name="recovery_code_confirm_button">Confirma código</string>
diff --git a/app/src/main/res/values-fr/strings.xml b/app/src/main/res/values-fr/strings.xml
index 80b59e8c..ee6ad5e2 100644
--- a/app/src/main/res/values-fr/strings.xml
+++ b/app/src/main/res/values-fr/strings.xml
@@ -16,7 +16,7 @@
     <string name="notification_error_action">Réparer</string>
     <string name="notification_channel_title">Notification de la sauvegarde</string>
     <string name="recovery_code_error_checksum_word">Votre code est invalide. Veuillez vérifier tous les mots et réessayer !</string>
-    <string name="recovery_code_error_invalid_word">Mot erroné. Vouliez-vous dire %1$s ou %2$s \?</string>
+    <string name="recovery_code_error_invalid_word">Mot erroné.</string>
     <string name="recovery_code_error_empty_word">Vous avez oublié d’entrer ce mot.</string>
     <string name="recovery_code_input_hint_12">Mot 12</string>
     <string name="recovery_code_input_hint_11">Mot 11</string>
diff --git a/app/src/main/res/values-he/strings.xml b/app/src/main/res/values-he/strings.xml
index a1efca53..29b4a1ce 100644
--- a/app/src/main/res/values-he/strings.xml
+++ b/app/src/main/res/values-he/strings.xml
@@ -6,7 +6,7 @@
     <string name="notification_title">הגיבוי פועל</string>
     <string name="notification_channel_title">התראת גיבוי</string>
     <string name="recovery_code_error_checksum_word">הקוד שלך שגוי. נא לאמת את כל המילים ולנסות שוב!</string>
-    <string name="recovery_code_error_invalid_word">מילה שגויה. התכוונת למילה %1$s או %2$s\?</string>
+    <string name="recovery_code_error_invalid_word">מילה שגויה.</string>
     <string name="recovery_code_error_empty_word">שכחת למלא את המילה הזאת.</string>
     <string name="recovery_code_input_hint_12">מילה 12</string>
     <string name="recovery_code_input_hint_11">מילה 11</string>
diff --git a/app/src/main/res/values-hr/strings.xml b/app/src/main/res/values-hr/strings.xml
index c68e40fa..d5d26369 100644
--- a/app/src/main/res/values-hr/strings.xml
+++ b/app/src/main/res/values-hr/strings.xml
@@ -49,7 +49,7 @@
     <string name="notification_title">Sigurnosna kopija pokrenuta</string>
     <string name="notification_channel_title">Obavijest sigurnosne kopije</string>
     <string name="recovery_code_error_checksum_word">Tvoja lozinka je neispravna. Provjeri sve riječi i pokušaj ponovo!</string>
-    <string name="recovery_code_error_invalid_word">Kriva riječ. Je li misliš %1$s ili %2$s\?</string>
+    <string name="recovery_code_error_invalid_word">Kriva riječ.</string>
     <string name="recovery_code_error_empty_word">Ova riječ nije upisana.</string>
     <string name="recovery_code_input_hint_12">Riječ 12</string>
     <string name="recovery_code_input_hint_11">Riječ 11</string>
diff --git a/app/src/main/res/values-is/strings.xml b/app/src/main/res/values-is/strings.xml
index 2e5cbbb6..1ceb3e91 100644
--- a/app/src/main/res/values-is/strings.xml
+++ b/app/src/main/res/values-is/strings.xml
@@ -47,7 +47,7 @@
     <string name="notification_title">Öryggisafritun í gangi</string>
     <string name="notification_channel_title">Tilkynning um öryggisafritatöku</string>
     <string name="recovery_code_error_checksum_word">Kóðinn er ógildur. Athugað öll orðin og prófaðu aftur!</string>
-    <string name="recovery_code_error_invalid_word">Rangt orð. Meintirðu %1$s or %2$s\?</string>
+    <string name="recovery_code_error_invalid_word">Rangt orð.</string>
     <string name="recovery_code_error_empty_word">Þú gleymdir að slá inn þetta orð.</string>
     <string name="recovery_code_input_hint_12">Orð 12</string>
     <string name="recovery_code_input_hint_11">Orð 11</string>
diff --git a/app/src/main/res/values-it/strings.xml b/app/src/main/res/values-it/strings.xml
index c48c143c..7252c597 100644
--- a/app/src/main/res/values-it/strings.xml
+++ b/app/src/main/res/values-it/strings.xml
@@ -9,7 +9,7 @@
     <string name="notification_title">Backup in esecuzione</string>
     <string name="notification_channel_title">Notificazione backup</string>
     <string name="recovery_code_error_checksum_word">Il tuo codice non è valido, Controlla tutte le parole e riprova!</string>
-    <string name="recovery_code_error_invalid_word">Parola sbagliata. Intendevi %1$s o %2$s\?</string>
+    <string name="recovery_code_error_invalid_word">Parola sbagliata.</string>
     <string name="recovery_code_error_empty_word">Hai dimenticato di inserire questa parola.</string>
     <string name="recovery_code_input_hint_12">Parola 12</string>
     <string name="recovery_code_input_hint_11">Parola 11</string>
diff --git a/app/src/main/res/values-ko/strings.xml b/app/src/main/res/values-ko/strings.xml
index d6e84788..0f1b1a69 100644
--- a/app/src/main/res/values-ko/strings.xml
+++ b/app/src/main/res/values-ko/strings.xml
@@ -41,7 +41,7 @@
     <string name="notification_restore_error_action">앱 설치 제거</string>
     <string name="notification_backup_already_running">백업이 이미 진행 중</string>
     <string name="recovery_code_error_checksum_word">코드가 잘못되었습니다. 모든 단어를 확인하고 다시 시도하세요!</string>
-    <string name="recovery_code_error_invalid_word">단어가 틀렸습니다. %1$s 또는 %2$s를 입력하려고 하셨나요\?</string>
+    <string name="recovery_code_error_invalid_word">단어가 틀렸습니다.</string>
     <string name="recovery_code_error_empty_word">이 단어를 입력하지 않았습니다.</string>
     <string name="recovery_code_confirm_intro">복구 코드가 맞는지 확인하려면 12개 단어로 이루어진 복구 코드를 입력하세요.</string>
     <string name="recovery_code_input_intro">백업을 설정할 때 지정했던 12개 단어로 이루어진 복구 코드를 입력하세요.</string>
diff --git a/app/src/main/res/values-nb-rNO/strings.xml b/app/src/main/res/values-nb-rNO/strings.xml
index 4428e1e4..4b79a885 100644
--- a/app/src/main/res/values-nb-rNO/strings.xml
+++ b/app/src/main/res/values-nb-rNO/strings.xml
@@ -61,7 +61,7 @@
     <string name="notification_title">Sikkerhetskopiering utføres</string>
     <string name="notification_channel_title">Sikkerhetskopieringsmerknad</string>
     <string name="recovery_code_error_checksum_word">Koden din er ugyldig. Sjekk alle ordene og prøv igjen.</string>
-    <string name="recovery_code_error_invalid_word">Feil ord. Mente du %1$s eller %2$s\?</string>
+    <string name="recovery_code_error_invalid_word">Feil ord.</string>
     <string name="recovery_code_error_empty_word">Du glemte å skrive inn dette ordet.</string>
     <string name="recovery_code_input_hint_12">Ord 12</string>
     <string name="recovery_code_input_hint_11">Ord 11</string>
diff --git a/app/src/main/res/values-night/bools.xml b/app/src/main/res/values-night/bools.xml
new file mode 100644
index 00000000..3b094f6e
--- /dev/null
+++ b/app/src/main/res/values-night/bools.xml
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <bool name="isLight">false</bool>
+</resources>
\ No newline at end of file
diff --git a/app/src/main/res/values-night/colors.xml b/app/src/main/res/values-night/colors.xml
new file mode 100644
index 00000000..7bb73bd0
--- /dev/null
+++ b/app/src/main/res/values-night/colors.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="accent">@*android:color/accent_device_default_dark</color>
+    <color name="primary">@*android:color/primary_device_default_settings</color>
+    <color name="primaryDark">@*android:color/primary_dark_device_default_settings</color>
+    <color name="background">@color/primaryDark</color>
+    <color name="actionBarPrimary">@color/background</color>
+    <color name="statusBarColor">@android:color/transparent</color>
+    <color name="red">@*android:color/error_color_device_default_dark</color>
+</resources>
diff --git a/app/src/main/res/values-pt-rBR/strings.xml b/app/src/main/res/values-pt-rBR/strings.xml
index 1e692a51..a84fb883 100644
--- a/app/src/main/res/values-pt-rBR/strings.xml
+++ b/app/src/main/res/values-pt-rBR/strings.xml
@@ -12,7 +12,7 @@
     <string name="notification_title">Backup em execução</string>
     <string name="notification_channel_title">Notificação de backup</string>
     <string name="recovery_code_error_checksum_word">Seu código é inválido. Por favor, verifique todas as palavras e tente novamente!</string>
-    <string name="recovery_code_error_invalid_word">Palavra errada. Você quis dizer %1$s ou %2$s\?</string>
+    <string name="recovery_code_error_invalid_word">Palavra errada.</string>
     <string name="recovery_code_error_empty_word">Você se esqueceu de inserir esta palavra.</string>
     <string name="recovery_code_input_hint_12">Palavra 12</string>
     <string name="recovery_code_input_hint_11">Palavra 11</string>
diff --git a/app/src/main/res/values-pt/strings.xml b/app/src/main/res/values-pt/strings.xml
index 521c917e..a00429da 100644
--- a/app/src/main/res/values-pt/strings.xml
+++ b/app/src/main/res/values-pt/strings.xml
@@ -49,7 +49,7 @@
     <string name="notification_title">Backup em execução</string>
     <string name="notification_channel_title">Notificação de backup</string>
     <string name="recovery_code_error_checksum_word">Seu código é inválido. Por favor, verifique todas as palavras e tente novamente!</string>
-    <string name="recovery_code_error_invalid_word">Palavra errada. Quis dizer %1$s ou %2$s\?</string>
+    <string name="recovery_code_error_invalid_word">Palavra errada.</string>
     <string name="recovery_code_error_empty_word">Se esqueceu de inserir esta palavra.</string>
     <string name="recovery_code_input_hint_12">Palavra 12</string>
     <string name="recovery_code_input_hint_11">Palavra 11</string>
diff --git a/app/src/main/res/values-ru/strings.xml b/app/src/main/res/values-ru/strings.xml
index ae511a53..4b2d9679 100644
--- a/app/src/main/res/values-ru/strings.xml
+++ b/app/src/main/res/values-ru/strings.xml
@@ -53,7 +53,7 @@
     <string name="notification_title">Резервное копирование запущено</string>
     <string name="notification_channel_title">Уведомление о резервном копировании</string>
     <string name="recovery_code_error_checksum_word">Ваш код недействителен. Пожалуйста, проверьте все слова и попробуйте еще раз!</string>
-    <string name="recovery_code_error_invalid_word">Неверное слово. Вы имели в виду %1$s или %2$s\?</string>
+    <string name="recovery_code_error_invalid_word">Неверное слово.</string>
     <string name="recovery_code_error_empty_word">Вы забыли ввести это слово.</string>
     <string name="recovery_code_input_hint_12">Слово 12</string>
     <string name="recovery_code_input_hint_11">Слово 11</string>
diff --git a/app/src/main/res/values-tr/strings.xml b/app/src/main/res/values-tr/strings.xml
index be1d199f..cb9975e6 100644
--- a/app/src/main/res/values-tr/strings.xml
+++ b/app/src/main/res/values-tr/strings.xml
@@ -48,7 +48,7 @@
     <string name="notification_title">Yedekleme çalışıyor</string>
     <string name="notification_channel_title">Yedekleme bildirimi</string>
     <string name="recovery_code_error_checksum_word">Kodunuz geçersiz. Lütfen tüm sözcükleri gözden geçirin ve tekrar deneyin!</string>
-    <string name="recovery_code_error_invalid_word">Yanlış sözcük. %1$s veya %2$s demek mi istediniz\?</string>
+    <string name="recovery_code_error_invalid_word">Yanlış sözcük.</string>
     <string name="recovery_code_error_empty_word">Bu sözcüğü girmeyi unuttunuz.</string>
     <string name="recovery_code_input_hint_12">12. sözcük</string>
     <string name="recovery_code_input_hint_11">11. sözcük</string>
diff --git a/app/src/main/res/values-zh-rCN/strings.xml b/app/src/main/res/values-zh-rCN/strings.xml
index da558c78..3abfcff3 100644
--- a/app/src/main/res/values-zh-rCN/strings.xml
+++ b/app/src/main/res/values-zh-rCN/strings.xml
@@ -75,7 +75,7 @@
     <string name="notification_title">备份运行中</string>
     <string name="notification_channel_title">备份提示</string>
     <string name="recovery_code_error_checksum_word">您的代码无效。请检查所有单词，然后重试！</string>
-    <string name="recovery_code_error_invalid_word">错误的词。你的意思是%1$s或%2$s？</string>
+    <string name="recovery_code_error_invalid_word">错误的词。</string>
     <string name="recovery_code_error_empty_word">你忘了输入这个词。</string>
     <string name="recovery_code_done_button">完成</string>
     <string name="recovery_code_confirm_button">确认代码</string>
diff --git a/app/src/main/res/values/bools.xml b/app/src/main/res/values/bools.xml
new file mode 100644
index 00000000..f4c5000d
--- /dev/null
+++ b/app/src/main/res/values/bools.xml
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <bool name="isLight">true</bool>
+</resources>
\ No newline at end of file
diff --git a/app/src/main/res/values/colors.xml b/app/src/main/res/values/colors.xml
index 5956cfd7..b2f95493 100644
--- a/app/src/main/res/values/colors.xml
+++ b/app/src/main/res/values/colors.xml
@@ -1,8 +1,13 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-    <color name="accent">#99cc00</color>
-    <color name="divider">#8A000000</color>
+    <color name="accent">@*android:color/accent_device_default_light</color>
+    <color name="primary">@*android:color/primary_device_default_settings_light</color>
+    <color name="primaryDark">@*android:color/primary_dark_device_default_settings_light</color>
+    <color name="background">@*android:color/background_device_default_light</color>
+    <color name="actionBarPrimary">@*android:color/primary_device_default_light</color>
+    <color name="statusBarColor">@*android:color/primary_dark_material_light_light_status_bar</color>
+    <color name="red">@*android:color/error_color_device_default_dark</color>
+    <color name="divider">#20ffffff</color>
     <color name="green">#558B2F</color>
-    <color name="red">#D32F2F</color>
     <color name="yellow">#F9A825</color>
 </resources>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 55706352..e502e9c7 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -8,7 +8,8 @@
     <string name="restore_backup_button">Restore backup</string>
 
     <!-- Settings -->
-    <string name="settings_backup">Backup my data</string>
+    <string name="settings_category_apps">App backup</string>
+    <string name="settings_backup">Backup my apps</string>
     <string name="settings_backup_location">Backup location</string>
     <string name="settings_backup_location_none">None</string>
     <string name="settings_backup_location_internal">Internal storage</string>
@@ -28,21 +29,33 @@
     <string name="settings_backup_status_summary">Last backup: %1$s</string>
     <string name="settings_backup_exclude_apps">Exclude apps</string>
     <string name="settings_backup_now">Backup now</string>
-    <string name="settings_backup_recovery_code">Recovery Code</string>
+    <string name="settings_category_storage">Storage backup (experimental)</string>
+    <string name="settings_backup_storage_title">Backup my files</string>
+    <string name="settings_backup_files_title">Included files and folders</string>
+    <string name="settings_backup_files_summary">None</string>
+    <string name="settings_backup_recovery_code">Recovery code</string>
     <string name="settings_backup_recovery_code_summary">Verify existing code or generate a new one</string>
+    <string name="settings_backup_storage_dialog_title">Experimental feature</string>
+    <string name="settings_backup_storage_dialog_message">Backing up files is still experimental and might not work. Do not rely on it for important data.</string>
+    <string name="settings_backup_storage_dialog_ok">Enable anyway</string>
+    <string name="settings_backup_storage_code_dialog_title">Recovery code verification required</string>
+    <string name="settings_backup_storage_code_dialog_message">To enable storage backup, you need to first verify your recovery code or generate a new one.</string>
+    <string name="settings_backup_storage_code_dialog_ok">Verify code</string>
 
-    <!-- Storage -->
+    <!-- Storage Location -->
     <string name="storage_fragment_backup_title">Choose where to store backups</string>
     <string name="storage_fragment_restore_title">Where to find your backups?</string>
     <string name="storage_fragment_warning">People with access to your storage location can learn which apps you use, but do not get access to the apps\' data.</string>
+    <string name="storage_fragment_warning_delete">Existing backups in this location will be deleted.</string>
     <string name="storage_fake_drive_title">USB flash drive</string>
     <string name="storage_fake_drive_summary">Needs to be plugged in</string>
     <string name="storage_available_bytes"><xliff:g example="1 GB" id="size">%1$s</xliff:g> free</string>
     <string name="storage_fake_nextcloud_title" translatable="false">Nextcloud</string>
-    <string name="storage_fake_nextcloud_summary">Click to install</string>
-    <string name="storage_fake_nextcloud_summary_installed">Click to set up account</string>
+    <string name="storage_fake_nextcloud_summary">Tap to install</string>
+    <string name="storage_fake_nextcloud_summary_installed">Tap to set up account</string>
     <string name="storage_fake_nextcloud_summary_unavailable">Account not available. Set one up (or disable passcode).</string>
     <string name="storage_check_fragment_backup_title">Initializing backup location…</string>
+    <string name="storage_check_fragment_patience">This may take some time…</string>
     <string name="storage_check_fragment_restore_title">Looking for backups…</string>
     <string name="storage_check_fragment_backup_error">An error occurred while accessing the backup location.</string>
     <string name="storage_check_fragment_permission_error">Unable to get the permission to write to the backup location.</string>
@@ -69,8 +82,8 @@
     <string name="recovery_code_input_hint_11">Word 11</string>
     <string name="recovery_code_input_hint_12">Word 12</string>
     <string name="recovery_code_error_empty_word">You forgot to enter this word.</string>
-    <string name="recovery_code_error_invalid_word">Wrong word. Did you mean %1$s or %2$s?</string>
-    <string name="recovery_code_error_checksum_word">Your code is invalid. Please check all words and try again!</string>
+    <string name="recovery_code_error_invalid_word">Wrong word.</string>
+    <string name="recovery_code_error_checksum_word">Your code is invalid. Please check all words as well as their position and try again!</string>
     <string name="recovery_code_verification_ok_title">Recovery code verified</string>
     <string name="recovery_code_verification_ok_message">Your code is correct and will work for restoring your backup.</string>
     <string name="recovery_code_verification_error_title">Incorrect recovery code</string>
@@ -125,6 +138,7 @@
     <string name="restore_choose_restore_set">Choose a backup to restore</string>
     <string name="restore_restore_set_times">Last backup %1$s · First %2$s.</string>
     <string name="restore_back">Don\'t restore</string>
+    <string name="restore_skip">Skip restoring apps</string>
     <string name="restore_invalid_location_title">No backups found</string>
     <string name="restore_invalid_location_message">We could not find any backups at this location.\n\nPlease choose another location that contains a %s folder.</string>
     <string name="restore_set_error">An error occurred while loading the backups.</string>
@@ -141,6 +155,13 @@
     <string name="restore_finished_success">Restore complete</string>
     <string name="restore_finished_error">An error occurred while restoring the backup.</string>
     <string name="restore_finished_button">Finish</string>
+
+    <string name="restore_storage_skip">Skip restoring files</string>
+    <string name="restore_storage_choose_snapshot">Choose a storage backup to restore (experimental)</string>
+    <string name="restore_storage_in_progress_title">Files are being restored…</string>
+    <string name="restore_storage_in_progress_info">Your files are being restored in the background. You can start using your phone while this is running.\n\nSome apps (e.g. Signal or WhatsApp) might require files to be fully restored to import a backup. Try to avoid starting those apps before file restore is not complete.</string>
+    <string name="restore_storage_got_it">Got it</string>
+
     <string name="storage_internal_warning_title">Warning</string>
     <string name="storage_internal_warning_message">You have chosen internal storage for your backup. This will not be available when your phone is lost or broken.</string>
     <string name="storage_internal_warning_choose_other">Choose other</string>
@@ -154,6 +175,6 @@
     <string name="about_author">Written by: <a href="https://github.com/stevesoltys">Steve Soltys</a> and <a href="https://blog.grobox.de">Torsten Grote</a></string>
     <string name="about_design">Design by: <a href="https://www.glennsorrentino.com/">Glenn Sorrentino</a></string>
     <string name="about_sponsor">Sponsored by: <a href="https://www.calyxinstitute.org">Calyx Institute</a> for use in <a href="https://calyxos.org">CalyxOS</a></string>
-    <string name="about_source_code">Source Code: https://github.com/seedvault-app/seedvault</string>
+    <string name="about_source_code">Source code: https://github.com/seedvault-app/seedvault</string>
 
 </resources>
diff --git a/app/src/main/res/values/themes.xml b/app/src/main/res/values/themes.xml
index c1b981cd..169dde24 100644
--- a/app/src/main/res/values/themes.xml
+++ b/app/src/main/res/values/themes.xml
@@ -1,8 +1,21 @@
 <resources>
 
-    <style name="AppTheme" parent="Theme.AppCompat.DayNight">
+    <style name="AppTheme" parent="@style/Theme.AppCompat.DayNight">
+        <item name="colorPrimary">@color/primary</item>
+        <item name="colorPrimaryDark">@color/primaryDark</item>
         <item name="colorAccent">@color/accent</item>
+        <item name="colorError">@color/red</item>
+        <item name="android:windowBackground">@color/background</item>
+        <item name="fontFamily">@*android:string/config_bodyFontFamily</item>
         <item name="preferenceTheme">@style/PreferenceThemeOverlay</item>
+        <item name="android:windowLightStatusBar">@bool/isLight</item>
+        <item name="android:statusBarColor">@color/statusBarColor</item>
+        <item name="actionBarTheme">@style/Theme.ActionBar</item>
+        <item name="android:navigationBarColor">@android:color/transparent</item>
+    </style>
+
+    <style name="Theme.ActionBar" parent="Theme.AppCompat.DayNight.DarkActionBar">
+        <item name="colorPrimary">@color/actionBarPrimary</item>
     </style>
 
     <style name="AppTheme.NoActionBar" parent="AppTheme">
@@ -10,4 +23,7 @@
         <item name="windowNoTitle">true</item>
     </style>
 
+    <!-- Copied from Settings -->
+    <style name="ActionPrimaryButton" parent="android:Widget.DeviceDefault.Button.Colored" />
+
 </resources>
diff --git a/app/src/main/res/xml/settings.xml b/app/src/main/res/xml/settings.xml
index a9954c06..e9034e67 100644
--- a/app/src/main/res/xml/settings.xml
+++ b/app/src/main/res/xml/settings.xml
@@ -1,53 +1,75 @@
-<androidx.preference.PreferenceScreen xmlns:app="http://schemas.android.com/apk/res-auto"
+<androidx.preference.PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools">
 
-    <androidx.preference.SwitchPreferenceCompat
-        app:icon="@drawable/ic_cloud_upload"
-        app:key="backup"
-        app:persistent="false"
-        app:title="@string/settings_backup" />
-
     <androidx.preference.Preference
-        app:allowDividerAbove="true"
-        app:fragment="com.stevesoltys.seedvault.settings.AppStatusFragment"
-        app:icon="@drawable/ic_apps"
-        app:key="backup_status"
-        app:title="@string/settings_backup_status_title"
-        tools:summary="Last backup: Never" />
-
-    <androidx.preference.Preference
-        app:dependency="backup"
-        app:icon="@drawable/ic_storage"
+        app:icon="@drawable/ic_save_alt"
         app:key="backup_location"
         app:summary="@string/settings_backup_location_none"
         app:title="@string/settings_backup_location" />
 
-    <androidx.preference.SwitchPreferenceCompat
-        app:dependency="backup"
-        app:key="auto_restore"
-        app:persistent="false"
-        app:summary="@string/settings_auto_restore_summary"
-        app:title="@string/settings_auto_restore_title" />
-
-    <androidx.preference.SwitchPreferenceCompat
-        app:defaultValue="true"
-        app:dependency="backup"
-        app:key="backup_apk"
-        app:summary="@string/settings_backup_apk_summary"
-        app:title="@string/settings_backup_apk_title" />
-
     <androidx.preference.Preference
-        app:dependency="backup"
         app:fragment="com.stevesoltys.seedvault.ui.recoverycode.RecoveryCodeInputFragment"
         app:icon="@drawable/ic_vpn_key"
         app:key="backup_recovery_code"
         app:summary="@string/settings_backup_recovery_code_summary"
         app:title="@string/settings_backup_recovery_code" />
 
+    <PreferenceCategory android:title="@string/settings_category_apps">
+
+        <androidx.preference.SwitchPreferenceCompat
+            app:allowDividerBelow="true"
+            app:icon="@drawable/ic_cloud_upload"
+            app:key="backup"
+            app:persistent="false"
+            app:title="@string/settings_backup" />
+
+        <androidx.preference.Preference
+            app:fragment="com.stevesoltys.seedvault.settings.AppStatusFragment"
+            app:icon="@drawable/ic_apps"
+            app:key="backup_status"
+            app:title="@string/settings_backup_status_title"
+            tools:summary="Last backup: Never" />
+
+        <androidx.preference.SwitchPreferenceCompat
+            app:dependency="backup"
+            app:key="auto_restore"
+            app:persistent="false"
+            app:summary="@string/settings_auto_restore_summary"
+            app:title="@string/settings_auto_restore_title"
+            tools:defaultValue="true" />
+
+        <androidx.preference.SwitchPreferenceCompat
+            app:defaultValue="true"
+            app:dependency="backup"
+            app:key="backup_apk"
+            app:summary="@string/settings_backup_apk_summary"
+            app:title="@string/settings_backup_apk_title" />
+
+    </PreferenceCategory>
+
+    <PreferenceCategory android:title="@string/settings_category_storage">
+
+        <androidx.preference.SwitchPreferenceCompat
+            app:defaultValue="false"
+            app:icon="@drawable/ic_storage"
+            app:key="backup_storage"
+            app:title="@string/settings_backup_storage_title" />
+
+        <androidx.preference.Preference
+            android:dependency="backup_storage"
+            app:dependency="backup_storage"
+            app:fragment="com.stevesoltys.seedvault.ui.files.FileSelectionFragment"
+            app:icon="@drawable/ic_library_add"
+            app:key="backup_files"
+            app:summary="@string/settings_backup_files_summary"
+            app:title="@string/settings_backup_files_title" />
+
+    </PreferenceCategory>
+
     <androidx.preference.Preference
         app:allowDividerAbove="true"
         app:allowDividerBelow="false"
-        app:dependency="backup"
         app:icon="@drawable/ic_info_outline"
         app:selectable="false"
         app:summary="@string/settings_info" />
diff --git a/app/src/sharedTest/java/com/stevesoltys/seedvault/TestUtils.kt b/app/src/sharedTest/java/com/stevesoltys/seedvault/TestUtils.kt
index be475cd5..9a9c0f95 100644
--- a/app/src/sharedTest/java/com/stevesoltys/seedvault/TestUtils.kt
+++ b/app/src/sharedTest/java/com/stevesoltys/seedvault/TestUtils.kt
@@ -44,7 +44,7 @@ fun ByteArray.toHexString(spacer: String = " "): String {
     for (b in this) {
         str += String.format("%02X$spacer", b)
     }
-    return str
+    return str.trimEnd()
 }
 
 fun ByteArray.toIntString(): String {
diff --git a/app/src/test/java/com/stevesoltys/seedvault/crypto/WordListTest.kt b/app/src/test/java/com/stevesoltys/seedvault/crypto/WordListTest.kt
index 58c771d3..3e54e42e 100644
--- a/app/src/test/java/com/stevesoltys/seedvault/crypto/WordListTest.kt
+++ b/app/src/test/java/com/stevesoltys/seedvault/crypto/WordListTest.kt
@@ -1,11 +1,10 @@
 package com.stevesoltys.seedvault.crypto
 
+import cash.z.ecc.android.bip39.Mnemonics
+import cash.z.ecc.android.bip39.WordList
+import cash.z.ecc.android.bip39.toSeed
 import com.stevesoltys.seedvault.toHexString
-import io.github.novacrypto.bip39.JavaxPBKDF2WithHmacSHA512
-import io.github.novacrypto.bip39.MnemonicGenerator
-import io.github.novacrypto.bip39.SeedCalculator
-import io.github.novacrypto.bip39.Words
-import io.github.novacrypto.bip39.wordlists.English
+import com.stevesoltys.seedvault.ui.recoverycode.toMnemonicChars
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertTrue
 import org.junit.jupiter.api.Test
@@ -2067,62 +2066,197 @@ class WordListTest {
 
     @Test
     fun `word list of library did not change`() {
+        val libWords = WordList().words
         for (i in words.indices) {
-            assertEquals(words[i], English.INSTANCE.getWord(i))
+            assertEquals(words[i], libWords[i])
         }
     }
 
     @Test
-    fun `test createMnemonic`() {
-        val entropy = ByteArray(Words.TWELVE.byteLength())
+    fun `test creating MnemonicCode from entropy`() {
+        val entropy = ByteArray(Mnemonics.WordCount.COUNT_12.bitLength / 8)
         Random.nextBytes(entropy)
-        val list = ArrayList<String>(12)
-        MnemonicGenerator(English.INSTANCE).createMnemonic(entropy) {
-            if (it != " ") list.add(it.toString())
-        }
-        assertEquals(12, list.size)
-        for (word in list) {
-            assertTrue(word in words)
+        val code = Mnemonics.MnemonicCode(entropy)
+        assertEquals(12, code.words.size)
+        for (word in code) {
+            assertTrue(word in words, "$word unknown")
         }
     }
 
     @Test
-    @Suppress("MaxLineLength")
-    fun `12 words generate expected seed`() {
+    fun `12 not validating words generate seed that novacrypt generated`() {
         assertEquals(
             "64AA8C388EC0F3A13C7E51653BC766E30668D30952AB34381C4B174BF3278774" +
                 "B4EE43D0BA08BCBCE0D0B806DEB7AA364A83525C34847078B2A8002A3E116066",
-            SeedCalculator(JavaxPBKDF2WithHmacSHA512.INSTANCE).calculateSeed(
-                "write wrong yard year yellow you young youth zebra zero zone zoo", ""
-            ).toHexString("")
+            Mnemonics.MnemonicCode(
+                "write wrong yard year yellow you young youth zebra zero zone zoo"
+            ).toSeed(validate = false).toHexString("")
         )
         assertEquals(
             "E911FAA42F389AA9F6D5A40B2ECB876B06D6D1FFBD5885C54720398EB11918CA" +
                 "B8F7BAD70FD5BE39BEB4EB065610700D1CFF1D4BFAA26F998357E15E79002779",
-            SeedCalculator(JavaxPBKDF2WithHmacSHA512.INSTANCE).calculateSeed(
-                "matrix lava they brand negative spray floor gym purity picture ritual disorder", ""
-            ).toHexString("")
+            Mnemonics.MnemonicCode(
+                "matrix lava they brand negative spray floor gym purity picture ritual disorder"
+            ).toSeed(validate = false).toHexString("")
         )
         assertEquals(
             "DDB26091680CF30D0DC615546E4612327DB287B6B2B8B8947A3E12580315D38C" +
                 "3BF7DD0EB4E9E50B10A41925332E0C8ED43C80DBA29281EF331A1DFA858BF1C9",
-            SeedCalculator(JavaxPBKDF2WithHmacSHA512.INSTANCE).calculateSeed(
-                "middle rack south alert ribbon tube hope involve defy oxygen gloom rabbit", ""
-            ).toHexString("")
+            Mnemonics.MnemonicCode(
+                "middle rack south alert ribbon tube hope involve defy oxygen gloom rabbit"
+            ).toSeed(validate = false).toHexString("")
         )
         assertEquals(
             "4815B580D0DCDA08334C92B3CB9A8436CD581C55841FB2794FB1E3D6E389F447" +
                 "C8C6520B2FE567720950F5B39BE7EC42C0BC98D3C63F8FEF642B5BD3EE4CDD7B",
-            SeedCalculator(JavaxPBKDF2WithHmacSHA512.INSTANCE).calculateSeed(
-                "interest mask trial hold foot segment fade page monitor apple garden shuffle", ""
-            ).toHexString("")
+            Mnemonics.MnemonicCode(
+                "interest mask trial hold foot segment fade page monitor apple garden shuffle"
+            ).toSeed(validate = false).toHexString("")
         )
         assertEquals(
             "FF462543D8FB9DAE6C17FA7BA047238664207FCC797D6688E10DD1B3CFD183D4" +
                 "928AD088E8287B69BABCAEB0F87A2DFF2ADD49A7FDB7EB2554D7344F09C41A76",
-            SeedCalculator(JavaxPBKDF2WithHmacSHA512.INSTANCE).calculateSeed(
-                "palace glory gospel garment obscure person edge total hunt fix setup uphold\n", ""
-            ).toHexString("")
+            Mnemonics.MnemonicCode(
+                "palace glory gospel garment obscure person edge total hunt fix setup uphold\n"
+            ).toSeed(validate = false).toHexString("")
+        )
+    }
+
+    @Test
+    fun `12 valid words generate seed that novacrypt generated`() {
+        assertEquals(
+            "C6F9762718449C9D0794FEC140D2C8D4E23FF8E3701D64C03DDD13C69BC73E48" +
+                "6AB89AB2C7C9BEA43F4AF839F2078595851D5D48FEC6A9FC6C25F399DBB909F9",
+            Mnemonics.MnemonicCode(
+                "script vault basic album cotton car entire jaguar correct anger select flower"
+            ).toSeed().toHexString("")
+        )
+        assertEquals(
+            "13C5188428B1DF8A5333E60BA7EC47F7E75585315C73BD19812D3591C5F4C52B" +
+                "B2FC1FF40B1942E2A1EF9F34F586114ED37D46A5A3907A43B317E937C1D9D2CD",
+            Mnemonics.MnemonicCode(
+                "drastic toy fatal goose treat saddle chalk fame dismiss employ super behind"
+            ).toSeed().toHexString("")
+        )
+        assertEquals(
+            "40B41BB22AC3A507F26A78E027A3B3C5C8F45FF0F5593D82762C74AE69FA548B" +
+                "A72C0CED31DED6211884B412E7B80F932F9830FA7A67CDB5B28604213DE6599C",
+            Mnemonics.MnemonicCode(
+                "nation infant heart virus argue two vivid slam lend decorate turn wish"
+            ).toSeed().toHexString("")
+        )
+        assertEquals(
+            "B6D755172B6E9353A25EB3559336C17A8619F3EBE55E8A9A74A44E1AB88EF5E2" +
+                "C6E12FE132E42A55CC3F8F9224E6A0ABC9C3FF4EB9523A4E9750CDAAEFBA6282",
+            Mnemonics.MnemonicCode(
+                "elbow boy powder robot eagle rival neutral pigeon oil shrimp demand health"
+            ).toSeed().toHexString("")
+        )
+        assertEquals(
+            "3EDB1292B4D124426201AC523FCC2572184E0B63667DA7DF105AD8FCCD16C074" +
+                "C6DAF9C7D644B4B48AF75185D21B9E7D778FFE55F836C539581DEBB98C331526",
+            Mnemonics.MnemonicCode(
+                "build setup screen solution prepare spice organ ten loud seek ask attract"
+            ).toSeed().toHexString("")
+        )
+        assertEquals(
+            "65986351CD054822B40E417855AC2B5651C5F87892F17ED2A984F6B59DD5FB4E" +
+                "6A4568ABF7E06D93CBCC69BB68F2625E3E8AF2751106380922D49C0D0D0B456B",
+            Mnemonics.MnemonicCode(
+                "unhappy welcome pizza inflict inherit village minimum orient cheap swear grunt giraffe" // ktlint-disable max-line-length
+            ).toSeed().toHexString("")
+        )
+        assertEquals(
+            "639034B381740A9FA5B8A84715CF18B21EBD343DD91F7B6124A0EFC32A636619" +
+                "49B02A7810B1A99D8E8CC4CD7D046CE59EAAADBB52DDC0B5036EFED007E1CFF6",
+            Mnemonics.MnemonicCode(
+                "rather suit pluck afford avocado diary swap library earn song rival fiber"
+            ).toSeed().toHexString("")
+        )
+        assertEquals(
+            "43E1417221BFB40851DE286B543B51DEE9C01D239B2C2E8A355D45B3DF95DFAA" +
+                "C8DBCAEF1D864D91759A07057DBDB891900D583CAB09BD0655493912108AE65A",
+            Mnemonics.MnemonicCode(
+                "toss note family morning silk edge high error appear tilt almost myth"
+            ).toSeed().toHexString("")
+        )
+        assertEquals(
+            "14084AAF9CFCAC386D4CE5B9140BEADBF727B1B09786A67A574B668A1A4AE0A3" +
+                "21B8D4E7BC005980B088A160B6EC08A1CB892C2090C58D95A7C6AAD16C14EE1E",
+            Mnemonics.MnemonicCode(
+                "parrot burden release bronze section fantasy ridge blood direct physical spoil asthma" // ktlint-disable max-line-length
+            ).toSeed().toHexString("")
+        )
+        assertEquals(
+            "E11E8737327EE6A640761B3888C349D829A60FEAEFB7914D2AE1616F0AC45B9A" +
+                "322F41D0030C89E209300FA25615FE6B5BDEF73F3E5CE21167685E8A27EE0790",
+            Mnemonics.MnemonicCode(
+                "version deliver worry sick flee submit pledge adapt night swear glare adult"
+            ).toSeed().toHexString("")
+        )
+        assertEquals(
+            "02652896F67695C03F379A354685A8A0B92D0F303F77461476E80BB594EAD84B" +
+                "D00B2943C2229ED843C65F6C53A376005871FF74F834E6B6E3B57FFD83D3FB12",
+            Mnemonics.MnemonicCode(
+                "exercise curtain initial model travel client twist neutral peace unfold start shell" // ktlint-disable max-line-length
+            ).toSeed().toHexString("")
+        )
+    }
+
+    @Test
+    fun `entropy generates same words that novacrypt generated`() {
+        assertEquals(
+            "B8 3F 0D 49 7F 2A F4 69 13 71 47 D5 54 9D 17 0B",
+            Mnemonics.MnemonicCode(
+                "return wear false wrestle quantum cruel evidence cigar stem pilot easy blood"
+            ).toEntropy().toHexString()
+        )
+        assertEquals(
+            "AA 8E 3F 1C EF 60 20 D7 D2 BB FD A0 AA AD 69 09",
+            Mnemonics.MnemonicCode(
+                "pride impose shrimp tell acoustic hip enough leisure pass fever fog basket"
+            ).toEntropy().toHexString()
+        )
+        assertEquals(
+            "CE E8 17 7E AB 9E 49 8A 0B 32 3C 97 94 07 0C 32",
+            Mnemonics.MnemonicCode(
+                "solve doll text fire tonight shallow coast elegant nurse parent seek grass"
+            ).toEntropy().toHexString()
+        )
+        assertEquals(
+            "AA 27 4B D8 7B 0D 18 EB 5D 08 BD 11 73 36 C1 06",
+            Mnemonics.MnemonicCode(
+                "pretty demise voyage voyage spice interest injury bless badge often raccoon artefact" // ktlint-disable max-line-length
+            ).toEntropy().toHexString()
+        )
+        assertEquals(
+            "16 5F A7 40 26 E9 51 70 1B 7A 5C D2 AB CD 73 7E",
+            Mnemonics.MnemonicCode(
+                "bind wood source evidence never retreat hospital entire sport fury fresh woman"
+            ).toEntropy().toHexString()
+        )
+    }
+
+    @Test
+    fun `test create MnemonicCode from List of CharSequence`() {
+        assertEquals(
+            "B8 3F 0D 49 7F 2A F4 69 13 71 47 D5 54 9D 17 0B",
+            Mnemonics.MnemonicCode(
+                listOf<CharSequence>(
+                    "return",
+                    "wear",
+                    "false",
+                    "wrestle",
+                    "quantum",
+                    "cruel",
+                    "evidence",
+                    "cigar",
+                    "stem",
+                    "pilot",
+                    "easy",
+                    "blood"
+                ).toMnemonicChars()
+            ).toEntropy().toHexString()
         )
     }
 
diff --git a/app/src/test/java/com/stevesoltys/seedvault/plugins/saf/DocumentFileTest.kt b/app/src/test/java/com/stevesoltys/seedvault/plugins/saf/DocumentFileTest.kt
index 49a182e4..b7346b2c 100644
--- a/app/src/test/java/com/stevesoltys/seedvault/plugins/saf/DocumentFileTest.kt
+++ b/app/src/test/java/com/stevesoltys/seedvault/plugins/saf/DocumentFileTest.kt
@@ -1,11 +1,13 @@
 package com.stevesoltys.seedvault.plugins.saf
 
 import android.content.Context
+import android.content.pm.PackageManager
 import android.net.Uri
 import android.provider.DocumentsContract
 import androidx.documentfile.provider.DocumentFile
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import com.stevesoltys.seedvault.TestApp
+import io.mockk.every
 import io.mockk.mockk
 import org.junit.After
 import org.junit.Assert.assertEquals
@@ -27,6 +29,14 @@ internal class DocumentFileTest {
         "content://com.android.externalstorage.documents/tree/" +
             "primary%3A/document/primary%3A.SeedVaultAndroidBackup"
     )
+
+    init {
+        // needed since 'androidx.documentfile:documentfile:1.0.1'
+        val pm: PackageManager = mockk()
+        every { context.packageManager } returns pm
+        every { pm.queryIntentContentProviders(any(), 0) } returns emptyList()
+    }
+
     private val parentFile: DocumentFile = DocumentFile.fromTreeUri(context, parentUri)!!
     private val uri: Uri = Uri.parse(
         "content://com.android.externalstorage.documents/tree/" +
diff --git a/build.gradle b/build.gradle
index 98c5c515..3acb684f 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,22 +1,33 @@
 buildscript {
-
     // 1.3.21 Android 10
     // 1.3.61 Android 11
     // Check:
     // https://android.googlesource.com/platform/external/kotlinc/+/refs/tags/android-11.0.0_r3/build.txt
-    ext.kotlin_version = '1.3.61'
+    ext.aosp_kotlin_version = '1.3.61'
+    ext.kotlin_version = '1.4.31'
 
     repositories {
+        mavenCentral()
         jcenter()
         google()
     }
     dependencies {
         //noinspection DifferentKotlinGradleVersion
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-        classpath 'com.android.tools.build:gradle:4.1.0'
+        classpath "com.google.protobuf:protobuf-gradle-plugin:0.8.14"
+        classpath 'com.android.tools.build:gradle:4.2.1'
     }
 }
 
+ext {
+    buildToolsVersion = '30.0.2'
+    compileSdkVersion = 30
+    minSdkVersion = 29
+    targetSdkVersion = 30
+}
+
+apply from: 'gradle/dependencies.gradle'
+
 allprojects {
     repositories {
         mavenCentral()
diff --git a/contactsbackup/Android.bp b/contactsbackup/Android.bp
index 9a4e2e60..e0d60206 100644
--- a/contactsbackup/Android.bp
+++ b/contactsbackup/Android.bp
@@ -13,11 +13,13 @@ android_app {
     required: [
         "default-permissions_org.calyxos.backup.contacts",
     ],
+    product_specific: true,
     sdk_version: "current",
 }
 
 prebuilt_etc {
     name: "default-permissions_org.calyxos.backup.contacts",
+    product_specific: true,
     sub_dir: "default-permissions",
     src: "default-permissions_org.calyxos.backup.contacts.xml",
     filename_from_src: true,
diff --git a/contactsbackup/build.gradle b/contactsbackup/build.gradle
index 9fcec7c5..8fb5026d 100644
--- a/contactsbackup/build.gradle
+++ b/contactsbackup/build.gradle
@@ -50,16 +50,12 @@ def aospDeps = fileTree(include: [
 dependencies {
     implementation aospDeps
 
-    //noinspection GradleDependency
     testImplementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
-    testImplementation 'junit:junit:4.13.1'
-    def mockk_version = "1.10.2"
+    testImplementation "junit:junit:$junit4_version"
     testImplementation "io.mockk:mockk:$mockk_version"
 
-    //noinspection GradleDependency
     androidTestImplementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
     androidTestImplementation 'androidx.test.ext:junit:1.1.2'
-    def espresso_version = "3.3.0"
     androidTestImplementation "androidx.test.espresso:espresso-core:$espresso_version"
     androidTestImplementation "io.mockk:mockk-android:$mockk_version"
 }
diff --git a/contactsbackup/src/main/AndroidManifest.xml b/contactsbackup/src/main/AndroidManifest.xml
index ba7bbb32..972604b2 100644
--- a/contactsbackup/src/main/AndroidManifest.xml
+++ b/contactsbackup/src/main/AndroidManifest.xml
@@ -2,8 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     package="org.calyxos.backup.contacts"
-    android:versionCode="30000011"
-    android:versionName="11-1.1">
+    android:versionCode="30000211"
+    android:versionName="11-2.1">
     <!--
     The version code is the targeted SDK_VERSION plus 6 digits for our own version code.
     The version name is the targeted Android version followed by - and our own version name.
diff --git a/gradle.properties b/gradle.properties
index f3edb44c..38138b6a 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,3 +1,5 @@
 org.gradle.jvmargs=-Xmx1g
+org.gradle.configureondemand=true
 android.useAndroidX=true
 android.enableJetifier=false
+kotlin.code.style=official
diff --git a/gradle/dependencies.gradle b/gradle/dependencies.gradle
index 103beeba..bcc29e99 100644
--- a/gradle/dependencies.gradle
+++ b/gradle/dependencies.gradle
@@ -1,130 +1,101 @@
+ext {
+    // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#2713
+    ext.room_version = "2.3.0-alpha02"
+    // http://aosp.opersys.com/xref/android-11.0.0_r27/xref/external/protobuf/java/pom.xml#7
+    ext.protobuf_version = "3.9.1"
+    junit4_version = "4.13.2"
+    junit5_version = "5.5.2" // careful, upgrading this can change a Cipher's IV size in tests!?
+    mockk_version = "1.10.2" // higher versions get us a kotlin version conflict
+    espresso_version = "3.3.0"
+}
+
 // To produce these binaries, in latest AOSP source tree, run
 // $ m
-def aospDeps = fileTree(include: [
-        // For more information about this module:
-        // https://android.googlesource.com/platform/frameworks/base/+/refs/tags/android-11.0.0_r3/Android.bp#507
-        // framework_intermediates/classes-header.jar works for gradle build as well,
-        // but not unit tests, so we use the actual classes (without updatable modules).
-        //
-        // out/target/common/obj/JAVA_LIBRARIES/framework-minus-apex_intermediates/classes.jar
-        'android.jar',
-        // out/target/common/obj/JAVA_LIBRARIES/core-libart.com.android.art.release_intermediates/classes.jar
-        'libcore.jar'
-], dir: 'libs')
+ext.aosp_libs = fileTree(include: [
+    // For more information about this module:
+    // https://android.googlesource.com/platform/frameworks/base/+/refs/tags/android-11.0.0_r3/Android.bp#507
+    // framework_intermediates/classes-header.jar works for gradle build as well,
+    // but not unit tests, so we use the actual classes (without updatable modules).
+    //
+    // out/target/common/obj/JAVA_LIBRARIES/framework-minus-apex_intermediates/classes.jar
+    'android.jar',
+    // out/target/common/obj/JAVA_LIBRARIES/core-libart.com.android.art.release_intermediates/classes.jar
+    'libcore.jar',
+], dir: "$projectDir/app/libs")
 
-dependencies {
-    compileOnly aospDeps
+ext.kotlin_libs = [
+    std: [
+        dependencies.create('org.jetbrains.kotlin:kotlin-stdlib') {
+            version { strictly "$aosp_kotlin_version" }
+        },
+        dependencies.create('org.jetbrains.kotlin:kotlin-stdlib-jdk8') {
+            version { strictly "$aosp_kotlin_version" }
+        },
+        dependencies.create('org.jetbrains.kotlin:kotlin-stdlib-common') {
+            version { strictly "$aosp_kotlin_version" }
+        },
+    ],
+    coroutines: [
+        dependencies.create('org.jetbrains.kotlinx:kotlinx-coroutines-core') {
+            // https://android.googlesource.com/platform/prebuilts/tools/+/refs/tags/android-11.0.0_r3/common/m2/Android.bp#326
+            version { strictly '1.3.0' }
+        },
+        dependencies.create('org.jetbrains.kotlinx:kotlinx-coroutines-android') {
+            // https://android.googlesource.com/platform/prebuilts/tools/+/refs/tags/android-11.0.0_r3/common/m2/Android.bp#340
+            version { strictly '1.3.0' }
+        },
+    ],
+]
 
-    /**
-     * Dependencies in AOSP
-     *
-     * We try to keep the dependencies in sync with what AOSP ships as Seedvault is meant to be built
-     * with the AOSP build system and gradle builds are just for more pleasant development.
-     * Using the AOSP versions in gradle builds allows us to spot issues early on.
-     */
-
-    implementation('org.jetbrains.kotlin:kotlin-stdlib-jdk8') {
-        version { strictly "$kotlin_version" }
-    }
-    implementation('org.jetbrains.kotlin:kotlin-stdlib-common') {
-        version { strictly "$kotlin_version" }
-    }
-    implementation('org.jetbrains.kotlin:kotlin-stdlib') {
-        version { strictly "$kotlin_version" }
-    }
-
-    // These coroutine libraries get upgraded otherwise to versions incompatible with kotlin version
-    implementation('org.jetbrains.kotlinx:kotlinx-coroutines-core') {
-        // https://android.googlesource.com/platform/prebuilts/tools/+/refs/tags/android-11.0.0_r3/common/m2/Android.bp#326
-        version { strictly '1.3.0' }
-    }
-    implementation('org.jetbrains.kotlinx:kotlinx-coroutines-android') {
-        // https://android.googlesource.com/platform/prebuilts/tools/+/refs/tags/android-11.0.0_r3/common/m2/Android.bp#340
-        version { strictly '1.3.0' }
-    }
-
-    implementation('androidx.core:core-ktx') {
-        // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#610
+ext.std_libs = [
+    // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#610
+    androidx_core: dependencies.create('androidx.core:core-ktx') {
         version { strictly '1.5.0-alpha01' }
-    }
-
-    // A newer version gets pulled in with AOSP via core, so we include this here explicitly
-    implementation('androidx.fragment:fragment-ktx') {
-        // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#930
+    },
+    // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#930
+    androidx_fragment: dependencies.create('androidx.fragment:fragment-ktx') {
         version { strictly '1.3.0-alpha07' }
-    }
-
-    implementation('androidx.preference:preference') {
-        // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#2412
+    },
+    // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#2412
+    androidx_preference: dependencies.create('androidx.preference:preference') {
         version { strictly '1.1.1' } // should be 1.2.0-alpha01, but that is not even released, yet
-    }
-
-    implementation('androidx.lifecycle:lifecycle-viewmodel-ktx') {
-        // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#1553
+    },
+    // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#1553
+    androidx_lifecycle_viewmodel_ktx: dependencies.create('androidx.lifecycle:lifecycle-viewmodel-ktx') {
         version { strictly '2.3.0-alpha05' }
-    }
-
-    implementation('androidx.lifecycle:lifecycle-livedata-ktx') {
-        // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#1353
+    },
+    // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#1353
+    androidx_lifecycle_livedata_ktx: dependencies.create('androidx.lifecycle:lifecycle-livedata-ktx') {
         version { strictly '2.3.0-alpha05' }
-    }
-
-    implementation('androidx.constraintlayout:constraintlayout') {
-        // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/extras/constraint-layout-x/Android.bp#30
+    },
+    // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/extras/constraint-layout-x/Android.bp#30
+    androidx_constraintlayout: dependencies.create('androidx.constraintlayout:constraintlayout') {
         version { strictly '2.0.0-beta7' }
-    }
-
-    implementation('com.google.android.material:material') {
-        // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/extras/material-design-x/Android.bp#6
+    },
+    // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#708
+    androidx_documentfile: dependencies.create('androidx.documentfile:documentfile') {
+        version { strictly '1.0.1' } // should be 1.1.0-alpha01, but that is not even released, yet
+    },
+    // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/extras/material-design-x/Android.bp#6
+    com_google_android_material: dependencies.create('com.google.android.material:material') {
         version { strictly '1.1.0-alpha05' }
-    }
+    },
+]
 
+ext.lint_libs = [
+    exceptions: 'com.github.thirdegg:lint-rules:0.0.6-beta'
+]
 
-    /**
-     * External Dependencies
-     *
-     * If the dependencies below are updated,
-     * please make sure to update the prebuilt libraries and the Android.bp files
-     * in the top-level `libs` folder to reflect that.
-     * You can copy these libraries from ~/.gradle/caches/modules-2
-     */
-
-    def koin_version = '2.1.1' // later versions require newer kotlin version
-    //noinspection GradleDependency
-    implementation("org.koin:koin-android:$koin_version") {
-        exclude group: 'org.jetbrains.kotlin', module: 'kotlin-stdlib'
-    }
-    //noinspection GradleDependency
-    implementation("org.koin:koin-androidx-viewmodel:$koin_version") {
-        exclude group: 'org.koin', module: 'koin-androidx-scope'
-        exclude group: 'androidx.lifecycle'
-    }
-
-    implementation('io.github.novacrypto:BIP39:2019.01.27') {
-        exclude group: 'com.madgag.spongycastle'
-    }
-
-    /**
-     * Test Dependencies (do not concern the AOSP build)
-     */
-
-    lintChecks 'com.github.thirdegg:lint-rules:0.0.5-alpha'
-
-    def junit_version = "5.5.2"  // careful, upgrading this can change a Cipher's IV size in tests!?
-    def mockk_version = "1.10.0"
-    testImplementation aospDeps  // anything less than 'implementation' fails tests run with gradlew
-    testImplementation 'androidx.test.ext:junit:1.1.2'
-    testImplementation('org.robolectric:robolectric:4.3.1') { // 4.4 has issue with non-idle Looper
-        // https://github.com/robolectric/robolectric/issues/5245
-        exclude group: "com.google.auto.service", module: "auto-service"
-    }
-    testImplementation "org.junit.jupiter:junit-jupiter-api:$junit_version"
-    testImplementation "io.mockk:mockk:$mockk_version"
-    testRuntimeOnly "org.junit.jupiter:junit-jupiter-engine:$junit_version"
-    testRuntimeOnly "org.junit.vintage:junit-vintage-engine:$junit_version"
-
-    androidTestImplementation 'androidx.test:runner:1.3.0'
-    androidTestImplementation 'androidx.test:rules:1.3.0'
-    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
-    androidTestImplementation "io.mockk:mockk-android:$mockk_version"
-}
+ext.storage_libs = [
+    // https://android.googlesource.com/platform/prebuilts/sdk/+/refs/tags/android-11.0.0_r3/current/androidx/Android.bp#2711
+    androidx_room_runtime: dependencies.create('androidx.room:room-runtime') {
+        version { strictly "$room_version" }
+    },
+    // http://aosp.opersys.com/xref/android-11.0.0_r27/xref/external/protobuf/java/pom.xml#7
+    com_google_protobuf_javalite: dependencies.create('com.google.protobuf:protobuf-javalite') {
+        version { strictly "$protobuf_version" }
+    },
+    com_google_crypto_tink_android: dependencies.create('com.google.crypto.tink:tink-android') {
+        version { strictly '1.5.0' }
+    },
+]
diff --git a/gradle/ktlint.gradle b/gradle/ktlint.gradle
new file mode 100644
index 00000000..2b6cd8fb
--- /dev/null
+++ b/gradle/ktlint.gradle
@@ -0,0 +1,11 @@
+ktlint {
+    version = "0.40.0"
+    android = true
+    enableExperimentalRules = false
+    verbose = true
+    disabledRules = [
+            "import-ordering",
+            "no-blank-line-before-rbrace",
+            "indent", // remove in 0.41 https://github.com/pinterest/ktlint/issues/764
+    ]
+}
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 9ff0d9fc..43550d32 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -3,5 +3,5 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.5.1-all.zip
-distributionSha256Sum=143a28f54f1ae93ef4f72d862dbc3c438050d81bb45b4601eb7076e998362920
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.7.1-all.zip
+distributionSha256Sum=22449f5231796abd892c98b2a07c9ceebe4688d192cd2d6763f8e3bf8acbedeb
diff --git a/libs/Android.bp b/libs/Android.bp
new file mode 100644
index 00000000..2fa04ce0
--- /dev/null
+++ b/libs/Android.bp
@@ -0,0 +1,5 @@
+java_import {
+    name: "seedvault-lib-kotlin-bip39",
+    jars: ["kotlin-bip39-1.0.2.jar"],
+    sdk_version: "current",
+}
diff --git a/libs/kotlin-bip39-1.0.2.jar b/libs/kotlin-bip39-1.0.2.jar
new file mode 100644
index 00000000..c05e1e05
Binary files /dev/null and b/libs/kotlin-bip39-1.0.2.jar differ
diff --git a/libs/novacrypto-bip39/Android.bp b/libs/novacrypto-bip39/Android.bp
deleted file mode 100644
index e1947407..00000000
--- a/libs/novacrypto-bip39/Android.bp
+++ /dev/null
@@ -1,27 +0,0 @@
-java_import {
-    name: "seedvault-lib-novacrypto-bip39-nodeps",
-    jars: ["BIP39-2019.01.27.jar"],
-    sdk_version: "current",
-}
-
-java_library_static {
-    name: "seedvault-lib-novacrypto-bip39",
-    static_libs: [
-        "seedvault-lib-novacrypto-bip39-nodeps",
-        "seedvault-lib-novacrypto-sha256",
-        "seedvault-lib-novacrypto-toruntime",
-    ],
-    sdk_version: "current",
-}
-
-java_import {
-    name: "seedvault-lib-novacrypto-sha256",
-    jars: ["SHA256-2019.01.27.jar"],
-    sdk_version: "current",
-}
-
-java_import {
-    name: "seedvault-lib-novacrypto-toruntime",
-    jars: ["ToRuntime-0.9.0.jar"],
-    sdk_version: "current",
-}
diff --git a/libs/novacrypto-bip39/BIP39-2019.01.27.jar b/libs/novacrypto-bip39/BIP39-2019.01.27.jar
deleted file mode 100644
index 806af43d..00000000
Binary files a/libs/novacrypto-bip39/BIP39-2019.01.27.jar and /dev/null differ
diff --git a/libs/novacrypto-bip39/SHA256-2019.01.27.jar b/libs/novacrypto-bip39/SHA256-2019.01.27.jar
deleted file mode 100644
index ae871853..00000000
Binary files a/libs/novacrypto-bip39/SHA256-2019.01.27.jar and /dev/null differ
diff --git a/libs/novacrypto-bip39/ToRuntime-0.9.0.jar b/libs/novacrypto-bip39/ToRuntime-0.9.0.jar
deleted file mode 100644
index d5aa5d63..00000000
Binary files a/libs/novacrypto-bip39/ToRuntime-0.9.0.jar and /dev/null differ
diff --git a/permissions_com.stevesoltys.seedvault.xml b/permissions_com.stevesoltys.seedvault.xml
index da36b245..62051bc3 100644
--- a/permissions_com.stevesoltys.seedvault.xml
+++ b/permissions_com.stevesoltys.seedvault.xml
@@ -5,5 +5,6 @@
         <permission name="android.permission.MANAGE_USB"/>
         <permission name="android.permission.INSTALL_PACKAGES"/>
         <permission name="android.permission.WRITE_SECURE_SETTINGS"/>
+        <permission name="android.permission.MANAGE_EXTERNAL_STORAGE"/>
     </privapp-permissions>
 </permissions>
\ No newline at end of file
diff --git a/settings.gradle b/settings.gradle
index 717326dd..87893e08 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -1,2 +1,4 @@
 include ':app'
 include ':contactsbackup'
+include ':storage:lib'
+include ':storage:demo'
\ No newline at end of file
diff --git a/storage/.gitignore b/storage/.gitignore
new file mode 100644
index 00000000..2481f867
--- /dev/null
+++ b/storage/.gitignore
@@ -0,0 +1 @@
+release.sh
diff --git a/storage/README.md b/storage/README.md
new file mode 100644
index 00000000..94de78e1
--- /dev/null
+++ b/storage/README.md
@@ -0,0 +1,15 @@
+# Seedvault Storage
+
+This is a library for Seedvault storage backup.
+It can also be used by other apps wanting to provide storage backup feature.
+
+Please see the [design document](doc/design.md) for more information.
+
+There is also a [demo app](demo) that illustrates the working of the library
+and does not need to be a system app with elevated permissions.
+It can be built and installed as a regular app requesting permissions at runtime.
+
+## Limitations
+
+The design document mentions several limitations of this initial implementation.
+One of them is that you cannot backup more than one device to the same storage location.
diff --git a/storage/demo/.gitignore b/storage/demo/.gitignore
new file mode 100644
index 00000000..4e4023c8
--- /dev/null
+++ b/storage/demo/.gitignore
@@ -0,0 +1,2 @@
+/build
+/debug
diff --git a/storage/demo/build.gradle b/storage/demo/build.gradle
new file mode 100644
index 00000000..1d4c63e9
--- /dev/null
+++ b/storage/demo/build.gradle
@@ -0,0 +1,57 @@
+plugins {
+    id 'com.android.application'
+    id 'com.google.protobuf'
+    id 'kotlin-android'
+    id 'kotlin-kapt'
+}
+
+android {
+    compileSdkVersion rootProject.ext.compileSdkVersion
+    buildToolsVersion rootProject.ext.buildToolsVersion
+
+    defaultConfig {
+        applicationId "de.grobox.storagebackuptester"
+        minSdkVersion rootProject.ext.minSdkVersion
+        targetSdkVersion rootProject.ext.targetSdkVersion
+        versionCode 20
+        versionName "0.9.7"
+
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+        testInstrumentationRunnerArguments disableAnalytics: 'true'
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled true
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+    kotlinOptions {
+        jvmTarget = '1.8'
+        freeCompilerArgs += "-Xopt-in=kotlin.RequiresOptIn"
+    }
+    packagingOptions {
+        exclude 'META-INF/*.kotlin_module'
+        exclude 'META-INF/androidx.*.version'
+        exclude 'META-INF/services/kotlin*'
+        exclude 'kotlin/internal/internal.kotlin_builtins'
+    }
+}
+
+dependencies {
+    implementation project(':storage:lib')
+
+    implementation rootProject.ext.std_libs.androidx_core
+    // A newer version gets pulled in with AOSP via core, so we include fragment here explicitly
+    implementation rootProject.ext.std_libs.androidx_fragment
+    implementation rootProject.ext.std_libs.androidx_lifecycle_viewmodel_ktx
+    implementation rootProject.ext.std_libs.androidx_lifecycle_livedata_ktx
+    implementation rootProject.ext.std_libs.androidx_constraintlayout
+    implementation rootProject.ext.std_libs.com_google_android_material
+
+    implementation rootProject.ext.storage_libs.com_google_protobuf_javalite
+}
diff --git a/storage/demo/proguard-rules.pro b/storage/demo/proguard-rules.pro
new file mode 100644
index 00000000..55835b34
--- /dev/null
+++ b/storage/demo/proguard-rules.pro
@@ -0,0 +1,23 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile
+
+-dontobfuscate
diff --git a/storage/demo/src/main/AndroidManifest.xml b/storage/demo/src/main/AndroidManifest.xml
new file mode 100644
index 00000000..6846fa36
--- /dev/null
+++ b/storage/demo/src/main/AndroidManifest.xml
@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="de.grobox.storagebackuptester">
+
+    <application
+        android:name=".App"
+        android:allowBackup="false"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.StorageBackupTester">
+
+        <activity android:name=".MainActivity">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+        <!-- Used to start actual BackupService depending on scheduling criteria -->
+        <service
+            android:name=".DemoBackupJobService"
+            android:exported="false"
+            android:label="BackupJobService"
+            android:permission="android.permission.BIND_JOB_SERVICE" />
+        <!-- Does the actual backup work as a foreground service -->
+        <service
+            android:name=".DemoBackupService"
+            android:exported="false"
+            android:foregroundServiceType="dataSync"
+            android:label="BackupService" />
+        <!-- Does restore as a foreground service -->
+        <service
+            android:name=".DemoRestoreService"
+            android:exported="false"
+            android:foregroundServiceType="dataSync"
+            android:label="RestoreService" />
+
+    </application>
+
+</manifest>
diff --git a/storage/demo/src/main/assets/test.jpg b/storage/demo/src/main/assets/test.jpg
new file mode 100644
index 00000000..06554645
Binary files /dev/null and b/storage/demo/src/main/assets/test.jpg differ
diff --git a/storage/demo/src/main/ic_launcher-playstore.png b/storage/demo/src/main/ic_launcher-playstore.png
new file mode 100644
index 00000000..927828be
Binary files /dev/null and b/storage/demo/src/main/ic_launcher-playstore.png differ
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/App.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/App.kt
new file mode 100644
index 00000000..d624041d
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/App.kt
@@ -0,0 +1,40 @@
+package de.grobox.storagebackuptester
+
+import android.app.Application
+import android.os.StrictMode
+import android.os.StrictMode.VmPolicy
+import android.util.Log
+import de.grobox.storagebackuptester.plugin.TestSafStoragePlugin
+import de.grobox.storagebackuptester.settings.SettingsManager
+import org.calyxos.backup.storage.api.StorageBackup
+
+class App : Application() {
+
+    val settingsManager: SettingsManager by lazy { SettingsManager(applicationContext) }
+    val storageBackup: StorageBackup by lazy {
+        val plugin = TestSafStoragePlugin(this) { settingsManager.getBackupLocation() }
+        StorageBackup(this, plugin)
+    }
+
+    override fun onCreate() {
+        super.onCreate()
+        StrictMode.setThreadPolicy(
+            StrictMode.ThreadPolicy.Builder()
+                .detectAll()
+                .penaltyLog()
+                .build()
+        )
+        StrictMode.setVmPolicy(
+            VmPolicy.Builder()
+                .detectAll()
+                .penaltyLog()
+                .build()
+        )
+    }
+
+    override fun onLowMemory() {
+        super.onLowMemory()
+        Log.e("TEST", "ON LOW MEMORY!!!")
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/Job.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/Job.kt
new file mode 100644
index 00000000..627f6e5a
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/Job.kt
@@ -0,0 +1,46 @@
+package de.grobox.storagebackuptester
+
+import android.content.Context
+import org.calyxos.backup.storage.api.BackupObserver
+import org.calyxos.backup.storage.api.RestoreObserver
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.backup.BackupJobService
+import org.calyxos.backup.storage.backup.BackupService
+import org.calyxos.backup.storage.backup.NotificationBackupObserver
+import org.calyxos.backup.storage.restore.NotificationRestoreObserver
+import org.calyxos.backup.storage.restore.RestoreService
+import java.util.concurrent.TimeUnit.HOURS
+
+// debug with:
+// adb shell dumpsys jobscheduler | grep -B 4 -A 24 "Service: de.grobox.storagebackuptester/.DemoBackupJobService"
+
+class DemoBackupJobService : BackupJobService(DemoBackupService::class.java) {
+    companion object {
+        fun scheduleJob(context: Context) {
+            scheduleJob(
+                context = context,
+                jobServiceClass = DemoBackupJobService::class.java,
+//                periodMillis = JobInfo.getMinPeriodMillis(), // for testing
+                periodMillis = HOURS.toMillis(12), // less than 15min won't work
+                deviceIdle = false,
+                charging = false,
+            )
+        }
+    }
+}
+
+class DemoBackupService : BackupService() {
+    // use lazy delegate because context isn't available during construction time
+    override val storageBackup: StorageBackup by lazy { (application as App).storageBackup }
+    override val backupObserver: BackupObserver by lazy {
+        NotificationBackupObserver(applicationContext)
+    }
+}
+
+class DemoRestoreService : RestoreService() {
+    // use lazy delegate because context isn't available during construction time
+    override val storageBackup: StorageBackup by lazy { (application as App).storageBackup }
+    override val restoreObserver: RestoreObserver by lazy {
+        NotificationRestoreObserver(applicationContext)
+    }
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/LogAdapter.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/LogAdapter.kt
new file mode 100644
index 00000000..70bc59c8
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/LogAdapter.kt
@@ -0,0 +1,43 @@
+package de.grobox.storagebackuptester
+
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.TextView
+import androidx.recyclerview.widget.RecyclerView
+
+class LogAdapter : RecyclerView.Adapter<LogAdapter.ViewHolder>() {
+
+    val items: ArrayList<String> = ArrayList()
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
+        val v = LayoutInflater.from(parent.context).inflate(R.layout.item_log, parent, false)
+        return ViewHolder(v)
+    }
+
+    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
+        val item = items[position]
+        holder.bind(item)
+    }
+
+    override fun getItemCount(): Int = items.size
+
+    fun addItem(item: String) {
+        items.add(item)
+        notifyItemInserted(items.size - 1)
+    }
+
+    fun clear() {
+        items.clear()
+        notifyDataSetChanged()
+    }
+
+    class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
+        private val logView: TextView = view.findViewById(R.id.logView)
+
+        fun bind(item: String) {
+            logView.text = item
+        }
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/LogFragment.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/LogFragment.kt
new file mode 100644
index 00000000..d60c220d
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/LogFragment.kt
@@ -0,0 +1,142 @@
+package de.grobox.storagebackuptester
+
+import android.Manifest.permission.ACCESS_MEDIA_LOCATION
+import android.Manifest.permission.WRITE_EXTERNAL_STORAGE
+import android.content.Intent
+import android.content.pm.PackageManager.PERMISSION_GRANTED
+import android.net.Uri
+import android.os.Build
+import android.os.Bundle
+import android.os.Environment
+import android.provider.Settings.ACTION_MANAGE_APP_ALL_FILES_ACCESS_PERMISSION
+import android.view.LayoutInflater
+import android.view.Menu
+import android.view.MenuInflater
+import android.view.MenuItem
+import android.view.View
+import android.view.View.INVISIBLE
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import android.widget.Button
+import android.widget.ProgressBar
+import android.widget.Toast
+import android.widget.Toast.LENGTH_SHORT
+import androidx.activity.result.contract.ActivityResultContracts.RequestMultiplePermissions
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.activityViewModels
+import androidx.recyclerview.widget.RecyclerView
+import de.grobox.storagebackuptester.settings.SettingsFragment
+
+private const val EMAIL = "incoming+grote-storage-backup-tester-22079635-issue-@incoming.gitlab.com"
+
+open class LogFragment : Fragment() {
+
+    companion object {
+        fun newInstance(): LogFragment = LogFragment()
+    }
+
+    private val viewModel: MainViewModel by activityViewModels()
+
+    private lateinit var list: RecyclerView
+    private lateinit var progressBar: ProgressBar
+    private lateinit var horizontalProgressBar: ProgressBar
+    private lateinit var button: Button
+    private val adapter = LogAdapter()
+
+    private val permissionRequest =
+        registerForActivityResult(RequestMultiplePermissions()) { grantedMap ->
+            if (grantedMap[WRITE_EXTERNAL_STORAGE] == true) {
+                Toast.makeText(requireContext(), "Please try again now!", LENGTH_SHORT).show()
+            }
+        }
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        setHasOptionsMenu(true)
+        val v = inflater.inflate(R.layout.fragment_log, container, false)
+        list = v.findViewById(R.id.listView)
+        list.adapter = adapter
+        progressBar = v.findViewById(R.id.progressBar)
+        horizontalProgressBar = v.findViewById(R.id.horizontalProgressBar)
+        button = v.findViewById(R.id.button)
+        viewModel.backupLog.observe(viewLifecycleOwner, { progress ->
+            progress.text?.let { adapter.addItem(it) }
+            horizontalProgressBar.max = progress.total
+            horizontalProgressBar.setProgress(progress.current, true)
+            list.postDelayed({
+                list.scrollToPosition(adapter.itemCount - 1)
+            }, 50)
+        })
+        viewModel.backupButtonEnabled.observe(viewLifecycleOwner, { enabled ->
+            button.isEnabled = enabled
+            progressBar.visibility = if (enabled) INVISIBLE else VISIBLE
+            if (!enabled) adapter.clear()
+        })
+        button.setOnClickListener {
+            if (!checkPermission()) return@setOnClickListener
+            viewModel.simulateBackup()
+        }
+        return v
+    }
+
+    override fun onStart() {
+        super.onStart()
+        requireActivity().setTitle(R.string.app_name)
+    }
+
+    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
+        inflater.inflate(R.menu.fragment_main, menu)
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        return when (item.itemId) {
+            R.id.settings -> {
+                if (!checkPermission()) return false
+                parentFragmentManager.beginTransaction()
+                    .replace(R.id.container, SettingsFragment.newInstance())
+                    .addToBackStack("SETTINGS")
+                    .commit()
+                true
+            }
+            R.id.share -> {
+                val subject = adapter.items.takeLast(2).joinToString(" - ").replace("\n", "")
+                val text = adapter.items.takeLast(333).joinToString("\n")
+                val sendIntent: Intent = Intent().apply {
+                    action = Intent.ACTION_SEND
+                    putExtra(Intent.EXTRA_EMAIL, arrayOf(EMAIL))
+                    putExtra(Intent.EXTRA_SUBJECT, subject)
+                    putExtra(Intent.EXTRA_TEXT, text)
+                    type = "text/plain"
+                }
+                val shareIntent = Intent.createChooser(sendIntent, null)
+                startActivity(shareIntent)
+                true
+            }
+            else -> super.onOptionsItemSelected(item)
+        }
+    }
+
+    private fun checkPermission(): Boolean {
+        return if (Build.VERSION.SDK_INT >= 30) {
+            if (Environment.isExternalStorageManager()) return true
+            Toast.makeText(requireContext(), "Permission needed", LENGTH_SHORT).show()
+            val i = Intent(ACTION_MANAGE_APP_ALL_FILES_ACCESS_PERMISSION).apply {
+                data = Uri.parse("package:${requireContext().packageName}")
+            }
+            startActivity(i)
+            false
+        } else {
+            if (requireContext().checkSelfPermission(WRITE_EXTERNAL_STORAGE) == PERMISSION_GRANTED) {
+                true
+            } else {
+                Toast.makeText(requireContext(), "No storage permission", LENGTH_SHORT).show()
+                permissionRequest.launch(arrayOf(WRITE_EXTERNAL_STORAGE, ACCESS_MEDIA_LOCATION))
+                false
+            }
+        }
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/MainActivity.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/MainActivity.kt
new file mode 100644
index 00000000..84e5b669
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/MainActivity.kt
@@ -0,0 +1,31 @@
+package de.grobox.storagebackuptester
+
+import android.os.Bundle
+import android.util.Log
+import androidx.appcompat.app.AppCompatActivity
+import de.grobox.storagebackuptester.crypto.KeyManager
+
+class MainActivity : AppCompatActivity() {
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_main)
+
+        if (savedInstanceState == null) {
+            supportFragmentManager.beginTransaction()
+                .replace(R.id.container, LogFragment.newInstance())
+                .commitNow()
+        }
+
+        KeyManager.storeMasterKey()
+
+        if (!KeyManager.hasMasterKey()) {
+            Log.e("TEST", "storing new key")
+            KeyManager.storeMasterKey()
+        } else {
+            Log.e("TEST", "already have key")
+        }
+
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/MainViewModel.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/MainViewModel.kt
new file mode 100644
index 00000000..777247b4
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/MainViewModel.kt
@@ -0,0 +1,141 @@
+package de.grobox.storagebackuptester
+
+import android.app.Application
+import android.net.Uri
+import android.util.Log
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.asLiveData
+import androidx.lifecycle.viewModelScope
+import de.grobox.storagebackuptester.backup.BackupProgress
+import de.grobox.storagebackuptester.backup.BackupStats
+import de.grobox.storagebackuptester.restore.RestoreProgress
+import de.grobox.storagebackuptester.restore.RestoreStats
+import de.grobox.storagebackuptester.scanner.scanTree
+import de.grobox.storagebackuptester.scanner.scanUri
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import org.calyxos.backup.storage.api.SnapshotItem
+import org.calyxos.backup.storage.api.SnapshotResult
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.backup.BackupJobService
+import org.calyxos.backup.storage.scanner.DocumentScanner
+import org.calyxos.backup.storage.scanner.MediaScanner
+import org.calyxos.backup.storage.ui.backup.BackupContentViewModel
+import org.calyxos.backup.storage.ui.restore.SnapshotViewModel
+
+private val logEmptyState = """
+    Press the button below to simulate a backup. Your files won't be changed and not uploaded anywhere. This is just to test code for a future real backup.
+    
+    Please come back to this app from time to time and run a backup again to see if it correctly identifies files that were added/changed.
+    
+    Note that after updating this app, it might need to re-backup all files again.
+    
+    Thanks for testing!
+""".trimIndent()
+private const val TAG = "MainViewModel"
+
+class MainViewModel(application: Application) : BackupContentViewModel(application),
+    SnapshotViewModel {
+
+    private val app: App = application as App
+    private val settingsManager = app.settingsManager
+    override val storageBackup: StorageBackup = app.storageBackup
+
+    private val _backupLog = MutableLiveData(BackupProgress(0, 0, logEmptyState))
+    val backupLog: LiveData<BackupProgress> = _backupLog
+
+    private val _buttonEnabled = MutableLiveData<Boolean>()
+    val backupButtonEnabled: LiveData<Boolean> = _buttonEnabled
+
+    private val _restoreLog = MutableLiveData<RestoreProgress>()
+    val restoreLog: LiveData<RestoreProgress> = _restoreLog
+
+    private val _restoreProgressVisible = MutableLiveData<Boolean>()
+    val restoreProgressVisible: LiveData<Boolean> = _restoreProgressVisible
+
+    override val snapshots: LiveData<SnapshotResult>
+        get() = storageBackup.getBackupSnapshots().asLiveData(Dispatchers.IO)
+
+    init {
+        viewModelScope.launch { loadContent() }
+    }
+
+    fun simulateBackup() {
+        _buttonEnabled.value = false
+        val backupObserver = BackupStats(app, storageBackup, _backupLog)
+        viewModelScope.launch(Dispatchers.IO) {
+            val text = storageBackup.getUriSummaryString()
+            _backupLog.postValue(BackupProgress(0, 0, "Scanning: $text\n"))
+            // FIXME: This might get killed if we navigate away from the activity.
+            //  A foreground service would avoid that.
+            if (storageBackup.runBackup(backupObserver)) {
+                // only prune old backups when backup run was successful
+                storageBackup.pruneOldBackups(backupObserver)
+            }
+            _buttonEnabled.postValue(true)
+        }
+    }
+
+    suspend fun scanMediaUri(uri: Uri): String = withContext(Dispatchers.Default) {
+        scanUri(app, MediaScanner(app), uri)
+    }
+
+    suspend fun scanDocumentUri(uri: Uri): String = withContext(Dispatchers.Default) {
+        scanTree(app, DocumentScanner(app), uri)
+    }
+
+    fun clearDb() {
+        viewModelScope.launch(Dispatchers.IO) { storageBackup.clearCache() }
+    }
+
+    fun setBackupLocation(uri: Uri?) {
+        if (uri != null) {
+            viewModelScope.launch(Dispatchers.IO) {
+                storageBackup.deleteAllSnapshots()
+                storageBackup.clearCache()
+            }
+        }
+        settingsManager.setBackupLocation(uri)
+    }
+
+    fun hasBackupLocation(): Boolean {
+        return settingsManager.getBackupLocation() != null
+    }
+
+    fun setAutomaticBackupsEnabled(enabled: Boolean) {
+        if (enabled) DemoBackupJobService.scheduleJob(app)
+        else BackupJobService.cancelJob(app)
+        settingsManager.setAutomaticBackupsEnabled(enabled)
+    }
+
+    fun areAutomaticBackupsEnabled(): Boolean {
+        val enabled = settingsManager.areAutomaticBackupsEnabled()
+        if (enabled && !BackupJobService.isScheduled(app)) {
+            Log.w(TAG, "Automatic backups enabled, but job not scheduled. Scheduling...")
+            DemoBackupJobService.scheduleJob(app)
+        }
+        return enabled
+    }
+
+    fun onSnapshotClicked(item: SnapshotItem) {
+        val snapshot = item.snapshot
+        check(snapshot != null)
+
+        // example for how to do restore via foreground service
+//        app.startForegroundService(Intent(app, DemoRestoreService::class.java).apply {
+//            putExtra(EXTRA_USER_ID, item.storedSnapshot.userId)
+//            putExtra(EXTRA_TIMESTAMP_START, snapshot.timeStart)
+//        })
+
+        // example for how to do restore via fragment
+        _restoreProgressVisible.value = true
+        val restoreObserver = RestoreStats(app, _restoreLog)
+        viewModelScope.launch {
+            storageBackup.restoreBackupSnapshot(item.storedSnapshot, snapshot, restoreObserver)
+            _restoreProgressVisible.value = false
+        }
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/backup/BackupStats.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/backup/BackupStats.kt
new file mode 100644
index 00000000..31468272
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/backup/BackupStats.kt
@@ -0,0 +1,182 @@
+package de.grobox.storagebackuptester.backup
+
+import android.content.Context
+import android.provider.MediaStore
+import android.text.format.DateUtils.FORMAT_ABBREV_ALL
+import android.text.format.DateUtils.getRelativeTimeSpanString
+import android.text.format.Formatter
+import android.util.Log
+import androidx.lifecycle.MutableLiveData
+import org.calyxos.backup.storage.api.BackupFile
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.backup.NotificationBackupObserver
+import kotlin.time.DurationUnit
+import kotlin.time.ExperimentalTime
+import kotlin.time.toDuration
+
+data class BackupProgress(
+    val current: Int,
+    val total: Int,
+    val text: String?,
+)
+
+internal class BackupStats(
+    private val context: Context,
+    private val storageBackup: StorageBackup,
+    private val liveData: MutableLiveData<BackupProgress>,
+) : NotificationBackupObserver(context) {
+    private var filesProcessed: Int = 0
+    private var totalFiles: Int = 0
+    private var filesUploaded: Int = 0
+    private var expectedSize: Long = 0L
+    private var size: Long = 0L
+    private var savedChunks: Int = 0
+    private val errorStrings = ArrayList<String>()
+
+    override suspend fun onBackupStart(
+        totalSize: Long,
+        numFiles: Int,
+        numSmallFiles: Int,
+        numLargeFiles: Int
+    ) {
+        super.onBackupStart(totalSize, numFiles, numSmallFiles, numLargeFiles)
+
+        totalFiles = numFiles
+        expectedSize = totalSize
+
+        val totalSizeStr = Formatter.formatShortFileSize(context, totalSize)
+        val text = "Backing up $totalFiles file(s) $totalSizeStr...\n" +
+                "  ($numSmallFiles small, $numLargeFiles large)\n"
+        liveData.postValue(BackupProgress(filesProcessed, totalFiles, text))
+    }
+
+    override suspend fun onFileBackedUp(
+        file: BackupFile,
+        wasUploaded: Boolean,
+        reusedChunks: Int,
+        bytesWritten: Long,
+        tag: String,
+    ) {
+        super.onFileBackedUp(file, wasUploaded, reusedChunks, bytesWritten, tag)
+
+        filesProcessed++
+        if (!wasUploaded) return
+
+        savedChunks += reusedChunks
+        filesUploaded++
+        size += bytesWritten
+
+        val sizeStr = Formatter.formatShortFileSize(context, file.size)
+        val now = System.currentTimeMillis()
+        val modStr = file.lastModified?.let {
+            getRelativeTimeSpanString(it, now, 0L, FORMAT_ABBREV_ALL)
+        } ?: "NULL"
+
+        val volume =
+            if (file.volume == MediaStore.VOLUME_EXTERNAL_PRIMARY) "" else "v: ${file.volume}"
+        val text = "${file.path}\n   s: $sizeStr m: $modStr $volume"
+        liveData.postValue(BackupProgress(filesProcessed, totalFiles, text))
+    }
+
+    override suspend fun onFileBackupError(file: BackupFile, tag: String) {
+        super.onFileBackupError(file, tag)
+
+        filesProcessed++
+        errorStrings.add("ERROR $tag: ${file.path}")
+        liveData.postValue(BackupProgress(filesProcessed, totalFiles, null))
+    }
+
+    @OptIn(ExperimentalTime::class)
+    override suspend fun onBackupComplete(backupDuration: Long?) {
+        super.onBackupComplete(backupDuration)
+
+        val sb = StringBuilder("\n")
+        errorStrings.forEach { sb.appendLine(it) }
+        sb.appendLine()
+
+        if (savedChunks > 0) sb.appendLine("Chunks re-used: $savedChunks")
+
+        Log.e("TEST", "Total file size: $expectedSize")
+        Log.e("TEST", "Actual size processed: $size")
+
+        val sizeStr = Formatter.formatShortFileSize(context, size)
+        if (backupDuration != null) {
+            val speed = getSpeed(size, backupDuration / 1000)
+
+            val duration = backupDuration.toDuration(DurationUnit.MILLISECONDS)
+            val perFile = if (filesUploaded > 0) duration.div(filesUploaded) else duration
+
+            sb.appendLine("New/changed files backed up: $filesUploaded ($sizeStr)")
+            if (filesUploaded > 0) sb.append("  ($perFile per file - ${speed}MB/sec)")
+        }
+        liveData.postValue(BackupProgress(filesProcessed, totalFiles, sb.toString()))
+    }
+
+    override suspend fun onPruneStart(snapshotsToDelete: List<Long>) {
+        super.onPruneStart(snapshotsToDelete)
+
+        filesProcessed = 0
+        totalFiles = snapshotsToDelete.size
+        size = 0L
+        val r = storageBackup.getSnapshotRetention()
+
+        if (totalFiles > 0) {
+            val text = """
+                Pruning $totalFiles old backup(s) from storage...
+                Retaining snapshots:
+                  - ${r.daily} daily
+                  - ${r.weekly} weekly
+                  - ${r.monthly} monthly
+                  - ${r.yearly} yearly
+                """.trimIndent()
+            liveData.postValue(BackupProgress(filesProcessed, totalFiles, text))
+        }
+    }
+
+    override suspend fun onPruneSnapshot(snapshot: Long, numChunksToDelete: Int, size: Long) {
+        super.onPruneSnapshot(snapshot, numChunksToDelete, size)
+
+        filesProcessed++
+        this.size += size
+        val now = System.currentTimeMillis()
+        val time = getRelativeTimeSpanString(snapshot, now, 0L, FORMAT_ABBREV_ALL)
+        val sizeStr = Formatter.formatShortFileSize(context, size)
+        val text = "Pruning snapshot from $time\n  deleting $numChunksToDelete chunks ($sizeStr)..."
+        liveData.postValue(BackupProgress(filesProcessed, totalFiles, text))
+    }
+
+    override suspend fun onPruneError(snapshot: Long?, e: Exception) {
+        super.onPruneError(snapshot, e)
+
+        val time = if (snapshot != null) {
+            filesProcessed++
+            val now = System.currentTimeMillis()
+            getRelativeTimeSpanString(snapshot, now, 0L, FORMAT_ABBREV_ALL)
+        } else "null"
+        val text = "ERROR $snapshot $time\n   e: ${e.message}"
+        liveData.postValue(BackupProgress(filesProcessed, totalFiles, text))
+    }
+
+    @OptIn(ExperimentalTime::class)
+    override suspend fun onPruneComplete(pruneDuration: Long) {
+        super.onPruneComplete(pruneDuration)
+
+        val sb = StringBuilder("\n")
+
+        val sizeStr = Formatter.formatShortFileSize(context, size)
+
+        val duration = pruneDuration.toDuration(DurationUnit.MILLISECONDS)
+        val perSnapshot = if (filesProcessed > 0) duration.div(filesProcessed) else duration
+
+        sb.appendLine("Deleting $filesProcessed old backup snapshot(s) took $duration.")
+        if (filesProcessed > 0) sb.append("  (freed $sizeStr - took $perSnapshot per snapshot)")
+        liveData.postValue(BackupProgress(filesProcessed, totalFiles, sb.toString()))
+    }
+
+}
+
+fun getSpeed(size: Long, duration: Long): Long {
+    val mb = size / 1024 / 1024
+    return if (duration == 0L) (mb.toDouble() / 0.01).toLong()
+    else mb / duration
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/crypto/KeyManager.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/crypto/KeyManager.kt
new file mode 100644
index 00000000..22b9a9b2
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/crypto/KeyManager.kt
@@ -0,0 +1,53 @@
+package de.grobox.storagebackuptester.crypto
+
+import android.security.keystore.KeyProperties.PURPOSE_DECRYPT
+import android.security.keystore.KeyProperties.PURPOSE_ENCRYPT
+import android.security.keystore.KeyProperties.PURPOSE_SIGN
+import android.security.keystore.KeyProperties.PURPOSE_VERIFY
+import android.security.keystore.KeyProtection
+import java.security.KeyStore
+import javax.crypto.SecretKey
+import javax.crypto.spec.SecretKeySpec
+
+object KeyManager {
+
+    private const val KEY_SIZE = 256
+    internal const val KEY_SIZE_BYTES = KEY_SIZE / 8
+    private const val KEY_ALIAS_MASTER = "com.stevesoltys.seedvault.master"
+    private const val ANDROID_KEY_STORE = "AndroidKeyStore"
+    private const val ALGORITHM_HMAC = "HmacSHA256"
+
+    private const val FAKE_SEED = "This is a legacy backup key 1234"
+
+    private val keyStore by lazy {
+        KeyStore.getInstance(ANDROID_KEY_STORE).apply {
+            load(null)
+        }
+    }
+
+    fun storeMasterKey() {
+        val seed = FAKE_SEED.toByteArray()
+        storeMasterKey(seed)
+    }
+
+    private fun storeMasterKey(seed: ByteArray) {
+        if (seed.size < KEY_SIZE_BYTES) throw IllegalArgumentException()
+        val secretKeySpec = SecretKeySpec(seed, 0, KEY_SIZE_BYTES, ALGORITHM_HMAC)
+        val ksEntry = KeyStore.SecretKeyEntry(secretKeySpec)
+        keyStore.setEntry(KEY_ALIAS_MASTER, ksEntry, getKeyProtection())
+    }
+
+    fun hasMasterKey(): Boolean = keyStore.containsAlias(KEY_ALIAS_MASTER)
+
+    fun getMasterKey(): SecretKey {
+        val ksEntry = keyStore.getEntry(KEY_ALIAS_MASTER, null) as KeyStore.SecretKeyEntry
+        return ksEntry.secretKey
+    }
+
+    private fun getKeyProtection(): KeyProtection {
+        val builder =
+            KeyProtection.Builder(PURPOSE_ENCRYPT or PURPOSE_DECRYPT or PURPOSE_SIGN or PURPOSE_VERIFY)
+        return builder.build()
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/plugin/TestSafStoragePlugin.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/plugin/TestSafStoragePlugin.kt
new file mode 100644
index 00000000..286f13d5
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/plugin/TestSafStoragePlugin.kt
@@ -0,0 +1,49 @@
+package de.grobox.storagebackuptester.plugin
+
+import android.content.Context
+import android.net.Uri
+import androidx.documentfile.provider.DocumentFile
+import de.grobox.storagebackuptester.crypto.KeyManager
+import org.calyxos.backup.storage.plugin.saf.SafStoragePlugin
+import java.io.IOException
+import java.io.OutputStream
+import javax.crypto.SecretKey
+
+@Suppress("BlockingMethodInNonBlockingContext")
+class TestSafStoragePlugin(
+    private val context: Context,
+    private val getLocationUri: () -> Uri?,
+) : SafStoragePlugin(context) {
+
+    override val root: DocumentFile?
+        get() {
+            val uri = getLocationUri() ?: return null
+            return DocumentFile.fromTreeUri(context, uri) ?: error("No doc file from tree Uri")
+        }
+
+    private val nullStream = object : OutputStream() {
+        override fun write(b: Int) {
+            // oops
+        }
+    }
+
+    override fun getMasterKey(): SecretKey {
+        return KeyManager.getMasterKey()
+    }
+
+    override fun hasMasterKey(): Boolean {
+        return KeyManager.hasMasterKey()
+    }
+
+    @Throws(IOException::class)
+    override fun getChunkOutputStream(chunkId: String): OutputStream {
+        if (getLocationUri() == null) return nullStream
+        return super.getChunkOutputStream(chunkId)
+    }
+
+    override fun getBackupSnapshotOutputStream(timestamp: Long): OutputStream {
+        if (root == null) return nullStream
+        return super.getBackupSnapshotOutputStream(timestamp)
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/restore/DemoSnapshotFragment.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/restore/DemoSnapshotFragment.kt
new file mode 100644
index 00000000..66990226
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/restore/DemoSnapshotFragment.kt
@@ -0,0 +1,42 @@
+package de.grobox.storagebackuptester.restore
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.view.ViewStub
+import android.widget.Button
+import androidx.fragment.app.activityViewModels
+import de.grobox.storagebackuptester.MainViewModel
+import de.grobox.storagebackuptester.R
+import org.calyxos.backup.storage.api.SnapshotItem
+import org.calyxos.backup.storage.ui.restore.SnapshotFragment
+
+class DemoSnapshotFragment : SnapshotFragment() {
+
+    override val viewModel: MainViewModel by activityViewModels()
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        val v = super.onCreateView(inflater, container, savedInstanceState)
+        val bottomStub: ViewStub = v.findViewById(R.id.bottomStub)
+        bottomStub.layoutResource = R.layout.footer_snapshot
+        val footer = bottomStub.inflate()
+        footer.findViewById<Button>(R.id.button).setOnClickListener {
+            requireActivity().onBackPressed()
+        }
+        return v
+    }
+
+    override fun onSnapshotClicked(item: SnapshotItem) {
+        viewModel.onSnapshotClicked(item)
+        parentFragmentManager.beginTransaction()
+            .replace(R.id.container, RestoreFragment.newInstance())
+            .addToBackStack("RESTORE")
+            .commit()
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/restore/RestoreFragment.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/restore/RestoreFragment.kt
new file mode 100644
index 00000000..c4eb831c
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/restore/RestoreFragment.kt
@@ -0,0 +1,68 @@
+package de.grobox.storagebackuptester.restore
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.View.GONE
+import android.view.View.INVISIBLE
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import android.widget.Button
+import android.widget.ProgressBar
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.activityViewModels
+import androidx.recyclerview.widget.RecyclerView
+import de.grobox.storagebackuptester.LogAdapter
+import de.grobox.storagebackuptester.MainViewModel
+import de.grobox.storagebackuptester.R
+
+class RestoreFragment : Fragment() {
+
+    companion object {
+        fun newInstance() = RestoreFragment()
+    }
+
+    private val viewModel: MainViewModel by activityViewModels()
+
+    private lateinit var list: RecyclerView
+    private lateinit var progressBar: ProgressBar
+    private lateinit var horizontalProgressBar: ProgressBar
+    private lateinit var button: Button
+    private val adapter = LogAdapter()
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        setHasOptionsMenu(true)
+        val v = inflater.inflate(R.layout.fragment_log, container, false)
+        list = v.findViewById(R.id.listView)
+        list.adapter = adapter
+        progressBar = v.findViewById(R.id.progressBar)
+        horizontalProgressBar = v.findViewById(R.id.horizontalProgressBar)
+        button = v.findViewById(R.id.button)
+        button.visibility = GONE
+        return v
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        viewModel.restoreLog.observe(viewLifecycleOwner, { progress ->
+            progress.text?.let { adapter.addItem(it) }
+            horizontalProgressBar.max = progress.total
+            horizontalProgressBar.setProgress(progress.current, true)
+            list.postDelayed({
+                list.scrollToPosition(adapter.itemCount - 1)
+            }, 50)
+        })
+        viewModel.restoreProgressVisible.observe(viewLifecycleOwner, { visible ->
+            progressBar.visibility = if (visible) VISIBLE else INVISIBLE
+        })
+    }
+
+    override fun onStart() {
+        super.onStart()
+        requireActivity().title = "Restore"
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/restore/RestoreStats.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/restore/RestoreStats.kt
new file mode 100644
index 00000000..ceda95b4
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/restore/RestoreStats.kt
@@ -0,0 +1,84 @@
+package de.grobox.storagebackuptester.restore
+
+import android.content.Context
+import android.text.format.DateUtils
+import android.text.format.Formatter
+import androidx.lifecycle.MutableLiveData
+import de.grobox.storagebackuptester.backup.getSpeed
+import org.calyxos.backup.storage.api.BackupFile
+import org.calyxos.backup.storage.restore.NotificationRestoreObserver
+import kotlin.time.DurationUnit
+import kotlin.time.ExperimentalTime
+import kotlin.time.toDuration
+
+data class RestoreProgress(
+    val current: Int,
+    val total: Int,
+    val text: String? = null,
+)
+
+class RestoreStats(
+    private val context: Context,
+    private val liveData: MutableLiveData<RestoreProgress>,
+) : NotificationRestoreObserver(context) {
+
+    private var filesProcessed: Int = 0
+    private var totalFiles: Int = 0
+    private var size: Long = 0L
+    private val errorStrings = ArrayList<String>()
+
+    override fun onRestoreStart(numFiles: Int, totalSize: Long) {
+        super.onRestoreStart(numFiles, totalSize)
+        totalFiles = numFiles
+
+        val totalSizeStr = Formatter.formatShortFileSize(context, totalSize)
+        val text = "Restoring $totalFiles file(s) $totalSizeStr...\n"
+        liveData.postValue(RestoreProgress(filesProcessed, totalFiles, text))
+    }
+
+    override fun onFileRestored(
+        file: BackupFile,
+        bytesWritten: Long,
+        tag: String,
+    ) {
+        super.onFileRestored(file, bytesWritten, tag)
+        filesProcessed++
+        size += bytesWritten
+
+        val sizeStr = Formatter.formatShortFileSize(context, file.size)
+        val now = System.currentTimeMillis()
+        val modStr = file.lastModified?.let {
+            DateUtils.getRelativeTimeSpanString(it, now, 0L, DateUtils.FORMAT_ABBREV_ALL)
+        } ?: "NULL"
+
+        val volume = if (file.volume == "") "" else "v: ${file.volume}"
+        val text = "${file.path}\n   s: $sizeStr m: $modStr $tag $volume"
+        liveData.postValue(RestoreProgress(filesProcessed, totalFiles, text))
+    }
+
+    override fun onFileRestoreError(file: BackupFile, e: Exception) {
+        super.onFileRestoreError(file, e)
+        filesProcessed++
+        errorStrings.add("E ${file.path}\n   e: ${e.message}")
+        liveData.postValue(RestoreProgress(filesProcessed, totalFiles))
+    }
+
+    @OptIn(ExperimentalTime::class)
+    override fun onRestoreComplete(restoreDuration: Long) {
+        super.onRestoreComplete(restoreDuration)
+        val sb = StringBuilder("\n")
+        errorStrings.forEach { sb.appendLine(it) }
+        sb.appendLine()
+
+        val sizeStr = Formatter.formatShortFileSize(context, size)
+        val speed = getSpeed(size, restoreDuration / 1000)
+
+        val duration = restoreDuration.toDuration(DurationUnit.MILLISECONDS)
+        val perFile = if (filesProcessed > 0) duration.div(filesProcessed) else duration
+
+        sb.appendLine("Files restored: $filesProcessed ($sizeStr)")
+        if (filesProcessed > 0) sb.append("  ($perFile per file - ${speed}MB/sec)")
+        liveData.postValue(RestoreProgress(filesProcessed, totalFiles, sb.toString()))
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/DocumentScanFragment.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/DocumentScanFragment.kt
new file mode 100644
index 00000000..7a163bec
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/DocumentScanFragment.kt
@@ -0,0 +1,21 @@
+package de.grobox.storagebackuptester.scanner
+
+import android.net.Uri
+import android.os.Bundle
+
+class DocumentScanFragment : MediaScanFragment() {
+
+    companion object {
+        fun newInstance(name: String, uri: Uri) = DocumentScanFragment().apply {
+            arguments = Bundle().apply {
+                putString("name", name)
+                putString("uri", uri.toString())
+            }
+        }
+    }
+
+    override suspend fun getText(): String {
+        return viewModel.scanDocumentUri(getUri())
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/DocumentScanner.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/DocumentScanner.kt
new file mode 100644
index 00000000..7552520b
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/DocumentScanner.kt
@@ -0,0 +1,56 @@
+package de.grobox.storagebackuptester.scanner
+
+import android.annotation.SuppressLint
+import android.content.Context
+import android.net.Uri
+import android.provider.DocumentsContract
+import android.text.format.Formatter
+import org.calyxos.backup.storage.api.BackupFile
+import org.calyxos.backup.storage.scanner.DocumentScanner
+import java.text.SimpleDateFormat
+import java.util.Date
+import kotlin.time.ExperimentalTime
+import kotlin.time.measureTimedValue
+
+@OptIn(ExperimentalTime::class)
+fun scanTree(context: Context, documentScanner: DocumentScanner, treeUri: Uri): String {
+    val sb = StringBuilder()
+    val timedResult = measureTimedValue {
+        val documentId = DocumentsContract.getTreeDocumentId(treeUri)
+        val documentUri = DocumentsContract.buildDocumentUriUsingTree(treeUri, documentId)
+        scanDocument(context, documentScanner.scanUri(documentUri), sb)
+    }
+    return appendStats(context, sb, timedResult)
+}
+
+@SuppressLint("SimpleDateFormat")
+private val dateFormat = SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
+
+fun scanDocument(
+    context: Context,
+    documentFiles: List<BackupFile>,
+    sb: StringBuilder? = null
+): ScanResult {
+    var totalSize = 0L
+    val warnings = StringBuilder()
+    for (documentFile in documentFiles) {
+        totalSize += documentFile.size
+        val lastModified = documentFile.lastModified?.let {
+            dateFormat.format(Date(it))
+        }
+        sb?.appendLine("┣ ${documentFile.path}")
+        sb?.appendLine("┃   lastModified: $lastModified")
+        sb?.appendLine("┃   size: ${Formatter.formatShortFileSize(context, documentFile.size)}")
+
+        if (lastModified == null) {
+            warnings.appendLine("WARNING: ${documentFile.path} has no lastModified timestamp.")
+        }
+        if (documentFile.size == 0L && !documentFile.path.endsWith(".nomedia")) {
+            warnings.appendLine("WARNING: ${documentFile.path} has no 0 size. Please check if real.")
+        }
+    }
+
+    if (sb?.isEmpty() == true) sb.appendLine("Empty folder")
+    else if (warnings.isNotEmpty()) sb?.appendLine()?.appendLine(warnings)
+    return ScanResult(documentFiles.size.toLong(), totalSize)
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/MediaScanFragment.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/MediaScanFragment.kt
new file mode 100644
index 00000000..1bd82dac
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/MediaScanFragment.kt
@@ -0,0 +1,108 @@
+package de.grobox.storagebackuptester.scanner
+
+import android.content.Intent
+import android.net.Uri
+import android.os.Bundle
+import android.util.Log
+import android.view.LayoutInflater
+import android.view.Menu
+import android.view.MenuInflater
+import android.view.MenuItem
+import android.view.View
+import android.view.View.FOCUS_DOWN
+import android.view.View.INVISIBLE
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import android.widget.ProgressBar
+import android.widget.TextView
+import androidx.annotation.UiThread
+import androidx.core.widget.NestedScrollView
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.activityViewModels
+import androidx.lifecycle.lifecycleScope
+import de.grobox.storagebackuptester.MainViewModel
+import de.grobox.storagebackuptester.R
+import kotlinx.coroutines.launch
+
+private const val EMAIL = "incoming+grote-storage-backup-tester-22079635-issue-@incoming.gitlab.com"
+
+open class MediaScanFragment : Fragment() {
+
+    companion object {
+        fun newInstance(name: String, uri: Uri) = MediaScanFragment().apply {
+            arguments = Bundle().apply {
+                putString("name", name)
+                putString("uri", uri.toString())
+            }
+        }
+    }
+
+    protected val viewModel: MainViewModel by activityViewModels()
+
+    private lateinit var scrollView: NestedScrollView
+    protected lateinit var logView: TextView
+    protected lateinit var progressBar: ProgressBar
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        setHasOptionsMenu(true)
+        requireActivity().title = arguments?.getString("name")
+        val v = inflater.inflate(R.layout.fragment_scan, container, false)
+        scrollView = v.findViewById(R.id.scrollView)
+        logView = v.findViewById(R.id.logView)
+        progressBar = v.findViewById(R.id.progressBar)
+        loadText()
+        return v
+    }
+
+    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
+        inflater.inflate(R.menu.fragment_scan, menu)
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        return when (item.itemId) {
+            R.id.refresh -> {
+                loadText()
+                true
+            }
+            R.id.share -> {
+                val sendIntent: Intent = Intent().apply {
+                    action = Intent.ACTION_SEND
+                    putExtra(Intent.EXTRA_EMAIL, arrayOf(EMAIL))
+                    putExtra(Intent.EXTRA_SUBJECT, arguments?.getString("name"))
+                    putExtra(Intent.EXTRA_TEXT, logView.text)
+                    type = "text/plain"
+                }
+                val shareIntent = Intent.createChooser(sendIntent, null)
+                startActivity(shareIntent)
+                true
+            }
+            else -> super.onOptionsItemSelected(item)
+        }
+    }
+
+    private fun loadText() {
+        progressBar.visibility = VISIBLE
+        lifecycleScope.launch {
+            logView.text = getText()
+            logView.postDelayed({
+                scrollView.fullScroll(FOCUS_DOWN)
+            }, 50)
+            progressBar.visibility = INVISIBLE
+        }
+    }
+
+    @UiThread
+    protected open suspend fun getText(): String {
+        Log.e("TEST", "loading text")
+        return viewModel.scanMediaUri(getUri())
+    }
+
+    protected fun getUri(): Uri {
+        return Uri.parse(arguments?.getString("uri"))
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/MediaScanner.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/MediaScanner.kt
new file mode 100644
index 00000000..88a5e9d0
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/scanner/MediaScanner.kt
@@ -0,0 +1,74 @@
+package de.grobox.storagebackuptester.scanner
+
+import android.annotation.SuppressLint
+import android.content.Context
+import android.net.Uri
+import android.text.format.Formatter
+import org.calyxos.backup.storage.api.BackupFile
+import org.calyxos.backup.storage.scanner.MediaScanner
+import java.text.SimpleDateFormat
+import java.util.Date
+import kotlin.time.ExperimentalTime
+import kotlin.time.TimedValue
+import kotlin.time.measureTimedValue
+
+data class ScanResult(
+    var itemsFound: Long,
+    var totalSize: Long
+) {
+    operator fun plusAssign(other: ScanResult) {
+        itemsFound += other.itemsFound
+        totalSize += other.totalSize
+    }
+}
+
+@OptIn(ExperimentalTime::class)
+fun scanUri(context: Context, mediaScanner: MediaScanner, uri: Uri): String {
+    val sb = StringBuilder()
+    val timedResult = measureTimedValue {
+        dump(context, mediaScanner.scanUri(uri), sb)
+    }
+    return appendStats(context, sb, timedResult)
+}
+
+@SuppressLint("SimpleDateFormat")
+private val dateFormat = SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
+
+fun dump(context: Context, mediaFiles: List<BackupFile>, sb: StringBuilder? = null): ScanResult {
+    var itemsFound = 0L
+    var totalSize = 0L
+    for (mediaFile in mediaFiles) {
+        itemsFound++
+        totalSize += mediaFile.size
+        val dateModified = mediaFile.lastModified?.let {
+            dateFormat.format(Date(it))
+        }
+        sb?.appendLine(mediaFile.path)
+        sb?.appendLine("  modified: $dateModified")
+        sb?.appendLine("  size: ${Formatter.formatShortFileSize(context, mediaFile.size)}")
+    }
+
+    if (sb?.isEmpty() == true) sb.appendLine("No files found")
+    return ScanResult(itemsFound, totalSize)
+}
+
+@OptIn(ExperimentalTime::class)
+fun appendStats(
+    context: Context,
+    sb: StringBuilder,
+    timedResult: TimedValue<ScanResult>,
+    title: String? = null
+): String {
+    val result = timedResult.value
+    if (title != null || sb.isNotEmpty()) {
+        sb.appendLine(title ?: "")
+        sb.appendLine("━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━")
+        sb.appendLine()
+    }
+    sb.appendLine("Scanning took ${timedResult.duration}")
+    sb.appendLine("Files found: ${result.itemsFound}")
+    sb.appendLine("Total size: ${Formatter.formatShortFileSize(context, result.totalSize)}")
+    val avgSize = if (result.itemsFound > 0) result.totalSize / result.itemsFound else 0
+    sb.appendLine("Average size: ${Formatter.formatShortFileSize(context, avgSize)}")
+    return sb.toString()
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/settings/InfoFragment.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/settings/InfoFragment.kt
new file mode 100644
index 00000000..272c1d0b
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/settings/InfoFragment.kt
@@ -0,0 +1,84 @@
+package de.grobox.storagebackuptester.settings
+
+import android.os.Build.VERSION.SDK_INT
+import android.os.Bundle
+import android.provider.DocumentsContract
+import android.provider.MediaStore
+import de.grobox.storagebackuptester.App
+import de.grobox.storagebackuptester.scanner.MediaScanFragment
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import org.calyxos.backup.storage.api.EXTERNAL_STORAGE_PROVIDER_AUTHORITY
+import org.calyxos.backup.storage.api.mediaUris
+import org.calyxos.backup.storage.scanner.DocumentScanner
+import org.calyxos.backup.storage.scanner.MediaScanner
+
+class InfoFragment : MediaScanFragment() {
+
+    companion object {
+        fun newInstance(name: String) = InfoFragment().apply {
+            arguments = Bundle().apply {
+                putString("name", name)
+            }
+        }
+    }
+
+    private val storageBackup by lazy { (requireActivity().application as App).storageBackup }
+    private val mediaScanner by lazy { MediaScanner(requireContext()) }
+    private val documentScanner by lazy { DocumentScanner(requireContext()) }
+
+    override suspend fun getText(): String {
+        val sb = StringBuilder()
+        val context = requireContext()
+
+        val volumeNames = MediaStore.getExternalVolumeNames(context)
+        sb.appendLine("Storage Volumes:")
+        for (volumeName in volumeNames) {
+            val version = try {
+                MediaStore.getVersion(context, volumeName)
+            } catch (e: IllegalArgumentException) {
+                e.toString()
+            }
+            val gen = if (SDK_INT >= 30) try {
+                MediaStore.getGeneration(context, volumeName)
+            } catch (e: IllegalArgumentException) {
+                e.toString()
+            } else null
+            sb.appendLine("  $volumeName")
+            sb.appendLine("    version: $version")
+            if (gen != null) {
+                sb.appendLine("    generation:  $gen")
+            }
+        }
+        sb.appendLine()
+        sb.appendLine("Media files smaller than 100 KB: ${mediaFilesSmallerThan(100 * 1024)}")
+        sb.appendLine("Media files smaller than 500 KB: ${mediaFilesSmallerThan(500 * 1024)}")
+        sb.appendLine("Media files smaller than 1 MB: ${mediaFilesSmallerThan(1024 * 1024)}")
+        sb.appendLine()
+        sb.appendLine("Storage files smaller than 100 KB: ${docFilesSmallerThan(100 * 1024)}")
+        sb.appendLine("Storage files smaller than 500 KB: ${docFilesSmallerThan(500 * 1024)}")
+        sb.appendLine("Storage files smaller than 1 MB: ${docFilesSmallerThan(1024 * 1024)}")
+        return sb.toString()
+    }
+
+    private suspend fun mediaFilesSmallerThan(size: Long): Int = withContext(Dispatchers.IO) {
+        var count = 0
+        mediaUris.forEach {
+            count += mediaScanner.scanUri(it, size).size
+        }
+        count
+    }
+
+    private suspend fun docFilesSmallerThan(size: Long): Int = withContext(Dispatchers.IO) {
+        var count = 0
+        storageBackup.uris.forEach { uri ->
+            if (uri.authority == EXTERNAL_STORAGE_PROVIDER_AUTHORITY) {
+                val documentId = DocumentsContract.getTreeDocumentId(uri)
+                val documentUri = DocumentsContract.buildDocumentUriUsingTree(uri, documentId)
+                count += documentScanner.scanUri(documentUri, size).size
+            }
+        }
+        count
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/settings/SettingsFragment.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/settings/SettingsFragment.kt
new file mode 100644
index 00000000..989b4c42
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/settings/SettingsFragment.kt
@@ -0,0 +1,152 @@
+package de.grobox.storagebackuptester.settings
+
+import android.content.Intent.FLAG_GRANT_READ_URI_PERMISSION
+import android.content.Intent.FLAG_GRANT_WRITE_URI_PERMISSION
+import android.net.Uri
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.Menu
+import android.view.MenuInflater
+import android.view.MenuItem
+import android.view.View
+import android.view.ViewGroup
+import android.widget.Toast
+import android.widget.Toast.LENGTH_SHORT
+import androidx.appcompat.app.AlertDialog
+import androidx.fragment.app.activityViewModels
+import de.grobox.storagebackuptester.MainViewModel
+import de.grobox.storagebackuptester.R
+import de.grobox.storagebackuptester.restore.DemoSnapshotFragment
+import de.grobox.storagebackuptester.scanner.DocumentScanFragment
+import de.grobox.storagebackuptester.scanner.MediaScanFragment
+import org.calyxos.backup.storage.api.MediaType
+import org.calyxos.backup.storage.ui.backup.BackupContentFragment
+import org.calyxos.backup.storage.ui.backup.BackupContentItem
+import org.calyxos.backup.storage.ui.backup.OpenTree
+
+class SettingsFragment : BackupContentFragment() {
+
+    companion object {
+        fun newInstance(): SettingsFragment = SettingsFragment()
+    }
+
+    override val viewModel: MainViewModel by activityViewModels()
+    private lateinit var backupLocationItem: MenuItem
+    private lateinit var jobItem: MenuItem
+    private lateinit var restoreItem: MenuItem
+
+    private val backupLocationRequest = registerForActivityResult(OpenTree()) { uri ->
+        onBackupUriReceived(uri)
+    }
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        setHasOptionsMenu(true)
+        requireActivity().title = "Settings"
+        return super.onCreateView(inflater, container, savedInstanceState)
+    }
+
+    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
+        inflater.inflate(R.menu.fragment_settings, menu)
+        backupLocationItem = menu.findItem(R.id.backup_location)
+        backupLocationItem.isChecked = viewModel.hasBackupLocation()
+        jobItem = menu.findItem(R.id.backup_job)
+        jobItem.isEnabled = backupLocationItem.isChecked
+        jobItem.isChecked = viewModel.areAutomaticBackupsEnabled()
+        restoreItem = menu.findItem(R.id.restore_backup)
+        restoreItem.isEnabled = backupLocationItem.isChecked
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        return when (item.itemId) {
+            R.id.info -> {
+                parentFragmentManager.beginTransaction()
+                    .replace(R.id.container, InfoFragment.newInstance("Media Info"))
+                    .addToBackStack("INFO")
+                    .commit()
+                true
+            }
+            R.id.backup_location -> {
+                if (item.isChecked) {
+                    viewModel.setBackupLocation(null)
+                    item.isChecked = false
+                    jobItem.isEnabled = false
+                    restoreItem.isEnabled = false
+                } else backupLocationRequest.launch(null)
+                true
+            }
+            R.id.backup_job -> {
+                if (item.isChecked) {
+                    viewModel.setAutomaticBackupsEnabled(false)
+                    item.isChecked = false
+                } else {
+                    viewModel.setAutomaticBackupsEnabled(true)
+                    item.isChecked = true
+                }
+                true
+            }
+            R.id.restore_backup -> {
+                onRestoreClicked()
+                true
+            }
+            R.id.clear_db -> {
+                viewModel.clearDb()
+                Toast.makeText(requireContext(), "Cache cleared", LENGTH_SHORT).show()
+                true
+            }
+            else -> super.onOptionsItemSelected(item)
+        }
+    }
+
+    override fun onContentClicked(view: View, item: BackupContentItem) {
+        val f = if (item.contentType is MediaType) {
+            MediaScanFragment.newInstance(item.getName(requireContext()), item.uri)
+        } else {
+            DocumentScanFragment.newInstance(item.getName(requireContext()), item.uri)
+        }
+        parentFragmentManager.beginTransaction()
+            .replace(R.id.container, f)
+            .addToBackStack("LOG")
+            .commit()
+    }
+
+    private fun onBackupUriReceived(uri: Uri?) {
+        if (uri == null) {
+            Toast.makeText(requireContext(), "No location set", LENGTH_SHORT).show()
+        } else {
+            requireContext().contentResolver.takePersistableUriPermission(
+                uri, FLAG_GRANT_READ_URI_PERMISSION or FLAG_GRANT_WRITE_URI_PERMISSION
+            )
+            viewModel.setBackupLocation(uri)
+            backupLocationItem.isChecked = true
+            jobItem.isEnabled = true
+            restoreItem.isEnabled = true
+        }
+    }
+
+    private fun onRestoreClicked() {
+        AlertDialog.Builder(requireContext())
+            .setIcon(android.R.drawable.stat_sys_warning)
+            .setTitle("Warning")
+            .setMessage("This will override data and should only be used on a clean phone. Not the one you just made the backup on.")
+            .setPositiveButton("I have been warned") { dialog, _ ->
+                onStartRestore()
+                dialog.dismiss()
+            }
+            .setNegativeButton(android.R.string.cancel) { dialog, _ ->
+                dialog.dismiss()
+            }
+            .show()
+    }
+
+    private fun onStartRestore() {
+        parentFragmentManager.beginTransaction()
+            .replace(R.id.container, DemoSnapshotFragment())
+            .addToBackStack("SNAPSHOTS")
+            .commit()
+    }
+
+}
diff --git a/storage/demo/src/main/java/de/grobox/storagebackuptester/settings/SettingsManager.kt b/storage/demo/src/main/java/de/grobox/storagebackuptester/settings/SettingsManager.kt
new file mode 100644
index 00000000..5f0fecfc
--- /dev/null
+++ b/storage/demo/src/main/java/de/grobox/storagebackuptester/settings/SettingsManager.kt
@@ -0,0 +1,37 @@
+package de.grobox.storagebackuptester.settings
+
+import android.content.Context
+import android.net.Uri
+
+private const val PREFS = "prefs"
+private const val PREF_BACKUP_LOCATION = "backupLocationUri"
+private const val PREF_AUTOMATIC_BACKUP = "automaticBackups"
+
+class SettingsManager(private val context: Context) {
+
+    fun setBackupLocation(uri: Uri?) {
+        context.getSharedPreferences(PREFS, 0)
+            .edit()
+            .putString(PREF_BACKUP_LOCATION, uri?.toString())
+            .apply()
+    }
+
+    fun getBackupLocation(): Uri? {
+        val uriStr = context.getSharedPreferences(PREFS, 0)
+            .getString(PREF_BACKUP_LOCATION, null)
+        return uriStr?.let { Uri.parse(it) }
+    }
+
+    fun setAutomaticBackupsEnabled(enabled: Boolean) {
+        context.getSharedPreferences(PREFS, 0)
+            .edit()
+            .putBoolean(PREF_AUTOMATIC_BACKUP, enabled)
+            .apply()
+    }
+
+    fun areAutomaticBackupsEnabled(): Boolean {
+        return context.getSharedPreferences(PREFS, 0)
+            .getBoolean(PREF_AUTOMATIC_BACKUP, false)
+    }
+
+}
diff --git a/storage/demo/src/main/res/drawable/ic_info.xml b/storage/demo/src/main/res/drawable/ic_info.xml
new file mode 100644
index 00000000..17255b7a
--- /dev/null
+++ b/storage/demo/src/main/res/drawable/ic_info.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?attr/colorControlNormal">
+  <path
+      android:fillColor="@android:color/white"
+      android:pathData="M12,2C6.48,2 2,6.48 2,12s4.48,10 10,10 10,-4.48 10,-10S17.52,2 12,2zM13,17h-2v-6h2v6zM13,9h-2L11,7h2v2z"/>
+</vector>
diff --git a/storage/demo/src/main/res/drawable/ic_launcher_background.xml b/storage/demo/src/main/res/drawable/ic_launcher_background.xml
new file mode 100644
index 00000000..a9e1f703
--- /dev/null
+++ b/storage/demo/src/main/res/drawable/ic_launcher_background.xml
@@ -0,0 +1,170 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path
+        android:fillColor="#303F9F"
+        android:pathData="M0,0h108v108h-108z" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M9,0L9,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,0L19,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M29,0L29,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M39,0L39,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M49,0L49,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M59,0L59,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M69,0L69,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M79,0L79,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M89,0L89,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M99,0L99,108"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,9L108,9"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,19L108,19"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,29L108,29"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,39L108,39"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,49L108,49"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,59L108,59"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,69L108,69"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,79L108,79"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,89L108,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M0,99L108,99"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,29L89,29"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,39L89,39"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,49L89,49"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,59L89,59"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,69L89,69"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M19,79L89,79"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M29,19L29,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M39,19L39,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M49,19L49,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M59,19L59,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M69,19L69,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+    <path
+        android:fillColor="#00000000"
+        android:pathData="M79,19L79,89"
+        android:strokeWidth="0.8"
+        android:strokeColor="#33FFFFFF" />
+</vector>
diff --git a/storage/demo/src/main/res/drawable/ic_launcher_foreground.xml b/storage/demo/src/main/res/drawable/ic_launcher_foreground.xml
new file mode 100644
index 00000000..1ac9aeb5
--- /dev/null
+++ b/storage/demo/src/main/res/drawable/ic_launcher_foreground.xml
@@ -0,0 +1,16 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:tint="#FFFFFF"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <group
+        android:scaleX="2.349"
+        android:scaleY="2.349"
+        android:translateX="25.812"
+        android:translateY="25.812">
+        <path
+            android:fillColor="@android:color/white"
+            android:pathData="M2,20h20v-4L2,16v4zM4,17h2v2L4,19v-2zM2,4v4h20L22,4L2,4zM6,7L4,7L4,5h2v2zM2,14h20v-4L2,10v4zM4,11h2v2L4,13v-2z" />
+    </group>
+</vector>
diff --git a/storage/demo/src/main/res/drawable/ic_refresh.xml b/storage/demo/src/main/res/drawable/ic_refresh.xml
new file mode 100644
index 00000000..0d768f68
--- /dev/null
+++ b/storage/demo/src/main/res/drawable/ic_refresh.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M17.65,6.35C16.2,4.9 14.21,4 12,4c-4.42,0 -7.99,3.58 -7.99,8s3.57,8 7.99,8c3.73,0 6.84,-2.55 7.73,-6h-2.08c-0.82,2.33 -3.04,4 -5.65,4 -3.31,0 -6,-2.69 -6,-6s2.69,-6 6,-6c1.66,0 3.14,0.69 4.22,1.78L13,11h7V4l-2.35,2.35z" />
+</vector>
diff --git a/storage/demo/src/main/res/drawable/ic_settings.xml b/storage/demo/src/main/res/drawable/ic_settings.xml
new file mode 100644
index 00000000..41a82ede
--- /dev/null
+++ b/storage/demo/src/main/res/drawable/ic_settings.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?attr/colorControlNormal">
+  <path
+      android:fillColor="@android:color/white"
+      android:pathData="M19.14,12.94c0.04,-0.3 0.06,-0.61 0.06,-0.94c0,-0.32 -0.02,-0.64 -0.07,-0.94l2.03,-1.58c0.18,-0.14 0.23,-0.41 0.12,-0.61l-1.92,-3.32c-0.12,-0.22 -0.37,-0.29 -0.59,-0.22l-2.39,0.96c-0.5,-0.38 -1.03,-0.7 -1.62,-0.94L14.4,2.81c-0.04,-0.24 -0.24,-0.41 -0.48,-0.41h-3.84c-0.24,0 -0.43,0.17 -0.47,0.41L9.25,5.35C8.66,5.59 8.12,5.92 7.63,6.29L5.24,5.33c-0.22,-0.08 -0.47,0 -0.59,0.22L2.74,8.87C2.62,9.08 2.66,9.34 2.86,9.48l2.03,1.58C4.84,11.36 4.8,11.69 4.8,12s0.02,0.64 0.07,0.94l-2.03,1.58c-0.18,0.14 -0.23,0.41 -0.12,0.61l1.92,3.32c0.12,0.22 0.37,0.29 0.59,0.22l2.39,-0.96c0.5,0.38 1.03,0.7 1.62,0.94l0.36,2.54c0.05,0.24 0.24,0.41 0.48,0.41h3.84c0.24,0 0.44,-0.17 0.47,-0.41l0.36,-2.54c0.59,-0.24 1.13,-0.56 1.62,-0.94l2.39,0.96c0.22,0.08 0.47,0 0.59,-0.22l1.92,-3.32c0.12,-0.22 0.07,-0.47 -0.12,-0.61L19.14,12.94zM12,15.6c-1.98,0 -3.6,-1.62 -3.6,-3.6s1.62,-3.6 3.6,-3.6s3.6,1.62 3.6,3.6S13.98,15.6 12,15.6z"/>
+</vector>
diff --git a/storage/demo/src/main/res/drawable/ic_share.xml b/storage/demo/src/main/res/drawable/ic_share.xml
new file mode 100644
index 00000000..59b0e84d
--- /dev/null
+++ b/storage/demo/src/main/res/drawable/ic_share.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M18,16.08c-0.76,0 -1.44,0.3 -1.96,0.77L8.91,12.7c0.05,-0.23 0.09,-0.46 0.09,-0.7s-0.04,-0.47 -0.09,-0.7l7.05,-4.11c0.54,0.5 1.25,0.81 2.04,0.81 1.66,0 3,-1.34 3,-3s-1.34,-3 -3,-3 -3,1.34 -3,3c0,0.24 0.04,0.47 0.09,0.7L8.04,9.81C7.5,9.31 6.79,9 6,9c-1.66,0 -3,1.34 -3,3s1.34,3 3,3c0.79,0 1.5,-0.31 2.04,-0.81l7.12,4.16c-0.05,0.21 -0.08,0.43 -0.08,0.65 0,1.61 1.31,2.92 2.92,2.92 1.61,0 2.92,-1.31 2.92,-2.92s-1.31,-2.92 -2.92,-2.92z" />
+</vector>
diff --git a/storage/demo/src/main/res/layout/activity_main.xml b/storage/demo/src/main/res/layout/activity_main.xml
new file mode 100644
index 00000000..1dfb73b5
--- /dev/null
+++ b/storage/demo/src/main/res/layout/activity_main.xml
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/container"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".MainActivity" />
\ No newline at end of file
diff --git a/storage/demo/src/main/res/layout/footer_snapshot.xml b/storage/demo/src/main/res/layout/footer_snapshot.xml
new file mode 100644
index 00000000..7f866ed2
--- /dev/null
+++ b/storage/demo/src/main/res/layout/footer_snapshot.xml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:padding="16dp">
+
+    <Button
+        android:id="@+id/button"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="Don't restore"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/storage/demo/src/main/res/layout/fragment_content.xml b/storage/demo/src/main/res/layout/fragment_content.xml
new file mode 100644
index 00000000..9ef41fc9
--- /dev/null
+++ b/storage/demo/src/main/res/layout/fragment_content.xml
@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/list"
+        android:name="de.grobox.storagebackuptester.MainFragment"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:layout_marginLeft="16dp"
+        android:layout_marginRight="16dp"
+        app:layoutManager="LinearLayoutManager"
+        tools:context=".settings.SettingsFragment"
+        tools:listitem="@layout/item_media" />
+
+    <com.google.android.material.floatingactionbutton.FloatingActionButton
+        android:id="@+id/fab"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="bottom|end"
+        android:layout_margin="16dp"
+        app:layout_behavior="com.google.android.material.behavior.HideBottomViewOnScrollBehavior"
+        android:contentDescription="Add"
+        android:src="@drawable/ic_add" />
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>
\ No newline at end of file
diff --git a/storage/demo/src/main/res/layout/fragment_log.xml b/storage/demo/src/main/res/layout/fragment_log.xml
new file mode 100644
index 00000000..25ac5f0e
--- /dev/null
+++ b/storage/demo/src/main/res/layout/fragment_log.xml
@@ -0,0 +1,53 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <ProgressBar
+        android:id="@+id/horizontalProgressBar"
+        style="?android:attr/progressBarStyleHorizontal"
+        android:layout_width="0dp"
+        android:layout_height="5dp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:max="10"
+        tools:progress="7" />
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/listView"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_margin="8dp"
+        android:focusable="true"
+        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
+        app:layout_constraintBottom_toTopOf="@+id/button"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/horizontalProgressBar"
+        tools:listitem="@layout/item_log" />
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:visibility="invisible"
+        app:layout_constraintBottom_toTopOf="@+id/button"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:visibility="visible" />
+
+    <Button
+        android:id="@+id/button"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="Run (Test) Backup Now"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/storage/demo/src/main/res/layout/fragment_scan.xml b/storage/demo/src/main/res/layout/fragment_scan.xml
new file mode 100644
index 00000000..9adcdc0a
--- /dev/null
+++ b/storage/demo/src/main/res/layout/fragment_scan.xml
@@ -0,0 +1,40 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <androidx.core.widget.NestedScrollView
+        android:id="@+id/scrollView"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:fadeScrollbars="false"
+        android:scrollbars="vertical"
+        app:layout_constraintTop_toTopOf="parent">
+
+        <TextView
+            android:id="@+id/logView"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_margin="8dp"
+            android:fontFamily="monospace"
+            android:lineSpacingExtra="8sp"
+            android:textIsSelectable="true"
+            android:textSize="12sp"
+            tools:text="@tools:sample/lorem/random" />
+
+    </androidx.core.widget.NestedScrollView>
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:visibility="visible" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/storage/demo/src/main/res/layout/item_log.xml b/storage/demo/src/main/res/layout/item_log.xml
new file mode 100644
index 00000000..c06fdcff
--- /dev/null
+++ b/storage/demo/src/main/res/layout/item_log.xml
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/logView"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:focusable="true"
+    android:fontFamily="monospace"
+    android:lineSpacingExtra="8sp"
+    android:textColor="@color/matrix"
+    android:textIsSelectable="true"
+    android:textSize="12sp"
+    tools:text="@tools:sample/lorem/random" />
diff --git a/storage/demo/src/main/res/menu/fragment_main.xml b/storage/demo/src/main/res/menu/fragment_main.xml
new file mode 100644
index 00000000..eb6a2ed5
--- /dev/null
+++ b/storage/demo/src/main/res/menu/fragment_main.xml
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/settings"
+        android:icon="@drawable/ic_settings"
+        android:title="Settings"
+        app:showAsAction="ifRoom" />
+
+    <item
+        android:id="@+id/share"
+        android:icon="@drawable/ic_share"
+        android:title="Share"
+        app:showAsAction="ifRoom" />
+
+</menu>
diff --git a/storage/demo/src/main/res/menu/fragment_scan.xml b/storage/demo/src/main/res/menu/fragment_scan.xml
new file mode 100644
index 00000000..babd3f12
--- /dev/null
+++ b/storage/demo/src/main/res/menu/fragment_scan.xml
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/refresh"
+        android:icon="@drawable/ic_refresh"
+        android:title="Refresh"
+        app:showAsAction="always"/>
+
+    <item
+        android:id="@+id/share"
+        android:icon="@drawable/ic_share"
+        android:title="Share"
+        app:showAsAction="always"/>
+
+</menu>
diff --git a/storage/demo/src/main/res/menu/fragment_settings.xml b/storage/demo/src/main/res/menu/fragment_settings.xml
new file mode 100644
index 00000000..80a671b9
--- /dev/null
+++ b/storage/demo/src/main/res/menu/fragment_settings.xml
@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/info"
+        android:icon="@drawable/ic_info"
+        android:title="Info"
+        app:showAsAction="ifRoom" />
+    <item
+        android:id="@+id/backup_location"
+        android:checkable="true"
+        android:title="Store backups"
+        app:showAsAction="never" />
+    <item
+        android:id="@+id/backup_job"
+        android:checkable="true"
+        android:enabled="false"
+        android:title="Automatic backups"
+        app:showAsAction="never" />
+    <item
+        android:id="@+id/restore_backup"
+        android:enabled="false"
+        android:title="Restore backup"
+        app:showAsAction="never" />
+    <item
+        android:id="@+id/clear_db"
+        android:title="Clear cache"
+        app:showAsAction="never" />
+
+</menu>
diff --git a/storage/demo/src/main/res/mipmap-anydpi-v26/ic_launcher.xml b/storage/demo/src/main/res/mipmap-anydpi-v26/ic_launcher.xml
new file mode 100644
index 00000000..6b78462d
--- /dev/null
+++ b/storage/demo/src/main/res/mipmap-anydpi-v26/ic_launcher.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>
diff --git a/storage/demo/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml b/storage/demo/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml
new file mode 100644
index 00000000..6b78462d
--- /dev/null
+++ b/storage/demo/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>
diff --git a/storage/demo/src/main/res/values-night/themes.xml b/storage/demo/src/main/res/values-night/themes.xml
new file mode 100644
index 00000000..52bc9c86
--- /dev/null
+++ b/storage/demo/src/main/res/values-night/themes.xml
@@ -0,0 +1,17 @@
+<resources xmlns:tools="http://schemas.android.com/tools">
+    <!-- Base application theme. -->
+    <style name="Theme.StorageBackupTester" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
+        <!-- Primary brand color. -->
+        <item name="colorPrimary">@color/matrix</item>
+        <item name="colorPrimaryVariant">@color/purple_700</item>
+        <item name="colorOnPrimary">@color/white</item>
+        <!-- Secondary brand color. -->
+        <item name="colorSecondary">@color/teal_200</item>
+        <item name="colorSecondaryVariant">@color/teal_200</item>
+        <item name="colorOnSecondary">@color/black</item>
+        <!-- Status bar color. -->
+        <item name="android:statusBarColor" tools:targetApi="l">?attr/colorPrimaryVariant</item>
+        <!-- Customize your theme here. -->
+        <item name="colorAccent">@color/matrix</item>
+    </style>
+</resources>
\ No newline at end of file
diff --git a/storage/demo/src/main/res/values/colors.xml b/storage/demo/src/main/res/values/colors.xml
new file mode 100644
index 00000000..cbb7d798
--- /dev/null
+++ b/storage/demo/src/main/res/values/colors.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="purple_200">#FFBB86FC</color>
+    <color name="purple_500">#FF6200EE</color>
+    <color name="purple_700">#FF3700B3</color>
+    <color name="teal_200">#FF03DAC5</color>
+    <color name="teal_700">#FF018786</color>
+    <color name="black">#151515</color>
+    <color name="white">#FAFAFA</color>
+    <color name="matrix">#689F38</color>
+</resources>
\ No newline at end of file
diff --git a/storage/demo/src/main/res/values/strings.xml b/storage/demo/src/main/res/values/strings.xml
new file mode 100644
index 00000000..0cf086d1
--- /dev/null
+++ b/storage/demo/src/main/res/values/strings.xml
@@ -0,0 +1,3 @@
+<resources>
+    <string name="app_name">Storage Backup Tester</string>
+</resources>
diff --git a/storage/demo/src/main/res/values/themes.xml b/storage/demo/src/main/res/values/themes.xml
new file mode 100644
index 00000000..d1bd3df3
--- /dev/null
+++ b/storage/demo/src/main/res/values/themes.xml
@@ -0,0 +1,13 @@
+<resources>
+    <style name="Theme.StorageBackupTester" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
+        <item name="colorPrimary">@color/matrix</item>
+        <item name="colorPrimaryVariant">@color/purple_700</item>
+        <item name="colorOnPrimary">@color/white</item>
+
+        <item name="colorSecondary">@color/teal_200</item>
+        <item name="colorSecondaryVariant">@color/teal_700</item>
+        <item name="colorOnSecondary">@color/black</item>
+
+        <item name="colorAccent">@color/matrix</item>
+    </style>
+</resources>
diff --git a/storage/doc/design.md b/storage/doc/design.md
new file mode 100644
index 00000000..f43c51f4
--- /dev/null
+++ b/storage/doc/design.md
@@ -0,0 +1,433 @@
+# Overview
+
+This is a design document for Seedvault storage backup.
+It is heavily inspired by borgbackup, but simplified and adapted to the Android context.
+
+The aim is to efficiently backup media files from Android's `MediaStore`
+and other files from external storage.
+Apps and their data are explicitly out of scope
+as this is handled already by Seedvault via the Android backup system.
+Techniques introduced here might be applied to app backups in the future.
+
+## Terminology
+
+A **backup snapshot** (or short backup) represents a collection of files at one point in time.
+Making a backup creates such a snapshot and writes it to **backup storage**
+which is an abstract location to save files to (e.g. flash drive or cloud storage).
+Technically the backup snapshot is a file containing metadata
+about the backup such as the included files.
+A **backup run** is the process of backing up files i.e. making a backup.
+
+Large files are split into **chunks** (smaller pieces) by a **chunker**.
+Small files are combined to **zip chunks**.
+
+File information is cached locally in the **files cache** to speed up operations.
+There is also the **chunks cache** to cache information about available chunks.
+
+# Operations
+
+## Making a backup
+
+A backup run is usually triggered automatically when
+
+* the device is charging and connected to an un-metered network in case network storage is used
+* a storage medium is plugged in (and the user confirmed the run) in case removable storage is used
+
+Files to be backed up are scanned based on the user's preference
+using Android's `MediaProvider` and `ExternalStorageProvider`.
+Tests on real world devices have shown ~200ms scan times for `MediaProvider`
+and `~10sec` for *all* of `ExternalStorageProvider`
+(which is unlikely to happen, because the entire storage volume cannot be selected on Android 11).
+
+All files included in backups will be scanned with every backup run.
+If a file is found in the cache, it is checked
+if its content-modification-indicating
+(size, lastModified and generation for media files)
+have not been modified
+and all its chunks are still present in the backup storage.
+For the latter check, we initially retrieve a list of all chunks available on backup storage.
+
+For present unchanged files, an entry will be added to the backup snapshot
+and the lastSeen timestamp in the files cache updated.
+If a file is not found in the cache, an entry will be added for it.
+New and modified files will be put through a chunker
+which splits up larger files into smaller chunks.
+Very small files are combined into larger zip chunks for transfer efficiency.
+
+A chunk is hashed (with a key / MACed),
+then (compressed and) encrypted (with authentication) and written to backup storage,
+if it is not already present.
+New chunks get added to the chunks cache.
+Only after the backup has completed and the backup snapshot was written,
+the reference counters of the included chunks will be incremented.
+
+When all chunks of a file have either been written or were present already,
+the file metadata is added to the backup snapshot with its list of chunk IDs and other metadata.
+
+When all files have been processed, the backup snapshot is finalized
+and written (encrypted) to storage.
+
+If the backup fails, a new run is attempted at the next opportunity creating a new backup snapshot.
+Chunks uploaded during the failed run should still be available in backup storage
+and in the cache with reference count `0`, providing a seamless auto-resume.
+
+After a *successful* backup run, chunks that still have reference count `0`
+can be deleted from storage and cache without risking to delete chunks that will be needed later.
+
+## Removing old backups
+
+Ideally, the user can decide how many backups should be kept based on available storage capacity.
+These could be a number in the yearly/monthly/weekly/daily categories.
+However, initially, we might simply auto-prune backups older than a month,
+if there have been at least 3 backups within that month (or some similar scheme).
+
+After a successful backup run is a good time to prune old backups.
+To determine which backups to delete, the backup snapshots need to be downloaded and inspected.
+Their file name can be derived from their `timeStart` timestamp to help with that task.
+If a backup is selected for deletion, the reference counter of all included chunks is decremented.
+Note that a backup snapshot can reference a single chunk several times.
+The reference counter however refers to the number of snapshots references it,
+not the number of files.
+The backup snapshot file and chunks with reference count of `0` are then deleted from storage.
+
+## Restoring from backup
+
+When the user wishes to restore a backup, they select the backup snapshot that should be used.
+The selection can be done based on time and name.
+We go through the list of files in the snapshot,
+download, authenticate, decrypt (and decompress) each chunk of the file
+and re-assemble the file this way.
+Once we have the original chunk,
+we could re-calculate the chunk ID to prevent an attacker from swapping chunks.
+However, we instead include the chunk ID
+in the associated data of the authenticated encryption (AEAD) which should have the same effect.
+The re-assembled file will be placed into the same directory under the same name
+with its attributes (e.g. lastModified) restored as much as possible on Android.
+
+Restoring to storage that is already in use is not supported.
+However, if a file already exists with the that name and path,
+we could check if the file is identical to the one we want to restore
+(by relying on file metadata or re-computing chunk IDs)
+and move to the next if it is indeed identical.
+If it is not identical, we rely on Android's Storage Access Framework
+to automatically give it a `(1)` suffix when writing it to disk or add one manually.
+Normally, restores are expected to happen to a clean file system anyway.
+
+However, if a restore fails, the above behavior (not implemented in first iteration)
+should give us a seamless auto-resume experience.
+The user can re-try the restore and it will quickly skip already restored files
+and continue to download the ones that are still missing.
+
+After all files have been written to a directory,
+we might want to attempt to restore its metadata (and flags?) as well.
+However, restoring directory metadata is not implemented in first iteration.
+
+
+# Cryptography
+
+The goal here is to be as simple as possible while still being secure
+meaning that we want to primarily conceal the content of the backed up files.
+Certain trade-offs have to be made though,
+so that for now we do not attempt to hide file sizes.
+E.g. an attacker with access to the backup storage might be able to infer
+that the Snowden files are part of our backup.
+We do however encrypt file names and paths.
+
+## Master Key
+
+Seedvault already uses [BIP39](https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki)
+to give users a mnemonic recovery code and for generating deterministic keys.
+The derived key has 512 bits
+and Seedvault uses the first 256 bits as an AES key to encrypt app data (out of scope here).
+Unfortunately, this key's usage is currently limited by Android to encryption and decryption.
+Therefore, the second 256 bits will be imported into Android's keystore for use with HMAC-SHA256,
+so that this key can act as a master key we can deterministically derive additional keys from
+by using HKDF ([RFC5869](https://tools.ietf.org/html/rfc5869)).
+These second 256 bits must not be used for any other purpose in the future.
+We use them for a master key to avoid users having to handle yet another secret.
+
+For deriving keys, we are only using the HKDF's second 'expand' step,
+because the Android Keystore does not give us access
+to the key's byte representation (required for first 'extract' step) after importing it.
+This should be fine as the input key material is already a cryptographically strong key
+(see section 3.3 of RFC 5869 above).
+
+## Choice of primitives
+
+AES-GCM and SHA256 have been chosen,
+because [both are hardware accelerated](https://en.wikichip.org/wiki/arm/armv8#ARMv8_Extensions_and_Processor_Features)
+on 64-bit ARMv8 CPUs that are used in modern phones.
+Our own tests against Java implementations of Blake2s, Blake3 and ChaCha20-Poly1305
+have confirmed that these indeed offer worse performance by a few factors.
+C implementations via JNI have not been evaluated though
+due to difficulties of building those as part of AOSP.
+
+## Chunk ID calculation
+
+We use a keyed hash instead of a normal hash for calculating the chunk ID
+to not leak the file content via the public hash.
+Using HMAC-SHA256 directly with the master key in Android's key store
+resulted in terrible throughput of around 4 MB/sec,
+presumably because file data needs to enter the secure element to get hashed there.
+Java implementations of Blake2s and Blake3 performed better,
+but by far the best performance gave HMAC-SHA256
+with a key we can hold the byte representation for in memory.
+
+Therefore, we derive a dedicated key for chunk ID calculation from the master key
+and keep it in memory for as long as we need it.
+If an attacker is able to read our memory,
+they have access to the entire device anyway
+and there's no point anymore in protecting content indicators such as chunk hashes.
+
+To derive the chunk ID calculation key, we use HKDF's expand step
+with the UTF-8 byte representation of "Chunk ID calculation" as info input.
+
+## Stream Encryption
+
+When a stream is written to backup storage,
+it starts with a header consisting of a single byte indicating the backup format version
+followed by the encrypted payload.
+
+Each chunk and backup snapshot written to backup storage will be encrypted with a fresh key
+to prevent issues with nonce/IV re-use of a single key.
+Similar to the chunk ID calculation key above, we derive a stream key from the master key
+by using HKDF's expand step with the UTF-8 byte representation of "stream key" as info input.
+This stream key is then used to derive a new key for each stream.
+
+Instead of encrypting, authenticating and segmenting a cleartext stream ourselves,
+we have chosen to employ the [tink library](https://github.com/google/tink) for that task.
+Since it does not allow us to work with imported or derived keys,
+we are only using its [AesGcmHkdfStreaming](https://google.github.io/tink/javadoc/tink-android/1.5.0/index.html?com/google/crypto/tink/subtle/AesGcmHkdfStreaming.html)
+to delegate encryption and decryption of byte streams.
+This follows the OAE2 definition as proposed in the paper
+"Online Authenticated-Encryption and its Nonce-Reuse Misuse-Resistance"
+([PDF](https://eprint.iacr.org/2015/189.pdf)).
+
+It adds its own 40 byte header consisting of header length (1 byte), salt and nonce prefix.
+Then it adds one or more segments, each up to 1 MB in size.
+All segments are encrypted with a fresh key that is derived by using HKDF
+on our stream key with another internal random salt (32 bytes) and associated data as info
+([documentation](https://github.com/google/tink/blob/v1.5.0/docs/WIRE-FORMAT.md#streaming-encryption)).
+
+When writing files/chunks to backup storage,
+the authenticated associated data (AAD) will contain the backup version as the first byte
+(to prevent downgrade attacks)
+followed by a second type byte depending on the type of file written:
+
+* chunks: `0x00` as type byte and then the byte representation of the chunk ID
+* backup snapshots: `0x01` as type byte and then the backup snapshot timestamp as int64 bytes
+
+The chunk ID and the backup snapshot timestamp get added
+to prevent an attacker from renaming and swapping files/chunks.
+
+# Data structures
+
+## Local caches
+
+### Files cache
+
+This cache is needed to quickly look up if a file has changed and if we have all of its chunks.
+It is implemented as a sqlite-based Room database
+which had shown promising performance in early tests.
+
+Contents:
+
+* URI (stripped by scheme and authority?) (`String` with index for fast lookups)
+* file size (`Long`)
+* last modified in milliseconds (`Long`)
+* generation modified (MediaStore only) (`Long`)
+* list of chunk IDs representing the file's contents
+* zip index in case this file is inside a single zip chunk (`Integer`)
+* last seen in epoch milliseconds (`Long`)
+
+If the file's size, last modified timestamp (and generation) is still the same,
+it is considered to not have changed.
+In that case, we check that all file content chunks are (still) present in storage.
+
+If the file has not changed and all chunks are present,
+the file is not read/chunked/hashed again.
+Only file metadata is added to the backup snapshot.
+
+If a file's URI should ever change, it will be considered as a new file,
+so read/chunked/hashed again, but if it hasn't otherwise changed,
+its chunks will not be written to storage again
+(except for small files that get added to a new zip chunk).
+
+As the cache grows over time, we need a way to evict files eventually
+(not implemented in first iteration).
+This can happen by checking the last seen timestamp
+and delete all files we haven't seen for some time (maybe a month).
+
+The files cache is local only and will not be included in the backup.
+After restoring from backup the cache needs to get repopulated on the next backup run.
+This will happen automatically, because before each backup run we check cache consistency
+and repopulate the cache if we find it inconsistent with what we have in backup storage.
+The URIs of the restored files will most likely differ from the backed up ones.
+When the `MediaStore` version changes,
+the chunk IDs of all files will need to get recalculated as well
+(not implemented in first iteration),
+because we can't be sure about their new state.
+
+### Chunks cache
+
+This is used to determine whether we already have a chunk,
+to count references to it and also for statistics.
+
+It is implemented as a table in the same database as the files cache.
+
+* chunk ID (hex representation of the chunk's MAC)
+* reference count
+* size
+* backup version byte (currently 0)
+
+If the reference count of a chunk reaches `0`,
+we can delete it from storage (after a successful backup run)
+as it isn't used by a backup snapshot anymore.
+
+References are only stored in this local chunks cache.
+If the cache is lost (or not available after restoring),
+it can be repopulated by inspecting all backup snapshots
+and setting the reference count to the number of backup snapshots a chunk is referenced from.
+
+When making a backup run and hit the files cache,
+we check that all chunks are still available on storage.
+
+The backup version number of a chunk is stored, so we can know without downloading the chunk
+with what backup version it was written.
+This might be useful when increasing the backup version and changing the chunk format in the future.
+
+## Remote Files
+
+All types of files written to backup storage have the following format:
+
+    ┏━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
+    ┃         ┃ tink payload (with 40 bytes header)                          ┃
+    ┃ version ┃ ┏━━━━━━━━━━━━━━━┳━━━━━━┳━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━┓ ┃
+    ┃  byte   ┃ ┃ header length ┃ salt ┃ nonce prefix ┃ encrypted segments ┃ ┃
+    ┃         ┃ ┗━━━━━━━━━━━━━━━┻━━━━━━┻━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━━┛ ┃
+    ┗━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
+
+### Backup Snapshot
+
+The backup snapshot contains metadata about a single backup
+and is written to the storage after a successful backup run.
+
+* version - the backup version
+* name - a name of the backup
+* media files - a list of all `MediaStore` files in this backup
+  * media type (enum: images, video, audio or downloads)
+  * name (string)
+  * relative path (string)
+  * last modified timestamp (long)
+  * owner package name (string)
+  * is favorite (boolean)
+  * file size (long)
+  * storage volume (string)
+  * ordered list of chunk IDs (to re-assemble the file)
+  * zip index (int)
+* document files - a list of all document files from external storage in this backup
+  * name (string)
+  * relative path (string)
+  * last modified timestamp (long)
+  * file size (long)
+  * storage volume (string)
+  * ordered list of chunk IDs (to re-assemble the file)
+  * zip index (int)
+* total size - sum of the size of all files, for stats
+* timeStart - when the backup run was started
+* timeEnd - when the backup run was finished
+
+All backup snapshots are stored in the root folder.
+The filename is the timeStart timestamp.
+
+### Chunks
+
+The encrypted payload of chunks is just the chunk data itself.
+We suggest that file-system based storage plugins store chunks in one of 256 sub-folders
+representing the first byte of the chunk ID encoded as a hex string.
+The file name is the chunk ID encoded as a (lower-case) hex string.
+This is similar to how git stores its repository objects
+and to avoid having to store all chunks in a single directory which might not scale.
+
+### Zip chunks
+
+Transferring many very small files causes a substantial overhead
+when transferring them to the storage medium.
+It would be nice to avoid that.
+Michael Rogers proposed the following idea to address this.
+
+A chunk can either be part of a large file, all of a medium-sized file,
+or a (deterministic) zip containing multiple small files.
+When creating a backup, we sort the files in the small category by last modification
+and pack as many files into each chunk as we can.
+Each small file will be stored in the zip chunk under some artificial name
+that is unique within the scope of the zip chunk like a counter.
+The path to unique name mapping will be stored in the backup snapshot (zip index).
+If a small file is inside a zip chunk,
+that chunk ID will be listed as the only chunk of the file in the backup snapshot
+and likewise for any other files inside that chunk.
+
+When creating the next backup, if none of the small files have changed,
+we just increase the ref count on the existing chunk.
+If some of them have changed, they will be added to a new zip chunk
+together with other new/changed small files.
+Hanging on to the old file inside the still referenced zip chunk longer than necessary
+should be ok as these files are small.
+
+When fetching a chunk for restore, we know in advance whether it is a zip chunk,
+because the file we need it for contains the zip index,
+so we will not confuse it with a medium-sized zip file.
+Then we unzip the zip chunk and extract the file by its zip index.
+
+# Out-of-Scope
+
+The following features would be nice to have,
+but are considered out-of-scope of the current design for time and budget reasons.
+
+* compression (we initially assume that most files are already sufficiently compressed)
+* using a rolling hash to produce chunks in order to increase likelihood of obtaining same chunks
+  even if file contents change slightly or shift
+* external secret-less corruption checks that would use checksums over encrypted data
+* concealing file sizes (though zip chunks helps a bit here)
+* implementing different storage plugins
+
+# Known issues
+
+## Changes to files can not be detected reliably
+
+Changes can be detected using file size and lastModified timestamps.
+These have only a precision of seconds,
+so we can't detect a changes happening within a second of a first change.
+Also other apps can reset the lastModified timestamp
+preventing us from registering a change if the file size doesn't change.
+On Android 11, media files have a generation counter that gets incremented when files changes
+to help with this issue.
+However, files on external storage still don't have anything similar
+and usually also don't trigger `ContentObserver` notifications.
+
+## Android's Storage Access Framework can be unreliable
+
+Since Seedvault already uses Android's Storage Access Framework (SAF) to store app backups,
+we re-use this storage that the user has already chosen.
+So we can avoid making the user choose two storage location
+and to avoid having to implement another storage backend in the first iteration.
+However, the SAF can be backed by different storage providers which are not equally reliable.
+Also, the API is very limited, doesn't allow for atomic operations
+and doesn't give feedback if file writes completed successfully as they happen asynchronously.
+The best solution will be to not (only) rely on this storage abstraction API,
+but at least offer different storage plugins that can operate more reliably.
+
+# Acknowledgements
+
+The following individuals have reviewed this document and provided helpful feedback.
+
+* Demi M. Obenour
+* Chirayu Desai
+* Kevin Niehage
+* Michael Rogers
+* Thomas Waldmann
+* Tom Hacohen
+
+As they have reviewed different parts and different versions at different times,
+this acknowledgement should not be mistaken for their endorsement of the current design
+or the final implementation.
diff --git a/storage/lib/.gitignore b/storage/lib/.gitignore
new file mode 100644
index 00000000..1f46c2d6
--- /dev/null
+++ b/storage/lib/.gitignore
@@ -0,0 +1,2 @@
+build/*
+!build/outputs/aar/lib-release.aar
diff --git a/storage/lib/Android.bp b/storage/lib/Android.bp
new file mode 100644
index 00000000..b5f86793
--- /dev/null
+++ b/storage/lib/Android.bp
@@ -0,0 +1,15 @@
+android_library_import {
+    name: "seedvault-lib-storage",
+    aars: ["libs/storage.aar"],
+    sdk_version: "current",
+    static_libs: [
+        "androidx-constraintlayout_constraintlayout",
+        "com.google.android.material_material",
+    ]
+}
+
+java_import {
+    name: "seedvault-lib-tink-android",
+    jars: ["libs/tink-android-1.5.0.jar"],
+    sdk_version: "current",
+}
diff --git a/storage/lib/build.gradle b/storage/lib/build.gradle
new file mode 100644
index 00000000..5702127f
--- /dev/null
+++ b/storage/lib/build.gradle
@@ -0,0 +1,95 @@
+plugins {
+    id 'com.android.library'
+    id 'com.google.protobuf'
+    id 'kotlin-android'
+    id 'kotlin-kapt'
+    id "org.jlleitschuh.gradle.ktlint" version "9.4.0"
+    id 'org.jetbrains.dokka' version '1.4.20'
+}
+
+android {
+    compileSdkVersion rootProject.ext.compileSdkVersion
+    buildToolsVersion rootProject.ext.buildToolsVersion
+
+    defaultConfig {
+        minSdkVersion rootProject.ext.minSdkVersion
+        targetSdkVersion rootProject.ext.targetSdkVersion
+        versionCode 1
+        versionName "0.1"
+
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+        testInstrumentationRunnerArguments disableAnalytics: 'true'
+
+        consumerProguardFiles "consumer-rules.pro"
+        javaCompileOptions {
+            annotationProcessorOptions {
+                arguments += ["room.schemaLocation": "$projectDir/schemas".toString()]
+            }
+        }
+    }
+
+    buildTypes {
+        all {
+            minifyEnabled true
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+    kotlinOptions {
+        jvmTarget = '1.8'
+        freeCompilerArgs += '-Xopt-in=kotlin.RequiresOptIn'
+        freeCompilerArgs += '-Xexplicit-api=strict'
+    }
+    protobuf {
+        protoc {
+            artifact = "com.google.protobuf:protoc:$protobuf_version"
+        }
+        generateProtoTasks {
+            all().each { task ->
+                task.builtins {
+                    java {
+                        option "lite"
+                    }
+                }
+            }
+        }
+    }
+}
+
+kotlin {
+    explicitApi = 'strict'
+}
+
+dependencies {
+    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
+
+    implementation rootProject.ext.std_libs.androidx_core
+    // A newer version gets pulled in with AOSP via core, so we include fragment here explicitly
+    implementation rootProject.ext.std_libs.androidx_fragment
+    implementation rootProject.ext.std_libs.androidx_lifecycle_viewmodel_ktx
+    implementation rootProject.ext.std_libs.androidx_lifecycle_livedata_ktx
+    implementation rootProject.ext.std_libs.androidx_constraintlayout
+    implementation rootProject.ext.std_libs.androidx_documentfile
+    implementation rootProject.ext.std_libs.com_google_android_material
+
+    implementation rootProject.ext.storage_libs.androidx_room_runtime
+    implementation rootProject.ext.storage_libs.com_google_protobuf_javalite
+    implementation rootProject.ext.storage_libs.com_google_crypto_tink_android
+    kapt('androidx.room:room-compiler') {
+        version { strictly "$room_version" }
+    }
+
+    lintChecks rootProject.ext.lint_libs.exceptions
+
+    testImplementation "junit:junit:$junit4_version"
+    testImplementation "io.mockk:mockk:$mockk_version"
+    testImplementation "org.jetbrains.kotlin:kotlin-test-junit:$kotlin_version"
+
+    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
+    androidTestImplementation "androidx.test.espresso:espresso-core:$espresso_version"
+}
+
+apply from: "${rootProject.rootDir}/gradle/ktlint.gradle"
diff --git a/storage/lib/build/outputs/aar/lib-release.aar b/storage/lib/build/outputs/aar/lib-release.aar
new file mode 100644
index 00000000..f364a6b4
Binary files /dev/null and b/storage/lib/build/outputs/aar/lib-release.aar differ
diff --git a/storage/lib/consumer-rules.pro b/storage/lib/consumer-rules.pro
new file mode 100644
index 00000000..e69de29b
diff --git a/storage/lib/libs/storage.aar b/storage/lib/libs/storage.aar
new file mode 120000
index 00000000..7af9e82b
--- /dev/null
+++ b/storage/lib/libs/storage.aar
@@ -0,0 +1 @@
+../build/outputs/aar/lib-release.aar
\ No newline at end of file
diff --git a/storage/lib/libs/tink-android-1.5.0.jar b/storage/lib/libs/tink-android-1.5.0.jar
new file mode 100644
index 00000000..626846e1
Binary files /dev/null and b/storage/lib/libs/tink-android-1.5.0.jar differ
diff --git a/storage/lib/proguard-rules.pro b/storage/lib/proguard-rules.pro
new file mode 100644
index 00000000..d5153406
--- /dev/null
+++ b/storage/lib/proguard-rules.pro
@@ -0,0 +1,23 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile
+
+-keep class org.calyxos.backup.storage.** {*;}
diff --git a/storage/lib/schemas/org.calyxos.backup.storage.db.Db/1.json b/storage/lib/schemas/org.calyxos.backup.storage.db.Db/1.json
new file mode 100644
index 00000000..695a8a9c
--- /dev/null
+++ b/storage/lib/schemas/org.calyxos.backup.storage.db.Db/1.json
@@ -0,0 +1,128 @@
+{
+  "formatVersion": 1,
+  "database": {
+    "version": 1,
+    "identityHash": "6286a22113131a780d1a28ba059d5a6d",
+    "entities": [
+      {
+        "tableName": "StoredUri",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`uri` TEXT NOT NULL, PRIMARY KEY(`uri`))",
+        "fields": [
+          {
+            "fieldPath": "uri",
+            "columnName": "uri",
+            "affinity": "TEXT",
+            "notNull": true
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "uri"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "CachedFile",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`uri` TEXT NOT NULL, `size` INTEGER NOT NULL, `last_modified` INTEGER, `generation_modified` INTEGER, `chunks` TEXT NOT NULL, `zip_index` INTEGER, `last_seen` INTEGER NOT NULL, PRIMARY KEY(`uri`))",
+        "fields": [
+          {
+            "fieldPath": "uri",
+            "columnName": "uri",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "size",
+            "columnName": "size",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "lastModified",
+            "columnName": "last_modified",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "generationModified",
+            "columnName": "generation_modified",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "chunks",
+            "columnName": "chunks",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "zipIndex",
+            "columnName": "zip_index",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "lastSeen",
+            "columnName": "last_seen",
+            "affinity": "INTEGER",
+            "notNull": true
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "uri"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "CachedChunk",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` TEXT NOT NULL, `ref_count` INTEGER NOT NULL, `size` INTEGER NOT NULL, `version` INTEGER NOT NULL, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "refCount",
+            "columnName": "ref_count",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "size",
+            "columnName": "size",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "version",
+            "columnName": "version",
+            "affinity": "INTEGER",
+            "notNull": true
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      }
+    ],
+    "views": [],
+    "setupQueries": [
+      "CREATE TABLE IF NOT EXISTS room_master_table (id INTEGER PRIMARY KEY,identity_hash TEXT)",
+      "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, '6286a22113131a780d1a28ba059d5a6d')"
+    ]
+  }
+}
\ No newline at end of file
diff --git a/storage/lib/src/androidTest/java/org/calyxos/backup/storage/db/ChunksCacheTest.kt b/storage/lib/src/androidTest/java/org/calyxos/backup/storage/db/ChunksCacheTest.kt
new file mode 100644
index 00000000..b8c05742
--- /dev/null
+++ b/storage/lib/src/androidTest/java/org/calyxos/backup/storage/db/ChunksCacheTest.kt
@@ -0,0 +1,125 @@
+package org.calyxos.backup.storage.db
+
+import android.content.Context
+import androidx.room.Room
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.After
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import kotlin.random.Random
+
+@RunWith(AndroidJUnit4::class)
+internal class ChunksCacheTest {
+
+    private lateinit var chunksCache: ChunksCache
+    private lateinit var db: Db
+
+    private val chunk1 = CachedChunk("id1", 1, Random.nextLong())
+    private val chunk2 = CachedChunk("id2", 2, Random.nextLong())
+    private val chunk3 = CachedChunk("id3", 3, Random.nextLong())
+
+    @Before
+    fun createDb() {
+        val context = ApplicationProvider.getApplicationContext<Context>()
+        db = Room.inMemoryDatabaseBuilder(context, Db::class.java).build()
+        chunksCache = db.getChunksCache()
+        chunksCache.insert(chunk1)
+        chunksCache.insert(chunk2)
+        chunksCache.insert(chunk3)
+    }
+
+    @After
+    fun closeDb() {
+        db.close()
+    }
+
+    @Test
+    fun testInsertAndGet() {
+        assertThat(chunksCache.get(chunk1.id), equalTo(chunk1))
+        assertThat(chunksCache.get(chunk2.id), equalTo(chunk2))
+        assertThat(chunksCache.get(chunk3.id), equalTo(chunk3))
+    }
+
+    @Test
+    fun testInsertAndDelete() {
+        chunksCache.deleteChunks(listOf(chunk1))
+        assertThat(chunksCache.get(chunk1.id), equalTo(null))
+        assertThat(chunksCache.get(chunk2.id), equalTo(chunk2))
+        assertThat(chunksCache.get(chunk3.id), equalTo(chunk3))
+
+        chunksCache.deleteChunks(listOf(chunk2, chunk3))
+        assertThat(chunksCache.get(chunk1.id), equalTo(null))
+        assertThat(chunksCache.get(chunk2.id), equalTo(null))
+        assertThat(chunksCache.get(chunk3.id), equalTo(null))
+
+        chunksCache.insert(chunk1)
+        chunksCache.deleteChunks(listOf(chunk1.copy(refCount = 1337)))
+        assertThat(chunksCache.get(chunk1.id), equalTo(null))
+    }
+
+    @Test
+    fun testRefCounts() {
+        assertThat(chunksCache.getUnreferencedChunks(), equalTo(emptyList()))
+
+        chunksCache.decrementRefCount(listOf(chunk1.id, chunk2.id))
+        chunksCache.decrementRefCount(listOf(chunk2.id))
+        assertThat(
+            chunksCache.getUnreferencedChunks(),
+            equalTo(listOf(chunk1.copy(refCount = 0), chunk2.copy(refCount = 0)))
+        )
+
+        chunksCache.decrementRefCount(listOf(chunk3.id))
+        chunksCache.decrementRefCount(listOf(chunk3.id))
+        chunksCache.decrementRefCount(listOf(chunk3.id))
+        assertThat(
+            chunksCache.getUnreferencedChunks(),
+            equalTo(
+                listOf(
+                    chunk1.copy(refCount = 0),
+                    chunk2.copy(refCount = 0),
+                    chunk3.copy(refCount = 0)
+                )
+            )
+        )
+
+        chunksCache.incrementRefCount(listOf(chunk1.id, chunk2.id))
+        assertThat(chunksCache.getUnreferencedChunks(), equalTo(listOf(chunk3.copy(refCount = 0))))
+    }
+
+    @Test
+    fun testAreAllAvailableChunksCached() {
+        assertTrue(chunksCache.areAllAvailableChunksCached(db, listOf()))
+        assertTrue(chunksCache.areAllAvailableChunksCached(db, listOf("id1")))
+        assertTrue(chunksCache.areAllAvailableChunksCached(db, listOf("id1", "id2")))
+        assertTrue(chunksCache.areAllAvailableChunksCached(db, listOf("id1", "id2", "id3")))
+        assertTrue(chunksCache.areAllAvailableChunksCached(db, listOf("id1", "id2", "id3")))
+        assertFalse(chunksCache.areAllAvailableChunksCached(db, listOf("id1", "id2", "id3", "id4")))
+        assertFalse(chunksCache.areAllAvailableChunksCached(db, listOf("foo", "bar")))
+    }
+
+    @Test
+    fun testClearAndRepopulate() {
+        val newChunks = listOf(
+            chunk1.copy(id = "newId1", refCount = 4),
+            chunk2.copy(id = "newId2", refCount = 6),
+            chunk3.copy(id = "newId3", refCount = 8)
+        )
+        chunksCache.clearAndRepopulate(db, newChunks)
+
+        assertNull(chunksCache.get("id1"))
+        assertNull(chunksCache.get("id2"))
+        assertNull(chunksCache.get("id3"))
+
+        assertThat(chunksCache.get("newId1"), equalTo(newChunks[0]))
+        assertThat(chunksCache.get("newId2"), equalTo(newChunks[1]))
+        assertThat(chunksCache.get("newId3"), equalTo(newChunks[2]))
+    }
+
+}
diff --git a/storage/lib/src/androidTest/java/org/calyxos/backup/storage/db/FilesCacheTest.kt b/storage/lib/src/androidTest/java/org/calyxos/backup/storage/db/FilesCacheTest.kt
new file mode 100644
index 00000000..75d90d62
--- /dev/null
+++ b/storage/lib/src/androidTest/java/org/calyxos/backup/storage/db/FilesCacheTest.kt
@@ -0,0 +1,60 @@
+package org.calyxos.backup.storage.db
+
+import android.content.Context
+import android.net.Uri
+import androidx.room.Room
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.After
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import kotlin.random.Random
+
+@RunWith(AndroidJUnit4::class)
+internal class FilesCacheTest {
+
+    private lateinit var filesCache: FilesCache
+    private lateinit var db: Db
+
+    @Before
+    fun createDb() {
+        val context = ApplicationProvider.getApplicationContext<Context>()
+        db = Room.inMemoryDatabaseBuilder(context, Db::class.java).build()
+        filesCache = db.getFilesCache()
+    }
+
+    @After
+    fun closeDb() {
+        db.close()
+    }
+
+    @Test
+    fun testWriteAndRead() {
+        val uri1 = Uri.parse("content://foo/bar")
+        val file1 = CachedFile(
+            uri = uri1,
+            size = Random.nextLong(),
+            lastModified = Random.nextLong(),
+            chunks = listOf("foo", "bar"),
+            lastSeen = Random.nextLong()
+        )
+        val uri2 = Uri.parse("content://media/external")
+        val file2 = CachedFile(
+            uri = uri2,
+            size = Random.nextLong(),
+            lastModified = Random.nextLong(),
+            chunks = listOf("23", "42"),
+            lastSeen = Random.nextLong()
+        )
+        filesCache.insert(file1)
+        filesCache.insert(file2)
+        assertThat(filesCache.getByUri(uri1), equalTo(file1))
+        assertThat(filesCache.getByUri(uri2), equalTo(file2))
+
+        assertThat(filesCache.getByUri(Uri.parse("doesntExist")), equalTo(null))
+    }
+
+}
diff --git a/storage/lib/src/androidTest/java/org/calyxos/backup/storage/db/UriStoreTest.kt b/storage/lib/src/androidTest/java/org/calyxos/backup/storage/db/UriStoreTest.kt
new file mode 100644
index 00000000..c63157eb
--- /dev/null
+++ b/storage/lib/src/androidTest/java/org/calyxos/backup/storage/db/UriStoreTest.kt
@@ -0,0 +1,60 @@
+package org.calyxos.backup.storage.db
+
+import android.content.Context
+import android.net.Uri
+import androidx.room.Room
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.calyxos.backup.storage.toStoredUri
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.After
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+internal class UriStoreTest {
+
+    private lateinit var uriStore: UriStore
+    private lateinit var db: Db
+
+    private val uri1 = Uri.parse("content://foo/bar/1").toStoredUri()
+    private val uri2 = Uri.parse("content://foo/bar/2").toStoredUri()
+    private val uri3 = Uri.parse("content://foo/bar/3").toStoredUri()
+
+    @Before
+    fun createDb() {
+        val context = ApplicationProvider.getApplicationContext<Context>()
+        db = Room.inMemoryDatabaseBuilder(context, Db::class.java).build()
+        uriStore = db.getUriStore()
+    }
+
+    @After
+    fun closeDb() {
+        db.close()
+    }
+
+    @Test
+    fun testInsertAndGet() {
+        uriStore.addStoredUri(uri1)
+        assertThat(uriStore.getStoredUris(), equalTo(listOf(uri1)))
+        uriStore.addStoredUri(uri2)
+        uriStore.addStoredUri(uri3)
+        assertThat(uriStore.getStoredUris(), equalTo(listOf(uri1, uri2, uri3)))
+    }
+
+    @Test
+    fun testInsertAndRemove() {
+        uriStore.addStoredUri(uri1)
+        assertThat(uriStore.getStoredUris(), equalTo(listOf(uri1)))
+        uriStore.removeStoredUri(uri1)
+        assertThat(uriStore.getStoredUris(), equalTo(emptyList()))
+        uriStore.addStoredUri(uri2)
+        uriStore.addStoredUri(uri3)
+        assertThat(uriStore.getStoredUris(), equalTo(listOf(uri2, uri3)))
+        uriStore.removeStoredUri(uri3)
+        assertThat(uriStore.getStoredUris(), equalTo(listOf(uri2)))
+    }
+
+}
diff --git a/storage/lib/src/main/AndroidManifest.xml b/storage/lib/src/main/AndroidManifest.xml
new file mode 100644
index 00000000..08d696be
--- /dev/null
+++ b/storage/lib/src/main/AndroidManifest.xml
@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    package="org.calyxos.backup.storage">
+
+    <uses-permission
+        android:name="android.permission.READ_EXTERNAL_STORAGE"
+        android:maxSdkVersion="29" />
+    <uses-permission
+        android:name="android.permission.WRITE_EXTERNAL_STORAGE"
+        android:maxSdkVersion="29" />
+
+    <uses-permission
+        android:name="android.permission.MANAGE_EXTERNAL_STORAGE"
+        tools:ignore="ScopedStorage" />
+
+    <!-- Needed to backup original media files e.g. without stripped EXIF metadata -->
+    <uses-permission android:name="android.permission.ACCESS_MEDIA_LOCATION" />
+
+    <!--
+    Needed to restore owning app of media files
+    http://aosp.opersys.com/xref/android-11.0.0_r17/xref/packages/providers/MediaProvider/src/com/android/providers/media/util/PermissionUtils.java#88
+    -->
+    <uses-permission
+        android:name="android.permission.BACKUP"
+        tools:ignore="ProtectedPermissions" />
+
+    <!-- Needed to schedule the periodic backup job -->
+    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
+
+    <!-- Needed to run a periodic backup service that doesn't get killed -->
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+
+</manifest>
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/ByteArrayUtils.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/ByteArrayUtils.kt
new file mode 100644
index 00000000..6a07eec1
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/ByteArrayUtils.kt
@@ -0,0 +1,5 @@
+package org.calyxos.backup.storage
+
+internal fun ByteArray.toHexString() = joinToString("") { "%02x".format(it) }
+
+internal fun String.toByteArrayFromHex() = chunked(2).map { it.toInt(16).toByte() }.toByteArray()
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/TimeUtils.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/TimeUtils.kt
new file mode 100644
index 00000000..ce39ec3c
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/TimeUtils.kt
@@ -0,0 +1,38 @@
+package org.calyxos.backup.storage
+
+import android.util.Log
+import kotlin.contracts.ExperimentalContracts
+import kotlin.contracts.InvocationKind
+import kotlin.contracts.contract
+import kotlin.time.Duration
+import kotlin.time.DurationUnit
+import kotlin.time.ExperimentalTime
+import kotlin.time.toDuration
+
+/**
+ * We don't use [kotlin.time.measureTime] or [kotlin.time.measureTimedValue],
+ * because those are not available in the Kotlin version shipped with Android 11.
+ * So when building with AOSP 11, things will blow up.
+ */
+
+@OptIn(ExperimentalContracts::class, ExperimentalTime::class)
+internal inline fun measure(block: () -> Unit): Duration {
+    contract {
+        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
+    }
+    val start = System.currentTimeMillis()
+    block()
+    return (System.currentTimeMillis() - start).toDuration(DurationUnit.MILLISECONDS)
+}
+
+@OptIn(ExperimentalContracts::class, ExperimentalTime::class)
+internal inline fun <T> measure(text: String, block: () -> T): T {
+    contract {
+        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
+    }
+    val start = System.currentTimeMillis()
+    val result = block()
+    val duration = (System.currentTimeMillis() - start).toDuration(DurationUnit.MILLISECONDS)
+    Log.e("Time", "$text took $duration")
+    return result
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/UriUtils.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/UriUtils.kt
new file mode 100644
index 00000000..a3aa96da
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/UriUtils.kt
@@ -0,0 +1,57 @@
+package org.calyxos.backup.storage
+
+import android.content.ContentResolver
+import android.net.Uri
+import android.provider.MediaStore
+import org.calyxos.backup.storage.api.MediaType
+import org.calyxos.backup.storage.api.mediaItems
+import org.calyxos.backup.storage.backup.BackupMediaFile
+import org.calyxos.backup.storage.db.StoredUri
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+
+internal fun Uri.toStoredUri(): StoredUri = StoredUri(this)
+
+internal fun Uri.getDocumentPath(): String? {
+    return lastPathSegment?.split(':')?.getOrNull(1)
+}
+
+internal fun Uri.getVolume(): String? {
+    val volume = lastPathSegment?.split(':')?.getOrNull(0)
+    return if (volume == "primary") MediaStore.VOLUME_EXTERNAL_PRIMARY else volume
+}
+
+@Throws(IOException::class)
+public fun Uri.openInputStream(contentResolver: ContentResolver): InputStream {
+    return try {
+        contentResolver.openInputStream(this)
+    } catch (e: IllegalArgumentException) {
+        // This is necessary, because contrary to the documentation, files that have been deleted
+        // after we retrieved their Uri, will throw an IllegalArgumentException
+        throw IOException(e)
+    } ?: throw IOException("Stream for $this returned null")
+}
+
+@Throws(IOException::class)
+public fun Uri.openOutputStream(contentResolver: ContentResolver): OutputStream {
+    return try {
+        contentResolver.openOutputStream(this, "wt")
+    } catch (e: IllegalArgumentException) {
+        // This is necessary, because contrary to the documentation, files that have been deleted
+        // after we retrieved their Uri, will throw an IllegalArgumentException
+        throw IOException(e)
+    } ?: throw IOException("Stream for $this returned null")
+}
+
+internal fun Uri.getMediaType(): MediaType? {
+    val str = toString()
+    for (item in mediaItems) {
+        if (str.startsWith(item.contentUri.toString())) return item
+    }
+    return null
+}
+
+internal fun Uri.getBackupMediaType(): BackupMediaFile.MediaType? {
+    return getMediaType()?.backupType
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/api/BackupContentType.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/api/BackupContentType.kt
new file mode 100644
index 00000000..15decb6a
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/api/BackupContentType.kt
@@ -0,0 +1,86 @@
+package org.calyxos.backup.storage.api
+
+import android.net.Uri
+import android.provider.MediaStore
+import androidx.annotation.DrawableRes
+import androidx.annotation.StringRes
+import org.calyxos.backup.storage.R
+import org.calyxos.backup.storage.backup.BackupMediaFile
+import org.calyxos.backup.storage.getDocumentPath
+
+// hidden in DocumentsContract
+public const val EXTERNAL_STORAGE_PROVIDER_AUTHORITY: String =
+    "com.android.externalstorage.documents"
+
+public val mediaItems: List<MediaType> = listOf(
+    MediaType.Images,
+    MediaType.Video,
+    MediaType.Audio,
+    MediaType.Downloads
+)
+
+public val mediaUris: List<Uri> = listOf(
+    MediaType.Images.contentUri,
+    MediaType.Video.contentUri,
+    MediaType.Audio.contentUri,
+    MediaType.Downloads.contentUri
+)
+
+public sealed class BackupContentType(
+    @DrawableRes
+    public val drawableRes: Int
+) {
+    public object Custom : BackupContentType(R.drawable.ic_folder) {
+        public fun getName(uri: Uri): String {
+            val path = uri.getDocumentPath()!!
+            return if (path.isBlank()) "/" else path
+        }
+    }
+}
+
+public sealed class MediaType(
+    public val contentUri: Uri,
+    @StringRes
+    public val nameRes: Int,
+    @DrawableRes
+    drawableRes: Int,
+    public val backupType: BackupMediaFile.MediaType,
+) : BackupContentType(drawableRes) {
+    public object Images : MediaType(
+        contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
+        nameRes = R.string.content_images,
+        drawableRes = R.drawable.ic_photo_library,
+        backupType = BackupMediaFile.MediaType.IMAGES,
+    )
+
+    public object Video : MediaType(
+        contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI,
+        nameRes = R.string.content_videos,
+        drawableRes = R.drawable.ic_video_library,
+        backupType = BackupMediaFile.MediaType.VIDEO,
+    )
+
+    public object Audio : MediaType(
+        contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
+        nameRes = R.string.content_audio,
+        drawableRes = R.drawable.ic_music_library,
+        backupType = BackupMediaFile.MediaType.AUDIO,
+    )
+
+    public object Downloads : MediaType(
+        contentUri = MediaStore.Downloads.EXTERNAL_CONTENT_URI,
+        nameRes = R.string.content_downloads,
+        drawableRes = R.drawable.ic_download_library,
+        backupType = BackupMediaFile.MediaType.DOWNLOADS,
+    )
+
+    internal companion object {
+        fun fromBackupMediaType(type: BackupMediaFile.MediaType): MediaType = when (type) {
+            BackupMediaFile.MediaType.IMAGES -> Images
+            BackupMediaFile.MediaType.VIDEO -> Video
+            BackupMediaFile.MediaType.AUDIO -> Audio
+            BackupMediaFile.MediaType.DOWNLOADS -> Downloads
+            else -> throw AssertionError("Unrecognized media type: $type")
+        }
+    }
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/api/BackupFile.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/api/BackupFile.kt
new file mode 100644
index 00000000..e22227ff
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/api/BackupFile.kt
@@ -0,0 +1,14 @@
+package org.calyxos.backup.storage.api
+
+import android.provider.MediaStore
+
+public interface BackupFile {
+    public val path: String
+
+    /**
+     * empty string for [MediaStore.VOLUME_EXTERNAL_PRIMARY]
+     */
+    public val volume: String
+    public val size: Long
+    public val lastModified: Long?
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/api/BackupObserver.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/api/BackupObserver.kt
new file mode 100644
index 00000000..35e7ab6a
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/api/BackupObserver.kt
@@ -0,0 +1,54 @@
+package org.calyxos.backup.storage.api
+
+public interface BackupObserver {
+
+    public suspend fun onStartScanning()
+
+    /**
+     * Called after scanning files when starting the backup.
+     *
+     * @param totalSize the total size of all files to be backed up.
+     * @param numFiles the number of all files to be backed up.
+     * The sum of [numSmallFiles] and [numLargeFiles].
+     * @param numSmallFiles the number of small files to be backed up.
+     * @param numLargeFiles the number of large files to be backed up.
+     */
+    public suspend fun onBackupStart(
+        totalSize: Long,
+        numFiles: Int,
+        numSmallFiles: Int,
+        numLargeFiles: Int,
+    )
+
+    public suspend fun onFileBackedUp(
+        file: BackupFile,
+        wasUploaded: Boolean,
+        reusedChunks: Int,
+        bytesWritten: Long,
+        tag: String,
+    )
+
+    public suspend fun onFileBackupError(
+        file: BackupFile,
+        tag: String,
+    )
+
+    /**
+     * If backupDuration is null, the overall backup failed.
+     */
+    public suspend fun onBackupComplete(backupDuration: Long?)
+
+    public suspend fun onPruneStartScanning()
+
+    public suspend fun onPruneStart(snapshotsToDelete: List<Long>)
+
+    public suspend fun onPruneSnapshot(snapshot: Long, numChunksToDelete: Int, size: Long)
+
+    /**
+     * If snapshot is null, the overall operation failed.
+     */
+    public suspend fun onPruneError(snapshot: Long?, e: Exception)
+
+    public suspend fun onPruneComplete(pruneDuration: Long)
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/api/RestoreObserver.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/api/RestoreObserver.kt
new file mode 100644
index 00000000..bad6e0b6
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/api/RestoreObserver.kt
@@ -0,0 +1,15 @@
+package org.calyxos.backup.storage.api
+
+public interface RestoreObserver {
+    public fun onRestoreStart(numFiles: Int, totalSize: Long)
+    public fun onFileRestored(file: BackupFile, bytesWritten: Long, tag: String)
+
+    /**
+     * Called when a file failed to restore.
+     * You might want to inform the user about this.
+     * The exception already gets logged.
+     */
+    public fun onFileRestoreError(file: BackupFile, e: Exception)
+
+    public fun onRestoreComplete(restoreDuration: Long)
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/api/Snapshot.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/api/Snapshot.kt
new file mode 100644
index 00000000..4e936664
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/api/Snapshot.kt
@@ -0,0 +1,51 @@
+package org.calyxos.backup.storage.api
+
+import org.calyxos.backup.storage.backup.BackupSnapshot
+
+public data class SnapshotItem(
+    public val storedSnapshot: StoredSnapshot,
+    public val snapshot: BackupSnapshot?,
+) {
+    val time: Long get() = storedSnapshot.timestamp
+}
+
+public sealed class SnapshotResult {
+    public data class Success(val snapshots: List<SnapshotItem>) : SnapshotResult()
+    public data class Error(val e: Exception) : SnapshotResult()
+}
+
+public data class StoredSnapshot(
+    /**
+     * The unique ID of the current device/user combination chosen by the [StoragePlugin].
+     */
+    public val userId: String,
+    /**
+     * The timestamp identifying a snapshot of the [userId].
+     */
+    public val timestamp: Long,
+)
+
+/**
+ * Defines which backup snapshots should be retained when pruning backups.
+ *
+ * If more than one snapshot exists in a given time frame,
+ * only the latest one will be kept.
+ */
+public data class SnapshotRetention(
+    /**
+     * Keep this many days worth of snapshots when pruning backups.
+     */
+    public val daily: Int,
+    /**
+     * Keep this many weeks worth of snapshots when pruning backups.
+     */
+    public val weekly: Int,
+    /**
+     * Keep this many months worth of snapshots when pruning backups.
+     */
+    public val monthly: Int,
+    /**
+     * Keep this many years worth of snapshots when pruning backups.
+     */
+    public val yearly: Int,
+)
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/api/StorageBackup.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/api/StorageBackup.kt
new file mode 100644
index 00000000..1bb556a6
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/api/StorageBackup.kt
@@ -0,0 +1,207 @@
+package org.calyxos.backup.storage.api
+
+import android.content.Context
+import android.net.Uri
+import android.provider.DocumentsContract.isTreeUri
+import android.provider.MediaStore
+import android.util.Log
+import androidx.annotation.WorkerThread
+import androidx.room.Room
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.withContext
+import org.calyxos.backup.storage.backup.Backup
+import org.calyxos.backup.storage.backup.BackupSnapshot
+import org.calyxos.backup.storage.backup.ChunksCacheRepopulater
+import org.calyxos.backup.storage.db.Db
+import org.calyxos.backup.storage.getDocumentPath
+import org.calyxos.backup.storage.getMediaType
+import org.calyxos.backup.storage.plugin.SnapshotRetriever
+import org.calyxos.backup.storage.prune.Pruner
+import org.calyxos.backup.storage.prune.RetentionManager
+import org.calyxos.backup.storage.restore.FileRestore
+import org.calyxos.backup.storage.restore.Restore
+import org.calyxos.backup.storage.scanner.DocumentScanner
+import org.calyxos.backup.storage.scanner.FileScanner
+import org.calyxos.backup.storage.scanner.MediaScanner
+import org.calyxos.backup.storage.toStoredUri
+import java.io.IOException
+import java.util.concurrent.atomic.AtomicBoolean
+
+private const val TAG = "StorageBackup"
+
+@Suppress("BlockingMethodInNonBlockingContext")
+public class StorageBackup(
+    private val context: Context,
+    private val plugin: StoragePlugin,
+    private val dispatcher: CoroutineDispatcher = Dispatchers.IO,
+) {
+
+    private val db: Db by lazy {
+        Room.databaseBuilder(context, Db::class.java, "seedvault-storage-local-cache")
+            .build()
+    }
+    private val uriStore by lazy { db.getUriStore() }
+
+    private val mediaScanner by lazy { MediaScanner(context) }
+    private val snapshotRetriever = SnapshotRetriever(plugin)
+    private val chunksCacheRepopulater = ChunksCacheRepopulater(db, plugin, snapshotRetriever)
+    private val backup by lazy {
+        val documentScanner = DocumentScanner(context)
+        val fileScanner = FileScanner(uriStore, mediaScanner, documentScanner)
+        Backup(context, db, fileScanner, plugin, chunksCacheRepopulater)
+    }
+    private val restore by lazy {
+        Restore(context, plugin, snapshotRetriever, FileRestore(context, mediaScanner))
+    }
+    private val retention = RetentionManager(context)
+    private val pruner by lazy { Pruner(db, retention, plugin, snapshotRetriever) }
+
+    private val backupRunning = AtomicBoolean(false)
+    private val restoreRunning = AtomicBoolean(false)
+
+    public val uris: Set<Uri>
+        @WorkerThread
+        get() {
+            return uriStore.getStoredUris().map { it.uri }.toSet()
+        }
+
+    @Throws(IllegalArgumentException::class)
+    public suspend fun addUri(uri: Uri): Unit = withContext(dispatcher) {
+        if (uri.authority == MediaStore.AUTHORITY) {
+            if (uri !in mediaUris) throw IllegalArgumentException("Not a supported MediaStore URI")
+        } else if (uri.authority == EXTERNAL_STORAGE_PROVIDER_AUTHORITY) {
+            if (!isTreeUri(uri)) throw IllegalArgumentException("Not a tree URI")
+        } else {
+            throw IllegalArgumentException()
+        }
+        Log.e(TAG, "Adding URI $uri")
+        uriStore.addStoredUri(uri.toStoredUri())
+    }
+
+    public suspend fun removeUri(uri: Uri): Unit = withContext(dispatcher) {
+        Log.e(TAG, "Removing URI $uri")
+        uriStore.removeStoredUri(uri.toStoredUri())
+    }
+
+    public suspend fun getUriSummaryString(): String = withContext(dispatcher) {
+        val uris = uris.sortedDescending()
+        val list = ArrayList<String>()
+        for (uri in uris) {
+            val nameRes = uri.getMediaType()?.nameRes
+            if (nameRes == null) {
+                uri.getDocumentPath()?.let { list.add(it) }
+            } else {
+                list.add(context.getString(nameRes))
+            }
+        }
+        list.joinToString(", ", limit = 5)
+    }
+
+    /**
+     * Run this on a new storage location to ensure that there are no old snapshots
+     * (potentially encrypted with an old key) laying around.
+     * Using a storage location with existing data is not supported.
+     * Using the same root folder for storage on different devices or user profiles is fine though
+     * as the [StoragePlugin] should isolate storage per [StoredSnapshot.userId].
+     */
+    public suspend fun deleteAllSnapshots(): Unit = withContext(dispatcher) {
+        try {
+            plugin.getCurrentBackupSnapshots().forEach {
+                try {
+                    plugin.deleteBackupSnapshot(it)
+                } catch (e: IOException) {
+                    Log.e(TAG, "Error deleting snapshot $it", e)
+                }
+            }
+        } catch (e: IOException) {
+            Log.e(TAG, "Error deleting all snapshots", e)
+        }
+    }
+
+    /**
+     * It is advised to clear existing cache when selecting a new storage location.
+     */
+    public suspend fun clearCache(): Unit = withContext(dispatcher) {
+        db.getChunksCache().clear()
+        db.getFilesCache().clear()
+    }
+
+    public suspend fun runBackup(backupObserver: BackupObserver?): Boolean =
+        withContext(dispatcher) {
+            if (backupRunning.getAndSet(true)) {
+                Log.w(TAG, "Backup already running, not starting a new one")
+                return@withContext false
+            }
+            try {
+                backup.runBackup(backupObserver)
+                true
+            } catch (e: Exception) {
+                Log.e(TAG, "Error during backup", e)
+                false
+            } finally {
+                backupRunning.set(false)
+            }
+        }
+
+    /**
+     * Sets how many backup snapshots to keep in storage when running [pruneOldBackups].
+     *
+     * @throws IllegalArgumentException if all retention values are set to 0.
+     */
+    public fun setSnapshotRetention(snapshotRetention: SnapshotRetention) {
+        retention.setSnapshotRetention(snapshotRetention)
+    }
+
+    /**
+     * Gets the current snapshot retention policy.
+     */
+    @WorkerThread
+    public fun getSnapshotRetention(): SnapshotRetention = retention.getSnapshotRetention()
+
+    /**
+     * Prunes old backup snapshots according to the parameters set via [setSnapshotRetention].
+     * This will delete backed up data. Use with care!
+     *
+     * Run this only after [runBackup] returns true to ensure
+     * that no chunks from partial backups get removed and need to be re-uploaded.
+     */
+    public suspend fun pruneOldBackups(backupObserver: BackupObserver?): Boolean =
+        withContext(dispatcher) {
+            backupObserver?.onPruneStartScanning()
+            try {
+                pruner.prune(backupObserver)
+                true
+            } catch (e: Exception) {
+                Log.e(TAG, "Error during pruning backups", e)
+                backupObserver?.onPruneError(null, e)
+                false
+            }
+        }
+
+    public fun getBackupSnapshots(): Flow<SnapshotResult> {
+        return restore.getBackupSnapshots()
+    }
+
+    public suspend fun restoreBackupSnapshot(
+        storedSnapshot: StoredSnapshot,
+        snapshot: BackupSnapshot? = null,
+        restoreObserver: RestoreObserver? = null,
+    ): Boolean = withContext(dispatcher) {
+        if (restoreRunning.getAndSet(true)) {
+            Log.w(TAG, "Restore already running, not starting a new one")
+            return@withContext false
+        }
+        try {
+            restore.restoreBackupSnapshot(storedSnapshot, snapshot, restoreObserver)
+            true
+        } catch (e: Exception) {
+            Log.e(TAG, "Error during restore", e)
+            false
+        } finally {
+            restoreRunning.set(false)
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/api/StoragePlugin.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/api/StoragePlugin.kt
new file mode 100644
index 00000000..aa1be4d6
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/api/StoragePlugin.kt
@@ -0,0 +1,71 @@
+package org.calyxos.backup.storage.api
+
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+import java.security.KeyStore
+import javax.crypto.SecretKey
+
+public interface StoragePlugin {
+
+    /**
+     * Called before starting a backup run to ensure that all cached chunks are still available.
+     * Plugins should use this opportunity
+     * to ensure they are ready to store a large number of chunks.
+     */
+    @Throws(IOException::class)
+    public suspend fun getAvailableChunkIds(): List<String>
+
+    /**
+     * Returns a [SecretKey] for HmacSHA256, ideally stored in the [KeyStore].
+     */
+    public fun getMasterKey(): SecretKey
+
+    /**
+     * Returns true if the key for [getMasterKey] exists, false otherwise.
+     */
+    public fun hasMasterKey(): Boolean
+
+    @Throws(IOException::class)
+    public fun getChunkOutputStream(chunkId: String): OutputStream
+
+    @Throws(IOException::class)
+    public fun getBackupSnapshotOutputStream(timestamp: Long): OutputStream
+
+    /* Restore */
+
+    /**
+     * Returns *all* [StoredSnapshot]s that are available on storage
+     * independent of user ID and whether they can be decrypted
+     * with the key returned by [getMasterKey].
+     */
+    @Throws(IOException::class)
+    public suspend fun getBackupSnapshotsForRestore(): List<StoredSnapshot>
+
+    @Throws(IOException::class)
+    public suspend fun getBackupSnapshotInputStream(storedSnapshot: StoredSnapshot): InputStream
+
+    @Throws(IOException::class)
+    public suspend fun getChunkInputStream(snapshot: StoredSnapshot, chunkId: String): InputStream
+
+    /* Pruning */
+
+    /**
+     * Returns [StoredSnapshot]s for the currently active user ID.
+     */
+    @Throws(IOException::class)
+    public suspend fun getCurrentBackupSnapshots(): List<StoredSnapshot>
+
+    /**
+     * Deletes the given [StoredSnapshot].
+     */
+    @Throws(IOException::class)
+    public suspend fun deleteBackupSnapshot(storedSnapshot: StoredSnapshot)
+
+    /**
+     * Deletes the given chunks of the *current* user ID only.
+     */
+    @Throws(IOException::class)
+    public suspend fun deleteChunks(chunkIds: List<String>)
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/backup/Backup.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/Backup.kt
new file mode 100644
index 00000000..50ccbb70
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/Backup.kt
@@ -0,0 +1,180 @@
+package org.calyxos.backup.storage.backup
+
+import android.Manifest.permission.ACCESS_MEDIA_LOCATION
+import android.content.Context
+import android.content.pm.PackageManager.PERMISSION_GRANTED
+import android.os.Build
+import android.text.format.Formatter
+import android.util.Log
+import org.calyxos.backup.storage.api.BackupObserver
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.crypto.ChunkCrypto
+import org.calyxos.backup.storage.crypto.StreamCrypto
+import org.calyxos.backup.storage.db.Db
+import org.calyxos.backup.storage.measure
+import org.calyxos.backup.storage.scanner.FileScanner
+import org.calyxos.backup.storage.scanner.FileScannerResult
+import java.io.IOException
+import java.security.GeneralSecurityException
+import kotlin.time.Duration
+import kotlin.time.ExperimentalTime
+
+internal class BackupResult(
+    val chunkIds: Set<String>,
+    val backupMediaFiles: List<BackupMediaFile>,
+    val backupDocumentFiles: List<BackupDocumentFile>,
+) {
+    operator fun plus(other: BackupResult) = BackupResult(
+        chunkIds = chunkIds + other.chunkIds,
+        backupMediaFiles = backupMediaFiles + other.backupMediaFiles,
+        backupDocumentFiles = backupDocumentFiles + other.backupDocumentFiles,
+    )
+}
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class Backup(
+    private val context: Context,
+    private val db: Db,
+    private val fileScanner: FileScanner,
+    private val storagePlugin: StoragePlugin,
+    private val cacheRepopulater: ChunksCacheRepopulater,
+    chunkSizeMax: Int = CHUNK_SIZE_MAX,
+    private val streamCrypto: StreamCrypto = StreamCrypto,
+) {
+
+    companion object {
+        const val VERSION: Byte = 0
+        const val CHUNK_SIZE_MAX = 15 * 1024 * 1024
+        const val SMALL_FILE_SIZE_MAX = 2 * 1024 * 1024
+        private const val TAG = "Backup"
+    }
+
+    private val contentResolver = context.contentResolver
+    private val filesCache = db.getFilesCache()
+    private val chunksCache = db.getChunksCache()
+
+    private val mac = try {
+        ChunkCrypto.getMac(ChunkCrypto.deriveChunkIdKey(storagePlugin.getMasterKey()))
+    } catch (e: GeneralSecurityException) {
+        throw AssertionError(e)
+    }
+    private val streamKey = try {
+        streamCrypto.deriveStreamKey(storagePlugin.getMasterKey())
+    } catch (e: GeneralSecurityException) {
+        throw AssertionError(e)
+    }
+    private val chunkWriter = ChunkWriter(streamCrypto, streamKey, chunksCache, storagePlugin)
+    private val hasMediaAccessPerm =
+        context.checkSelfPermission(ACCESS_MEDIA_LOCATION) == PERMISSION_GRANTED
+    private val fileBackup = FileBackup(
+        contentResolver = contentResolver,
+        hasMediaAccessPerm = hasMediaAccessPerm,
+        filesCache = filesCache,
+        chunker = Chunker(mac, chunkSizeMax),
+        chunkWriter = chunkWriter,
+    )
+    private val smallFileBackup = SmallFileBackup(
+        contentResolver = context.contentResolver,
+        hasMediaAccessPerm = hasMediaAccessPerm,
+        filesCache = filesCache,
+        zipChunker = ZipChunker(mac, chunkWriter),
+    )
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    @OptIn(ExperimentalTime::class)
+    suspend fun runBackup(backupObserver: BackupObserver?) {
+        backupObserver?.onStartScanning()
+        var duration: Duration? = null
+        try {
+            // get available chunks, so we do not need to rely solely on local cache
+            // for checking if a chunk already exists on storage
+            val availableChunkIds = storagePlugin.getAvailableChunkIds().toHashSet()
+            if (!chunksCache.areAllAvailableChunksCached(db, availableChunkIds)) {
+                cacheRepopulater.repopulate(streamKey, availableChunkIds)
+            }
+
+            val scanResult = measure("Scanning") {
+                fileScanner.getFiles()
+            }
+            val smallFiles = scanResult.smallFiles
+            val largeFiles = scanResult.files
+            val totalFiles = smallFiles.size + largeFiles.size
+            val totalSize = smallFiles.sumOf { it.size } + largeFiles.sumOf { it.size }
+            backupObserver?.onBackupStart(totalSize, totalFiles, smallFiles.size, largeFiles.size)
+
+            // If a file's size changes so it moves into another size category,
+            // it will get backed up normally again in the new category
+            // with its old (unreferenced) chunks eventually deleted.
+            // If (one of) its chunk(s) is missing, it will count as changed and chunked again.
+            duration = measure {
+                backupFiles(scanResult, availableChunkIds, backupObserver)
+            }
+            Log.e(TAG, "Changed files backup took $duration")
+        } finally {
+            backupObserver?.onBackupComplete(duration?.toLongMilliseconds())
+        }
+    }
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    private suspend fun backupFiles(
+        filesResult: FileScannerResult,
+        availableChunkIds: HashSet<String>,
+        backupObserver: BackupObserver?
+    ) {
+        val startTime = System.currentTimeMillis()
+        val numSmallFiles = filesResult.smallFiles.size
+        val smallResult = measure("Backing up $numSmallFiles small files") {
+            smallFileBackup.backupFiles(filesResult.smallFiles, availableChunkIds, backupObserver)
+        }
+        val numLargeFiles = filesResult.files.size
+        val largeResult = measure("Backing up $numLargeFiles files") {
+            fileBackup.backupFiles(filesResult.files, availableChunkIds, backupObserver)
+        }
+        val result = largeResult + smallResult
+        val backupSize = result.backupMediaFiles.sumOf { it.size } +
+                result.backupDocumentFiles.sumOf { it.size }
+        val endTime = System.currentTimeMillis()
+
+        val backupSnapshot: BackupSnapshot
+        val snapshotWriteTime = measure {
+            backupSnapshot = BackupSnapshot.newBuilder()
+                .setVersion(VERSION.toInt())
+                .setName("Backup on ${Build.MANUFACTURER} ${Build.MODEL}")
+                .addAllMediaFiles(result.backupMediaFiles)
+                .addAllDocumentFiles(result.backupDocumentFiles)
+                .setSize(backupSize)
+                .setTimeStart(startTime)
+                .setTimeEnd(endTime)
+                .build()
+            storagePlugin.getBackupSnapshotOutputStream(startTime).use { outputStream ->
+                outputStream.write(VERSION.toInt())
+                val ad = streamCrypto.getAssociatedDataForSnapshot(startTime)
+                streamCrypto.newEncryptingStream(streamKey, outputStream, ad)
+                    .use { encryptingStream ->
+                        backupSnapshot.writeTo(encryptingStream)
+                    }
+            }
+        }
+        val snapshotSize = backupSnapshot.serializedSize.toLong()
+        val snapshotSizeStr = Formatter.formatShortFileSize(context, snapshotSize)
+        Log.e(TAG, "Creating/writing snapshot took $snapshotWriteTime ($snapshotSizeStr)")
+
+        val chunkIncrementTime = measure {
+            db.applyInParts(result.chunkIds) {
+                chunksCache.incrementRefCount(it)
+            }
+        }
+        Log.e(TAG, "Incrementing chunk ref counters took $chunkIncrementTime")
+
+        // updating the lastSeen time only here is an optimization (faster than file by file)
+        // which we need to remember when purging old files from the cache
+        val lastSeenUpdateTime = measure {
+            val uris = filesResult.smallFiles.map { it.uri } + filesResult.files.map { it.uri }
+            db.applyInParts(uris) {
+                filesCache.updateLastSeen(it)
+            }
+        }
+        Log.e(TAG, "Updating last seen time took $lastSeenUpdateTime")
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/backup/BackupJobService.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/BackupJobService.kt
new file mode 100644
index 00000000..e4419b1c
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/BackupJobService.kt
@@ -0,0 +1,62 @@
+package org.calyxos.backup.storage.backup
+
+import android.app.Service
+import android.app.job.JobInfo
+import android.app.job.JobParameters
+import android.app.job.JobScheduler
+import android.app.job.JobService
+import android.content.ComponentName
+import android.content.Context
+import android.content.Intent
+import android.util.Log
+import java.util.concurrent.TimeUnit
+
+private const val BACKUP_JOB_ID = 0
+private const val TAG = "BackupJobService"
+
+public abstract class BackupJobService(private val serviceClass: Class<out Service>) :
+    JobService() {
+
+    public companion object {
+        public fun scheduleJob(
+            context: Context,
+            jobServiceClass: Class<*>,
+            periodMillis: Long = TimeUnit.HOURS.toMillis(24),
+            networkType: Int? = JobInfo.NETWORK_TYPE_UNMETERED,
+            deviceIdle: Boolean = true,
+            charging: Boolean = true,
+        ) {
+            val serviceComponent = ComponentName(context, jobServiceClass)
+            val jobInfoBuilder = JobInfo.Builder(BACKUP_JOB_ID, serviceComponent)
+                .setRequiresDeviceIdle(deviceIdle)
+                .setRequiresCharging(charging)
+                .setPeriodic(periodMillis)
+                .setPersisted(true)
+            if (networkType != null) jobInfoBuilder.setRequiredNetworkType(networkType)
+            val jobScheduler: JobScheduler = context.getSystemService(JobScheduler::class.java)
+            jobScheduler.schedule(jobInfoBuilder.build())
+        }
+
+        public fun isScheduled(context: Context): Boolean {
+            val jobScheduler: JobScheduler = context.getSystemService(JobScheduler::class.java)
+            return jobScheduler.getPendingJob(BACKUP_JOB_ID) != null
+        }
+
+        public fun cancelJob(context: Context) {
+            val jobScheduler: JobScheduler = context.getSystemService(JobScheduler::class.java)
+            jobScheduler.cancel(BACKUP_JOB_ID)
+        }
+    }
+
+    override fun onStartJob(params: JobParameters?): Boolean {
+        Log.i(TAG, "onStartJob ${params?.jobId} ${params?.extras} ${params?.network}")
+        val i = Intent(applicationContext, serviceClass)
+        startForegroundService(i)
+        return false
+    }
+
+    override fun onStopJob(params: JobParameters?): Boolean {
+        Log.i(TAG, "onStopJob ${params?.jobId}")
+        return true
+    }
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/backup/BackupService.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/BackupService.kt
new file mode 100644
index 00000000..318bcbdf
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/BackupService.kt
@@ -0,0 +1,58 @@
+package org.calyxos.backup.storage.backup
+
+import android.app.Service
+import android.content.Intent
+import android.os.IBinder
+import android.util.Log
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.launch
+import org.calyxos.backup.storage.R
+import org.calyxos.backup.storage.api.BackupObserver
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.ui.NOTIFICATION_ID_BACKUP
+import org.calyxos.backup.storage.ui.NOTIFICATION_ID_PRUNE
+import org.calyxos.backup.storage.ui.Notifications
+
+private const val TAG = "BackupService"
+
+public abstract class BackupService : Service() {
+
+    private val n by lazy { Notifications(applicationContext) }
+    protected abstract val storageBackup: StorageBackup
+    protected abstract val backupObserver: BackupObserver?
+
+    override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
+        Log.d(TAG, "onStartCommand $intent $flags $startId")
+        startForeground(
+            NOTIFICATION_ID_BACKUP,
+            n.getBackupNotification(R.string.notification_backup_scanning)
+        )
+        GlobalScope.launch {
+            val success = storageBackup.runBackup(backupObserver)
+            if (success) {
+                // only prune old backups when backup run was successful
+                startForeground(
+                    NOTIFICATION_ID_PRUNE,
+                    n.getPruneNotification(R.string.notification_prune)
+                )
+                storageBackup.pruneOldBackups(backupObserver)
+            }
+            onBackupFinished(intent, success)
+            stopSelf(startId)
+        }
+        return super.onStartCommand(intent, flags, startId)
+    }
+
+    protected open fun onBackupFinished(intent: Intent, success: Boolean) {
+    }
+
+    override fun onBind(intent: Intent?): IBinder? {
+        return null
+    }
+
+    override fun onDestroy() {
+        Log.d(TAG, "onDestroy")
+        super.onDestroy()
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/backup/ChunkWriter.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/ChunkWriter.kt
new file mode 100644
index 00000000..76bc91fa
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/ChunkWriter.kt
@@ -0,0 +1,131 @@
+package org.calyxos.backup.storage.backup
+
+import android.util.Log
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.backup.Backup.Companion.VERSION
+import org.calyxos.backup.storage.crypto.StreamCrypto
+import org.calyxos.backup.storage.db.ChunksCache
+import java.io.ByteArrayOutputStream
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+import java.nio.file.attribute.FileTime
+import java.security.GeneralSecurityException
+import java.util.zip.ZipEntry
+import java.util.zip.ZipOutputStream
+import kotlin.math.min
+
+internal data class ChunkWriterResult(
+    val numChunksWritten: Int,
+    val bytesWritten: Long,
+)
+
+private const val TAG = "ChunkWriter"
+
+internal class ChunkWriter(
+    private val streamCrypto: StreamCrypto,
+    private val streamKey: ByteArray,
+    private val chunksCache: ChunksCache,
+    private val storagePlugin: StoragePlugin,
+    private val bufferSize: Int = DEFAULT_BUFFER_SIZE,
+) {
+
+    private val buffer = ByteArray(bufferSize)
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    fun writeChunk(
+        inputStream: InputStream,
+        chunks: List<Chunk>,
+        missingChunkIds: List<String>
+    ): ChunkWriterResult {
+        var writtenChunks = 0
+        var writtenBytes = 0L
+        chunks.forEach { chunk ->
+            val cachedChunk = chunksCache.get(chunk.id)
+            val isMissing = chunk.id in missingChunkIds
+            val notCached = cachedChunk == null
+            if (isMissing) Log.w(TAG, "Chunk ${chunk.id} is missing (cached: ${!notCached})")
+            if (notCached || isMissing) { // chunk not in storage
+                writeChunkData(chunk.id) { encryptingStream ->
+                    copyChunkFromInputStream(inputStream, chunk, encryptingStream)
+                }
+                if (notCached) chunksCache.insert(chunk.toCachedChunk())
+                writtenChunks++
+                writtenBytes += chunk.size
+            } else { // chunk already uploaded
+                val skipped = inputStream.skip(chunk.size)
+                check(chunk.size == skipped) { "skipping error" }
+            }
+        }
+        val endByte = inputStream.read()
+        check(endByte == -1) { "Stream did continue with $endByte" }
+        return ChunkWriterResult(writtenChunks, writtenBytes)
+    }
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    private fun writeChunkData(chunkId: String, writer: (OutputStream) -> Unit) {
+        storagePlugin.getChunkOutputStream(chunkId).use { chunkStream ->
+            chunkStream.write(VERSION.toInt())
+            val ad = streamCrypto.getAssociatedDataForChunk(chunkId)
+            streamCrypto.newEncryptingStream(streamKey, chunkStream, ad).use { encryptingStream ->
+                writer(encryptingStream)
+            }
+        }
+    }
+
+    @Throws(IOException::class)
+    private fun copyChunkFromInputStream(
+        inputStream: InputStream,
+        chunk: Chunk,
+        outputStream: OutputStream
+    ) {
+        var totalBytesRead = 0L
+        do {
+            val sizeLeft = (chunk.size - totalBytesRead).toInt()
+            val bytesRead = inputStream.read(buffer, 0, min(bufferSize, sizeLeft))
+            if (bytesRead == -1) throw IOException("unexpected end of stream for ${chunk.id}")
+            outputStream.write(buffer, 0, bytesRead)
+            totalBytesRead += bytesRead
+        } while (bytesRead >= 0 && totalBytesRead < chunk.size)
+        check(totalBytesRead == chunk.size) {
+            "copyChunkFromInputStream: $totalBytesRead != ${chunk.size}"
+        }
+    }
+
+    /**
+     * Writes the zip chunk to backup storage.
+     *
+     * @return true if the chunk was written or false, if it was present already.
+     */
+    @Throws(IOException::class, GeneralSecurityException::class)
+    fun writeZipChunk(
+        chunk: ZipChunk,
+        zip: ByteArrayOutputStream,
+        missingChunkIds: List<String>
+    ): Boolean {
+        val cachedChunk = chunksCache.get(chunk.id)
+        val isMissing = chunk.id in missingChunkIds
+        if (isMissing) Log.w(TAG, "Chunk ${chunk.id} is missing (cached: ${cachedChunk != null})")
+        if (cachedChunk != null && !isMissing) return false
+        // chunk not yet uploaded
+        writeChunkData(chunk.id) { encryptingStream ->
+            zip.writeTo(encryptingStream)
+        }
+        if (cachedChunk == null) chunksCache.insert(chunk.toCachedChunk())
+        return true
+    }
+
+    @Throws(IOException::class)
+    fun writeNewZipEntry(zipOutputStream: ZipOutputStream, counter: Int, inputStream: InputStream) {
+        val entry = createNewZipEntry(counter)
+        zipOutputStream.putNextEntry(entry)
+        inputStream.copyTo(zipOutputStream)
+        zipOutputStream.closeEntry()
+    }
+
+    private fun createNewZipEntry(counter: Int) = ZipEntry(counter.toString()).apply {
+        // needed to make the ZIP and thus the MAC deterministic
+        lastModifiedTime = FileTime.fromMillis(0)
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/backup/Chunker.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/Chunker.kt
new file mode 100644
index 00000000..8d257445
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/Chunker.kt
@@ -0,0 +1,55 @@
+package org.calyxos.backup.storage.backup
+
+import org.calyxos.backup.storage.db.CachedChunk
+import org.calyxos.backup.storage.toHexString
+import java.io.IOException
+import java.io.InputStream
+import javax.crypto.Mac
+import kotlin.math.min
+
+internal data class Chunk(
+    val id: String,
+    val offset: Long,
+    val size: Long
+) {
+    fun toCachedChunk() = CachedChunk(id, 0, size)
+}
+
+internal class Chunker(
+    private val mac: Mac,
+    private val chunkSizeMax: Int,
+    private val bufferSize: Int = DEFAULT_BUFFER_SIZE,
+) {
+
+    private val buffer = ByteArray(bufferSize)
+
+    /**
+     * Returns a list of chunks
+     */
+    @Throws(IOException::class)
+    fun makeChunks(inputStream: InputStream): List<Chunk> {
+        val chunks = ArrayList<Chunk>()
+        var chunkStart = 0L
+        var chunkBytesRead = 0
+        var totalBytesRead = 0L
+
+        var bytesRead: Int
+        do {
+            bytesRead = inputStream.read(buffer, 0, min(bufferSize, chunkSizeMax - chunkBytesRead))
+            if (bytesRead > 0) {
+                mac.update(buffer, 0, bytesRead)
+                chunkBytesRead += bytesRead
+                totalBytesRead += bytesRead
+            }
+            if ((bytesRead < 0 && chunkStart != totalBytesRead) || chunkBytesRead >= chunkSizeMax) {
+                val chunkId = mac.doFinal().toHexString()
+                val chunkLength = totalBytesRead - chunkStart
+                val chunk = Chunk(chunkId, chunkStart, chunkLength)
+                chunks.add(chunk)
+                chunkStart = totalBytesRead
+                chunkBytesRead = 0
+            }
+        } while (bytesRead >= 0)
+        return chunks
+    }
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/backup/ChunksCacheRepopulater.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/ChunksCacheRepopulater.kt
new file mode 100644
index 00000000..5e7afc06
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/ChunksCacheRepopulater.kt
@@ -0,0 +1,102 @@
+package org.calyxos.backup.storage.backup
+
+import android.util.Log
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.db.CachedChunk
+import org.calyxos.backup.storage.db.Db
+import org.calyxos.backup.storage.measure
+import org.calyxos.backup.storage.plugin.SnapshotRetriever
+import java.io.IOException
+import java.security.GeneralSecurityException
+import java.util.concurrent.TimeUnit.MILLISECONDS
+import kotlin.time.ExperimentalTime
+import kotlin.time.toDuration
+
+private const val TAG = "ChunksCacheRepopulater"
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class ChunksCacheRepopulater(
+    private val db: Db,
+    private val storagePlugin: StoragePlugin,
+    private val snapshotRetriever: SnapshotRetriever,
+) {
+
+    suspend fun repopulate(streamKey: ByteArray, availableChunkIds: HashSet<String>) {
+        Log.i(TAG, "Starting to repopulate chunks cache")
+        try {
+            repopulateInternal(streamKey, availableChunkIds)
+        } catch (e: Exception) {
+            // TODO what can we do now? Just try again next time?
+            Log.e(TAG, "Error while repopulating chunks cache", e)
+        }
+    }
+
+    @Throws(IOException::class)
+    @OptIn(ExperimentalTime::class)
+    private suspend fun repopulateInternal(
+        streamKey: ByteArray,
+        availableChunkIds: HashSet<String>
+    ) {
+        val start = System.currentTimeMillis()
+        val snapshots = storagePlugin.getCurrentBackupSnapshots().mapNotNull { storedSnapshot ->
+            try {
+                snapshotRetriever.getSnapshot(streamKey, storedSnapshot)
+            } catch (e: GeneralSecurityException) {
+                Log.w(TAG, "Error fetching snapshot $storedSnapshot", e)
+                null
+            }
+        }
+        val snapshotDuration = (System.currentTimeMillis() - start).toDuration(MILLISECONDS)
+        Log.i(TAG, "Retrieving and parsing all snapshots took $snapshotDuration")
+
+        val cachedChunks = getCachedChunks(snapshots, availableChunkIds)
+        val repopulateDuration = measure {
+            db.getChunksCache().clearAndRepopulate(db, cachedChunks)
+        }
+        Log.i(TAG, "Repopulating chunks cache took $repopulateDuration")
+
+        // delete chunks that are not references by any snapshot anymore
+        val chunksToDelete = availableChunkIds.subtract(cachedChunks.map { it.id })
+        val deletionDuration = measure {
+            storagePlugin.deleteChunks(chunksToDelete.toList())
+        }
+        Log.i(TAG, "Deleting ${chunksToDelete.size} chunks took $deletionDuration")
+    }
+
+    private fun getCachedChunks(
+        snapshots: List<BackupSnapshot>,
+        availableChunks: HashSet<String>,
+    ): Collection<CachedChunk> {
+        val chunkMap = HashMap<String, CachedChunk>()
+        snapshots.forEach { snapshot ->
+            val chunksInSnapshot = HashSet<String>()
+            snapshot.mediaFilesList.forEach { file ->
+                file.chunkIdsList.forEach { chunkId -> chunksInSnapshot.add(chunkId) }
+            }
+            snapshot.documentFilesList.forEach { file ->
+                file.chunkIdsList.forEach { chunkId -> chunksInSnapshot.add(chunkId) }
+            }
+            addCachedChunksToMap(snapshot.timeStart, availableChunks, chunkMap, chunksInSnapshot)
+        }
+        return chunkMap.values
+    }
+
+    private fun addCachedChunksToMap(
+        snapshotTimeStamp: Long,
+        availableChunks: HashSet<String>,
+        chunkMap: HashMap<String, CachedChunk>,
+        chunksInSnapshot: HashSet<String>
+    ) = chunksInSnapshot.forEach { chunkId ->
+        if (!availableChunks.contains(chunkId)) {
+            Log.w(TAG, "ChunkId $chunkId referenced in $snapshotTimeStamp, but not in storage.")
+            return@forEach
+        }
+        val cachedChunk = chunkMap.getOrElse(chunkId) {
+            // TODO get actual chunk size (isn't used for anything critical, yet)
+            val size = 0L
+            CachedChunk(chunkId, 0, size)
+        }
+        chunkMap[chunkId] = cachedChunk.copy(refCount = cachedChunk.refCount + 1)
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/backup/FileBackup.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/FileBackup.kt
new file mode 100644
index 00000000..4235ff25
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/FileBackup.kt
@@ -0,0 +1,102 @@
+package org.calyxos.backup.storage.backup
+
+import android.content.ContentResolver
+import android.util.Log
+import org.calyxos.backup.storage.api.BackupObserver
+import org.calyxos.backup.storage.content.ContentFile
+import org.calyxos.backup.storage.content.DocFile
+import org.calyxos.backup.storage.content.MediaFile
+import org.calyxos.backup.storage.db.CachedFile
+import org.calyxos.backup.storage.db.FilesCache
+import org.calyxos.backup.storage.openInputStream
+import java.io.IOException
+import java.security.GeneralSecurityException
+
+internal class FileBackup(
+    private val contentResolver: ContentResolver,
+    private val hasMediaAccessPerm: Boolean,
+    private val filesCache: FilesCache,
+    private val chunker: Chunker,
+    private val chunkWriter: ChunkWriter,
+) {
+
+    companion object {
+        private const val TAG = "FileBackup"
+    }
+
+    suspend fun backupFiles(
+        files: List<ContentFile>,
+        availableChunkIds: HashSet<String>,
+        backupObserver: BackupObserver?
+    ): BackupResult {
+        val chunkIds = HashSet<String>()
+        val backupMediaFiles = ArrayList<BackupMediaFile>()
+        val backupDocumentFiles = ArrayList<BackupDocumentFile>()
+        var bytesWritten = 0L
+        files.forEach { file ->
+            val result = try {
+                backupFile(file, availableChunkIds)
+            } catch (e: IOException) {
+                backupObserver?.onFileBackupError(file, "L")
+                Log.e(TAG, "Error backing up ${file.uri}", e)
+                null
+            } catch (e: GeneralSecurityException) {
+                Log.e(TAG, "Error backing up ${file.uri}", e)
+                throw AssertionError(e)
+            } ?: return@forEach
+            when (file) {
+                is MediaFile -> backupMediaFiles.add(file.toBackupFile(result.chunkIds))
+                is DocFile -> backupDocumentFiles.add(file.toBackupFile(result.chunkIds))
+            }
+            chunkIds.addAll(result.chunkIds)
+            bytesWritten += result.bytesWritten
+            backupObserver?.onFileBackedUp(
+                file = file,
+                wasUploaded = result.hasChanged,
+                reusedChunks = result.savedChunks,
+                bytesWritten = result.bytesWritten,
+                tag = "L"
+            )
+        }
+        return BackupResult(chunkIds, backupMediaFiles, backupDocumentFiles)
+    }
+
+    private class FileBackupResult(
+        val chunkIds: List<String>,
+        val savedChunks: Int,
+        val bytesWritten: Long,
+        val hasChanged: Boolean,
+    )
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    private fun backupFile(
+        file: ContentFile,
+        availableChunkIds: HashSet<String>
+    ): FileBackupResult {
+        val cachedFile = filesCache.getByUri(file.uri)
+        val missingChunkIds = cachedFile?.chunks?.minus(availableChunkIds) ?: emptyList()
+        if (missingChunkIds.isEmpty() && file.hasNotChanged(cachedFile)) {
+            cachedFile as CachedFile // not null because hasNotChanged() returned true
+            return FileBackupResult(cachedFile.chunks, cachedFile.chunks.size, 0L, false)
+        }
+        val uri = file.getOriginalUri(hasMediaAccessPerm)
+        val chunks = uri.openInputStream(contentResolver).use { inputStream ->
+            chunker.makeChunks(inputStream)
+        }
+        val chunkWriterResult = uri.openInputStream(contentResolver).use { inputStream ->
+            chunkWriter.writeChunk(inputStream, chunks, missingChunkIds)
+        }
+
+        val chunkIds = chunks.map { it.id }
+        // Attention: don't modify the same file concurrently or this will cause bugs
+        filesCache.upsert(file.toCachedFile(chunkIds))
+
+        return FileBackupResult(
+            chunkIds = chunkIds,
+            savedChunks = chunks.size - chunkWriterResult.numChunksWritten,
+            bytesWritten = chunkWriterResult.bytesWritten,
+            hasChanged = true,
+        )
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/backup/NotificationBackupObserver.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/NotificationBackupObserver.kt
new file mode 100644
index 00000000..82d6b81d
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/NotificationBackupObserver.kt
@@ -0,0 +1,97 @@
+package org.calyxos.backup.storage.backup
+
+import android.content.Context
+import org.calyxos.backup.storage.R
+import org.calyxos.backup.storage.api.BackupFile
+import org.calyxos.backup.storage.api.BackupObserver
+import org.calyxos.backup.storage.ui.Notifications
+
+public open class NotificationBackupObserver internal constructor(private val n: Notifications) :
+    BackupObserver {
+
+    public constructor(context: Context) : this(Notifications(context))
+
+    private var totalFiles = 0
+    private var filesBackedUp = 0
+    private var filesWithError = 0
+    private var snapshotsToPrune = 0
+    private var snapshotsPruned = 0
+
+    override suspend fun onStartScanning() {
+        n.updateBackupNotification(R.string.notification_backup_scanning)
+    }
+
+    override suspend fun onBackupStart(
+        totalSize: Long,
+        numFiles: Int,
+        numSmallFiles: Int,
+        numLargeFiles: Int
+    ) {
+        totalFiles = numFiles
+        n.updateBackupNotification(
+            R.string.notification_backup_backup_files,
+            filesBackedUp + filesWithError,
+            totalFiles
+        )
+    }
+
+    override suspend fun onFileBackedUp(
+        file: BackupFile,
+        wasUploaded: Boolean,
+        reusedChunks: Int,
+        bytesWritten: Long,
+        tag: String
+    ) {
+        filesBackedUp++
+        n.updateBackupNotification(
+            R.string.notification_backup_backup_files,
+            filesBackedUp + filesWithError,
+            totalFiles
+        )
+    }
+
+    override suspend fun onFileBackupError(file: BackupFile, tag: String) {
+        filesWithError++
+        n.updateBackupNotification(
+            R.string.notification_backup_backup_files,
+            filesBackedUp + filesWithError,
+            totalFiles
+        )
+    }
+
+    override suspend fun onBackupComplete(backupDuration: Long?) {
+        n.cancelBackupNotification()
+    }
+
+    override suspend fun onPruneStartScanning() {
+        n.updatePruneNotification(R.string.notification_prune)
+    }
+
+    override suspend fun onPruneStart(snapshotsToDelete: List<Long>) {
+        snapshotsToPrune = snapshotsToDelete.size
+        n.updatePruneNotification(R.string.notification_prune, snapshotsPruned, snapshotsToPrune)
+    }
+
+    override suspend fun onPruneSnapshot(snapshot: Long, numChunksToDelete: Int, size: Long) {
+        snapshotsPruned++
+        n.updatePruneNotification(R.string.notification_prune, snapshotsPruned, snapshotsToPrune)
+    }
+
+    override suspend fun onPruneError(snapshot: Long?, e: Exception) {
+        if (snapshot == null) {
+            n.cancelPruneNotification()
+        } else {
+            snapshotsPruned++
+            n.updatePruneNotification(
+                R.string.notification_prune,
+                snapshotsPruned,
+                snapshotsToPrune
+            )
+        }
+    }
+
+    override suspend fun onPruneComplete(pruneDuration: Long) {
+        n.cancelPruneNotification()
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/backup/SmallFileBackup.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/SmallFileBackup.kt
new file mode 100644
index 00000000..a7c90523
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/SmallFileBackup.kt
@@ -0,0 +1,151 @@
+package org.calyxos.backup.storage.backup
+
+import android.content.ContentResolver
+import android.util.Log
+import org.calyxos.backup.storage.api.BackupObserver
+import org.calyxos.backup.storage.content.ContentFile
+import org.calyxos.backup.storage.content.DocFile
+import org.calyxos.backup.storage.content.MediaFile
+import org.calyxos.backup.storage.db.CachedFile
+import org.calyxos.backup.storage.db.FilesCache
+import org.calyxos.backup.storage.openInputStream
+import java.io.IOException
+import java.security.GeneralSecurityException
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class SmallFileBackup(
+    private val contentResolver: ContentResolver,
+    private val filesCache: FilesCache,
+    private val zipChunker: ZipChunker,
+    private val hasMediaAccessPerm: Boolean,
+) {
+
+    companion object {
+        private const val TAG = "SmallFileBackup"
+    }
+
+    suspend fun backupFiles(
+        files: List<ContentFile>,
+        availableChunkIds: HashSet<String>,
+        backupObserver: BackupObserver?
+    ): BackupResult {
+        val chunkIds = HashSet<String>()
+        val missingChunkIds = ArrayList<String>()
+        val backupMediaFiles = ArrayList<BackupMediaFile>()
+        val backupDocumentFiles = ArrayList<BackupDocumentFile>()
+        var bytesWritten = 0L
+        var zipChunks = 0
+
+        val changedFiles = files.filter { file ->
+            val cachedFile = filesCache.getByUri(file.uri)
+            val fileMissingChunkIds = cachedFile?.chunks?.minus(availableChunkIds) ?: emptyList()
+            missingChunkIds.addAll(fileMissingChunkIds)
+            if (fileMissingChunkIds.isEmpty() && file.hasNotChanged(cachedFile)) {
+                Log.d(TAG, "File has NOT changed: ${file.fileName}")
+                cachedFile as CachedFile // not null because hasNotChanged() returned true
+                if (file is MediaFile) {
+                    val backupFile = file.toBackupFile(cachedFile.chunks, cachedFile.zipIndex)
+                    backupMediaFiles.add(backupFile)
+                }
+                if (file is DocFile) {
+                    val backupFile = file.toBackupFile(cachedFile.chunks, cachedFile.zipIndex)
+                    backupDocumentFiles.add(backupFile)
+                }
+                if (chunkIds.add(cachedFile.chunks[0])) zipChunks++
+                backupObserver?.onFileBackedUp(file, false, 0, 0, "S")
+                false // filter out
+            } else true
+        }
+        changedFiles.windowed(2, 1, true).forEach { window ->
+            val file = window[0]
+            val result = try {
+                makeZipChunk(window, missingChunkIds)
+            } catch (e: IOException) {
+                backupObserver?.onFileBackupError(file, "S")
+                Log.e(TAG, "Error backing up ${file.uri}", e)
+                // Continuing here will ignore the file.
+                // There's a risk that the next file will exceed max zip chunk size,
+                // but as all files here are supposed to be small and the size limit isn't enforced,
+                // we accept this risk for now.
+                return@forEach
+            }
+            if (result == null) {
+                // null means file will be added to zip chunk
+                backupObserver?.onFileBackedUp(file, true, 0, 0, "S")
+                return@forEach
+            }
+            backupMediaFiles.addAll(result.backupMediaFiles)
+            backupDocumentFiles.addAll(result.backupDocumentFiles)
+            if (chunkIds.add(result.chunkId)) zipChunks++
+            bytesWritten += result.bytesWritten
+
+            backupObserver?.onFileBackedUp(file, result.hasChanged, 0, result.bytesWritten, "S")
+        }
+        Log.d(TAG, "Zip Chunks: $zipChunks")
+        return BackupResult(chunkIds, backupMediaFiles, backupDocumentFiles)
+    }
+
+    private class SmallFileBackupResult(
+        val chunkId: String,
+        val backupMediaFiles: List<BackupMediaFile>,
+        val backupDocumentFiles: List<BackupDocumentFile>,
+        val bytesWritten: Long,
+        val hasChanged: Boolean,
+    )
+
+    /**
+     * Adds the first file of the given window to a [ZipChunk].
+     *
+     * @param window a list of exactly one or two [ContentFile]s.
+     *
+     * @return [SmallFileBackupResult] if the chunk is full
+     * or the window contained only a single (last) file.
+     * Returns null, if there's space in the zip chunk and the next file can be added.
+     */
+    @Throws(IOException::class, GeneralSecurityException::class)
+    private fun makeZipChunk(
+        window: List<ContentFile>,
+        missingChunkIds: List<String>
+    ): SmallFileBackupResult? {
+        val file = window[0]
+        val nextFile = window.getOrNull(1)
+
+        // add file content to zip chunk
+        val uri = file.getOriginalUri(hasMediaAccessPerm)
+        uri.openInputStream(contentResolver).use { inputStream ->
+            zipChunker.addFile(file, inputStream)
+        }
+        return if (nextFile == null || !zipChunker.fitsFile(nextFile)) {
+            // Close zip chunk, if the next file would not fit in any more (or this is the last)
+            finalizeAndReset(zipChunker, missingChunkIds)
+        } else null
+    }
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    private fun finalizeAndReset(
+        zipChunker: ZipChunker,
+        missingChunkIds: List<String>
+    ): SmallFileBackupResult {
+        val zipChunk = zipChunker.finalizeAndReset(missingChunkIds)
+        val chunkIds = listOf(zipChunk.id)
+        val backupMediaFiles = ArrayList<BackupMediaFile>()
+        val backupDocumentFiles = ArrayList<BackupDocumentFile>()
+
+        zipChunk.files.forEachIndexed { index, file ->
+            // Attention: don't modify the same file concurrently or this will cause bugs
+            filesCache.upsert(file.toCachedFile(chunkIds, index + 1))
+            when (file) {
+                is MediaFile -> backupMediaFiles.add(file.toBackupFile(chunkIds, index + 1))
+                is DocFile -> backupDocumentFiles.add(file.toBackupFile(chunkIds, index + 1))
+            }
+        }
+        return SmallFileBackupResult(
+            chunkId = zipChunk.id,
+            backupMediaFiles = backupMediaFiles,
+            backupDocumentFiles = backupDocumentFiles,
+            bytesWritten = if (zipChunk.wasUploaded) zipChunk.size else 0L,
+            hasChanged = zipChunk.wasUploaded,
+        )
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/backup/ZipChunker.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/ZipChunker.kt
new file mode 100644
index 00000000..27a63d54
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/backup/ZipChunker.kt
@@ -0,0 +1,79 @@
+package org.calyxos.backup.storage.backup
+
+import org.calyxos.backup.storage.content.ContentFile
+import org.calyxos.backup.storage.db.CachedChunk
+import org.calyxos.backup.storage.toHexString
+import java.io.ByteArrayOutputStream
+import java.io.IOException
+import java.io.InputStream
+import java.security.GeneralSecurityException
+import java.util.zip.ZipOutputStream
+import javax.crypto.Mac
+
+private const val ZIP_CHUNK_SIZE_MAX = 7 * 1024 * 1024
+
+internal data class ZipChunk(
+    val id: String,
+    val files: List<ContentFile>,
+    val size: Long,
+    var wasUploaded: Boolean = false,
+) {
+    fun toCachedChunk() = CachedChunk(id, 0, size)
+}
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class ZipChunker(
+    private val mac: Mac,
+    private val chunkWriter: ChunkWriter,
+    private val chunkSizeMax: Int = ZIP_CHUNK_SIZE_MAX,
+) {
+
+    private val files = ArrayList<ContentFile>()
+
+    private val outputStream = ByteArrayOutputStream(chunkSizeMax)
+    private var zipOutputStream = ZipOutputStream(outputStream)
+
+    // we start with 1, because 0 is the default value in protobuf 3
+    private var counter = 1
+
+    fun fitsFile(file: ContentFile): Boolean {
+        return outputStream.size() + file.size <= chunkSizeMax
+    }
+
+    @Throws(IOException::class)
+    fun addFile(file: ContentFile, inputStream: InputStream) {
+        chunkWriter.writeNewZipEntry(zipOutputStream, counter, inputStream)
+        files.add(file)
+        counter++
+    }
+
+    /**
+     * Finalizes the operation and returns a [ZipChunk] including the previous files.
+     * This zip chunk will be uploaded to the backup storage.
+     *
+     * This object gets reset for the next operation.
+     */
+    @Throws(IOException::class, GeneralSecurityException::class)
+    fun finalizeAndReset(missingChunkIds: List<String>): ZipChunk = try {
+        zipOutputStream.finish()
+        zipOutputStream.close()
+
+        val chunkId = mac.doFinal(outputStream.toByteArray()).toHexString()
+        val zipChunk = ZipChunk(chunkId, files.toList(), outputStream.size().toLong())
+        val wasUploaded = chunkWriter.writeZipChunk(zipChunk, outputStream, missingChunkIds)
+        zipChunk.wasUploaded = wasUploaded
+
+        zipChunk
+    } finally {
+        // reset the state of the zip chunker for the next operation even if an exception was thrown
+        reset()
+    }
+
+    private fun reset() {
+        files.clear()
+        outputStream.reset()
+        zipOutputStream = ZipOutputStream(outputStream)
+        counter = 1
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/content/ContentFile.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/content/ContentFile.kt
new file mode 100644
index 00000000..d7ba22a8
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/content/ContentFile.kt
@@ -0,0 +1,134 @@
+package org.calyxos.backup.storage.content
+
+import android.net.Uri
+import android.provider.MediaStore
+import android.util.Log
+import org.calyxos.backup.storage.api.BackupFile
+import org.calyxos.backup.storage.backup.BackupDocumentFile
+import org.calyxos.backup.storage.backup.BackupMediaFile
+import org.calyxos.backup.storage.db.CachedFile
+import org.calyxos.backup.storage.getBackupMediaType
+
+internal sealed class ContentFile : BackupFile {
+    abstract val uri: Uri
+    abstract val dirPath: String
+    abstract val fileName: String
+    abstract override val size: Long
+    abstract override val volume: String
+    abstract override val lastModified: Long?
+    open val generationModified: Long? = null
+    override val path: String get() = "$dirPath/$fileName"
+
+    /**
+     * We use this to identify duplicate files and prevent them from getting backed up.
+     * Unfortunately, MediaStoreProvider and ExternalStorageProvider have different ideas about
+     * file sizes and lastModified timestamps, so that we can only use [volume] and [path].
+     */
+    internal val id get() = "$volume:$path"
+
+    internal fun toCachedFile(chunkIds: List<String>, zipIndex: Int? = null) = CachedFile(
+        uri = uri,
+        size = size,
+        lastModified = lastModified,
+        generationModified = generationModified,
+        chunks = chunkIds,
+        zipIndex = zipIndex,
+        lastSeen = System.currentTimeMillis(),
+    )
+
+    /**
+     * Returns an [Uri] that returns the original file for backup.
+     * http://aosp.opersys.com/xref/android-11.0.0_r8/xref/packages/providers/MediaProvider/apex/framework/java/android/provider/MediaStore.java#751
+     */
+    internal fun getOriginalUri(hasMediaAccessPerm: Boolean): Uri = when (this) {
+        is MediaFile -> if (hasMediaAccessPerm) MediaStore.setRequireOriginal(uri) else uri
+        is DocFile -> uri
+    }
+
+    internal open fun hasNotChanged(cachedFile: CachedFile?): Boolean {
+        if (cachedFile == null) return false
+        val sizeUnchanged = size == cachedFile.size
+        val notModified = lastModified != null && lastModified == cachedFile.lastModified
+        if (!sizeUnchanged || !notModified) {
+            Log.d("ContentFile", "$path has changed, because")
+            if (!sizeUnchanged) Log.d("ContentFile", "  size was ${cachedFile.size}, now is $size.")
+            if (!notModified) Log.d(
+                "ContentFile",
+                "  lastModified was ${cachedFile.lastModified}, now is $lastModified."
+            )
+        }
+        return sizeUnchanged && notModified
+    }
+}
+
+internal data class MediaFile(
+    override val uri: Uri,
+    val dir: String,
+    override val fileName: String,
+    val dateModified: Long?,
+    override val generationModified: Long?,
+    override val size: Long,
+    override val volume: String,
+    val isFavorite: Boolean,
+    val ownerPackageName: String?,
+) : ContentFile() {
+    override val dirPath: String = dir.trimEnd('/')
+    override val lastModified: Long? = dateModified?.times(1000)
+
+    override fun hasNotChanged(cachedFile: CachedFile?): Boolean {
+        if (cachedFile == null) return false
+        val generationMod = generationModified != cachedFile.generationModified
+        if (generationMod) {
+            Log.e(
+                "TEST", "$path has changed, because generation was " +
+                        "${cachedFile.generationModified}, now is $generationModified."
+            )
+        }
+        return super.hasNotChanged(cachedFile) && !generationMod
+    }
+
+    internal fun toBackupFile(chunkIds: List<String>, zipIndex: Int? = null): BackupMediaFile {
+        val type = uri.getBackupMediaType() ?: error("Could not get MediaType for $uri")
+        val builder = BackupMediaFile.newBuilder()
+            .setType(type)
+            .setPath(dirPath)
+            .setName(fileName)
+            .setSize(size)
+            .addAllChunkIds(chunkIds)
+            .setVolume(if (volume == MediaStore.VOLUME_EXTERNAL_PRIMARY) "" else volume)
+        if (lastModified != null) {
+            builder.lastModified = lastModified
+        }
+        if (zipIndex != null) {
+            builder.zipIndex = zipIndex
+        }
+        return builder.build()
+    }
+}
+
+internal data class DocFile(
+    override val uri: Uri,
+    override val dirPath: String,
+    override val fileName: String,
+    override val lastModified: Long?,
+    override val size: Long,
+    override val volume: String,
+) : ContentFile() {
+    internal fun toBackupFile(chunkIds: List<String>, zipIndex: Int? = null): BackupDocumentFile {
+        val builder = BackupDocumentFile.newBuilder()
+            .setPath(dirPath)
+            .setName(fileName)
+            .setSize(size)
+            .addAllChunkIds(chunkIds)
+        if (volume != MediaStore.VOLUME_EXTERNAL_PRIMARY) {
+            builder.volume = volume
+        }
+        if (lastModified != null) {
+            builder.lastModified = lastModified
+        }
+        if (zipIndex != null) {
+            builder.zipIndex = zipIndex
+        }
+        return builder.build()
+    }
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/crypto/ChunkCrypto.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/crypto/ChunkCrypto.kt
new file mode 100644
index 00000000..9af11ac2
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/crypto/ChunkCrypto.kt
@@ -0,0 +1,42 @@
+package org.calyxos.backup.storage.crypto
+
+import org.calyxos.backup.storage.backup.Chunker
+import org.calyxos.backup.storage.crypto.Hkdf.ALGORITHM_HMAC
+import org.calyxos.backup.storage.crypto.Hkdf.KEY_SIZE_BYTES
+import java.security.GeneralSecurityException
+import java.security.KeyStore
+import javax.crypto.Mac
+import javax.crypto.SecretKey
+import javax.crypto.spec.SecretKeySpec
+
+internal object ChunkCrypto {
+
+    private const val INFO_CHUNK_ID = "Chunk ID calculation"
+
+    /**
+     * We are deriving a dedicated key for chunk ID derivation,
+     * because using a [ByteArray] instead of a key inside the [KeyStore]
+     * is orders of magnitude faster.
+     */
+    @Throws(GeneralSecurityException::class)
+    fun deriveChunkIdKey(
+        masterKey: SecretKey,
+        info: ByteArray = INFO_CHUNK_ID.toByteArray()
+    ): ByteArray = Hkdf.expand(
+        secretKey = masterKey,
+        info = info,
+        outLengthBytes = KEY_SIZE_BYTES
+    )
+
+    /**
+     * Gets a re-usable [Mac] instance to be used with [Chunker.makeChunks].
+     */
+    @Throws(GeneralSecurityException::class)
+    fun getMac(chunkKey: ByteArray): Mac = Mac.getInstance(ALGORITHM_HMAC).apply {
+        check(chunkKey.size == KEY_SIZE_BYTES) {
+            "Chunk key has ${chunkKey.size} bytes, but $KEY_SIZE_BYTES expected."
+        }
+        init(SecretKeySpec(chunkKey, ALGORITHM_HMAC))
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/crypto/Hkdf.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/crypto/Hkdf.kt
new file mode 100644
index 00000000..9776fffe
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/crypto/Hkdf.kt
@@ -0,0 +1,56 @@
+package org.calyxos.backup.storage.crypto
+
+import java.nio.ByteBuffer
+import java.security.GeneralSecurityException
+import javax.crypto.Mac
+import javax.crypto.SecretKey
+import kotlin.math.ceil
+import kotlin.math.min
+
+internal object Hkdf {
+
+    private const val KEY_SIZE = 256
+    internal const val KEY_SIZE_BYTES = KEY_SIZE / 8
+    internal const val ALGORITHM_HMAC = "HmacSHA256"
+
+    /**
+     * Step 2 of RFC 5869.
+     *
+     * Based on the Apache2 licensed HKDF library by Patrick Favre-Bulle.
+     * Link: https://github.com/patrickfav/hkdf
+     *
+     * @param secretKey a pseudorandom key of at least hmac hash length in bytes (usually, the output from the extract step)
+     * @param info            optional context and application specific information; may be null
+     * @param outLengthBytes  length of output keying material in bytes (must be <= 255 * mac hash length)
+     * @return new byte array of output keying material (OKM)
+     */
+    @Throws(GeneralSecurityException::class)
+    internal fun expand(secretKey: SecretKey, info: ByteArray?, outLengthBytes: Int): ByteArray {
+        require(outLengthBytes > 0) { "out length bytes must be at least 1" }
+
+        val hmacHasher: Mac = Mac.getInstance(ALGORITHM_HMAC).apply {
+            init(secretKey)
+        }
+
+        val iterations = ceil(outLengthBytes.toDouble() / hmacHasher.macLength).toInt()
+        require(iterations <= 255) {
+            "out length must be maximal 255 * hash-length; requested: $outLengthBytes bytes"
+        }
+
+        val buffer: ByteBuffer = ByteBuffer.allocate(outLengthBytes)
+        var blockN = ByteArray(0)
+        var remainingBytes = outLengthBytes
+        var stepSize: Int
+        for (i in 0 until iterations) {
+            hmacHasher.update(blockN)
+            hmacHasher.update(info ?: ByteArray(0))
+            hmacHasher.update((i + 1).toByte())
+            blockN = hmacHasher.doFinal()
+            stepSize = min(remainingBytes, blockN.size)
+            buffer.put(blockN, 0, stepSize)
+            remainingBytes -= stepSize
+        }
+        return buffer.array()
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/crypto/StreamCrypto.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/crypto/StreamCrypto.kt
new file mode 100644
index 00000000..27123ae6
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/crypto/StreamCrypto.kt
@@ -0,0 +1,88 @@
+package org.calyxos.backup.storage.crypto
+
+import com.google.crypto.tink.subtle.AesGcmHkdfStreaming
+import org.calyxos.backup.storage.backup.Backup.Companion.VERSION
+import org.calyxos.backup.storage.crypto.Hkdf.ALGORITHM_HMAC
+import org.calyxos.backup.storage.crypto.Hkdf.KEY_SIZE_BYTES
+import org.calyxos.backup.storage.toByteArrayFromHex
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+import java.nio.ByteBuffer
+import java.security.GeneralSecurityException
+import javax.crypto.SecretKey
+
+public object StreamCrypto {
+
+    private const val INFO_STREAM_KEY = "stream key"
+    private const val SIZE_SEGMENT = 1 shl 20 // 1024 * 1024
+    private const val TYPE_CHUNK: Byte = 0x00
+    private const val TYPE_SNAPSHOT: Byte = 0x01
+
+    @Throws(GeneralSecurityException::class)
+    public fun deriveStreamKey(
+        masterKey: SecretKey,
+        info: ByteArray = INFO_STREAM_KEY.toByteArray()
+    ): ByteArray = Hkdf.expand(
+        secretKey = masterKey,
+        info = info,
+        outLengthBytes = KEY_SIZE_BYTES
+    )
+
+    internal fun getAssociatedDataForChunk(chunkId: String, version: Byte = VERSION): ByteArray =
+        ByteBuffer.allocate(2 + KEY_SIZE_BYTES)
+            .put(version)
+            .put(TYPE_CHUNK) // type ID for chunks
+            .put(chunkId.toByteArrayFromHex().apply { check(size == KEY_SIZE_BYTES) })
+            .array()
+
+    internal fun getAssociatedDataForSnapshot(timestamp: Long, version: Byte = VERSION): ByteArray =
+        ByteBuffer.allocate(2 + 8)
+            .put(version)
+            .put(TYPE_SNAPSHOT) // type ID for chunks
+            .put(timestamp.toByteArray())
+            .array()
+
+    /**
+     * Returns a [AesGcmHkdfStreaming] encrypting stream
+     * that gets encrypted with the given secret.
+     */
+    @Throws(IOException::class, GeneralSecurityException::class)
+    public fun newEncryptingStream(
+        secret: ByteArray,
+        outputStream: OutputStream,
+        associatedData: ByteArray = ByteArray(0)
+    ): OutputStream {
+        return AesGcmHkdfStreaming(
+            secret,
+            ALGORITHM_HMAC,
+            KEY_SIZE_BYTES,
+            SIZE_SEGMENT,
+            0
+        ).newEncryptingStream(outputStream, associatedData)
+    }
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    public fun newDecryptingStream(
+        secret: ByteArray,
+        inputStream: InputStream,
+        associatedData: ByteArray = ByteArray(0)
+    ): InputStream {
+        return AesGcmHkdfStreaming(
+            secret,
+            ALGORITHM_HMAC,
+            KEY_SIZE_BYTES,
+            SIZE_SEGMENT,
+            0
+        ).newDecryptingStream(inputStream, associatedData)
+    }
+
+    private fun Long.toByteArray() = ByteArray(8).apply {
+        var l = this@toByteArray
+        for (i in 7 downTo 0) {
+            this[i] = (l and 0xFF).toByte()
+            l = l shr 8
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/db/ChunksCache.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/db/ChunksCache.kt
new file mode 100644
index 00000000..501f0a5a
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/db/ChunksCache.kt
@@ -0,0 +1,72 @@
+package org.calyxos.backup.storage.db
+
+import androidx.room.ColumnInfo
+import androidx.room.Dao
+import androidx.room.Delete
+import androidx.room.Entity
+import androidx.room.Insert
+import androidx.room.PrimaryKey
+import androidx.room.Query
+import org.calyxos.backup.storage.backup.Backup
+
+@Entity
+internal data class CachedChunk(
+    @PrimaryKey val id: String,
+    /**
+     * How many snapshots are referencing this chunk.
+     * Note that this is *not* about how many files across various snapshots are referencing it.
+     */
+    @ColumnInfo(name = "ref_count") val refCount: Long,
+    val size: Long,
+    val version: Byte = Backup.VERSION,
+)
+
+@Dao
+internal interface ChunksCache {
+    @Insert
+    fun insert(chunk: CachedChunk)
+
+    @Insert
+    fun insert(chunks: Collection<CachedChunk>)
+
+    @Query("SELECT * FROM CachedChunk WHERE id == (:id)")
+    fun get(id: String): CachedChunk?
+
+    @Query("SELECT COUNT(id) FROM CachedChunk WHERE id IN (:ids)")
+    fun getNumberOfCachedChunks(ids: Collection<String>): Int
+
+    @Query("SELECT * FROM CachedChunk WHERE ref_count <= 0")
+    fun getUnreferencedChunks(): List<CachedChunk>
+
+    @Query("UPDATE CachedChunk SET ref_count = ref_count + 1 WHERE id IN (:ids)")
+    fun incrementRefCount(ids: Collection<String>)
+
+    @Query("UPDATE CachedChunk SET ref_count = ref_count - 1 WHERE id IN (:ids)")
+    fun decrementRefCount(ids: Collection<String>)
+
+    @Delete
+    fun deleteChunks(chunks: List<CachedChunk>)
+
+    @Query("DELETE FROM CachedChunk")
+    fun clear()
+
+    fun areAllAvailableChunksCached(db: Db, availableChunks: Collection<String>): Boolean {
+        return db.runInTransaction<Boolean> {
+            var allCached = true
+            availableChunks.chunked(DB_MAX_OP).forEach { availableChunkIds ->
+                val num = getNumberOfCachedChunks(availableChunkIds)
+                allCached = allCached && availableChunkIds.size == num
+                if (!allCached) return@runInTransaction false
+            }
+            return@runInTransaction allCached
+        }
+    }
+
+    fun clearAndRepopulate(db: Db, chunks: Collection<CachedChunk>) = db.runInTransaction {
+        clear()
+        chunks.chunked(DB_MAX_OP).forEach {
+            insert(it)
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/db/Db.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/db/Db.kt
new file mode 100644
index 00000000..33b09b7c
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/db/Db.kt
@@ -0,0 +1,46 @@
+package org.calyxos.backup.storage.db
+
+import android.net.Uri
+import androidx.room.Database
+import androidx.room.RoomDatabase
+import androidx.room.TypeConverter
+import androidx.room.TypeConverters
+
+internal const val DB_MAX_OP = 750
+
+@Database(entities = [StoredUri::class, CachedFile::class, CachedChunk::class], version = 1)
+@TypeConverters(Converters::class)
+internal abstract class Db : RoomDatabase() {
+    abstract fun getUriStore(): UriStore
+    abstract fun getFilesCache(): FilesCache
+    abstract fun getChunksCache(): ChunksCache
+
+    fun <T> applyInParts(list: Collection<T>, apply: (list: Collection<T>) -> Unit) =
+        runInTransaction {
+            list.chunked(DB_MAX_OP).forEach {
+                apply(it)
+            }
+        }
+}
+
+internal class Converters {
+    @TypeConverter
+    fun uriToString(value: Uri?): String? {
+        return value?.toString()
+    }
+
+    @TypeConverter
+    fun stringToUri(value: String?): Uri? {
+        return value?.let { Uri.parse(it) }
+    }
+
+    @TypeConverter
+    fun chunkIdsToString(value: List<String>?): String? {
+        return value?.joinToString("#")
+    }
+
+    @TypeConverter
+    fun stringToChunkIds(value: String?): List<String>? {
+        return value?.split("#")
+    }
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/db/FilesCache.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/db/FilesCache.kt
new file mode 100644
index 00000000..99d8eba3
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/db/FilesCache.kt
@@ -0,0 +1,48 @@
+package org.calyxos.backup.storage.db
+
+import android.net.Uri
+import androidx.room.ColumnInfo
+import androidx.room.Dao
+import androidx.room.Entity
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
+import androidx.room.PrimaryKey
+import androidx.room.Query
+import androidx.room.Update
+
+@Entity
+internal data class CachedFile(
+    @PrimaryKey val uri: Uri,
+    val size: Long,
+    @ColumnInfo(name = "last_modified") val lastModified: Long?,
+    @ColumnInfo(name = "generation_modified") val generationModified: Long? = null,
+    val chunks: List<String>,
+    /**
+     * The index in the single Zip Chunk.
+     * If this is not null, [chunks] must be of size 1.
+     */
+    @ColumnInfo(name = "zip_index") val zipIndex: Int? = null,
+    // TODO also purge files from the cache from time to time
+    @ColumnInfo(name = "last_seen") val lastSeen: Long
+)
+
+@Dao
+internal interface FilesCache {
+    @Insert
+    fun insert(file: CachedFile)
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    fun upsert(file: CachedFile)
+
+    @Update
+    fun update(file: CachedFile)
+
+    @Query("DELETE FROM CachedFile")
+    fun clear()
+
+    @Query("UPDATE CachedFile SET last_seen = :now WHERE uri IN (:uris)")
+    fun updateLastSeen(uris: Collection<Uri>, now: Long = System.currentTimeMillis())
+
+    @Query("SELECT * FROM CachedFile WHERE uri == (:uri)")
+    fun getByUri(uri: Uri): CachedFile?
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/db/UriStore.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/db/UriStore.kt
new file mode 100644
index 00000000..5214962f
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/db/UriStore.kt
@@ -0,0 +1,29 @@
+package org.calyxos.backup.storage.db
+
+import android.net.Uri
+import androidx.room.Dao
+import androidx.room.Delete
+import androidx.room.Entity
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
+import androidx.room.PrimaryKey
+import androidx.room.Query
+
+@Entity
+internal data class StoredUri(
+    @PrimaryKey val uri: Uri,
+)
+
+@Dao
+internal interface UriStore {
+
+    @Insert(onConflict = OnConflictStrategy.IGNORE)
+    fun addStoredUri(uri: StoredUri)
+
+    @Delete
+    fun removeStoredUri(uri: StoredUri)
+
+    @Query("SELECT * FROM StoredUri")
+    fun getStoredUris(): List<StoredUri>
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/SnapshotRetriever.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/SnapshotRetriever.kt
new file mode 100644
index 00000000..38fdcc14
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/SnapshotRetriever.kt
@@ -0,0 +1,34 @@
+package org.calyxos.backup.storage.plugin
+
+import com.google.protobuf.InvalidProtocolBufferException
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.backup.BackupSnapshot
+import org.calyxos.backup.storage.crypto.StreamCrypto
+import org.calyxos.backup.storage.restore.readVersion
+import java.io.IOException
+import java.security.GeneralSecurityException
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class SnapshotRetriever(
+    private val storagePlugin: StoragePlugin,
+    private val streamCrypto: StreamCrypto = StreamCrypto,
+) {
+
+    @Throws(
+        IOException::class,
+        GeneralSecurityException::class,
+        InvalidProtocolBufferException::class,
+    )
+    suspend fun getSnapshot(streamKey: ByteArray, storedSnapshot: StoredSnapshot): BackupSnapshot {
+        return storagePlugin.getBackupSnapshotInputStream(storedSnapshot).use { inputStream ->
+            val version = inputStream.readVersion()
+            val timestamp = storedSnapshot.timestamp
+            val ad = streamCrypto.getAssociatedDataForSnapshot(timestamp, version.toByte())
+            streamCrypto.newDecryptingStream(streamKey, inputStream, ad).use { decryptedStream ->
+                BackupSnapshot.parseFrom(decryptedStream)
+            }
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/saf/DocumentFileExt.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/saf/DocumentFileExt.kt
new file mode 100644
index 00000000..9e6431c4
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/saf/DocumentFileExt.kt
@@ -0,0 +1,189 @@
+@file:Suppress("BlockingMethodInNonBlockingContext")
+
+package org.calyxos.backup.storage.plugin.saf
+
+import android.annotation.SuppressLint
+import android.content.ContentResolver
+import android.content.Context
+import android.database.ContentObserver
+import android.database.Cursor
+import android.net.Uri
+import android.provider.DocumentsContract.Document.COLUMN_DOCUMENT_ID
+import android.provider.DocumentsContract.EXTRA_LOADING
+import android.provider.DocumentsContract.buildChildDocumentsUriUsingTree
+import android.provider.DocumentsContract.buildDocumentUriUsingTree
+import android.provider.DocumentsContract.getDocumentId
+import android.util.Log
+import androidx.annotation.VisibleForTesting
+import androidx.documentfile.provider.DocumentFile
+import kotlinx.coroutines.TimeoutCancellationException
+import kotlinx.coroutines.suspendCancellableCoroutine
+import kotlinx.coroutines.withTimeout
+import org.calyxos.backup.storage.openInputStream
+import org.calyxos.backup.storage.openOutputStream
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+import kotlin.coroutines.resume
+
+public object DocumentFileExt {
+
+    private const val TAG = "DocumentFileExt"
+
+    @Throws(IOException::class)
+    public fun DocumentFile.getInputStream(contentResolver: ContentResolver): InputStream {
+        return uri.openInputStream(contentResolver)
+    }
+
+    @Throws(IOException::class)
+    public fun DocumentFile.getOutputStream(contentResolver: ContentResolver): OutputStream {
+        return uri.openOutputStream(contentResolver)
+    }
+
+    @Throws(IOException::class)
+    public fun DocumentFile.createDirectoryOrThrow(name: String): DocumentFile {
+        val directory = createDirectory(name)
+            ?: throw IOException("Unable to create directory: $name")
+        if (directory.name != name) {
+            directory.delete()
+            throw IOException("Wanted to directory $name, but got ${directory.name}")
+        }
+        return directory
+    }
+
+    @Throws(IOException::class)
+    public fun DocumentFile.createFileOrThrow(name: String, mimeType: String): DocumentFile {
+        val file = createFile(mimeType, name) ?: throw IOException("Unable to create file: $name")
+        if (file.name != name) {
+            file.delete()
+            if (file.name == null) { // this happens when file existed already
+                // try to find the original file we were looking for
+                val foundFile = findFile(name)
+                if (foundFile?.name == name) return foundFile
+            }
+            throw IOException("Wanted to create $name, but got ${file.name}")
+        }
+        return file
+    }
+
+    /**
+     * Works like [DocumentFile.listFiles] except
+     * that it waits until the DocumentProvider has a result.
+     * This prevents getting an empty list even though there are children to be listed.
+     */
+    @Throws(IOException::class)
+    public suspend fun DocumentFile.listFilesBlocking(context: Context): List<DocumentFile> {
+        val resolver = context.contentResolver
+        val childrenUri = buildChildDocumentsUriUsingTree(uri, getDocumentId(uri))
+        val projection = arrayOf(COLUMN_DOCUMENT_ID)
+        val result = ArrayList<DocumentFile>()
+
+        try {
+            getLoadedCursor {
+                resolver.query(childrenUri, projection, null, null, null)
+            }
+        } catch (e: TimeoutCancellationException) {
+            throw IOException(e)
+        }.use { cursor ->
+            while (cursor.moveToNext()) {
+                val documentId = cursor.getString(0)
+                val documentUri = buildDocumentUriUsingTree(uri, documentId)
+                result.add(getTreeDocumentFile(this, context, documentUri))
+            }
+        }
+        return result
+    }
+
+    /**
+     * An extremely dirty reflection hack to instantiate a TreeDocumentFile with a parent.
+     *
+     * All other public ways to get a TreeDocumentFile only work from [Uri]s
+     * (e.g. [DocumentFile.fromTreeUri]) and always set parent to null.
+     *
+     * We have a test for this method to ensure CI will alert us when this reflection breaks.
+     * Also, [DocumentFile] is part of AndroidX, so we control the dependency and notice when it fails.
+     */
+    @VisibleForTesting
+    @SuppressLint("CheckedExceptions")
+    public fun getTreeDocumentFile(
+        parent: DocumentFile,
+        context: Context,
+        uri: Uri
+    ): DocumentFile {
+        @SuppressWarnings("MagicNumber")
+        val constructor = parent.javaClass.declaredConstructors.find {
+            it.name == "androidx.documentfile.provider.TreeDocumentFile" && it.parameterCount == 3
+        }
+        check(constructor != null) { "Could not find constructor for TreeDocumentFile" }
+        constructor.isAccessible = true
+        return constructor.newInstance(parent, context, uri) as DocumentFile
+    }
+
+    /**
+     * Same as [DocumentFile.findFile] only that it re-queries when the first result was stale.
+     *
+     * Most documents providers including Nextcloud are listing the full directory content
+     * when querying for a specific file in a directory,
+     * so there is no point in trying to optimize the query by not listing all children.
+     */
+    public suspend fun DocumentFile.findFileBlocking(
+        context: Context,
+        displayName: String
+    ): DocumentFile? {
+        val files = try {
+            listFilesBlocking(context)
+        } catch (e: IOException) {
+            Log.e(TAG, "Error finding file blocking", e)
+            return null
+        }
+        for (doc in files) {
+            if (displayName == doc.name) return doc
+        }
+        return null
+    }
+
+    /**
+     * Returns a cursor for the given query while ensuring that the cursor was loaded.
+     *
+     * When the SAF backend is a cloud storage provider (e.g. Nextcloud),
+     * it can happen that the query returns an outdated (e.g. empty) cursor
+     * which will only be updated in response to this query.
+     *
+     * See: https://commonsware.com/blog/2019/12/14/scoped-storage-stories-listfiles-woe.html
+     *
+     * This method uses a [suspendCancellableCoroutine] to wait for the result of a [ContentObserver]
+     * registered on the cursor in case the cursor is still loading ([EXTRA_LOADING]).
+     * If the cursor is not loading, it will be returned right away.
+     *
+     * @param timeout an optional time-out in milliseconds
+     * @throws TimeoutCancellationException if there was no result before the time-out
+     * @throws IOException if the query returns null
+     */
+    @VisibleForTesting
+    @Throws(IOException::class, TimeoutCancellationException::class)
+    public suspend fun getLoadedCursor(timeout: Long = 15_000, query: () -> Cursor?): Cursor =
+        withTimeout(timeout) {
+            suspendCancellableCoroutine { cont ->
+                val cursor = query() ?: throw IOException()
+                cont.invokeOnCancellation { cursor.close() }
+                val loading = cursor.extras.getBoolean(EXTRA_LOADING, false)
+                if (loading) {
+                    Log.d(TAG, "Wait for children to get loaded...")
+                    cursor.registerContentObserver(object : ContentObserver(null) {
+                        override fun onChange(selfChange: Boolean, uri: Uri?) {
+                            Log.d(TAG, "Children loaded. Continue...")
+                            cursor.close()
+                            val newCursor = query()
+                            if (newCursor == null) {
+                                cont.cancel(IOException("query returned no results"))
+                            } else cont.resume(newCursor)
+                        }
+                    })
+                } else {
+                    // not loading, return cursor right away
+                    cont.resume(cursor)
+                }
+            }
+        }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/saf/SafCache.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/saf/SafCache.kt
new file mode 100644
index 00000000..0480a1eb
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/saf/SafCache.kt
@@ -0,0 +1,32 @@
+package org.calyxos.backup.storage.plugin.saf
+
+import androidx.documentfile.provider.DocumentFile
+import org.calyxos.backup.storage.api.StoredSnapshot
+
+/**
+ * Accessing files and attributes via SAF is costly.
+ * This class caches them to speed up SAF related operations.
+ */
+internal class SafCache {
+
+    /**
+     * The folder for the current user ID (here "${ANDROID_ID}.sv").
+     */
+    var currentFolder: DocumentFile? = null
+
+    /**
+     * Folders containing chunks for backups of the current user ID.
+     */
+    val backupChunkFolders = HashMap<String, DocumentFile>(CHUNK_FOLDER_COUNT)
+
+    /**
+     * Folders containing chunks for restore of a chosen [StoredSnapshot].
+     */
+    val restoreChunkFolders = HashMap<String, DocumentFile>(CHUNK_FOLDER_COUNT)
+
+    /**
+     * Files for each [StoredSnapshot].
+     */
+    val snapshotFiles = HashMap<StoredSnapshot, DocumentFile>()
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/saf/SafStoragePlugin.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/saf/SafStoragePlugin.kt
new file mode 100644
index 00000000..9d4b3168
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/plugin/saf/SafStoragePlugin.kt
@@ -0,0 +1,271 @@
+package org.calyxos.backup.storage.plugin.saf
+
+import android.annotation.SuppressLint
+import android.content.Context
+import android.provider.Settings
+import android.provider.Settings.Secure.ANDROID_ID
+import android.util.Log
+import androidx.documentfile.provider.DocumentFile
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.measure
+import org.calyxos.backup.storage.plugin.saf.DocumentFileExt.createDirectoryOrThrow
+import org.calyxos.backup.storage.plugin.saf.DocumentFileExt.createFileOrThrow
+import org.calyxos.backup.storage.plugin.saf.DocumentFileExt.findFileBlocking
+import org.calyxos.backup.storage.plugin.saf.DocumentFileExt.getInputStream
+import org.calyxos.backup.storage.plugin.saf.DocumentFileExt.getOutputStream
+import org.calyxos.backup.storage.plugin.saf.DocumentFileExt.listFilesBlocking
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+
+private val folderRegex = Regex("^[a-f0-9]{16}\\.sv$")
+private val chunkFolderRegex = Regex("[a-f0-9]{2}")
+private val chunkRegex = Regex("[a-f0-9]{64}")
+private val snapshotRegex = Regex("([0-9]{13})\\.SeedSnap") // good until the year 2286
+private const val MIME_TYPE: String = "application/octet-stream"
+internal const val CHUNK_FOLDER_COUNT = 256
+
+private const val TAG = "SafStoragePlugin"
+
+@Suppress("BlockingMethodInNonBlockingContext")
+public abstract class SafStoragePlugin(
+    private val context: Context,
+) : StoragePlugin {
+
+    private val cache = SafCache()
+    protected abstract val root: DocumentFile?
+
+    private val folder: DocumentFile?
+        get() {
+            val root = this.root ?: return null
+            if (cache.currentFolder != null) return cache.currentFolder
+
+            @SuppressLint("HardwareIds")
+            // this is unique to each combination of app-signing key, user, and device
+            // so we don't leak anything by not hashing this and can use it as is
+            val androidId = Settings.Secure.getString(context.contentResolver, ANDROID_ID)
+            // the folder name is our user ID
+            val folderName = "$androidId.sv"
+            cache.currentFolder = try {
+                root.findFile(folderName) ?: root.createDirectoryOrThrow(folderName)
+            } catch (e: IOException) {
+                Log.e(TAG, "Error creating storage folder $folderName")
+                null
+            }
+            return cache.currentFolder
+        }
+
+    private val contentResolver = context.contentResolver
+
+    private fun timestampToSnapshot(timestamp: Long): String {
+        return "$timestamp.SeedSnap"
+    }
+
+    @Throws(IOException::class)
+    override suspend fun getAvailableChunkIds(): List<String> {
+        val folder = folder ?: return emptyList()
+        val chunkIds = ArrayList<String>()
+        populateChunkFolders(folder, cache.backupChunkFolders) { file, name ->
+            if (chunkFolderRegex.matches(name)) {
+                chunkIds.addAll(getChunksFromFolder(file))
+            }
+        }
+        Log.i(TAG, "Got ${chunkIds.size} available chunks")
+        return chunkIds
+    }
+
+    /**
+     * Goes through all files in the given [folder] and performs the optional [fileOp] on them.
+     * Afterwards, it creates missing chunk folders, as needed.
+     * Chunk folders will get cached in the given [chunkFolders] for faster access.
+     */
+    @Throws(IOException::class)
+    private suspend fun populateChunkFolders(
+        folder: DocumentFile,
+        chunkFolders: HashMap<String, DocumentFile>,
+        fileOp: ((DocumentFile, String) -> Unit)? = null
+    ) {
+        val expectedChunkFolders = (0x00..0xff).map {
+            Integer.toHexString(it).padStart(2, '0')
+        }.toHashSet()
+        val duration = measure {
+            for (file in folder.listFilesBlocking(context)) {
+                val name = file.name ?: continue
+                if (chunkFolderRegex.matches(name)) {
+                    chunkFolders[name] = file
+                    expectedChunkFolders.remove(name)
+                }
+                fileOp?.invoke(file, name)
+            }
+        }
+        Log.i(TAG, "Retrieving chunk folders took $duration")
+        createMissingChunkFolders(folder, chunkFolders, expectedChunkFolders)
+    }
+
+    @Throws(IOException::class)
+    private fun getChunksFromFolder(chunkFolder: DocumentFile): List<String> {
+        val chunkFiles = try {
+            chunkFolder.listFiles()
+        } catch (e: UnsupportedOperationException) {
+            // can happen if this wasn't a directory after all
+            throw IOException(e)
+        }
+        return chunkFiles.mapNotNull { chunkFile ->
+            val name = chunkFile.name ?: return@mapNotNull null
+            if (chunkRegex.matches(name)) name else null
+        }
+    }
+
+    @Throws(IOException::class)
+    private fun createMissingChunkFolders(
+        root: DocumentFile,
+        chunkFolders: HashMap<String, DocumentFile>,
+        expectedChunkFolders: Set<String>
+    ) {
+        val s = expectedChunkFolders.size
+        val duration = measure {
+            for ((i, chunkFolderName) in expectedChunkFolders.withIndex()) {
+                val file = root.createDirectoryOrThrow(chunkFolderName)
+                chunkFolders[chunkFolderName] = file
+                Log.d(TAG, "Created missing folder $chunkFolderName (${i + 1}/$s)")
+            }
+            if (chunkFolders.size != 256) {
+                throw IOException("Only have ${chunkFolders.size} chunk folders.")
+            }
+        }
+        if (s > 0) Log.i(TAG, "Creating $s missing chunk folders took $duration")
+    }
+
+    @Throws(IOException::class)
+    override fun getChunkOutputStream(chunkId: String): OutputStream {
+        val chunkFolderName = chunkId.substring(0, 2)
+        val chunkFolder =
+            cache.backupChunkFolders[chunkFolderName] ?: error("No folder for chunk $chunkId")
+        // TODO should we check if it exists first?
+        val chunkFile = chunkFolder.createFileOrThrow(chunkId, MIME_TYPE)
+        return chunkFile.getOutputStream(context.contentResolver)
+    }
+
+    @Throws(IOException::class)
+    override fun getBackupSnapshotOutputStream(timestamp: Long): OutputStream {
+        val folder = folder ?: throw IOException()
+        val name = timestampToSnapshot(timestamp)
+        // TODO should we check if it exists first?
+        val snapshotFile = folder.createFileOrThrow(name, MIME_TYPE)
+        return snapshotFile.getOutputStream(contentResolver)
+    }
+
+    /************************* Restore *******************************/
+
+    @Throws(IOException::class)
+    override suspend fun getBackupSnapshotsForRestore(): List<StoredSnapshot> {
+        val snapshots = ArrayList<StoredSnapshot>()
+
+        root?.listFilesBlocking(context)?.forEach { folder ->
+            val folderName = folder.name ?: ""
+            if (!folderRegex.matches(folderName)) return@forEach
+
+            Log.i(TAG, "Checking $folderName for snapshots...")
+            for (file in folder.listFilesBlocking(context)) {
+                val name = file.name ?: continue
+                val match = snapshotRegex.matchEntire(name)
+                if (match != null) {
+                    val timestamp = match.groupValues[1].toLong()
+                    val storedSnapshot = StoredSnapshot(folderName, timestamp)
+                    snapshots.add(storedSnapshot)
+                    cache.snapshotFiles[storedSnapshot] = file
+                }
+            }
+        }
+        Log.i(TAG, "Got ${snapshots.size} snapshots while populating chunk folders")
+        return snapshots
+    }
+
+    @Throws(IOException::class)
+    override suspend fun getBackupSnapshotInputStream(storedSnapshot: StoredSnapshot): InputStream {
+        val timestamp = storedSnapshot.timestamp
+        val snapshotFile = cache.snapshotFiles.getOrElse(storedSnapshot) {
+            getFolder(storedSnapshot).findFileBlocking(context, timestampToSnapshot(timestamp))
+        } ?: throw IOException("Could not get file for snapshot $timestamp")
+        return snapshotFile.getInputStream(contentResolver)
+    }
+
+    @Throws(IOException::class)
+    override suspend fun getChunkInputStream(
+        snapshot: StoredSnapshot,
+        chunkId: String
+    ): InputStream {
+        if (cache.restoreChunkFolders.size < CHUNK_FOLDER_COUNT) {
+            populateChunkFolders(getFolder(snapshot), cache.restoreChunkFolders)
+        }
+        val chunkFolderName = chunkId.substring(0, 2)
+        val chunkFolder = cache.restoreChunkFolders[chunkFolderName]
+            ?: throw IOException("No folder for chunk $chunkId")
+        val chunkFile = chunkFolder.findFileBlocking(context, chunkId)
+            ?: throw IOException("No chunk $chunkId")
+        return chunkFile.getInputStream(context.contentResolver)
+    }
+
+    @Throws(IOException::class)
+    private suspend fun getFolder(storedSnapshot: StoredSnapshot): DocumentFile {
+        // not cached, because used in several places only once and
+        // [getBackupSnapshotInputStream] uses snapshot files cache and
+        // [getChunkInputStream] uses restore chunk folders cache
+        return root?.findFileBlocking(context, storedSnapshot.userId)
+            ?: throw IOException("Could not find snapshot $storedSnapshot")
+    }
+
+    /************************* Pruning *******************************/
+
+    @Throws(IOException::class)
+    override suspend fun getCurrentBackupSnapshots(): List<StoredSnapshot> {
+        val folder = folder ?: return emptyList()
+        val folderName = folder.name ?: error("Folder suddenly has no more name")
+        val snapshots = ArrayList<StoredSnapshot>()
+
+        populateChunkFolders(folder, cache.backupChunkFolders) { file, name ->
+            val match = snapshotRegex.matchEntire(name)
+            if (match != null) {
+                val timestamp = match.groupValues[1].toLong()
+                val storedSnapshot = StoredSnapshot(folderName, timestamp)
+                snapshots.add(storedSnapshot)
+                cache.snapshotFiles[storedSnapshot] = file
+            }
+        }
+        Log.i(TAG, "Got ${snapshots.size} snapshots while populating chunk folders")
+        return snapshots
+    }
+
+    @Throws(IOException::class)
+    override suspend fun deleteBackupSnapshot(storedSnapshot: StoredSnapshot) {
+        val timestamp = storedSnapshot.timestamp
+        Log.d(TAG, "Deleting snapshot $timestamp")
+        val snapshotFile = cache.snapshotFiles.getOrElse(storedSnapshot) {
+            getFolder(storedSnapshot).findFileBlocking(context, timestampToSnapshot(timestamp))
+        } ?: throw IOException("Could not get file for snapshot $timestamp")
+        if (!snapshotFile.delete()) throw IOException("Could not delete snapshot $timestamp")
+        cache.snapshotFiles.remove(storedSnapshot)
+    }
+
+    @Throws(IOException::class)
+    override suspend fun deleteChunks(chunkIds: List<String>) {
+        if (cache.backupChunkFolders.size < CHUNK_FOLDER_COUNT) {
+            val folder = folder ?: throw IOException("Could not get current folder in root")
+            populateChunkFolders(folder, cache.backupChunkFolders)
+        }
+        for (chunkId in chunkIds) {
+            Log.d(TAG, "Deleting chunk $chunkId")
+            val chunkFolderName = chunkId.substring(0, 2)
+            val chunkFolder = cache.backupChunkFolders[chunkFolderName]
+                ?: throw IOException("No folder for chunk $chunkId")
+            val chunkFile = chunkFolder.findFileBlocking(context, chunkId)
+            if (chunkFile == null) {
+                Log.w(TAG, "Could not find $chunkId")
+            } else {
+                if (!chunkFile.delete()) throw IOException("Could not delete chunk $chunkId")
+            }
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/prune/Pruner.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/prune/Pruner.kt
new file mode 100644
index 00000000..9426cf5e
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/prune/Pruner.kt
@@ -0,0 +1,80 @@
+package org.calyxos.backup.storage.prune
+
+import android.util.Log
+import org.calyxos.backup.storage.api.BackupObserver
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.crypto.StreamCrypto
+import org.calyxos.backup.storage.db.Db
+import org.calyxos.backup.storage.measure
+import org.calyxos.backup.storage.plugin.SnapshotRetriever
+import java.io.IOException
+import java.security.GeneralSecurityException
+import kotlin.time.ExperimentalTime
+
+private val TAG = Pruner::class.java.simpleName
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class Pruner(
+    private val db: Db,
+    private val retentionManager: RetentionManager,
+    private val storagePlugin: StoragePlugin,
+    private val snapshotRetriever: SnapshotRetriever,
+    streamCrypto: StreamCrypto = StreamCrypto,
+) {
+
+    private val chunksCache = db.getChunksCache()
+    private val streamKey = try {
+        streamCrypto.deriveStreamKey(storagePlugin.getMasterKey())
+    } catch (e: GeneralSecurityException) {
+        throw AssertionError(e)
+    }
+
+    @OptIn(ExperimentalTime::class)
+    @Throws(IOException::class)
+    suspend fun prune(backupObserver: BackupObserver?) {
+        val duration = measure {
+            val storedSnapshots = storagePlugin.getCurrentBackupSnapshots()
+            val toDelete = retentionManager.getSnapshotsToDelete(storedSnapshots)
+            backupObserver?.onPruneStart(toDelete.map { it.timestamp })
+            for (snapshot in toDelete) {
+                try {
+                    pruneSnapshot(snapshot, backupObserver)
+                } catch (e: Exception) {
+                    Log.e(TAG, "Error pruning $snapshot", e)
+                    backupObserver?.onPruneError(snapshot.timestamp, e)
+                }
+            }
+        }
+        Log.i(TAG, "Pruning took $duration")
+        backupObserver?.onPruneComplete(duration.toLongMilliseconds())
+    }
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    private suspend fun pruneSnapshot(
+        storedSnapshot: StoredSnapshot,
+        backupObserver: BackupObserver?
+    ) {
+        val snapshot = snapshotRetriever.getSnapshot(streamKey, storedSnapshot)
+        val chunks = HashSet<String>()
+        snapshot.mediaFilesList.forEach { chunks.addAll(it.chunkIdsList) }
+        snapshot.documentFilesList.forEach { chunks.addAll(it.chunkIdsList) }
+        storagePlugin.deleteBackupSnapshot(storedSnapshot)
+        db.applyInParts(chunks) {
+            chunksCache.decrementRefCount(it)
+        }
+        var size = 0L
+        // TODO add integration test for a failed backup that later resumes with unreferenced chunks
+        //  and here only deletes those that are still unreferenced afterwards
+        val cachedChunksToDelete = chunksCache.getUnreferencedChunks()
+        val chunkIdsToDelete = cachedChunksToDelete.map {
+            if (it.refCount < 0) Log.w(TAG, "${it.id} has ref count ${it.refCount}")
+            size += it.size
+            it.id
+        }
+        backupObserver?.onPruneSnapshot(storedSnapshot.timestamp, chunkIdsToDelete.size, size)
+        storagePlugin.deleteChunks(chunkIdsToDelete)
+        chunksCache.deleteChunks(cachedChunksToDelete)
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/prune/RetentionManager.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/prune/RetentionManager.kt
new file mode 100644
index 00000000..8f2097ef
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/prune/RetentionManager.kt
@@ -0,0 +1,90 @@
+package org.calyxos.backup.storage.prune
+
+import android.content.Context
+import org.calyxos.backup.storage.api.SnapshotRetention
+import org.calyxos.backup.storage.api.StoredSnapshot
+import java.io.IOException
+import java.time.LocalDate
+import java.time.temporal.ChronoField
+import java.time.temporal.Temporal
+import java.time.temporal.TemporalAdjuster
+import java.time.temporal.TemporalAdjusters.firstDayOfMonth
+import java.time.temporal.TemporalAdjusters.firstDayOfYear
+
+internal const val PREFS = "org.calyxos.backup.storage.prune.retention"
+internal const val PREF_DAILY = "daily"
+internal const val PREF_WEEKLY = "weekly"
+internal const val PREF_MONTHLY = "monthly"
+internal const val PREF_YEARLY = "yearly"
+internal const val PREF_DEFAULT_DAILY = 3
+internal const val PREF_DEFAULT_WEEKLY = 2
+internal const val PREF_DEFAULT_MONTHLY = 2
+internal const val PREF_DEFAULT_YEARLY = 1
+
+internal class RetentionManager(private val context: Context) {
+
+    fun setSnapshotRetention(retention: SnapshotRetention) {
+        if (retention.daily == 0 &&
+            retention.weekly == 0 &&
+            retention.monthly == 0 &&
+            retention.yearly == 0
+        ) throw IllegalArgumentException("Not all values can be 0")
+        context.getSharedPreferences(PREFS, 0)
+            .edit()
+            .putInt(PREF_DAILY, retention.daily)
+            .putInt(PREF_WEEKLY, retention.weekly)
+            .putInt(PREF_MONTHLY, retention.monthly)
+            .putInt(PREF_YEARLY, retention.yearly)
+            .apply()
+    }
+
+    fun getSnapshotRetention(): SnapshotRetention {
+        val prefs = context.getSharedPreferences(PREFS, 0)
+        return SnapshotRetention(
+            daily = prefs.getInt(PREF_DAILY, 3),
+            weekly = prefs.getInt(PREF_WEEKLY, 1),
+            monthly = prefs.getInt(PREF_MONTHLY, 1),
+            yearly = prefs.getInt(PREF_YEARLY, 1),
+        )
+    }
+
+    /**
+     * Takes a list of [StoredSnapshot]s and returns a list of those
+     * that can be deleted according to the current snapshot retention policy.
+     */
+    @Throws(IOException::class)
+    fun getSnapshotsToDelete(storedSnapshots: List<StoredSnapshot>): List<StoredSnapshot> {
+        val retention = getSnapshotRetention()
+        val datePairs = storedSnapshots.sortedByDescending { it.timestamp }.map { s ->
+            Pair(s, LocalDate.ofEpochDay(s.timestamp / 1000 / 60 / 60 / 24))
+        }
+        val toKeep = HashSet<StoredSnapshot>()
+        toKeep += getToKeep(datePairs, retention.daily)
+        toKeep += getToKeep(datePairs, retention.weekly) { temporal: Temporal ->
+            temporal.with(ChronoField.DAY_OF_WEEK, 1)
+        }
+        toKeep += getToKeep(datePairs, retention.monthly, firstDayOfMonth())
+        toKeep += getToKeep(datePairs, retention.yearly, firstDayOfYear())
+        return storedSnapshots - toKeep
+    }
+
+    private fun getToKeep(
+        pairs: List<Pair<StoredSnapshot, LocalDate>>,
+        keep: Int,
+        temporalAdjuster: TemporalAdjuster? = null,
+    ): List<StoredSnapshot> {
+        val toKeep = ArrayList<StoredSnapshot>()
+        if (keep == 0) return toKeep
+        var last: LocalDate? = null
+        for ((snapshot, date) in pairs) {
+            val period = if (temporalAdjuster == null) date else date.with(temporalAdjuster)
+            if (period != last) {
+                toKeep.add(snapshot)
+                if (toKeep.size >= keep) break
+                last = period
+            }
+        }
+        return toKeep
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/restore/AbstractChunkRestore.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/AbstractChunkRestore.kt
new file mode 100644
index 00000000..6b22c5a8
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/AbstractChunkRestore.kt
@@ -0,0 +1,48 @@
+package org.calyxos.backup.storage.restore
+
+import org.calyxos.backup.storage.api.RestoreObserver
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.crypto.StreamCrypto
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+import java.security.GeneralSecurityException
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal abstract class AbstractChunkRestore(
+    private val storagePlugin: StoragePlugin,
+    private val fileRestore: FileRestore,
+    private val streamCrypto: StreamCrypto,
+    private val streamKey: ByteArray,
+) {
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    protected suspend fun getAndDecryptChunk(
+        version: Int,
+        storedSnapshot: StoredSnapshot,
+        chunkId: String,
+        streamReader: suspend (InputStream) -> Unit,
+    ) {
+        storagePlugin.getChunkInputStream(storedSnapshot, chunkId).use { inputStream ->
+            inputStream.readVersion(version)
+            val ad = streamCrypto.getAssociatedDataForChunk(chunkId, version.toByte())
+            streamCrypto.newDecryptingStream(streamKey, inputStream, ad).use { decryptedStream ->
+                streamReader(decryptedStream)
+            }
+        }
+    }
+
+    @Throws(IOException::class)
+    protected suspend fun restoreFile(
+        file: RestorableFile,
+        observer: RestoreObserver?,
+        tag: String,
+        streamWriter: suspend (outputStream: OutputStream) -> Long,
+    ) {
+        // TODO check if the file exists already (same name, size, chunk IDs)
+        //  and skip it in this case
+        fileRestore.restoreFile(file, observer, tag, streamWriter)
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/restore/FileRestore.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/FileRestore.kt
new file mode 100644
index 00000000..01decb79
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/FileRestore.kt
@@ -0,0 +1,188 @@
+package org.calyxos.backup.storage.restore
+
+import android.content.ContentValues
+import android.content.Context
+import android.media.MediaScannerConnection
+import android.net.Uri
+import android.os.Build.VERSION.SDK_INT
+import android.os.Environment.getExternalStorageDirectory
+import android.provider.MediaStore.MediaColumns
+import android.util.Log
+import org.calyxos.backup.storage.api.MediaType
+import org.calyxos.backup.storage.api.RestoreObserver
+import org.calyxos.backup.storage.backup.BackupMediaFile
+import org.calyxos.backup.storage.openOutputStream
+import org.calyxos.backup.storage.scanner.MediaScanner
+import java.io.File
+import java.io.IOException
+import java.io.OutputStream
+import kotlin.random.Random
+
+private const val TAG = "FileRestore"
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class FileRestore(
+    private val context: Context,
+    private val mediaScanner: MediaScanner,
+) {
+
+    private val contentResolver = context.contentResolver
+
+    @Throws(IOException::class)
+    suspend fun restoreFile(
+        file: RestorableFile,
+        observer: RestoreObserver?,
+        tag: String,
+        streamWriter: suspend (outputStream: OutputStream) -> Long,
+    ) {
+        val bytes: Long
+        val finalTag: String
+        when {
+            file.mediaFile != null -> {
+                bytes = if (SDK_INT < 30) {
+                    // MediaProvider on API 29 doesn't let us write files into any folders freely,
+                    // so don't attempt to restore via MediaStore API
+                    restoreFile(file, streamWriter)
+                } else {
+                    restoreFile(file.mediaFile, streamWriter)
+                }
+                finalTag = "M$tag"
+            }
+            file.docFile != null -> {
+                bytes = restoreFile(file, streamWriter)
+                finalTag = "D$tag"
+            }
+            else -> {
+                error("unexpected file: $file")
+            }
+        }
+        observer?.onFileRestored(file, bytes, finalTag)
+    }
+
+    @Throws(IOException::class)
+    private suspend fun restoreFile(
+        docFile: RestorableFile,
+        streamWriter: suspend (outputStream: OutputStream) -> Long,
+    ): Long {
+        // ensure directory exists
+        @Suppress("DEPRECATION")
+        val dir = File("${getExternalStorageDirectory()}/${docFile.dir}")
+        if (!dir.mkdirs() && !dir.isDirectory) {
+            throw IOException("Could not create ${dir.absolutePath}")
+        }
+        // find non-existing file-name
+        var file = File(dir, docFile.name)
+        var i = 0
+        // we don't support existing files, but at least don't overwrite them when they do exist
+        while (file.exists()) {
+            i++
+            val lastDot = docFile.name.lastIndexOf('.')
+            val newName = if (lastDot == -1) "${docFile.name} ($i)"
+            else docFile.name.replaceRange(lastDot..lastDot, " ($i).")
+            file = File(dir, newName)
+        }
+        val bytesWritten = try {
+            // copy chunk(s) into file
+            file.outputStream().use { outputStream ->
+                streamWriter(outputStream)
+            }
+        } catch (e: IOException) {
+            file.delete()
+            throw e
+        }
+        // re-set lastModified timestamp
+        file.setLastModified(docFile.lastModified ?: 0)
+
+        // This might be a media file, so do we need to index it.
+        // Otherwise things like a wrong size of 0 bytes in MediaStore can happen.
+        indexFile(file)
+
+        return bytesWritten
+    }
+
+    @Throws(IOException::class)
+    private suspend fun restoreFile(
+        mediaFile: BackupMediaFile,
+        streamWriter: suspend (outputStream: OutputStream) -> Long,
+    ): Long {
+        // Insert pending media item into MediaStore
+        val contentValues = ContentValues().apply {
+            put(MediaColumns.DISPLAY_NAME, mediaFile.name)
+            put(MediaColumns.RELATIVE_PATH, mediaFile.path)
+            // changing owner requires backup permission
+            put(MediaColumns.OWNER_PACKAGE_NAME, mediaFile.ownerPackageName)
+            put(MediaColumns.IS_PENDING, 1)
+            if (SDK_INT >= 30) {
+                val isFavorite = if (mediaFile.isFavorite) 1 else 0
+                put(MediaColumns.IS_FAVORITE, isFavorite)
+            }
+        }
+        val contentUri = MediaType.fromBackupMediaType(mediaFile.type).contentUri
+        val uri = contentResolver.insert(contentUri, contentValues)!!
+
+        // copy backed up file into new item
+        val bytesWritten = uri.openOutputStream(contentResolver).use { outputStream ->
+            streamWriter(outputStream)
+        }
+
+        // after write, set it to non-pending (renames file to final name)
+        contentValues.clear()
+        contentValues.apply {
+            put(MediaColumns.IS_PENDING, 0)
+        }
+        try {
+            contentResolver.update(uri, contentValues, null, null)
+        } catch (e: IllegalStateException) {
+            // can happen if there's close to 100 files with the same name and (??) suffix already
+            if (e.message?.startsWith("Failed to build unique file") == true) {
+                // try again with a changed the file name
+                val name = " [${Random.nextInt(Int.MAX_VALUE)}]-${mediaFile.name}"
+                contentValues.put(MediaColumns.DISPLAY_NAME, name)
+                contentResolver.update(uri, contentValues, null, null)
+            } else throw e
+        }
+
+        setLastModifiedOnMediaFile(mediaFile, uri)
+
+        return bytesWritten
+    }
+
+    private fun setLastModifiedOnMediaFile(mediaFile: BackupMediaFile, uri: Uri) {
+        @Suppress("DEPRECATION")
+        val extDir = getExternalStorageDirectory()
+
+        // re-set lastModified as we can't use the MediaStore for this (read-only property)
+        val path = "$extDir/${mediaFile.path}/${mediaFile.name}"
+        val file = File(path)
+        if (file.isFile) {
+            file.setLastModified(mediaFile.lastModified)
+            // update lastModified in MediaStore
+            indexFile(file)
+        } else {
+            // file does not exist, probably because it was renamed on restore
+            // so try to find it in MediaStore
+            val relPath = mediaScanner.getPath(uri)
+            if (relPath == null) {
+                Log.w(TAG, "Did not find $path with $uri, can't set lastModified")
+            } else {
+                val newPath = "$extDir/$relPath"
+                val newFile = File(newPath)
+                Log.w(TAG, "WARNING: ${mediaFile.name} is now ${newFile.path}")
+                if (newFile.isFile) {
+                    newFile.setLastModified(mediaFile.lastModified)
+                    // update lastModified in MediaStore
+                    indexFile(newFile)
+                } else {
+                    Log.e(TAG, "Could not setLastModified on ${newFile.absolutePath}")
+                }
+            }
+        }
+    }
+
+    private fun indexFile(file: File) {
+        // Intent(ACTION_MEDIA_SCANNER_SCAN_FILE) is deprecated
+        // and does not pick up lastModified changes done in file-system
+        MediaScannerConnection.scanFile(context, arrayOf(file.path), null, null)
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/restore/FileSplitter.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/FileSplitter.kt
new file mode 100644
index 00000000..301f0f00
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/FileSplitter.kt
@@ -0,0 +1,148 @@
+package org.calyxos.backup.storage.restore
+
+import org.calyxos.backup.storage.api.BackupFile
+import org.calyxos.backup.storage.backup.BackupDocumentFile
+import org.calyxos.backup.storage.backup.BackupMediaFile
+import org.calyxos.backup.storage.backup.BackupSnapshot
+
+internal data class RestorableChunk(
+    val chunkId: String
+) {
+    val files: ArrayList<RestorableFile> = ArrayList()
+    val isSingle: Boolean get() = files.size == 1 && files[0].chunkIdsCount == 1
+
+    fun add(file: BackupMediaFile): Boolean = files.add(RestorableFile(file))
+    fun add(file: BackupDocumentFile): Boolean = files.add(RestorableFile(file))
+
+    /**
+     * Call this after the RestorableChunk is complete and **before** using it for restore.
+     */
+    fun finalize() {
+        // entries in the zip chunk need to be sorted by their index in the zip
+        files.sortBy { it.zipIndex }
+        // There might be duplicates in case the *exact* same set of files exists more than once
+        // so they'll produce the same chunk ID.
+        // But since the content is there and this is an unlikely scenario, we drop the duplicates.
+        var lastIndex = 0
+        val iterator = files.iterator()
+        while (iterator.hasNext()) {
+            val file = iterator.next()
+            val i = file.zipIndex
+            when {
+                i < lastIndex -> error("unsorted list")
+                i == lastIndex -> iterator.remove() // remove duplicate
+                i > lastIndex -> lastIndex = i // gaps are possible when we don't restore all files
+            }
+        }
+    }
+}
+
+internal data class RestorableFile(
+    val mediaFile: BackupMediaFile?,
+    val docFile: BackupDocumentFile?,
+) : BackupFile {
+    constructor(file: BackupMediaFile) : this(file, null)
+    constructor(file: BackupDocumentFile) : this(null, file)
+
+    init {
+        check((mediaFile == null) xor (docFile == null)) { "Only one file" }
+    }
+
+    val chunkIdsCount: Int get() = mediaFile?.chunkIdsCount ?: docFile!!.chunkIdsCount
+    val chunkIds: List<String> get() = mediaFile?.chunkIdsList ?: docFile!!.chunkIdsList
+    val zipIndex: Int get() = mediaFile?.zipIndex ?: docFile!!.zipIndex
+    val dir: String get() = mediaFile?.path ?: docFile!!.path
+    val name: String get() = mediaFile?.name ?: docFile!!.name
+    override val path: String = "$dir/$name"
+    override val size: Long get() = mediaFile?.size ?: docFile!!.size
+    override val volume: String get() = mediaFile?.volume ?: docFile!!.volume
+    override val lastModified: Long?
+        get() {
+            val mod = mediaFile?.lastModified ?: docFile!!.lastModified
+            return if (mod == 0L) null else mod
+        }
+}
+
+internal data class FileSplitterResult(
+    /**
+     * Zip chunks containing several small files.
+     */
+    val zipChunks: Collection<RestorableChunk>,
+    /**
+     * Chunks that contains exactly one single file.
+     */
+    val singleChunks: Collection<RestorableChunk>,
+    /**
+     * A map of chunk ID to chunks
+     * where either the chunk is used by more than one file
+     * or a file needs more than one chunk.
+     */
+    val multiChunkMap: Map<String, RestorableChunk>,
+    /**
+     * Files referenced in [multiChunkMap] sorted for restoring.
+     */
+    val multiChunkFiles: Collection<RestorableFile>,
+)
+
+/**
+ * Splits files to be restored into several types that can be restored in parallel.
+ */
+internal object FileSplitter {
+
+    fun splitSnapshot(snapshot: BackupSnapshot): FileSplitterResult {
+        val zipChunkMap = HashMap<String, RestorableChunk>()
+        val chunkMap = HashMap<String, RestorableChunk>()
+
+        snapshot.mediaFilesList.forEach { mediaFile ->
+            if (mediaFile.zipIndex > 0) {
+                check(mediaFile.chunkIdsCount == 1) { "More than 1 zip chunk: $mediaFile" }
+                val chunkId = mediaFile.chunkIdsList[0]
+                val zipChunk = zipChunkMap.getOrPut(chunkId) { RestorableChunk(chunkId) }
+                zipChunk.add(mediaFile)
+            } else for (chunkId in mediaFile.chunkIdsList) {
+                val chunk = chunkMap.getOrPut(chunkId) { RestorableChunk(chunkId) }
+                chunk.add(mediaFile)
+            }
+        }
+        snapshot.documentFilesList.forEach { docFile ->
+            if (docFile.zipIndex > 0) {
+                check(docFile.chunkIdsCount == 1) { "More than 1 zip chunk: $docFile" }
+                val chunkId = docFile.chunkIdsList[0]
+                val zipChunk = zipChunkMap.getOrPut(chunkId) { RestorableChunk(chunkId) }
+                zipChunk.add(docFile)
+            } else for (chunkId in docFile.chunkIdsList) {
+                val chunk = chunkMap.getOrPut(chunkId) { RestorableChunk(chunkId) }
+                chunk.add(docFile)
+            }
+        }
+        // entries in the zip chunk need to be sorted by their index in the zip, duplicated removed
+        zipChunkMap.values.forEach { zipChunk -> zipChunk.finalize() }
+        val singleChunks = chunkMap.values.filter { it.isSingle }
+        val multiChunks = chunkMap.filterValues { !it.isSingle }
+        return FileSplitterResult(
+            zipChunks = zipChunkMap.values,
+            singleChunks = singleChunks,
+            multiChunkMap = multiChunks,
+            multiChunkFiles = getMultiFiles(multiChunks),
+        )
+    }
+
+    private fun getMultiFiles(chunkMap: Map<String, RestorableChunk>): List<RestorableFile> {
+        val files = HashSet<RestorableFile>()
+        chunkMap.values.forEach { chunk ->
+            chunk.files.forEach { file ->
+                files.add(file)
+            }
+        }
+        return files.sortedWith { f1, f2 ->
+            when {
+                f1.chunkIdsCount < f2.chunkIdsCount -> -1
+                f1.chunkIdsCount == f2.chunkIdsCount -> {
+                    f1.chunkIds.joinToString().compareTo(f2.chunkIds.joinToString())
+                }
+                else -> 1
+            }
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/restore/MultiChunkRestore.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/MultiChunkRestore.kt
new file mode 100644
index 00000000..372f91d7
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/MultiChunkRestore.kt
@@ -0,0 +1,109 @@
+package org.calyxos.backup.storage.restore
+
+import android.content.Context
+import android.util.Log
+import org.calyxos.backup.storage.api.RestoreObserver
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.crypto.StreamCrypto
+import java.io.File
+import java.io.FileInputStream
+import java.io.FileOutputStream
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+import java.security.GeneralSecurityException
+
+private const val TAG = "MultiChunkRestore"
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class MultiChunkRestore(
+    private val context: Context,
+    storagePlugin: StoragePlugin,
+    fileRestore: FileRestore,
+    streamCrypto: StreamCrypto,
+    streamKey: ByteArray
+) : AbstractChunkRestore(storagePlugin, fileRestore, streamCrypto, streamKey) {
+
+    suspend fun restore(
+        version: Int,
+        storedSnapshot: StoredSnapshot,
+        chunkMap: Map<String, RestorableChunk>,
+        files: Collection<RestorableFile>,
+        observer: RestoreObserver?,
+    ): Int {
+        var restoredFiles = 0
+        files.forEach { file ->
+            try {
+                restoreFile(file, observer, "L") { outputStream ->
+                    writeChunks(version, storedSnapshot, file, chunkMap, outputStream)
+                }
+                restoredFiles++
+            } catch (e: Exception) {
+                Log.e(TAG, "Failed to restore single chunk file ${file.path}", e)
+                observer?.onFileRestoreError(file, e)
+                // we try to continue to restore as many files as possible
+            }
+        }
+        return restoredFiles
+    }
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    private suspend fun writeChunks(
+        version: Int,
+        storedSnapshot: StoredSnapshot,
+        file: RestorableFile,
+        chunkMap: Map<String, RestorableChunk>,
+        outputStream: OutputStream,
+    ): Long {
+        var bytes = 0L
+        file.chunkIds.forEach { chunkId ->
+            val otherFiles =
+                chunkMap[chunkId]?.files ?: error("chunk id $chunkId not in map")
+            val chunkWriter: suspend (InputStream) -> Unit = { decryptedStream ->
+                bytes += decryptedStream.copyTo(outputStream)
+            }
+            val isCached = isCached(chunkId)
+            if (isCached || otherFiles.size > 1) {
+                getAndCacheChunk(version, storedSnapshot, chunkId, chunkWriter)
+            } else {
+                getAndDecryptChunk(version, storedSnapshot, chunkId, chunkWriter)
+            }
+
+            otherFiles.remove(file)
+            if (isCached && otherFiles.isEmpty()) removeCachedChunk(chunkId)
+        }
+        return bytes
+    }
+
+    private fun isCached(chunkId: String): Boolean {
+        return getChunkCacheFile(chunkId).isFile
+    }
+
+    @Throws(IOException::class, GeneralSecurityException::class)
+    private suspend fun getAndCacheChunk(
+        version: Int,
+        storedSnapshot: StoredSnapshot,
+        chunkId: String,
+        streamReader: suspend (InputStream) -> Unit,
+    ) {
+        val file = getChunkCacheFile(chunkId)
+        if (!file.isFile) {
+            FileOutputStream(file).use { outputStream ->
+                getAndDecryptChunk(version, storedSnapshot, chunkId) { decryptedStream ->
+                    decryptedStream.copyTo(outputStream)
+                }
+            }
+        }
+        FileInputStream(file).use { inputStream ->
+            streamReader(inputStream)
+        }
+    }
+
+    private fun removeCachedChunk(chunkId: String) {
+        getChunkCacheFile(chunkId).delete()
+    }
+
+    private fun getChunkCacheFile(chunkId: String) = File(context.cacheDir, chunkId)
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/restore/NotificationRestoreObserver.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/NotificationRestoreObserver.kt
new file mode 100644
index 00000000..061c85f6
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/NotificationRestoreObserver.kt
@@ -0,0 +1,41 @@
+package org.calyxos.backup.storage.restore
+
+import android.app.PendingIntent
+import android.content.Context
+import org.calyxos.backup.storage.api.BackupFile
+import org.calyxos.backup.storage.api.RestoreObserver
+import org.calyxos.backup.storage.ui.Notifications
+
+public open class NotificationRestoreObserver internal constructor(private val n: Notifications) :
+    RestoreObserver {
+
+    public constructor(context: Context) : this(Notifications(context))
+
+    private var totalFiles = 0
+    private var filesRestored = 0
+    private var filesWithError = 0
+
+    override fun onRestoreStart(numFiles: Int, totalSize: Long) {
+        totalFiles = numFiles
+        n.updateRestoreNotification(filesRestored + filesWithError, totalFiles)
+    }
+
+    override fun onFileRestored(file: BackupFile, bytesWritten: Long, tag: String) {
+        filesRestored++
+        n.updateRestoreNotification(filesRestored + filesWithError, totalFiles)
+    }
+
+    override fun onFileRestoreError(file: BackupFile, e: Exception) {
+        filesWithError++
+        n.updateRestoreNotification(filesRestored + filesWithError, totalFiles)
+    }
+
+    override fun onRestoreComplete(restoreDuration: Long) {
+        n.showRestoreCompleteNotification(filesRestored, totalFiles, getRestoreCompleteIntent())
+    }
+
+    protected open fun getRestoreCompleteIntent(): PendingIntent? {
+        return null
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/restore/Restore.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/Restore.kt
new file mode 100644
index 00000000..297c1d5c
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/Restore.kt
@@ -0,0 +1,159 @@
+package org.calyxos.backup.storage.restore
+
+import android.content.Context
+import android.util.Log
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flow
+import org.calyxos.backup.storage.api.RestoreObserver
+import org.calyxos.backup.storage.api.SnapshotItem
+import org.calyxos.backup.storage.api.SnapshotResult
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.backup.Backup
+import org.calyxos.backup.storage.backup.BackupSnapshot
+import org.calyxos.backup.storage.crypto.StreamCrypto
+import org.calyxos.backup.storage.measure
+import org.calyxos.backup.storage.plugin.SnapshotRetriever
+import java.io.IOException
+import java.io.InputStream
+import java.security.GeneralSecurityException
+import kotlin.time.ExperimentalTime
+
+private const val TAG = "Restore"
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class Restore(
+    context: Context,
+    private val storagePlugin: StoragePlugin,
+    private val snapshotRetriever: SnapshotRetriever,
+    fileRestore: FileRestore,
+    streamCrypto: StreamCrypto = StreamCrypto,
+) {
+
+    private val streamKey by lazy {
+        // This class might get instantiated before the StoragePlugin had time to provide the key
+        // so we need to get it lazily here to prevent crashes. We can still crash later,
+        // if the plugin is not providing a key as it should when performing calls into this class.
+        try {
+            streamCrypto.deriveStreamKey(storagePlugin.getMasterKey())
+        } catch (e: GeneralSecurityException) {
+            throw AssertionError(e)
+        }
+    }
+
+    // lazily instantiate these, so they don't try to get the streamKey too early
+    private val zipChunkRestore by lazy {
+        ZipChunkRestore(storagePlugin, fileRestore, streamCrypto, streamKey)
+    }
+    private val singleChunkRestore by lazy {
+        SingleChunkRestore(storagePlugin, fileRestore, streamCrypto, streamKey)
+    }
+    private val multiChunkRestore by lazy {
+        MultiChunkRestore(context, storagePlugin, fileRestore, streamCrypto, streamKey)
+    }
+
+    fun getBackupSnapshots(): Flow<SnapshotResult> = flow {
+        val numSnapshots: Int
+        val time = measure {
+            val list = try {
+                storagePlugin.getBackupSnapshotsForRestore().sortedByDescending { storedSnapshot ->
+                    storedSnapshot.timestamp
+                }.map { storedSnapshot ->
+                    SnapshotItem(storedSnapshot, null)
+                }.toMutableList()
+            } catch (e: Exception) {
+                Log.e("TAG", "Error retrieving snapshots", e)
+                emit(SnapshotResult.Error(e))
+                return@flow
+            }
+            // return list copies, so this works with ListAdapter and DiffUtils
+            emit(SnapshotResult.Success(ArrayList(list)))
+            numSnapshots = list.size
+            val iterator = list.listIterator()
+            while (iterator.hasNext()) {
+                val oldItem = iterator.next()
+                val item = try {
+                    oldItem.copy(
+                        snapshot = snapshotRetriever.getSnapshot(streamKey, oldItem.storedSnapshot)
+                    )
+                } catch (e: Exception) {
+                    Log.e("TAG", "Error retrieving snapshot X ${oldItem.time}", e)
+                    null
+                }
+                if (item == null) {
+                    iterator.remove() // remove the failing item from the list
+                } else {
+                    iterator.set(item) // replace old item with new item
+                }
+                emit(SnapshotResult.Success(ArrayList(list)))
+            }
+        }
+        Log.e(TAG, "Decrypting and parsing $numSnapshots snapshots took $time")
+    }
+
+    @OptIn(ExperimentalTime::class)
+    @Throws(IOException::class, GeneralSecurityException::class)
+    suspend fun restoreBackupSnapshot(
+        storedSnapshot: StoredSnapshot,
+        optionalSnapshot: BackupSnapshot? = null,
+        observer: RestoreObserver? = null,
+    ) {
+        val snapshot = optionalSnapshot ?: snapshotRetriever.getSnapshot(streamKey, storedSnapshot)
+
+        val filesTotal = snapshot.mediaFilesList.size + snapshot.documentFilesList.size
+        val totalSize =
+            snapshot.mediaFilesList.sumOf { it.size } + snapshot.documentFilesList.sumOf { it.size }
+        observer?.onRestoreStart(filesTotal, totalSize)
+
+        val split = FileSplitter.splitSnapshot(snapshot)
+        val version = snapshot.version
+        var restoredFiles = 0
+        val smallFilesDuration = measure {
+            restoredFiles += zipChunkRestore.restore(
+                version,
+                storedSnapshot,
+                split.zipChunks,
+                observer,
+            )
+        }
+        Log.e(TAG, "Restoring ${split.zipChunks.size} zip chunks took $smallFilesDuration.")
+        val singleChunkDuration = measure {
+            restoredFiles += singleChunkRestore.restore(
+                version,
+                storedSnapshot,
+                split.singleChunks,
+                observer,
+            )
+        }
+        Log.e(TAG, "Restoring ${split.singleChunks.size} single chunks took $singleChunkDuration.")
+        val multiChunkDuration = measure {
+            restoredFiles += multiChunkRestore.restore(
+                version,
+                storedSnapshot,
+                split.multiChunkMap,
+                split.multiChunkFiles,
+                observer,
+            )
+        }
+        Log.e(TAG, "Restoring ${split.multiChunkFiles.size} multi chunks took $multiChunkDuration.")
+
+        val totalDuration = smallFilesDuration + singleChunkDuration + multiChunkDuration
+        observer?.onRestoreComplete(totalDuration.toLongMilliseconds())
+        Log.e(TAG, "Restored $restoredFiles/$filesTotal files.")
+    }
+
+}
+
+@Throws(IOException::class, GeneralSecurityException::class)
+internal fun InputStream.readVersion(expectedVersion: Int? = null): Int {
+    val version = read()
+    if (version == -1) throw IOException()
+    if (expectedVersion != null && version != expectedVersion) {
+        throw GeneralSecurityException("Expected version $expectedVersion, not $version")
+    }
+    if (version > Backup.VERSION) {
+        // TODO maybe throw a different exception here and tell the user?
+        throw IOException()
+    }
+    return version
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/restore/RestoreService.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/RestoreService.kt
new file mode 100644
index 00000000..1917e420
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/RestoreService.kt
@@ -0,0 +1,61 @@
+package org.calyxos.backup.storage.restore
+
+import android.app.Service
+import android.content.Intent
+import android.os.IBinder
+import android.util.Log
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.launch
+import org.calyxos.backup.storage.api.RestoreObserver
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.restore.RestoreService.Companion.EXTRA_TIMESTAMP_START
+import org.calyxos.backup.storage.restore.RestoreService.Companion.EXTRA_USER_ID
+import org.calyxos.backup.storage.ui.NOTIFICATION_ID_RESTORE
+import org.calyxos.backup.storage.ui.Notifications
+
+/**
+ * Start to trigger restore as a foreground service. Ensure that you provide the snapshot
+ * to be restored with [Intent.putExtra]:
+ *   * the user ID of the snapshot as a [String] in [EXTRA_USER_ID]
+ *   * the snapshot's timestamp as a [Long] in [EXTRA_TIMESTAMP_START].
+ *     See [BackupSnapshot.getTimeStart].
+ */
+public abstract class RestoreService : Service() {
+
+    public companion object {
+        private const val TAG = "RestoreService"
+        public const val EXTRA_USER_ID: String = "userId"
+        public const val EXTRA_TIMESTAMP_START: String = "timestamp"
+    }
+
+    private val n by lazy { Notifications(applicationContext) }
+    protected abstract val storageBackup: StorageBackup
+    protected abstract val restoreObserver: RestoreObserver?
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
+        Log.d(TAG, "onStartCommand $intent $flags $startId")
+        val userId = intent?.getStringExtra(EXTRA_USER_ID) ?: error("No user ID in intent: $intent")
+        val timestamp = intent.getLongExtra(EXTRA_TIMESTAMP_START, -1)
+        if (timestamp < 0) error("No timestamp in intent: $intent")
+        val storedSnapshot = StoredSnapshot(userId, timestamp)
+
+        startForeground(NOTIFICATION_ID_RESTORE, n.getRestoreNotification())
+        GlobalScope.launch {
+            // TODO offer a way to try again if failed, or do an automatic retry here
+            storageBackup.restoreBackupSnapshot(storedSnapshot, null, restoreObserver)
+            stopSelf(startId)
+        }
+        return START_STICKY_COMPATIBILITY
+    }
+
+    override fun onBind(intent: Intent?): IBinder? {
+        return null
+    }
+
+    override fun onDestroy() {
+        Log.d(TAG, "onDestroy")
+        super.onDestroy()
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/restore/SingleChunkRestore.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/SingleChunkRestore.kt
new file mode 100644
index 00000000..f6e23806
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/SingleChunkRestore.kt
@@ -0,0 +1,45 @@
+package org.calyxos.backup.storage.restore
+
+import android.util.Log
+import org.calyxos.backup.storage.api.RestoreObserver
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.crypto.StreamCrypto
+
+private const val TAG = "SingleChunkRestore"
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class SingleChunkRestore(
+    storagePlugin: StoragePlugin,
+    fileRestore: FileRestore,
+    streamCrypto: StreamCrypto,
+    streamKey: ByteArray
+) : AbstractChunkRestore(storagePlugin, fileRestore, streamCrypto, streamKey) {
+
+    suspend fun restore(
+        version: Int,
+        storedSnapshot: StoredSnapshot,
+        chunks: Collection<RestorableChunk>,
+        observer: RestoreObserver?
+    ): Int {
+        var restoredFiles = 0
+        chunks.forEach { chunk ->
+            check(chunk.files.size == 1)
+            val file = chunk.files[0]
+            try {
+                getAndDecryptChunk(version, storedSnapshot, chunk.chunkId) { decryptedStream ->
+                    restoreFile(file, observer, "M") { outputStream ->
+                        decryptedStream.copyTo(outputStream)
+                    }
+                }
+                restoredFiles++
+            } catch (e: Exception) {
+                Log.e(TAG, "Failed to restore single chunk file ${file.path}", e)
+                observer?.onFileRestoreError(file, e)
+                // we try to continue to restore as many files as possible
+            }
+        }
+        return restoredFiles
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/restore/ZipChunkRestore.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/ZipChunkRestore.kt
new file mode 100644
index 00000000..b937bc85
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/restore/ZipChunkRestore.kt
@@ -0,0 +1,90 @@
+package org.calyxos.backup.storage.restore
+
+import android.util.Log
+import org.calyxos.backup.storage.api.RestoreObserver
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.crypto.StreamCrypto
+import java.io.IOException
+import java.io.InputStream
+import java.io.OutputStream
+import java.util.zip.ZipInputStream
+
+private const val TAG = "ZipChunkRestore"
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class ZipChunkRestore(
+    storagePlugin: StoragePlugin,
+    fileRestore: FileRestore,
+    streamCrypto: StreamCrypto,
+    streamKey: ByteArray
+) : AbstractChunkRestore(storagePlugin, fileRestore, streamCrypto, streamKey) {
+
+    /**
+     * Assumes that files in [zipChunks] are sorted by zipIndex with no duplicate indices.
+     */
+    suspend fun restore(
+        version: Int,
+        storedSnapshot: StoredSnapshot,
+        zipChunks: Collection<RestorableChunk>,
+        observer: RestoreObserver?
+    ): Int {
+        var restoredFiles = 0
+        zipChunks.forEach { zipChunk ->
+            try {
+                getAndDecryptChunk(version, storedSnapshot, zipChunk.chunkId) { decryptedStream ->
+                    restoredFiles += restoreZipChunk(zipChunk, decryptedStream, observer)
+                }
+            } catch (e: Exception) {
+                // we also swallow exceptions in [restoreZipChunk]
+                // so should only get something from [getAndDecryptChunk] here.
+                Log.e(TAG, "Failed to decrypt chunk ${zipChunk.chunkId}", e)
+                zipChunk.files.forEach { file ->
+                    observer?.onFileRestoreError(file, e)
+                }
+                // we try to continue to restore as many files as possible
+            }
+        }
+        return restoredFiles
+    }
+
+    private suspend fun restoreZipChunk(
+        zipChunk: RestorableChunk,
+        decryptedStream: InputStream,
+        observer: RestoreObserver?
+    ): Int {
+        var restoredFiles = 0
+        ZipInputStream(decryptedStream).use { zip ->
+            zipChunk.files.forEach { file ->
+                try {
+                    restoreZipEntry(zip, file, observer)
+                    restoredFiles++
+                } catch (e: Exception) {
+                    Log.e(TAG, "Failed to restore zip entry for ${file.path}", e)
+                    observer?.onFileRestoreError(file, e)
+                    // we try to continue to restore as many files as possible
+                }
+            }
+        }
+        return restoredFiles
+    }
+
+    @Throws(IOException::class)
+    private suspend fun restoreZipEntry(
+        zip: ZipInputStream,
+        file: RestorableFile,
+        observer: RestoreObserver?,
+    ) {
+        var entry = zip.nextEntry
+        while (entry != null && entry.name != file.zipIndex.toString()) {
+            entry = zip.nextEntry
+        }
+        check(entry != null) { "zip entry was null for: $file" }
+        restoreFile(file, observer, "S") { outputStream: OutputStream ->
+            val bytes = zip.copyTo(outputStream)
+            zip.closeEntry()
+            bytes
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/scanner/DocumentScanner.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/scanner/DocumentScanner.kt
new file mode 100644
index 00000000..3751a9dc
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/scanner/DocumentScanner.kt
@@ -0,0 +1,84 @@
+package org.calyxos.backup.storage.scanner
+
+import android.content.Context
+import android.net.Uri
+import android.provider.DocumentsContract
+import android.provider.DocumentsContract.Document.MIME_TYPE_DIR
+import android.provider.MediaStore
+import androidx.core.database.getLongOrNull
+import androidx.core.database.getStringOrNull
+import org.calyxos.backup.storage.api.BackupFile
+import org.calyxos.backup.storage.content.DocFile
+import org.calyxos.backup.storage.getDocumentPath
+import org.calyxos.backup.storage.getVolume
+
+public class DocumentScanner(context: Context) {
+
+    private companion object {
+        private val PROJECTION = arrayOf(
+            DocumentsContract.Document.COLUMN_DOCUMENT_ID,
+            DocumentsContract.Document.COLUMN_DISPLAY_NAME,
+            DocumentsContract.Document.COLUMN_MIME_TYPE,
+            DocumentsContract.Document.COLUMN_LAST_MODIFIED,
+            DocumentsContract.Document.COLUMN_SIZE,
+            DocumentsContract.Document.COLUMN_FLAGS
+        )
+        private const val PROJECTION_ID = 0
+        private const val PROJECTION_NAME = 1
+        private const val PROJECTION_MIME_TYPE = 2
+        private const val PROJECTION_LAST_MODIFIED = 3
+        private const val PROJECTION_COLUMN_SIZE = 4
+        private const val PROJECTION_COLUMN_FLAGS = 5
+    }
+
+    private val contentResolver = context.contentResolver
+
+    public fun scanUri(uri: Uri, maxSize: Long = Long.MAX_VALUE): List<BackupFile> {
+        return scanDocumentUri(uri, "", maxSize)
+    }
+
+    internal fun scanDocumentUri(
+        uri: Uri,
+        dir: String = uri.getDocumentPath() ?: "",
+        maxSize: Long = Long.MAX_VALUE
+    ): List<DocFile> {
+        // http://aosp.opersys.com/xref/android-11.0.0_r8/xref/frameworks/base/core/java/com/android/internal/content/FileSystemProvider.java
+        // http://aosp.opersys.com/xref/android-11.0.0_r8/xref/frameworks/base/packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java
+
+        val docId = DocumentsContract.getDocumentId(uri)
+        val queryUri = DocumentsContract.buildChildDocumentsUriUsingTree(uri, docId)
+        val cursor = contentResolver.query(
+            queryUri, PROJECTION, null, null, null
+        )
+        val documentFiles = ArrayList<DocFile>(cursor?.count ?: 0)
+        cursor?.use { it ->
+            while (it.moveToNext()) {
+                val id = it.getString(PROJECTION_ID)
+                val documentUri = DocumentsContract.buildDocumentUriUsingTree(uri, id)
+                val name = it.getString(PROJECTION_NAME)
+                if (it.getStringOrNull(PROJECTION_MIME_TYPE) == MIME_TYPE_DIR) {
+                    // don't include directories, but do include their contents
+                    val dirPath = "$dir/$name".trimStart('/')
+                    documentFiles.addAll(scanDocumentUri(documentUri, dirPath, maxSize))
+                    continue
+                }
+                val flags = it.getInt(PROJECTION_COLUMN_FLAGS)
+                val isVirtual = flags and DocumentsContract.Document.FLAG_VIRTUAL_DOCUMENT != 0
+                if (isVirtual) continue // don't include virtual files
+                val size = it.getLong(PROJECTION_COLUMN_SIZE)
+                if (size > maxSize) continue // don't include files larger tha max (for testing)
+                val docFile = DocFile(
+                    uri = documentUri,
+                    dirPath = dir,
+                    fileName = name,
+                    lastModified = it.getLongOrNull(PROJECTION_LAST_MODIFIED),
+                    size = size,
+                    volume = documentUri.getVolume() ?: MediaStore.VOLUME_EXTERNAL_PRIMARY,
+                )
+                documentFiles.add(docFile)
+            }
+        }
+        return documentFiles
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/scanner/FileScanner.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/scanner/FileScanner.kt
new file mode 100644
index 00000000..bbce61c4
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/scanner/FileScanner.kt
@@ -0,0 +1,90 @@
+package org.calyxos.backup.storage.scanner
+
+import android.net.Uri
+import android.provider.DocumentsContract
+import android.provider.MediaStore
+import android.util.Log
+import org.calyxos.backup.storage.api.EXTERNAL_STORAGE_PROVIDER_AUTHORITY
+import org.calyxos.backup.storage.backup.Backup.Companion.SMALL_FILE_SIZE_MAX
+import org.calyxos.backup.storage.content.ContentFile
+import org.calyxos.backup.storage.content.DocFile
+import org.calyxos.backup.storage.content.MediaFile
+import org.calyxos.backup.storage.db.UriStore
+import org.calyxos.backup.storage.measure
+
+internal class FileScannerResult(
+    val smallFiles: List<ContentFile>,
+    val files: List<ContentFile>,
+)
+
+internal class FileScanner(
+    private val uriStore: UriStore,
+    private val mediaScanner: MediaScanner,
+    private val documentScanner: DocumentScanner,
+    private val smallFileSizeMax: Int = SMALL_FILE_SIZE_MAX,
+) {
+
+    companion object {
+        private const val TAG = "FileScanner"
+        private const val FILES_SMALL = "small"
+        private const val FILES_LARGE = "large"
+    }
+
+    fun getFiles(): FileScannerResult {
+        // scan both APIs
+        val mediaFiles = ArrayList<ContentFile>()
+        val docFiles = ArrayList<ContentFile>()
+        val scanning = measure {
+            uriStore.getStoredUris().forEach { (uri) ->
+                when (uri.authority) {
+                    MediaStore.AUTHORITY -> {
+                        mediaFiles.addAll(getMediaFiles(uri))
+                    }
+                    EXTERNAL_STORAGE_PROVIDER_AUTHORITY -> {
+                        docFiles.addAll(getDocumentFiles(uri))
+                    }
+                    else -> throw AssertionError("unsupported authority")
+                }
+            }
+        }
+        Log.e(TAG, "Scanning took $scanning")
+
+        // remove duplicates from document files (as MediaStore has generation counter)
+        val duplicateRemoving = measure {
+            val mediaSet = HashSet<String>(mediaFiles.size)
+            mediaFiles.forEach { mediaSet.add(it.id) }
+            docFiles.removeIf {
+                mediaSet.contains(it.id)
+            }
+        }
+        Log.e(TAG, "Removing duplicates took $duplicateRemoving")
+
+        // prep for zip chunks
+        val smallFiles: List<ContentFile>
+        val largeFiles: List<ContentFile>
+        val sizeSorting = measure {
+            val filesMap = (mediaFiles + docFiles).groupBy { file ->
+                if (file.size > smallFileSizeMax) FILES_LARGE else FILES_SMALL
+            }
+            val scannerComparator = compareBy<ContentFile> {
+                it.lastModified ?: Long.MAX_VALUE
+            }
+            smallFiles = filesMap[FILES_SMALL]?.sortedWith(scannerComparator) ?: emptyList()
+            largeFiles = filesMap[FILES_LARGE]?.sortedWith(scannerComparator) ?: emptyList()
+        }
+        Log.e(TAG, "Grouping per size took $sizeSorting")
+
+        return FileScannerResult(smallFiles, largeFiles)
+    }
+
+    private fun getMediaFiles(uri: Uri): List<MediaFile> {
+        return mediaScanner.scanMediaUri(uri)
+    }
+
+    private fun getDocumentFiles(uri: Uri): List<DocFile> {
+        val documentId = DocumentsContract.getTreeDocumentId(uri)
+        val documentUri = DocumentsContract.buildDocumentUriUsingTree(uri, documentId)
+        return documentScanner.scanDocumentUri(documentUri)
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/scanner/MediaScanner.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/scanner/MediaScanner.kt
new file mode 100644
index 00000000..673175e4
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/scanner/MediaScanner.kt
@@ -0,0 +1,126 @@
+package org.calyxos.backup.storage.scanner
+
+import android.content.ContentResolver.QUERY_ARG_SQL_SELECTION
+import android.content.ContentUris
+import android.content.Context
+import android.database.Cursor
+import android.net.Uri
+import android.os.Build.VERSION.SDK_INT
+import android.os.Bundle
+import android.os.Environment
+import android.provider.MediaStore
+import android.provider.MediaStore.MediaColumns.IS_DOWNLOAD
+import android.util.Log
+import androidx.annotation.RequiresApi
+import androidx.core.database.getIntOrNull
+import androidx.core.database.getLongOrNull
+import androidx.core.database.getStringOrNull
+import org.calyxos.backup.storage.api.BackupFile
+import org.calyxos.backup.storage.api.MediaType
+import org.calyxos.backup.storage.content.MediaFile
+import java.io.File
+
+public class MediaScanner(context: Context) {
+
+    private companion object {
+        private val PROJECTION_29 = arrayOf(
+            MediaStore.MediaColumns._ID,
+            MediaStore.MediaColumns.RELATIVE_PATH,
+            MediaStore.MediaColumns.DISPLAY_NAME,
+            MediaStore.MediaColumns.DATE_MODIFIED,
+            MediaStore.MediaColumns.SIZE,
+            MediaStore.MediaColumns.OWNER_PACKAGE_NAME,
+            MediaStore.MediaColumns.VOLUME_NAME,
+        )
+
+        @RequiresApi(30)
+        private val PROJECTION_30 = arrayOf(
+            MediaStore.MediaColumns.IS_FAVORITE,
+            MediaStore.MediaColumns.GENERATION_MODIFIED,
+        )
+        private const val PROJECTION_ID = 0
+        private const val PROJECTION_PATH = 1
+        private const val PROJECTION_NAME = 2
+        private const val PROJECTION_DATE_MODIFIED = 3
+        private const val PROJECTION_SIZE = 4
+        private const val PROJECTION_OWNER_PACKAGE_NAME = 5
+        private const val PROJECTION_VOLUME_NAME = 6
+        private const val PROJECTION_IS_FAVORITE = 7
+        private const val PROJECTION_GENERATION_MODIFIED = 8
+
+    }
+
+    private val contentResolver = context.contentResolver
+
+    public fun scanUri(uri: Uri, maxSize: Long = Long.MAX_VALUE): List<BackupFile> {
+        return scanMediaUri(uri, "${MediaStore.MediaColumns.SIZE}<$maxSize")
+    }
+
+    internal fun scanMediaUri(uri: Uri, extraQuery: String? = null): List<MediaFile> {
+        val extras = Bundle().apply {
+            val query = StringBuilder()
+            if (SDK_INT >= 30 && uri != MediaType.Downloads.contentUri) {
+                query.append("$IS_DOWNLOAD=0")
+            }
+            extraQuery?.let {
+                if (query.isNotEmpty()) query.append(" AND ")
+                query.append(it)
+            }
+            if (query.isNotEmpty()) putString(QUERY_ARG_SQL_SELECTION, query.toString())
+        }
+        val projection = if (SDK_INT >= 30) PROJECTION_29 + PROJECTION_30 else PROJECTION_29
+        val cursor = contentResolver.query(uri, projection, extras, null)
+        return ArrayList<MediaFile>(cursor?.count ?: 0).apply {
+            cursor?.use { c ->
+                while (c.moveToNext()) add(createMediaFile(c, uri))
+            }
+        }
+    }
+
+    internal fun getPath(uri: Uri): String? {
+        val projection = arrayOf(
+            MediaStore.MediaColumns.RELATIVE_PATH,
+            MediaStore.MediaColumns.DISPLAY_NAME,
+        )
+        return contentResolver.query(uri, projection, null, null)?.use { c ->
+            if (c.moveToNext()) "${c.getString(0)}/${c.getString(1)}".trimEnd('/')
+            else null
+        }
+    }
+
+    private fun createMediaFile(cursor: Cursor, queryUri: Uri): MediaFile {
+        val mediaFile = MediaFile(
+            uri = ContentUris.withAppendedId(queryUri, cursor.getLong(PROJECTION_ID)),
+            dir = cursor.getString(PROJECTION_PATH),
+            fileName = cursor.getString(PROJECTION_NAME),
+            dateModified = cursor.getLongOrNull(PROJECTION_DATE_MODIFIED),
+            generationModified = if (SDK_INT >= 30) cursor.getLongOrNull(
+                PROJECTION_GENERATION_MODIFIED
+            ) else null,
+            size = cursor.getLong(PROJECTION_SIZE),
+            isFavorite = if (SDK_INT >= 30) {
+                cursor.getIntOrNull(PROJECTION_IS_FAVORITE) == 1
+            } else false,
+            ownerPackageName = cursor.getStringOrNull(PROJECTION_OWNER_PACKAGE_NAME),
+            volume = cursor.getString(PROJECTION_VOLUME_NAME)
+        )
+        if (mediaFile.size == 0L) {
+            // we can't trust this and it can cause OOMs if file is really big
+            return mediaFile.copy(size = getRealSize(mediaFile))
+        }
+        return mediaFile
+    }
+
+    private fun getRealSize(mediaFile: MediaFile): Long {
+        @Suppress("DEPRECATION")
+        val extDir = Environment.getExternalStorageDirectory()
+        val path = "$extDir/${mediaFile.dirPath}/${mediaFile.fileName}"
+        return try {
+            File(path).length()
+        } catch (e: Exception) {
+            Log.e("MediaScanner", "Error getting real size for $path", e)
+            0L
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/ui/Notifications.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/Notifications.kt
new file mode 100644
index 00000000..bac3e04e
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/Notifications.kt
@@ -0,0 +1,149 @@
+package org.calyxos.backup.storage.ui
+
+import android.app.Notification
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.NotificationManager.IMPORTANCE_LOW
+import android.app.PendingIntent
+import android.content.Context
+import androidx.annotation.DrawableRes
+import androidx.annotation.StringRes
+import androidx.core.app.NotificationCompat
+import androidx.core.app.NotificationCompat.PRIORITY_DEFAULT
+import org.calyxos.backup.storage.R
+
+private const val CHANNEL_ID_BACKUP = "seedvault.storage.backup"
+private const val CHANNEL_ID_RESTORE = "seedvault.storage.restore"
+internal const val NOTIFICATION_ID_BACKUP = 1000
+internal const val NOTIFICATION_ID_PRUNE = 1001
+internal const val NOTIFICATION_ID_RESTORE = 1002
+internal const val NOTIFICATION_ID_RESTORE_COMPLETE = 1003
+
+internal class Notifications(private val context: Context) {
+
+    private val nm = context.getSystemService(NotificationManager::class.java).apply {
+        createNotificationChannel(createBackupChannel())
+        createNotificationChannel(createRestoreChannel())
+    }
+
+    private fun createBackupChannel(): NotificationChannel {
+        val title = context.getString(R.string.notification_backup_title)
+        return NotificationChannel(CHANNEL_ID_BACKUP, title, IMPORTANCE_LOW).apply {
+            enableVibration(false)
+        }
+    }
+
+    private fun createRestoreChannel(): NotificationChannel {
+        val title = context.getString(R.string.notification_restore_title)
+        return NotificationChannel(CHANNEL_ID_RESTORE, title, IMPORTANCE_LOW).apply {
+            enableVibration(false)
+        }
+    }
+
+    internal fun getBackupNotification(
+        @StringRes textRes: Int,
+        transferred: Int = 0,
+        expected: Int = 0,
+    ) = getNotification(
+        icon = R.drawable.ic_cloud_upload,
+        title = context.getString(R.string.notification_backup_title),
+        infoText = context.getString(textRes),
+        transferred = transferred,
+        expected = expected
+    )
+
+    internal fun updateBackupNotification(
+        @StringRes textRes: Int,
+        transferred: Int = 0,
+        expected: Int = 0,
+    ) {
+        val notification = getBackupNotification(textRes, transferred, expected)
+        nm.notify(NOTIFICATION_ID_BACKUP, notification)
+    }
+
+    internal fun cancelBackupNotification() {
+        nm.cancel(NOTIFICATION_ID_BACKUP)
+    }
+
+    internal fun getPruneNotification(
+        @StringRes textRes: Int,
+        transferred: Int = 0,
+        expected: Int = 0,
+    ) = getNotification(
+        icon = R.drawable.ic_auto_delete,
+        title = context.getString(R.string.notification_backup_title),
+        infoText = context.getString(textRes),
+        transferred = transferred,
+        expected = expected
+    )
+
+    internal fun updatePruneNotification(
+        @StringRes textRes: Int,
+        transferred: Int = 0,
+        expected: Int = 0,
+    ) {
+        val notification = getPruneNotification(textRes, transferred, expected)
+        nm.notify(NOTIFICATION_ID_PRUNE, notification)
+    }
+
+    internal fun cancelPruneNotification() {
+        nm.cancel(NOTIFICATION_ID_PRUNE)
+    }
+
+    internal fun getRestoreNotification(restored: Int = 0, expected: Int = 0): Notification {
+        val info = if (expected > 0) {
+            context.getString(R.string.notification_restore_info, restored, expected)
+        } else null
+        return getNotification(
+            icon = R.drawable.ic_cloud_restore,
+            title = context.getString(R.string.notification_restore_title),
+            infoText = info,
+            transferred = restored,
+            expected = expected
+        )
+    }
+
+    internal fun updateRestoreNotification(restored: Int, expected: Int) {
+        val notification = getRestoreNotification(restored, expected)
+        nm.notify(NOTIFICATION_ID_RESTORE, notification)
+    }
+
+    internal fun showRestoreCompleteNotification(
+        restored: Int,
+        total: Int,
+        intent: PendingIntent?
+    ) {
+        val title = context.getString(R.string.notification_restore_complete_title, restored, total)
+        val notification = NotificationCompat.Builder(context, CHANNEL_ID_BACKUP).apply {
+            setSmallIcon(R.drawable.ic_cloud_done)
+            setContentTitle(title)
+            setOngoing(false)
+            setShowWhen(true)
+            setAutoCancel(true)
+            setContentIntent(intent)
+            setWhen(System.currentTimeMillis())
+            priority = PRIORITY_DEFAULT
+        }.build()
+        // use a new notification, so it can stick around after the foreground service stopped
+        nm.cancel(NOTIFICATION_ID_RESTORE)
+        nm.notify(NOTIFICATION_ID_RESTORE_COMPLETE, notification)
+    }
+
+    private fun getNotification(
+        @DrawableRes icon: Int,
+        title: CharSequence,
+        infoText: CharSequence?,
+        transferred: Int = 0,
+        expected: Int = 0,
+    ) = NotificationCompat.Builder(context, CHANNEL_ID_BACKUP).apply {
+        setSmallIcon(icon)
+        setContentTitle(title)
+        setContentText(infoText)
+        setOngoing(true)
+        setShowWhen(false)
+        setWhen(System.currentTimeMillis())
+        setProgress(expected, transferred, expected == 0)
+        priority = PRIORITY_DEFAULT
+    }.build()
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentAdapter.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentAdapter.kt
new file mode 100644
index 00000000..b6972771
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentAdapter.kt
@@ -0,0 +1,92 @@
+package org.calyxos.backup.storage.ui.backup
+
+import android.provider.MediaStore
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.ImageButton
+import android.widget.ImageView
+import android.widget.TextView
+import androidx.appcompat.widget.SwitchCompat
+import androidx.recyclerview.widget.RecyclerView
+import androidx.recyclerview.widget.RecyclerView.Adapter
+import org.calyxos.backup.storage.R
+import org.calyxos.backup.storage.api.EXTERNAL_STORAGE_PROVIDER_AUTHORITY
+
+internal class BackupContentAdapter(private val listener: ContentClickListener) :
+    Adapter<BackupContentAdapter.ViewHolder>() {
+
+    private val items = ArrayList<BackupContentItem>()
+
+    override fun getItemViewType(position: Int): Int {
+        return when (items[position].uri.authority) {
+            MediaStore.AUTHORITY -> R.layout.item_media
+            EXTERNAL_STORAGE_PROVIDER_AUTHORITY -> R.layout.item_custom
+            else -> throw IllegalStateException("unknown item type")
+        }
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
+        val v = LayoutInflater.from(parent.context).inflate(viewType, parent, false)
+        return when (viewType) {
+            R.layout.item_media -> MediaHolder(v)
+            R.layout.item_custom -> CustomHolder(v)
+            else -> throw IllegalStateException("unknown view type")
+        }
+    }
+
+    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
+        val item = items[position]
+        holder.bind(item)
+    }
+
+    override fun getItemCount(): Int = items.size
+
+    internal fun setItems(items: List<BackupContentItem>) {
+        this.items.clear()
+        this.items.addAll(items)
+        notifyDataSetChanged()
+    }
+
+    internal abstract class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
+        protected val layout: ViewGroup = view.findViewById(R.id.layout)
+        private val icon: ImageView = view.findViewById(R.id.icon)
+        private val title: TextView = view.findViewById(R.id.title)
+
+        open fun bind(item: BackupContentItem) {
+            icon.setImageResource(item.contentType.drawableRes)
+            title.text = item.getName(title.context)
+        }
+    }
+
+    internal inner class MediaHolder(view: View) : ViewHolder(view) {
+        private val switch: SwitchCompat = view.findViewById(R.id.switchView)
+
+        override fun bind(item: BackupContentItem) {
+            super.bind(item)
+            layout.setOnClickListener {
+                listener.onContentClicked(layout, item)
+            }
+            switch.setOnCheckedChangeListener(null)
+            switch.isChecked = item.enabled
+            switch.setOnCheckedChangeListener { _, isChecked ->
+                switch.isChecked = listener.onMediaContentEnabled(item, isChecked)
+            }
+        }
+    }
+
+    internal inner class CustomHolder(view: View) : ViewHolder(view) {
+        private val overflow: ImageButton = view.findViewById(R.id.overflow)
+
+        override fun bind(item: BackupContentItem) {
+            super.bind(item)
+            layout.setOnClickListener {
+                listener.onContentClicked(overflow, item)
+            }
+            overflow.setOnClickListener {
+                listener.onFolderOverflowClicked(overflow, item)
+            }
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentFragment.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentFragment.kt
new file mode 100644
index 00000000..35c70adf
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentFragment.kt
@@ -0,0 +1,116 @@
+package org.calyxos.backup.storage.ui.backup
+
+import android.content.Context
+import android.content.Intent
+import android.content.Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION
+import android.content.Intent.FLAG_GRANT_READ_URI_PERMISSION
+import android.content.Intent.FLAG_GRANT_WRITE_URI_PERMISSION
+import android.net.Uri
+import android.os.Bundle
+import android.provider.DocumentsContract
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.Toast
+import android.widget.Toast.LENGTH_LONG
+import androidx.activity.result.contract.ActivityResultContracts.OpenDocumentTree
+import androidx.appcompat.widget.PopupMenu
+import androidx.fragment.app.Fragment
+import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.floatingactionbutton.FloatingActionButton
+import org.calyxos.backup.storage.R
+import org.calyxos.backup.storage.api.BackupContentType
+import org.calyxos.backup.storage.api.EXTERNAL_STORAGE_PROVIDER_AUTHORITY
+
+internal interface ContentClickListener {
+    fun onContentClicked(view: View, item: BackupContentItem)
+    fun onMediaContentEnabled(item: BackupContentItem, enabled: Boolean): Boolean
+    fun onFolderOverflowClicked(view: View, item: BackupContentItem)
+}
+
+public class OpenTree : OpenDocumentTree() {
+    override fun createIntent(context: Context, input: Uri?): Intent {
+        return super.createIntent(context, input).apply {
+            addFlags(
+                FLAG_GRANT_READ_URI_PERMISSION or FLAG_GRANT_WRITE_URI_PERMISSION or
+                        FLAG_GRANT_PERSISTABLE_URI_PERMISSION
+            )
+        }
+    }
+}
+
+public abstract class BackupContentFragment : Fragment(), ContentClickListener {
+
+    protected abstract val viewModel: BackupContentViewModel
+
+    private val addRequest = registerForActivityResult(OpenTree()) { uri ->
+        onTreeUriReceived(uri)
+    }
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        val v = inflater.inflate(R.layout.fragment_backup_content, container, false)
+        val list: RecyclerView = v.findViewById(R.id.list)
+
+        val adapter = BackupContentAdapter(this)
+        list.adapter = adapter
+        viewModel.content.observe(viewLifecycleOwner, {
+            adapter.setItems(it)
+        })
+        v.findViewById<FloatingActionButton>(R.id.fab).setOnClickListener {
+            addRequest.launch(DocumentsContract.buildRootsUri(EXTERNAL_STORAGE_PROVIDER_AUTHORITY))
+        }
+        return v
+    }
+
+    override fun onContentClicked(view: View, item: BackupContentItem): Unit = when {
+        item.contentType == BackupContentType.Custom -> {
+            onFolderOverflowClicked(view, item)
+        }
+        item.enabled -> {
+            viewModel.removeUri(item.uri)
+        }
+        else -> {
+            viewModel.addUri(item.uri)
+        }
+    }
+
+    override fun onMediaContentEnabled(item: BackupContentItem, enabled: Boolean): Boolean {
+        if (enabled) {
+            viewModel.addUri(item.uri)
+        } else {
+            viewModel.removeUri(item.uri)
+        }
+        return enabled
+    }
+
+    override fun onFolderOverflowClicked(view: View, item: BackupContentItem) {
+        val popup = PopupMenu(requireContext(), view)
+        popup.menuInflater.inflate(R.menu.item_custom, popup.menu)
+        popup.setOnMenuItemClickListener {
+            if (it.itemId == R.id.delete) {
+                viewModel.removeUri(item.uri)
+                true
+            } else {
+                false
+            }
+        }
+        popup.show()
+    }
+
+    private fun onTreeUriReceived(uri: Uri?) {
+        if (uri?.authority == EXTERNAL_STORAGE_PROVIDER_AUTHORITY) {
+            requireContext().contentResolver.takePersistableUriPermission(
+                uri, FLAG_GRANT_READ_URI_PERMISSION
+            )
+            viewModel.addUri(uri)
+        } else {
+            Toast.makeText(requireContext(), "Backup not supported for location", LENGTH_LONG)
+                .show()
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentItem.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentItem.kt
new file mode 100644
index 00000000..7a4d15d5
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentItem.kt
@@ -0,0 +1,17 @@
+package org.calyxos.backup.storage.ui.backup
+
+import android.content.Context
+import android.net.Uri
+import org.calyxos.backup.storage.api.BackupContentType
+import org.calyxos.backup.storage.api.MediaType
+
+public data class BackupContentItem(
+    val uri: Uri,
+    val contentType: BackupContentType,
+    val enabled: Boolean
+) {
+    public fun getName(context: Context): String = when (contentType) {
+        is BackupContentType.Custom -> BackupContentType.Custom.getName(uri)
+        is MediaType -> context.getString(contentType.nameRes)
+    }
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentViewModel.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentViewModel.kt
new file mode 100644
index 00000000..671bd076
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/backup/BackupContentViewModel.kt
@@ -0,0 +1,60 @@
+package org.calyxos.backup.storage.ui.backup
+
+import android.app.Application
+import android.net.Uri
+import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.viewModelScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import org.calyxos.backup.storage.api.BackupContentType
+import org.calyxos.backup.storage.api.EXTERNAL_STORAGE_PROVIDER_AUTHORITY
+import org.calyxos.backup.storage.api.SnapshotRetention
+import org.calyxos.backup.storage.api.StorageBackup
+import org.calyxos.backup.storage.api.mediaItems
+
+public abstract class BackupContentViewModel(app: Application) : AndroidViewModel(app) {
+
+    protected abstract val storageBackup: StorageBackup
+
+    private val _content = MutableLiveData<List<BackupContentItem>>()
+    internal val content: LiveData<List<BackupContentItem>> = _content
+
+    internal fun addUri(uri: Uri) {
+        viewModelScope.launch {
+            storageBackup.addUri(uri)
+            loadContent()
+        }
+    }
+
+    internal fun removeUri(uri: Uri) {
+        viewModelScope.launch {
+            storageBackup.removeUri(uri)
+            loadContent()
+        }
+    }
+
+    protected suspend fun loadContent(): Unit = withContext(Dispatchers.Default) {
+        val uris = storageBackup.uris
+        val items = ArrayList<BackupContentItem>(uris.size)
+        mediaItems.forEach { mediaType ->
+            items.add(
+                BackupContentItem(
+                    mediaType.contentUri,
+                    mediaType,
+                    uris.contains(mediaType.contentUri)
+                )
+            )
+        }
+        uris.forEach { uri ->
+            if (uri.authority == EXTERNAL_STORAGE_PROVIDER_AUTHORITY) {
+                items.add(BackupContentItem(uri, BackupContentType.Custom, true))
+            }
+        }
+        _content.postValue(items)
+        storageBackup.setSnapshotRetention(SnapshotRetention(15, 10, 5, 2))
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/ui/restore/SnapshotAdapter.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/restore/SnapshotAdapter.kt
new file mode 100644
index 00000000..d46d3382
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/restore/SnapshotAdapter.kt
@@ -0,0 +1,64 @@
+package org.calyxos.backup.storage.ui.restore
+
+import android.text.format.DateUtils.FORMAT_ABBREV_ALL
+import android.text.format.DateUtils.getRelativeTimeSpanString
+import android.text.format.Formatter
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.TextView
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.ListAdapter
+import androidx.recyclerview.widget.RecyclerView
+import org.calyxos.backup.storage.R
+import org.calyxos.backup.storage.api.SnapshotItem
+import org.calyxos.backup.storage.ui.restore.SnapshotAdapter.SnapshotViewHolder
+
+private class SnapshotItemCallback : DiffUtil.ItemCallback<SnapshotItem>() {
+    override fun areItemsTheSame(oldItem: SnapshotItem, newItem: SnapshotItem): Boolean {
+        return newItem.time == oldItem.time
+    }
+
+    override fun areContentsTheSame(oldItem: SnapshotItem, newItem: SnapshotItem): Boolean {
+        val newSnapshot = newItem.snapshot
+        val oldSnapshot = oldItem.snapshot
+        return newSnapshot?.name == oldSnapshot?.name &&
+                newSnapshot?.size == oldSnapshot?.size
+    }
+}
+
+internal class SnapshotAdapter(private val listener: SnapshotClickListener) :
+    ListAdapter<SnapshotItem, SnapshotViewHolder>(SnapshotItemCallback()) {
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SnapshotViewHolder {
+        val v = LayoutInflater.from(parent.context).inflate(R.layout.item_snapshot, parent, false)
+        return SnapshotViewHolder(v)
+    }
+
+    override fun onBindViewHolder(holder: SnapshotViewHolder, position: Int) {
+        holder.bind(getItem(position))
+    }
+
+    inner class SnapshotViewHolder(view: View) : RecyclerView.ViewHolder(view) {
+        private val layout: ViewGroup = view.findViewById(R.id.layout)
+        private val nameView: TextView = view.findViewById(R.id.nameView)
+        private val timeView: TextView = view.findViewById(R.id.timeView)
+        private val sizeView: TextView = view.findViewById(R.id.sizeView)
+
+        fun bind(item: SnapshotItem) {
+            if (item.snapshot == null) {
+                // TODO also remove clickable background
+                layout.setOnClickListener(null)
+            } else {
+                layout.setOnClickListener { listener.onSnapshotClicked(item) }
+            }
+            nameView.text = item.snapshot?.name
+            val now = System.currentTimeMillis()
+            timeView.text = getRelativeTimeSpanString(item.time, now, 0L, FORMAT_ABBREV_ALL)
+            sizeView.text = item.snapshot?.size?.let { size ->
+                Formatter.formatShortFileSize(sizeView.context, size)
+            }
+        }
+    }
+
+}
diff --git a/storage/lib/src/main/java/org/calyxos/backup/storage/ui/restore/SnapshotFragment.kt b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/restore/SnapshotFragment.kt
new file mode 100644
index 00000000..22335ea0
--- /dev/null
+++ b/storage/lib/src/main/java/org/calyxos/backup/storage/ui/restore/SnapshotFragment.kt
@@ -0,0 +1,63 @@
+package org.calyxos.backup.storage.ui.restore
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.View.INVISIBLE
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import android.widget.ProgressBar
+import android.widget.TextView
+import androidx.fragment.app.Fragment
+import androidx.lifecycle.LiveData
+import androidx.recyclerview.widget.RecyclerView
+import org.calyxos.backup.storage.R
+import org.calyxos.backup.storage.api.SnapshotItem
+import org.calyxos.backup.storage.api.SnapshotResult
+
+public interface SnapshotViewModel {
+    public val snapshots: LiveData<SnapshotResult>
+}
+
+internal interface SnapshotClickListener {
+    fun onSnapshotClicked(item: SnapshotItem)
+}
+
+public abstract class SnapshotFragment : Fragment(), SnapshotClickListener {
+
+    protected abstract val viewModel: SnapshotViewModel
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        requireActivity().setTitle(R.string.snapshots_title)
+
+        val v = inflater.inflate(R.layout.fragment_snapshot, container, false)
+        val list: RecyclerView = v.findViewById(R.id.list)
+        val progressBar: ProgressBar = v.findViewById(R.id.progressBar)
+        val emptyStateView: TextView = v.findViewById(R.id.emptyStateView)
+
+        val adapter = SnapshotAdapter(this)
+        list.adapter = adapter
+        viewModel.snapshots.observe(viewLifecycleOwner, {
+            progressBar.visibility = INVISIBLE
+            when (it) {
+                is SnapshotResult.Success -> {
+                    if (it.snapshots.isEmpty()) {
+                        emptyStateView.visibility = VISIBLE
+                    } else adapter.submitList(it.snapshots)
+                }
+                is SnapshotResult.Error -> {
+                    val color = resources.getColor(R.color.design_default_color_error, null)
+                    emptyStateView.setTextColor(color)
+                    emptyStateView.setText(R.string.snapshots_error)
+                    emptyStateView.visibility = VISIBLE
+                }
+            }
+        })
+        return v
+    }
+
+}
diff --git a/storage/lib/src/main/proto/backup_document_file.proto b/storage/lib/src/main/proto/backup_document_file.proto
new file mode 100644
index 00000000..712362de
--- /dev/null
+++ b/storage/lib/src/main/proto/backup_document_file.proto
@@ -0,0 +1,32 @@
+syntax = "proto3";
+
+package org.calyxos.backup.storage.backup;
+
+option java_multiple_files = true;
+
+/**
+ * A file in Android's DocumentsProvider.
+ *
+ * Excluded for now, but maybe interesting for later:
+ *   - DocumentsContract.Document.COLUMN_MIME_TYPE
+ *   - DocumentsContract.Document.COLUMN_SUMMARY
+ */
+message BackupDocumentFile {
+  string name = 1;
+  string path = 2;
+  int64 last_modified = 3;
+  int64 size = 4;
+  /**
+   * This is empty for MediaStore.VOLUME_EXTERNAL_PRIMARY or "primary"
+   */
+  string volume = 5;
+  /**
+   * An ordered list of chunk IDs whose chunks that make up the file's content.
+   */
+  repeated string chunk_ids = 6;
+  /**
+    * If there is a single chunk ID and this is not 0, then the chunk ID refers to a zip chunk
+    * and this file can be found at the zip entry with this index name.
+    */
+  int32 zip_index = 7;
+}
diff --git a/storage/lib/src/main/proto/backup_media_file.proto b/storage/lib/src/main/proto/backup_media_file.proto
new file mode 100644
index 00000000..e947c891
--- /dev/null
+++ b/storage/lib/src/main/proto/backup_media_file.proto
@@ -0,0 +1,70 @@
+syntax = "proto3";
+
+package org.calyxos.backup.storage.backup;
+
+option java_multiple_files = true;
+
+/**
+ * A file in Android's MediaStore.
+ *
+ * Excluded for now, but maybe interesting for later:
+ *   - MediaStore.MediaColumns.VOLUME_NAME
+ *   - MediaStore.MediaColumns.IS_DRM
+ *   - MediaStore.Images.ImageColumns.IS_PRIVATE
+ *   - MediaStore.Images.ImageColumns.DESCRIPTION
+ *   - MediaStore.Video.VideoColumns.IS_PRIVATE
+ *   - MediaStore.Video.VideoColumns.DESCRIPTION
+ *   - MediaStore.Video.VideoColumns.TAGS
+ *   - MediaStore.Video.VideoColumns.CATEGORY
+ *   - MediaStore.Video.VideoColumns.LANGUAGE
+ *   - MediaStore.Video.VideoColumns.BOOKMARK
+ *   - MediaStore.Audio.AudioColumns.BOOKMARK
+ */
+message BackupMediaFile {
+  enum MediaType {
+    IMAGES = 0;
+    VIDEO = 1;
+    AUDIO = 2;
+    DOWNLOADS = 3;
+  }
+  MediaType type = 1;
+  /**
+   * MediaStore.MediaColumns.DISPLAY_NAME
+   */
+  string name = 2;
+  /**
+   * MediaStore.MediaColumns.RELATIVE_PATH
+   */
+  string path = 3;
+  /**
+   * MediaStore.MediaColumns.DATE_MODIFIED
+   */
+  int64 last_modified = 4;
+  /**
+   * MediaStore.MediaColumns.OWNER_PACKAGE_NAME
+   */
+  string owner_package_name = 5;
+  /**
+   * MediaStore.MediaColumns.IS_FAVORITE
+   */
+  bool is_favorite = 6;
+  /**
+   * The size of the file in bytes.
+   *
+   * MediaStore.MediaColumns.SIZE
+   */
+  int64 size = 7;
+  /**
+   * This is empty for MediaStore.VOLUME_EXTERNAL_PRIMARY
+   */
+  string volume = 8;
+  /**
+   * An ordered list of chunk IDs whose chunks that make up the file's content.
+   */
+  repeated string chunk_ids = 9;
+  /**
+    * If there is a single chunk ID and this is not 0, then the chunk ID refers to a zip chunk
+    * and this file can be found at the zip entry with this index name.
+    */
+  int32 zip_index = 10;
+}
diff --git a/storage/lib/src/main/proto/backup_snapshot.proto b/storage/lib/src/main/proto/backup_snapshot.proto
new file mode 100644
index 00000000..30a91d7e
--- /dev/null
+++ b/storage/lib/src/main/proto/backup_snapshot.proto
@@ -0,0 +1,18 @@
+syntax = "proto3";
+
+package org.calyxos.backup.storage.backup;
+
+import "backup_media_file.proto";
+import "backup_document_file.proto";
+
+option java_multiple_files = true;
+
+message BackupSnapshot {
+  int32 version = 1;
+  string name = 2;
+  repeated BackupMediaFile media_files = 3;
+  repeated BackupDocumentFile document_files = 4;
+  int64 size = 5;
+  int64 time_start = 6;
+  int64 time_end = 7;
+}
diff --git a/storage/lib/src/main/res/drawable/ic_add.xml b/storage/lib/src/main/res/drawable/ic_add.xml
new file mode 100644
index 00000000..eb988c0e
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_add.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M19,13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z" />
+</vector>
diff --git a/storage/lib/src/main/res/drawable/ic_auto_delete.xml b/storage/lib/src/main/res/drawable/ic_auto_delete.xml
new file mode 100644
index 00000000..d25a2610
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_auto_delete.xml
@@ -0,0 +1,16 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M15,2l-3.5,0l-1,-1l-5,0l-1,1l-3.5,0l0,2l14,0z" />
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M16,9c-0.7,0 -1.37,0.1 -2,0.29V5H2v12c0,1.1 0.9,2 2,2h5.68c1.12,2.36 3.53,4 6.32,4c3.87,0 7,-3.13 7,-7C23,12.13 19.87,9 16,9zM16,21c-2.76,0 -5,-2.24 -5,-5s2.24,-5 5,-5s5,2.24 5,5S18.76,21 16,21z" />
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M16.5,12l-1.5,0l0,5l3.6,2.1l0.8,-1.2l-2.9,-1.7z" />
+</vector>
diff --git a/storage/lib/src/main/res/drawable/ic_cloud_done.xml b/storage/lib/src/main/res/drawable/ic_cloud_done.xml
new file mode 100644
index 00000000..5486f9b8
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_cloud_done.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M19.35,10.04C18.67,6.59 15.64,4 12,4 9.11,4 6.6,5.64 5.35,8.04 2.34,8.36 0,10.91 0,14c0,3.31 2.69,6 6,6h13c2.76,0 5,-2.24 5,-5 0,-2.64 -2.05,-4.78 -4.65,-4.96zM10,17l-3.5,-3.5 1.41,-1.41L10,14.17 15.18,9l1.41,1.41L10,17z" />
+</vector>
diff --git a/storage/lib/src/main/res/drawable/ic_cloud_restore.xml b/storage/lib/src/main/res/drawable/ic_cloud_restore.xml
new file mode 100644
index 00000000..7125abf9
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_cloud_restore.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M12,4C9.11,4 6.5996,5.6391 5.3496,8.0391C2.3396,8.3591 -0,10.91 0,14C0,17.31 2.69,20 6,20L19,20C21.76,20 24,17.76 24,15C24,12.36 21.9496,10.2191 19.3496,10.0391C18.6696,6.5891 15.64,4 12,4zM12.1758,8.123C14.9358,8.123 17.1758,10.363 17.1758,13.123C17.1758,15.883 14.9358,18.123 12.1758,18.123C10.1258,18.123 8.3657,16.883 7.5957,15.123L9.3066,15.123C9.9366,16.023 10.9858,16.623 12.1758,16.623C14.1058,16.623 15.6758,15.053 15.6758,13.123C15.6758,11.193 14.1058,9.623 12.1758,9.623C10.8258,9.623 9.6562,10.4015 9.0762,11.5215L10.6758,13.123L6.6758,13.123L6.6758,9.123L7.9766,10.4219C8.8666,9.0419 10.4058,8.123 12.1758,8.123z" />
+</vector>
diff --git a/storage/lib/src/main/res/drawable/ic_cloud_upload.xml b/storage/lib/src/main/res/drawable/ic_cloud_upload.xml
new file mode 100644
index 00000000..f78b98da
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_cloud_upload.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M19.35,10.04C18.67,6.59 15.64,4 12,4 9.11,4 6.6,5.64 5.35,8.04 2.34,8.36 0,10.91 0,14c0,3.31 2.69,6 6,6h13c2.76,0 5,-2.24 5,-5 0,-2.64 -2.05,-4.78 -4.65,-4.96zM14,13v4h-4v-4H7l5,-5 5,5h-3z" />
+</vector>
diff --git a/storage/lib/src/main/res/drawable/ic_download_library.xml b/storage/lib/src/main/res/drawable/ic_download_library.xml
new file mode 100644
index 00000000..72ca8298
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_download_library.xml
@@ -0,0 +1,13 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M2,6L2,20C2,21.1046 2.8954,22 4,22L18,22L18,20L4,20L4,6L2,6z" />
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M8,2C6.8954,2 6,2.8954 6,4L6,16C6,17.1046 6.8954,18 8,18L20,18C21.1046,18 22,17.1046 22,16L22,4C22,2.8954 21.1046,2 20,2L8,2zM12.5,5L15.5,5L15.5,8L18,8L14,12L10,8L12.5,8L12.5,5zM10,13L18,13L18,15L10,15L10,13z" />
+</vector>
diff --git a/storage/lib/src/main/res/drawable/ic_folder.xml b/storage/lib/src/main/res/drawable/ic_folder.xml
new file mode 100644
index 00000000..77e822b4
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_folder.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M10,4H4c-1.1,0 -1.99,0.9 -1.99,2L2,18c0,1.1 0.9,2 2,2h16c1.1,0 2,-0.9 2,-2V8c0,-1.1 -0.9,-2 -2,-2h-8l-2,-2z" />
+</vector>
diff --git a/storage/lib/src/main/res/drawable/ic_more_vert.xml b/storage/lib/src/main/res/drawable/ic_more_vert.xml
new file mode 100644
index 00000000..ece2fc7e
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_more_vert.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M12,8c1.1,0 2,-0.9 2,-2s-0.9,-2 -2,-2 -2,0.9 -2,2 0.9,2 2,2zM12,10c-1.1,0 -2,0.9 -2,2s0.9,2 2,2 2,-0.9 2,-2 -0.9,-2 -2,-2zM12,16c-1.1,0 -2,0.9 -2,2s0.9,2 2,2 2,-0.9 2,-2 -0.9,-2 -2,-2z" />
+</vector>
diff --git a/storage/lib/src/main/res/drawable/ic_music_library.xml b/storage/lib/src/main/res/drawable/ic_music_library.xml
new file mode 100644
index 00000000..886dbd50
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_music_library.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M20,2L8,2c-1.1,0 -2,0.9 -2,2v12c0,1.1 0.9,2 2,2h12c1.1,0 2,-0.9 2,-2L22,4c0,-1.1 -0.9,-2 -2,-2zM18,7h-3v5.5c0,1.38 -1.12,2.5 -2.5,2.5S10,13.88 10,12.5s1.12,-2.5 2.5,-2.5c0.57,0 1.08,0.19 1.5,0.51L14,5h4v2zM4,6L2,6v14c0,1.1 0.9,2 2,2h14v-2L4,20L4,6z" />
+</vector>
diff --git a/storage/lib/src/main/res/drawable/ic_photo_library.xml b/storage/lib/src/main/res/drawable/ic_photo_library.xml
new file mode 100644
index 00000000..5fac1845
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_photo_library.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M22,16L22,4c0,-1.1 -0.9,-2 -2,-2L8,2c-1.1,0 -2,0.9 -2,2v12c0,1.1 0.9,2 2,2h12c1.1,0 2,-0.9 2,-2zM11,12l2.03,2.71L16,11l4,5L8,16l3,-4zM2,6v14c0,1.1 0.9,2 2,2h14v-2L4,20L4,6L2,6z" />
+</vector>
diff --git a/storage/lib/src/main/res/drawable/ic_video_library.xml b/storage/lib/src/main/res/drawable/ic_video_library.xml
new file mode 100644
index 00000000..d8ac0853
--- /dev/null
+++ b/storage/lib/src/main/res/drawable/ic_video_library.xml
@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?android:attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M4,6L2,6v14c0,1.1 0.9,2 2,2h14v-2L4,20L4,6zM20,2L8,2c-1.1,0 -2,0.9 -2,2v12c0,1.1 0.9,2 2,2h12c1.1,0 2,-0.9 2,-2L22,4c0,-1.1 -0.9,-2 -2,-2zM12,14.5v-9l6,4.5 -6,4.5z" />
+</vector>
diff --git a/storage/lib/src/main/res/layout/fragment_backup_content.xml b/storage/lib/src/main/res/layout/fragment_backup_content.xml
new file mode 100644
index 00000000..99e6145e
--- /dev/null
+++ b/storage/lib/src/main/res/layout/fragment_backup_content.xml
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/list"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:padding="16dp"
+        app:layoutManager="LinearLayoutManager"
+        tools:listitem="@layout/item_media" />
+
+    <com.google.android.material.floatingactionbutton.FloatingActionButton
+        android:id="@+id/fab"
+        style="@style/Widget.Design.FloatingActionButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="bottom|end"
+        android:layout_margin="16dp"
+        android:contentDescription="@string/content_add"
+        android:src="@drawable/ic_add"
+        app:layout_behavior="com.google.android.material.behavior.HideBottomViewOnScrollBehavior" />
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>
diff --git a/storage/lib/src/main/res/layout/fragment_snapshot.xml b/storage/lib/src/main/res/layout/fragment_snapshot.xml
new file mode 100644
index 00000000..6fcd08a6
--- /dev/null
+++ b/storage/lib/src/main/res/layout/fragment_snapshot.xml
@@ -0,0 +1,67 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <ViewStub
+        android:id="@+id/topStub"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:inflatedId="@+id/topStub"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:layout="@layout/item_custom"
+        tools:visibility="visible" />
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/list"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        android:padding="16dp"
+        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
+        app:layout_constraintBottom_toTopOf="@+id/bottomStub"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/topStub"
+        tools:listitem="@layout/item_snapshot" />
+
+    <TextView
+        android:id="@+id/emptyStateView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:gravity="center"
+        android:text="@string/snapshots_empty"
+        android:visibility="invisible"
+        app:layout_constraintBottom_toTopOf="@+id/bottomStub"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/topStub"
+        tools:visibility="visible" />
+
+    <ProgressBar
+        android:id="@+id/progressBar"
+        style="?android:attr/progressBarStyleLarge"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <ViewStub
+        android:id="@+id/bottomStub"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:inflatedId="@+id/bottomStub"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/list"
+        tools:layout="@layout/item_custom"
+        tools:visibility="visible" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/storage/lib/src/main/res/layout/item_custom.xml b/storage/lib/src/main/res/layout/item_custom.xml
new file mode 100644
index 00000000..3e841db2
--- /dev/null
+++ b/storage/lib/src/main/res/layout/item_custom.xml
@@ -0,0 +1,51 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:layout_margin="8dp"
+    app:cardCornerRadius="8dp">
+
+    <androidx.constraintlayout.widget.ConstraintLayout
+        android:id="@+id/layout"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:background="?attr/selectableItemBackground"
+        android:padding="8dp">
+
+        <ImageView
+            android:id="@+id/icon"
+            android:layout_width="24dp"
+            android:layout_height="24dp"
+            android:layout_marginStart="8dp"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toTopOf="parent"
+            tools:src="@drawable/ic_folder" />
+
+        <TextView
+            android:id="@+id/title"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="16dp"
+            android:textAppearance="?attr/textAppearanceListItem"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toStartOf="@+id/overflow"
+            app:layout_constraintStart_toEndOf="@+id/icon"
+            app:layout_constraintTop_toTopOf="parent"
+            tools:text="Folder/custom" />
+
+        <ImageButton
+            android:id="@+id/overflow"
+            android:layout_width="48dp"
+            android:layout_height="48dp"
+            android:background="?attr/selectableItemBackgroundBorderless"
+            android:src="@drawable/ic_more_vert"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintTop_toTopOf="parent" />
+
+    </androidx.constraintlayout.widget.ConstraintLayout>
+
+</androidx.cardview.widget.CardView>
diff --git a/storage/lib/src/main/res/layout/item_media.xml b/storage/lib/src/main/res/layout/item_media.xml
new file mode 100644
index 00000000..de319867
--- /dev/null
+++ b/storage/lib/src/main/res/layout/item_media.xml
@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:layout_margin="8dp"
+    app:cardCornerRadius="8dp">
+
+    <androidx.constraintlayout.widget.ConstraintLayout
+        android:id="@+id/layout"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:background="?attr/selectableItemBackground"
+        android:padding="8dp">
+
+        <ImageView
+            android:id="@+id/icon"
+            android:layout_width="24dp"
+            android:layout_height="24dp"
+            android:layout_marginStart="8dp"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toTopOf="parent"
+            tools:src="@drawable/ic_music_library" />
+
+        <TextView
+            android:id="@+id/title"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="16dp"
+            android:textAppearance="?attr/textAppearanceListItem"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toStartOf="@+id/switchView"
+            app:layout_constraintStart_toEndOf="@+id/icon"
+            app:layout_constraintTop_toTopOf="parent"
+            tools:text="@string/content_videos" />
+
+        <androidx.appcompat.widget.SwitchCompat
+            android:id="@+id/switchView"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:padding="16dp"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintTop_toTopOf="parent" />
+
+    </androidx.constraintlayout.widget.ConstraintLayout>
+
+</androidx.cardview.widget.CardView>
diff --git a/storage/lib/src/main/res/layout/item_snapshot.xml b/storage/lib/src/main/res/layout/item_snapshot.xml
new file mode 100644
index 00000000..78243111
--- /dev/null
+++ b/storage/lib/src/main/res/layout/item_snapshot.xml
@@ -0,0 +1,53 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:layout_marginBottom="16dp"
+    app:cardCornerRadius="8dp"
+    tools:showIn="@layout/fragment_snapshot">
+
+    <androidx.constraintlayout.widget.ConstraintLayout
+        android:id="@+id/layout"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:background="?attr/selectableItemBackground"
+        android:padding="8dp">
+
+        <TextView
+            android:id="@+id/nameView"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:textAppearance="?android:attr/textAppearanceListItem"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toTopOf="parent"
+            tools:text="Backup name which might be quite long, who knows...?" />
+
+        <TextView
+            android:id="@+id/timeView"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="8dp"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toStartOf="@+id/sizeView"
+            app:layout_constraintHorizontal_chainStyle="spread_inside"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@+id/nameView"
+            tools:text="24h ago" />
+
+        <TextView
+            android:id="@+id/sizeView"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="8dp"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toEndOf="@+id/nameView"
+            app:layout_constraintStart_toEndOf="@+id/timeView"
+            app:layout_constraintTop_toBottomOf="@+id/nameView"
+            tools:text="35 GB" />
+
+    </androidx.constraintlayout.widget.ConstraintLayout>
+
+</androidx.cardview.widget.CardView>
diff --git a/storage/lib/src/main/res/menu/item_custom.xml b/storage/lib/src/main/res/menu/item_custom.xml
new file mode 100644
index 00000000..fe5cd8c2
--- /dev/null
+++ b/storage/lib/src/main/res/menu/item_custom.xml
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <item
+        android:id="@+id/delete"
+        android:title="Remove" />
+
+</menu>
diff --git a/storage/lib/src/main/res/values/strings.xml b/storage/lib/src/main/res/values/strings.xml
new file mode 100644
index 00000000..77a8ed9a
--- /dev/null
+++ b/storage/lib/src/main/res/values/strings.xml
@@ -0,0 +1,20 @@
+<resources>
+    <string name="content_images">Photos and images</string>
+    <string name="content_videos">Videos</string>
+    <string name="content_audio">Audio files</string>
+    <string name="content_downloads">Downloads</string>
+    <string name="content_add">Add</string>
+
+    <string name="notification_backup_title">Storage backup</string>
+    <string name="notification_backup_scanning">Scanning files…</string>
+    <string name="notification_backup_backup_files">Backing up files…</string>
+    <string name="notification_prune">Removing old backups…</string>
+    <string name="notification_restore_channel_title">Storage restore</string>
+    <string name="notification_restore_title">Restoring files…</string>
+    <string name="notification_restore_info">%1$d/%2$d</string>
+    <string name="notification_restore_complete_title">%1$d of %2$d files restored</string>
+
+    <string name="snapshots_title">Available storage backups</string>
+    <string name="snapshots_empty">No storage backups found\n\nSorry, but there is nothing that can be restored.</string>
+    <string name="snapshots_error">Error loading snapshots</string>
+</resources>
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/BackupRestoreTest.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/BackupRestoreTest.kt
new file mode 100644
index 00000000..78ef34a6
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/BackupRestoreTest.kt
@@ -0,0 +1,467 @@
+package org.calyxos.backup.storage
+
+import android.Manifest.permission.ACCESS_MEDIA_LOCATION
+import android.content.ContentResolver
+import android.content.Context
+import android.content.pm.PackageManager.PERMISSION_DENIED
+import android.provider.MediaStore
+import android.text.format.Formatter
+import io.mockk.Runs
+import io.mockk.coEvery
+import io.mockk.coVerify
+import io.mockk.every
+import io.mockk.just
+import io.mockk.mockk
+import io.mockk.mockkStatic
+import io.mockk.slot
+import io.mockk.verify
+import kotlinx.coroutines.flow.toList
+import kotlinx.coroutines.runBlocking
+import org.calyxos.backup.storage.api.SnapshotResult
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.backup.Backup
+import org.calyxos.backup.storage.backup.Backup.Companion.CHUNK_SIZE_MAX
+import org.calyxos.backup.storage.backup.Backup.Companion.SMALL_FILE_SIZE_MAX
+import org.calyxos.backup.storage.backup.BackupMediaFile
+import org.calyxos.backup.storage.backup.BackupSnapshot
+import org.calyxos.backup.storage.backup.ChunksCacheRepopulater
+import org.calyxos.backup.storage.content.ContentFile
+import org.calyxos.backup.storage.content.DocFile
+import org.calyxos.backup.storage.content.MediaFile
+import org.calyxos.backup.storage.crypto.Hkdf.ALGORITHM_HMAC
+import org.calyxos.backup.storage.crypto.Hkdf.KEY_SIZE_BYTES
+import org.calyxos.backup.storage.db.CachedChunk
+import org.calyxos.backup.storage.db.CachedFile
+import org.calyxos.backup.storage.db.ChunksCache
+import org.calyxos.backup.storage.db.Db
+import org.calyxos.backup.storage.db.FilesCache
+import org.calyxos.backup.storage.plugin.SnapshotRetriever
+import org.calyxos.backup.storage.restore.FileRestore
+import org.calyxos.backup.storage.restore.RestorableFile
+import org.calyxos.backup.storage.restore.Restore
+import org.calyxos.backup.storage.scanner.FileScanner
+import org.calyxos.backup.storage.scanner.FileScannerResult
+import org.junit.Assert.assertArrayEquals
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Rule
+import org.junit.Test
+import org.junit.rules.TemporaryFolder
+import java.io.ByteArrayInputStream
+import java.io.ByteArrayOutputStream
+import java.io.OutputStream
+import javax.crypto.spec.SecretKeySpec
+import kotlin.random.Random
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class BackupRestoreTest {
+
+    @get:Rule
+    var folder: TemporaryFolder = TemporaryFolder()
+
+    private val context: Context = mockk()
+    private val db: Db = mockk()
+    private val filesCache: FilesCache = mockk()
+    private val chunksCache: ChunksCache = mockk()
+    private val contentResolver: ContentResolver = mockk()
+
+    private val fileScanner: FileScanner = mockk()
+    private val plugin: StoragePlugin = mockk()
+    private val fileRestore: FileRestore = mockk()
+    private val snapshotRetriever = SnapshotRetriever(plugin)
+    private val cacheRepopulater: ChunksCacheRepopulater = mockk()
+
+    init {
+        mockLog()
+
+        mockkStatic(Formatter::class)
+        every { Formatter.formatShortFileSize(any(), any()) } returns ""
+
+        mockkStatic("org.calyxos.backup.storage.UriUtilsKt")
+
+        every { db.getFilesCache() } returns filesCache
+        every { db.getChunksCache() } returns chunksCache
+        every { plugin.getMasterKey() } returns SecretKeySpec(
+            "This is a backup key for testing".toByteArray(),
+            0, KEY_SIZE_BYTES, ALGORITHM_HMAC
+        )
+        every { context.checkSelfPermission(ACCESS_MEDIA_LOCATION) } returns PERMISSION_DENIED
+        every { context.contentResolver } returns contentResolver
+    }
+
+    private val restore = Restore(context, plugin, snapshotRetriever, fileRestore)
+
+    @Test
+    fun testZipAndSingleRandom(): Unit = runBlocking {
+        val backup = Backup(context, db, fileScanner, plugin, cacheRepopulater)
+
+        val smallFileMBytes = Random.nextBytes(Random.nextInt(SMALL_FILE_SIZE_MAX))
+        val smallFileM = getRandomMediaFile(smallFileMBytes.size)
+        val smallFileDBytes = Random.nextBytes(Random.nextInt(SMALL_FILE_SIZE_MAX))
+        val smallFileD = getRandomDocFile(smallFileDBytes.size)
+        val fileMBytes = Random.nextBytes(Random.nextInt(SMALL_FILE_SIZE_MAX + 1, CHUNK_SIZE_MAX))
+        val fileM = getRandomMediaFile(fileMBytes.size)
+        val fileDBytes = Random.nextBytes(Random.nextInt(SMALL_FILE_SIZE_MAX + 1, CHUNK_SIZE_MAX))
+        val fileD = getRandomDocFile(fileDBytes.size)
+        val scannedFiles = FileScannerResult(
+            smallFiles = listOf(smallFileM, smallFileD),
+            files = listOf(fileM, fileD),
+        )
+        val cachedFiles = mutableListOf<CachedFile>()
+        val zipChunkOutputStream = ByteArrayOutputStream()
+        val mOutputStream = ByteArrayOutputStream()
+        val dOutputStream = ByteArrayOutputStream()
+        val snapshotTimestamp = slot<Long>()
+        val snapshotOutputStream = ByteArrayOutputStream()
+
+        // provide files and empty cache
+        val availableChunks = emptyList<String>()
+        coEvery { plugin.getAvailableChunkIds() } returns availableChunks
+        every {
+            chunksCache.areAllAvailableChunksCached(db, availableChunks.toHashSet())
+        } returns true
+        every { fileScanner.getFiles() } returns scannedFiles
+        every { filesCache.getByUri(any()) } returns null // nothing is cached, all is new
+        every { chunksCache.get(any()) } returns null // no chunks are cached, all are new
+
+        // media types
+        every { smallFileM.uri.getBackupMediaType() } returns BackupMediaFile.MediaType.IMAGES
+        every { fileM.uri.getBackupMediaType() } returns BackupMediaFile.MediaType.DOWNLOADS
+
+        // file input streams
+        every {
+            contentResolver.openInputStream(smallFileM.uri)
+        } returns ByteArrayInputStream(smallFileMBytes)
+        every {
+            contentResolver.openInputStream(smallFileD.uri)
+        } returns ByteArrayInputStream(smallFileDBytes)
+        // don't return the same stream twice here, as we don't reset it, but read it twice
+        every {
+            contentResolver.openInputStream(fileM.uri)
+        } returns ByteArrayInputStream(fileMBytes) andThen ByteArrayInputStream(fileMBytes)
+        every {
+            contentResolver.openInputStream(fileD.uri)
+        } returns ByteArrayInputStream(fileDBytes) andThen ByteArrayInputStream(fileDBytes)
+
+        // output streams and caching
+        every { plugin.getChunkOutputStream(any()) } returnsMany listOf(
+            zipChunkOutputStream, mOutputStream, dOutputStream
+        )
+        every { chunksCache.insert(any<CachedChunk>()) } just Runs
+        every { filesCache.upsert(capture(cachedFiles)) } just Runs
+
+        // snapshot writing
+        every {
+            plugin.getBackupSnapshotOutputStream(capture(snapshotTimestamp))
+        } returns snapshotOutputStream
+        every { db.applyInParts<String>(any(), any()) } just Runs
+
+        backup.runBackup(null)
+
+        // assert file cache info
+        assertEquals(4, cachedFiles.size)
+        assertEquals(smallFileM.size, cachedFiles[0].size)
+        assertEquals(smallFileM.lastModified, cachedFiles[0].lastModified)
+        assertEquals(1, cachedFiles[0].zipIndex)
+        assertEquals(smallFileD.size, cachedFiles[1].size)
+        assertEquals(smallFileD.lastModified, cachedFiles[1].lastModified)
+        assertEquals(2, cachedFiles[1].zipIndex)
+        assertEquals(fileM.size, cachedFiles[2].size)
+        assertEquals(fileM.lastModified, cachedFiles[2].lastModified)
+        assertEquals(fileD.size, cachedFiles[3].size)
+        assertEquals(fileD.lastModified, cachedFiles[3].lastModified)
+
+        // RESTORE
+
+        val storedSnapshot = StoredSnapshot("test", snapshotTimestamp.captured)
+
+        val smallFileMOutputStream = ByteArrayOutputStream()
+        val smallFileDOutputStream = ByteArrayOutputStream()
+        val fileMOutputStream = ByteArrayOutputStream()
+        val fileDOutputStream = ByteArrayOutputStream()
+
+        coEvery { plugin.getBackupSnapshotsForRestore() } returns listOf(storedSnapshot)
+        coEvery {
+            plugin.getBackupSnapshotInputStream(storedSnapshot)
+        } returns ByteArrayInputStream(snapshotOutputStream.toByteArray())
+
+        // retrieve snapshots
+        val snapshotResultList = restore.getBackupSnapshots().toList()
+
+        // assert snapshot
+        assertEquals(2, snapshotResultList.size)
+        val snapshots = (snapshotResultList[1] as SnapshotResult.Success).snapshots
+        assertEquals(1, snapshots.size)
+        assertEquals(snapshotTimestamp.captured, snapshots[0].time)
+        val snapshot = snapshots[0].snapshot ?: error("snapshot was null")
+        assertEquals(2, snapshot.mediaFilesList.size)
+        assertEquals(2, snapshot.documentFilesList.size)
+
+        // pipe chunks back in
+        coEvery {
+            plugin.getChunkInputStream(storedSnapshot, cachedFiles[0].chunks[0])
+        } returns ByteArrayInputStream(zipChunkOutputStream.toByteArray())
+        // cachedFiles[0].chunks[1] is in previous zipChunk
+        coEvery {
+            plugin.getChunkInputStream(storedSnapshot, cachedFiles[2].chunks[0])
+        } returns ByteArrayInputStream(mOutputStream.toByteArray())
+        coEvery {
+            plugin.getChunkInputStream(storedSnapshot, cachedFiles[3].chunks[0])
+        } returns ByteArrayInputStream(dOutputStream.toByteArray())
+
+        // provide file output streams for restore
+        val smallFileMRestorable = getRestorableFileM(smallFileM, snapshot)
+        expectRestoreFile(smallFileMRestorable, smallFileMOutputStream)
+        val smallFileDRestorable = getRestorableFileD(smallFileD, snapshot)
+        expectRestoreFile(smallFileDRestorable, smallFileDOutputStream)
+        val fileMRestorable = getRestorableFileM(fileM, snapshot)
+        expectRestoreFile(fileMRestorable, fileMOutputStream)
+        val fileDRestorable = getRestorableFileD(fileD, snapshot)
+        expectRestoreFile(fileDRestorable, fileDOutputStream)
+
+        restore.restoreBackupSnapshot(storedSnapshot, snapshot, null)
+
+        // restored files match backed up files exactly
+        assertArrayEquals(smallFileMBytes, smallFileMOutputStream.toByteArray())
+        assertArrayEquals(smallFileDBytes, smallFileDOutputStream.toByteArray())
+        assertArrayEquals(fileMBytes, fileMOutputStream.toByteArray())
+        assertArrayEquals(fileDBytes, fileDOutputStream.toByteArray())
+    }
+
+    @Test
+    fun testMultiChunks(): Unit = runBlocking {
+        val backup = Backup(context, db, fileScanner, plugin, cacheRepopulater, 4)
+
+        val chunk1 = byteArrayOf(0x00, 0x01, 0x02, 0x03)
+        val chunk2 = byteArrayOf(0x04, 0x05, 0x06, 0x07)
+        val chunk3 = byteArrayOf(0x08, 0x09, 0x10, 0x11)
+        val chunk4 = byteArrayOf(0x12, 0x13)
+        val file1Bytes = chunk1 + chunk2 + chunk3
+        val file2Bytes = chunk3 + chunk2 + chunk1 + chunk4
+        val file1 = getRandomDocFile(file1Bytes.size)
+        val file2 = getRandomDocFile(file2Bytes.size)
+        val file1OutputStream = ByteArrayOutputStream()
+        val file2OutputStream = ByteArrayOutputStream()
+        val snapshotTimestamp = slot<Long>()
+        val snapshotOutputStream = ByteArrayOutputStream()
+
+        val scannedFiles = FileScannerResult(
+            smallFiles = emptyList(),
+            files = listOf(file1, file2),
+        )
+        val cachedFiles = mutableListOf<CachedFile>()
+
+        // provide files and empty cache
+        val availableChunks = emptyList<String>()
+        coEvery { plugin.getAvailableChunkIds() } returns availableChunks
+        every {
+            chunksCache.areAllAvailableChunksCached(db, availableChunks.toHashSet())
+        } returns true
+        every { fileScanner.getFiles() } returns scannedFiles
+        every { filesCache.getByUri(any()) } returns null // nothing is cached, all is new
+
+        // first 3 chunks are not cached on 1st invocation, but afterwards. Last chunk never cached
+        // also needed to ensure that we don't write chunks more than once into the same stream
+        expectCacheMissAndThenHit(
+            "040f3204869543c4015d92c04bf875b25ebde55f9645380f4172aa439b2825d3"
+        )
+        expectCacheMissAndThenHit(
+            "901fbcf9a94271fc0455d0052522cab994f9392d0bb85187860282b4beadfb29"
+        )
+        expectCacheMissAndThenHit(
+            "5adea3149fe6cf9c6e3270a52ee2c31bc9dfcef5f2080b583a4dd3b779c9182d"
+        )
+        every {
+            chunksCache.get("40d00c1be4b0f89e8b12d47f3658aa42f568a8d02b978260da6d0050e7007e67")
+        } returns null
+
+        // file input streams
+        // don't return the same stream twice here, as we don't reset it, but read it twice
+        every {
+            contentResolver.openInputStream(file1.uri)
+        } returns ByteArrayInputStream(file1Bytes) andThen ByteArrayInputStream(file1Bytes)
+        every {
+            contentResolver.openInputStream(file2.uri)
+        } returns ByteArrayInputStream(file2Bytes) andThen ByteArrayInputStream(file2Bytes)
+
+        // use temporary directory as cache dir
+        val tmpDir = folder.newFolder()
+        every { context.cacheDir } returns tmpDir
+
+        // output streams for deterministic chunks
+        val id040f32 = ByteArrayOutputStream()
+        every {
+            plugin.getChunkOutputStream(
+                "040f3204869543c4015d92c04bf875b25ebde55f9645380f4172aa439b2825d3"
+            )
+        } returns id040f32
+        val id901fbc = ByteArrayOutputStream()
+        every {
+            plugin.getChunkOutputStream(
+                "901fbcf9a94271fc0455d0052522cab994f9392d0bb85187860282b4beadfb29"
+            )
+        } returns id901fbc
+        val id5adea3 = ByteArrayOutputStream()
+        every {
+            plugin.getChunkOutputStream(
+                "5adea3149fe6cf9c6e3270a52ee2c31bc9dfcef5f2080b583a4dd3b779c9182d"
+            )
+        } returns id5adea3
+        val id40d00c = ByteArrayOutputStream()
+        every {
+            plugin.getChunkOutputStream(
+                "40d00c1be4b0f89e8b12d47f3658aa42f568a8d02b978260da6d0050e7007e67"
+            )
+        } returns id40d00c
+
+        every { chunksCache.insert(any<CachedChunk>()) } just Runs
+        every { filesCache.upsert(capture(cachedFiles)) } just Runs
+
+        // snapshot writing
+        every {
+            plugin.getBackupSnapshotOutputStream(capture(snapshotTimestamp))
+        } returns snapshotOutputStream
+        every { db.applyInParts<String>(any(), any()) } just Runs
+
+        backup.runBackup(null)
+
+        // chunks were only written to storage once
+        verify(exactly = 1) {
+            plugin.getChunkOutputStream(
+                "040f3204869543c4015d92c04bf875b25ebde55f9645380f4172aa439b2825d3")
+            plugin.getChunkOutputStream(
+                "901fbcf9a94271fc0455d0052522cab994f9392d0bb85187860282b4beadfb29")
+            plugin.getChunkOutputStream(
+                "5adea3149fe6cf9c6e3270a52ee2c31bc9dfcef5f2080b583a4dd3b779c9182d")
+            plugin.getChunkOutputStream(
+                "40d00c1be4b0f89e8b12d47f3658aa42f568a8d02b978260da6d0050e7007e67")
+        }
+
+        // RESTORE
+
+        val storedSnapshot = StoredSnapshot("test", snapshotTimestamp.captured)
+
+        coEvery { plugin.getBackupSnapshotsForRestore() } returns listOf(storedSnapshot)
+        coEvery {
+            plugin.getBackupSnapshotInputStream(storedSnapshot)
+        } returns ByteArrayInputStream(snapshotOutputStream.toByteArray())
+
+        // retrieve snapshots
+        val snapshotResultList = restore.getBackupSnapshots().toList()
+
+        // assert snapshot
+        val snapshots = (snapshotResultList[1] as SnapshotResult.Success).snapshots
+        val snapshot = snapshots[0].snapshot ?: error("snapshot was null")
+        assertEquals(0, snapshot.mediaFilesList.size)
+        assertEquals(2, snapshot.documentFilesList.size)
+
+        // pipe chunks back in
+        coEvery {
+            plugin.getChunkInputStream(
+                storedSnapshot,
+                "040f3204869543c4015d92c04bf875b25ebde55f9645380f4172aa439b2825d3"
+            )
+        } returns ByteArrayInputStream(id040f32.toByteArray())
+        coEvery {
+            plugin.getChunkInputStream(
+                storedSnapshot,
+                "901fbcf9a94271fc0455d0052522cab994f9392d0bb85187860282b4beadfb29"
+            )
+        } returns ByteArrayInputStream(id901fbc.toByteArray())
+        coEvery {
+            plugin.getChunkInputStream(
+                storedSnapshot,
+                "5adea3149fe6cf9c6e3270a52ee2c31bc9dfcef5f2080b583a4dd3b779c9182d"
+            )
+        } returns ByteArrayInputStream(id5adea3.toByteArray())
+        coEvery {
+            plugin.getChunkInputStream(
+                storedSnapshot,
+                "40d00c1be4b0f89e8b12d47f3658aa42f568a8d02b978260da6d0050e7007e67"
+            )
+        } returns ByteArrayInputStream(id40d00c.toByteArray())
+
+        // provide file output streams for restore
+        val file1Restorable = getRestorableFileD(file1, snapshot)
+        expectRestoreFile(file1Restorable, file1OutputStream)
+        val file2Restorable = getRestorableFileD(file2, snapshot)
+        expectRestoreFile(file2Restorable, file2OutputStream)
+
+        restore.restoreBackupSnapshot(storedSnapshot, snapshot, null)
+
+        // restored files match backed up files exactly
+        assertArrayEquals(file1Bytes, file1OutputStream.toByteArray())
+        assertArrayEquals(file2Bytes, file2OutputStream.toByteArray())
+
+        // chunks were only read from storage once
+        coVerify(exactly = 1) {
+            plugin.getChunkInputStream(
+                storedSnapshot,
+                "040f3204869543c4015d92c04bf875b25ebde55f9645380f4172aa439b2825d3"
+            )
+            plugin.getChunkInputStream(
+                storedSnapshot,
+                "901fbcf9a94271fc0455d0052522cab994f9392d0bb85187860282b4beadfb29"
+            )
+            plugin.getChunkInputStream(
+                storedSnapshot,
+                "5adea3149fe6cf9c6e3270a52ee2c31bc9dfcef5f2080b583a4dd3b779c9182d"
+            )
+            plugin.getChunkInputStream(
+                storedSnapshot,
+                "40d00c1be4b0f89e8b12d47f3658aa42f568a8d02b978260da6d0050e7007e67"
+            )
+        }
+    }
+
+    private fun getRandomMediaFile(size: Int) = MediaFile(
+        uri = mockk(),
+        dir = getRandomString(),
+        fileName = getRandomString(),
+        dateModified = Random.nextLong(),
+        generationModified = Random.nextLong(),
+        size = size.toLong(),
+        isFavorite = Random.nextBoolean(),
+        ownerPackageName = getRandomString(),
+        volume = MediaStore.VOLUME_EXTERNAL_PRIMARY,
+    )
+
+    private fun getRandomDocFile(size: Int) = DocFile(
+        uri = mockk(),
+        dirPath = getRandomString(),
+        fileName = getRandomString(),
+        lastModified = Random.nextLong(),
+        size = size.toLong(),
+        volume = MediaStore.VOLUME_EXTERNAL_PRIMARY,
+    )
+
+    private fun getRestorableFileM(file: ContentFile, snapshot: BackupSnapshot): RestorableFile {
+        return RestorableFile(snapshot.mediaFilesList.find {
+            file.size == it.size
+        } ?: error("not found"))
+    }
+
+    private fun getRestorableFileD(file: ContentFile, snapshot: BackupSnapshot): RestorableFile {
+        return RestorableFile(snapshot.documentFilesList.find {
+            file.size == it.size
+        } ?: error("not found"))
+    }
+
+    private fun expectRestoreFile(restorableFile: RestorableFile, outputStream: OutputStream) {
+        coEvery {
+            fileRestore.restoreFile(restorableFile, null, any(), captureLambda())
+        } coAnswers {
+            val l = lambda<suspend (outputStream: OutputStream) -> Long>()
+            assertTrue(l.isCaptured)
+            l.captured.invoke(outputStream)
+        }
+    }
+
+    private fun expectCacheMissAndThenHit(chunkId: String, chunkSize: Long = 4) {
+        every {
+            chunksCache.get(chunkId)
+        } returns null andThen CachedChunk(chunkId, 0, chunkSize)
+    }
+
+}
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/TestUtils.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/TestUtils.kt
new file mode 100644
index 00000000..205ff84f
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/TestUtils.kt
@@ -0,0 +1,64 @@
+package org.calyxos.backup.storage
+
+import android.util.Log
+import io.mockk.InternalPlatformDsl
+import io.mockk.InternalPlatformDsl.toStr
+import io.mockk.Matcher
+import io.mockk.MockKMatcherScope
+import io.mockk.every
+import io.mockk.mockk
+import io.mockk.mockkStatic
+import org.calyxos.backup.storage.content.DocFile
+import org.calyxos.backup.storage.db.CachedFile
+import kotlin.random.Random
+
+private val charPool: List<Char> = ('a'..'z') + ('A'..'Z') + ('0'..'9')
+
+internal fun getRandomString(length: Int = Random.nextInt(1, 64)): String = (1..length)
+    .map { Random.nextInt(0, charPool.size) }
+    .map(charPool::get)
+    .joinToString("")
+
+internal fun mockLog(error: Boolean = true) {
+    mockkStatic(Log::class)
+    every { Log.v(any(), any()) } returns 0
+    every { Log.d(any(), any()) } returns 0
+    every { Log.i(any(), any()) } returns 0
+    every { Log.w(any(), ofType(String::class)) } returns 0
+    every { Log.w(any(), ofType(String::class), any()) } returns 0
+    if (error) {
+        every { Log.e(any(), any()) } returns 0
+        every { Log.e(any(), any(), any()) } returns 0
+    }
+}
+
+internal fun getRandomDocFile(size: Long = Random.nextLong()): DocFile {
+    return DocFile(
+        uri = mockk(),
+        dirPath = getRandomString(),
+        fileName = getRandomString(),
+        lastModified = Random.nextLong(),
+        size = size,
+        volume = getRandomString()
+    )
+}
+
+/**
+ * Checks [CachedFile] equality, but ignores [CachedFile.lastSeen].
+ */
+internal fun MockKMatcherScope.sameCachedFile(value: CachedFile): CachedFile =
+    match(CachedFileMatcher(value))
+
+internal data class CachedFileMatcher(private val value: CachedFile) : Matcher<CachedFile> {
+    override fun match(arg: CachedFile?): Boolean {
+        return if (arg == null) {
+            false
+        } else {
+            InternalPlatformDsl.deepEquals(arg.copy(lastSeen = value.lastSeen), value)
+        }
+    }
+
+    override fun toString(): String {
+        return "eq(${value.toStr()})"
+    }
+}
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ChunkWriterTest.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ChunkWriterTest.kt
new file mode 100644
index 00000000..eb103eb6
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ChunkWriterTest.kt
@@ -0,0 +1,214 @@
+package org.calyxos.backup.storage.backup
+
+import io.mockk.MockKMatcherScope
+import io.mockk.Runs
+import io.mockk.every
+import io.mockk.just
+import io.mockk.mockk
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.backup.Backup.Companion.VERSION
+import org.calyxos.backup.storage.crypto.Hkdf.KEY_SIZE_BYTES
+import org.calyxos.backup.storage.crypto.StreamCrypto
+import org.calyxos.backup.storage.db.ChunksCache
+import org.calyxos.backup.storage.mockLog
+import org.calyxos.backup.storage.toHexString
+import org.junit.Assert.assertArrayEquals
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import java.io.ByteArrayInputStream
+import java.io.ByteArrayOutputStream
+import kotlin.random.Random
+
+internal class ChunkWriterTest {
+
+    private val streamCrypto: StreamCrypto = mockk()
+    private val chunksCache: ChunksCache = mockk()
+    private val storagePlugin: StoragePlugin = mockk()
+    private val streamKey: ByteArray = Random.nextBytes(KEY_SIZE_BYTES)
+    private val ad1: ByteArray = Random.nextBytes(34)
+    private val ad2: ByteArray = Random.nextBytes(34)
+    private val ad3: ByteArray = Random.nextBytes(34)
+    private val chunkWriter =
+        ChunkWriter(streamCrypto, streamKey, chunksCache, storagePlugin, Random.nextInt(1, 42))
+
+    private val chunkId1 = Random.nextBytes(KEY_SIZE_BYTES).toHexString()
+    private val chunkId2 = Random.nextBytes(KEY_SIZE_BYTES).toHexString()
+    private val chunkId3 = Random.nextBytes(KEY_SIZE_BYTES).toHexString()
+
+    init {
+        mockLog()
+    }
+
+    @Test
+    fun testTwoByteChunksNotCached() {
+        val inputBytes = byteArrayOf(0x00, 0x01, 0x02, 0x03, 0x04, 0x05)
+        val inputStream = ByteArrayInputStream(inputBytes)
+        val chunks = listOf(
+            Chunk(chunkId1, 0, 2),
+            Chunk(chunkId2, 2, 2),
+            Chunk(chunkId3, 4, 2),
+        )
+        val chunk1Output = ByteArrayOutputStream()
+        val chunk2Output = ByteArrayOutputStream()
+        val chunk3Output = ByteArrayOutputStream()
+        val outputStreams = listOf(chunk1Output, chunk2Output, chunk3Output)
+
+        // chunks are not cached
+        every { chunksCache.get(chunkId1) } returns null
+        every { chunksCache.get(chunkId2) } returns null
+        every { chunksCache.get(chunkId3) } returns null
+
+        // get the output streams for the chunks
+        every { storagePlugin.getChunkOutputStream(chunkId1) } returns chunk1Output
+        every { storagePlugin.getChunkOutputStream(chunkId2) } returns chunk2Output
+        every { storagePlugin.getChunkOutputStream(chunkId3) } returns chunk3Output
+
+        // get AD
+        every { streamCrypto.getAssociatedDataForChunk(chunkId1) } returns ad1
+        every { streamCrypto.getAssociatedDataForChunk(chunkId2) } returns ad2
+        every { streamCrypto.getAssociatedDataForChunk(chunkId3) } returns ad3
+
+        // wrap output stream in crypto stream
+        every {
+            streamCrypto.newEncryptingStream(streamKey, chunk1Output, ad1)
+        } returns chunk1Output
+        every {
+            streamCrypto.newEncryptingStream(streamKey, chunk2Output, ad2)
+        } returns chunk2Output
+        every {
+            streamCrypto.newEncryptingStream(streamKey, chunk3Output, ad3)
+        } returns chunk3Output
+
+        // insert chunks into cache after upload
+        every { chunksCache.insert(chunks[0].toCachedChunk()) } just Runs
+        every { chunksCache.insert(chunks[1].toCachedChunk()) } just Runs
+        every { chunksCache.insert(chunks[2].toCachedChunk()) } just Runs
+
+        chunkWriter.writeChunk(inputStream, chunks, emptyList())
+
+        // check that version was written as the first byte
+        outputStreams.forEach { outputStream ->
+            assertEquals(VERSION, outputStream.toByteArray()[0])
+        }
+
+        // check that output matches chunk data
+        assertArrayEquals(byteArrayOf(0x00, 0x01), chunk1Output.toByteArray().copyOfRange(1, 3))
+        assertArrayEquals(byteArrayOf(0x02, 0x03), chunk2Output.toByteArray().copyOfRange(1, 3))
+        assertArrayEquals(byteArrayOf(0x04, 0x05), chunk3Output.toByteArray().copyOfRange(1, 3))
+    }
+
+    @Test
+    fun testCachedChunksSkippedIfNotMissing() {
+        val inputBytes = byteArrayOf(0x00, 0x01, 0x02, 0x03, 0x04, 0x05)
+        val inputStream = ByteArrayInputStream(inputBytes)
+        val chunks = listOf(
+            Chunk(chunkId1, 0, 2), // cached and missing
+            Chunk(chunkId2, 2, 2), // cached and available
+            Chunk(chunkId3, 4, 2), // not cached
+        )
+        val chunk1Output = ByteArrayOutputStream()
+        val chunk3Output = ByteArrayOutputStream()
+
+        // only first two chunks are cached (first chunk is missing from storage)
+        every { chunksCache.get(chunkId1) } returns chunks[0].toCachedChunk()
+        every { chunksCache.get(chunkId2) } returns chunks[1].toCachedChunk()
+        every { chunksCache.get(chunkId3) } returns null
+
+        // get and wrap the output stream for chunk that is missing
+        every { storagePlugin.getChunkOutputStream(chunkId1) } returns chunk1Output
+        every { streamCrypto.getAssociatedDataForChunk(chunkId1) } returns ad1
+        every {
+            streamCrypto.newEncryptingStream(streamKey, chunk1Output, bytes(34))
+        } returns chunk1Output
+
+        // insert missing cached chunk into cache after upload
+        every { chunksCache.insert(chunks[0].toCachedChunk()) } just Runs
+
+        // get and wrap the output stream for chunk that isn't cached
+        every { storagePlugin.getChunkOutputStream(chunkId3) } returns chunk3Output
+        every { streamCrypto.getAssociatedDataForChunk(chunkId3) } returns ad3
+        every {
+            streamCrypto.newEncryptingStream(streamKey, chunk3Output, bytes(34))
+        } returns chunk3Output
+
+        // insert last not cached chunk into cache after upload
+        every { chunksCache.insert(chunks[2].toCachedChunk()) } just Runs
+
+        chunkWriter.writeChunk(inputStream, chunks, listOf(chunkId1))
+
+        // check that output matches chunk data
+        assertEquals(VERSION, chunk1Output.toByteArray()[0])
+        assertArrayEquals(byteArrayOf(0x00, 0x01), chunk1Output.toByteArray().copyOfRange(1, 3))
+        assertEquals(VERSION, chunk3Output.toByteArray()[0])
+        assertArrayEquals(byteArrayOf(0x04, 0x05), chunk3Output.toByteArray().copyOfRange(1, 3))
+    }
+
+    @Test
+    fun testLargerRandomChunks() {
+        val chunk1Bytes = Random.nextBytes(Random.nextInt(1, 1024 * 1024))
+        val chunk2Bytes = Random.nextBytes(Random.nextInt(1, 1024 * 1024))
+        val chunk3Bytes = Random.nextBytes(Random.nextInt(1, 1024 * 1024))
+        val inputStream = ByteArrayInputStream(chunk1Bytes + chunk2Bytes + chunk3Bytes)
+        val chunks = listOf(
+            Chunk(chunkId1, 0, chunk1Bytes.size.toLong()),
+            Chunk(chunkId2, chunk1Bytes.size.toLong(), chunk2Bytes.size.toLong()),
+            Chunk(
+                chunkId3,
+                (chunk1Bytes.size + chunk2Bytes.size).toLong(),
+                chunk3Bytes.size.toLong()
+            ),
+        )
+        val chunk1Output = ByteArrayOutputStream()
+        val chunk3Output = ByteArrayOutputStream()
+        val outputStreams = listOf(chunk1Output, chunk3Output)
+
+        // first and last chunk are not cached
+        every { chunksCache.get(chunkId1) } returns null
+        every { chunksCache.get(chunkId2) } returns chunks[1].toCachedChunk()
+        every { chunksCache.get(chunkId3) } returns null
+
+        // get the output streams for the chunks
+        every { storagePlugin.getChunkOutputStream(chunkId1) } returns chunk1Output
+        every { storagePlugin.getChunkOutputStream(chunkId3) } returns chunk3Output
+
+        // get AD
+        every { streamCrypto.getAssociatedDataForChunk(chunkId1) } returns ad1
+        every { streamCrypto.getAssociatedDataForChunk(chunkId3) } returns ad3
+
+        // wrap output streams in crypto streams
+        every {
+            streamCrypto.newEncryptingStream(streamKey, chunk1Output, ad1)
+        } returns chunk1Output
+        every {
+            streamCrypto.newEncryptingStream(streamKey, chunk3Output, ad3)
+        } returns chunk3Output
+
+        // insert chunks into cache after upload
+        every { chunksCache.insert(chunks[0].toCachedChunk()) } just Runs
+        every { chunksCache.insert(chunks[2].toCachedChunk()) } just Runs
+
+        chunkWriter.writeChunk(inputStream, chunks, emptyList())
+
+        // check that version and wrapped key was written as the first byte
+        outputStreams.forEach { outputStream ->
+            assertEquals(VERSION, outputStream.toByteArray()[0])
+        }
+
+        // check that output matches chunk data
+        assertEquals(1 + chunks[0].size.toInt(), chunk1Output.size())
+        assertArrayEquals(
+            chunk1Bytes,
+            chunk1Output.toByteArray().copyOfRange(1, 1 + chunks[0].size.toInt())
+        )
+        assertEquals(1 + chunks[2].size.toInt(), chunk3Output.size())
+        assertArrayEquals(
+            chunk3Bytes,
+            chunk3Output.toByteArray().copyOfRange(1, 1 + chunks[2].size.toInt())
+        )
+    }
+
+    private fun MockKMatcherScope.bytes(size: Int) = match<ByteArray> {
+        it.size == size
+    }
+
+}
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ChunkerTest.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ChunkerTest.kt
new file mode 100644
index 00000000..40d50681
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ChunkerTest.kt
@@ -0,0 +1,125 @@
+package org.calyxos.backup.storage.backup
+
+import org.calyxos.backup.storage.crypto.ChunkCrypto
+import org.calyxos.backup.storage.crypto.Hkdf.KEY_SIZE_BYTES
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import java.io.ByteArrayInputStream
+import kotlin.random.Random
+
+internal class ChunkerTest {
+
+    private val chunkId0Byte1 = "6620b31f2924b8c01547745f41825d322336f83ebb13d723678789d554d8a3ef"
+    private val chunkId0Byte2 = "b31825742c7dffdfdcea617f81eadcfb55e1f85f3a260abf40f38e6d00472c5a"
+    private val chunkId0Byte3 = "e7655205039eddec669bdc5099863024deef1a609430f10dac5f7889f03bf139"
+    private val chunkId0Byte4 = "aa7855e13839dd767cd5da7c1ff5036540c9264b7a803029315e55375287b4af"
+
+    @Test
+    fun testTwoByteChunks() {
+        val mac = ChunkCrypto.getMac(ByteArray(KEY_SIZE_BYTES))
+        val chunker = Chunker(mac, 2)
+
+        val input0 = ByteArrayInputStream(ByteArray(0))
+        assertEquals(emptyList<Chunk>(), chunker.makeChunks(input0))
+
+        val input1 = ByteArrayInputStream(ByteArray(1))
+        val chunk1 = Chunk(chunkId0Byte1, 0, 1)
+        assertEquals(listOf(chunk1), chunker.makeChunks(input1))
+
+        val input2 = ByteArrayInputStream(ByteArray(2))
+        val chunk2 = Chunk(chunkId0Byte2, 0, 2)
+        assertEquals(listOf(chunk2), chunker.makeChunks(input2))
+
+        val input3 = ByteArrayInputStream(ByteArray(3))
+        val chunk3a = Chunk(chunkId0Byte2, 0, 2)
+        val chunk3b = Chunk(chunkId0Byte1, 2, 1)
+        assertEquals(listOf(chunk3a, chunk3b), chunker.makeChunks(input3))
+
+        val input4 = ByteArrayInputStream(ByteArray(4))
+        val chunk4a = Chunk(chunkId0Byte2, 0, 2)
+        val chunk4b = Chunk(chunkId0Byte2, 2, 2)
+        assertEquals(listOf(chunk4a, chunk4b), chunker.makeChunks(input4))
+
+        val input5 = ByteArrayInputStream(ByteArray(5))
+        val chunk5a = Chunk(chunkId0Byte2, 0, 2)
+        val chunk5b = Chunk(chunkId0Byte2, 2, 2)
+        val chunk5c = Chunk(chunkId0Byte1, 4, 1)
+        assertEquals(listOf(chunk5a, chunk5b, chunk5c), chunker.makeChunks(input5))
+
+        val input6 = ByteArrayInputStream(ByteArray(6))
+        val chunk6a = Chunk(chunkId0Byte2, 0, 2)
+        val chunk6b = Chunk(chunkId0Byte2, 2, 2)
+        val chunk6c = Chunk(chunkId0Byte2, 4, 2)
+        assertEquals(listOf(chunk6a, chunk6b, chunk6c), chunker.makeChunks(input6))
+    }
+
+    @Test
+    fun testThreeByteChunks() {
+        val mac = ChunkCrypto.getMac(ByteArray(KEY_SIZE_BYTES))
+        val chunker = Chunker(mac, 3)
+
+        val input0 = ByteArrayInputStream(ByteArray(0))
+        assertEquals(emptyList<Chunk>(), chunker.makeChunks(input0))
+
+        val input1 = ByteArrayInputStream(ByteArray(1))
+        val chunk1 = Chunk(chunkId0Byte1, 0, 1)
+        assertEquals(listOf(chunk1), chunker.makeChunks(input1))
+
+        val input2 = ByteArrayInputStream(ByteArray(2))
+        val chunk2 = Chunk(chunkId0Byte2, 0, 2)
+        assertEquals(listOf(chunk2), chunker.makeChunks(input2))
+
+        val input3 = ByteArrayInputStream(ByteArray(3))
+        val chunk3 = Chunk(chunkId0Byte3, 0, 3)
+        assertEquals(listOf(chunk3), chunker.makeChunks(input3))
+
+        val input4 = ByteArrayInputStream(ByteArray(4))
+        val chunk4a = Chunk(chunkId0Byte3, 0, 3)
+        val chunk4b = Chunk(chunkId0Byte1, 3, 1)
+        assertEquals(listOf(chunk4a, chunk4b), chunker.makeChunks(input4))
+
+        val input5 = ByteArrayInputStream(ByteArray(5))
+        val chunk5a = Chunk(chunkId0Byte3, 0, 3)
+        val chunk5b = Chunk(chunkId0Byte2, 3, 2)
+        assertEquals(listOf(chunk5a, chunk5b), chunker.makeChunks(input5))
+
+        val input6 = ByteArrayInputStream(ByteArray(6))
+        val chunk6a = Chunk(chunkId0Byte3, 0, 3)
+        val chunk6b = Chunk(chunkId0Byte3, 3, 3)
+        assertEquals(listOf(chunk6a, chunk6b), chunker.makeChunks(input6))
+    }
+
+    @Test
+    fun testChunksGreaterThanBuffer() {
+        val mac = ChunkCrypto.getMac(ByteArray(KEY_SIZE_BYTES))
+        val chunker = Chunker(mac, 4, Random.nextInt(1, 4))
+
+        val input0 = ByteArrayInputStream(ByteArray(0))
+        assertEquals(emptyList<Chunk>(), chunker.makeChunks(input0))
+
+        val input1 = ByteArrayInputStream(ByteArray(1))
+        val chunk1 = Chunk(chunkId0Byte1, 0, 1)
+        assertEquals(listOf(chunk1), chunker.makeChunks(input1))
+
+        val input5 = ByteArrayInputStream(ByteArray(5))
+        val chunk5a = Chunk(chunkId0Byte4, 0, 4)
+        val chunk5b = Chunk(chunkId0Byte1, 4, 1)
+        assertEquals(listOf(chunk5a, chunk5b), chunker.makeChunks(input5))
+
+        val input7 = ByteArrayInputStream(ByteArray(7))
+        val chunk7a = Chunk(chunkId0Byte4, 0, 4)
+        val chunk7b = Chunk(chunkId0Byte3, 4, 3)
+        assertEquals(listOf(chunk7a, chunk7b), chunker.makeChunks(input7))
+
+        val input16 = ByteArrayInputStream(ByteArray(16))
+        val chunk16a = Chunk(chunkId0Byte4, 0, 4)
+        val chunk16b = Chunk(chunkId0Byte4, 4, 4)
+        val chunk16c = Chunk(chunkId0Byte4, 8, 4)
+        val chunk16d = Chunk(chunkId0Byte4, 12, 4)
+        assertEquals(
+            listOf(chunk16a, chunk16b, chunk16c, chunk16d),
+            chunker.makeChunks(input16)
+        )
+    }
+
+}
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ChunksCacheRepopulaterTest.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ChunksCacheRepopulaterTest.kt
new file mode 100644
index 00000000..b1fb556a
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ChunksCacheRepopulaterTest.kt
@@ -0,0 +1,88 @@
+package org.calyxos.backup.storage.backup
+
+import io.mockk.Runs
+import io.mockk.coEvery
+import io.mockk.coVerify
+import io.mockk.every
+import io.mockk.just
+import io.mockk.mockk
+import io.mockk.slot
+import kotlinx.coroutines.runBlocking
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.db.CachedChunk
+import org.calyxos.backup.storage.db.ChunksCache
+import org.calyxos.backup.storage.db.Db
+import org.calyxos.backup.storage.getRandomString
+import org.calyxos.backup.storage.mockLog
+import org.calyxos.backup.storage.plugin.SnapshotRetriever
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import kotlin.random.Random
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class ChunksCacheRepopulaterTest {
+
+    private val db: Db = mockk()
+    private val chunksCache: ChunksCache = mockk()
+    private val plugin: StoragePlugin = mockk()
+    private val snapshotRetriever: SnapshotRetriever = mockk()
+    private val streamKey = "This is a backup key for testing".toByteArray()
+    private val cacheRepopulater = ChunksCacheRepopulater(db, plugin, snapshotRetriever)
+
+    init {
+        mockLog()
+        every { db.getChunksCache() } returns chunksCache
+    }
+
+    @Test
+    fun test(): Unit = runBlocking {
+        val chunk1 = getRandomString(6) // in 2 snapshots
+        val chunk2 = getRandomString(6) // in 2 snapshots
+        val chunk3 = getRandomString(6) // not referenced by any snapshot
+        val chunk4 = getRandomString(6) // in 1 snapshot
+        val chunk5 = getRandomString(6) // in 1 snapshot, but not available in storage
+        val availableChunkIds = hashSetOf(chunk1, chunk2, chunk3, chunk4)
+        val snapshot1 = BackupSnapshot.newBuilder()
+            .setTimeStart(Random.nextLong())
+            .addMediaFiles(BackupMediaFile.newBuilder().addChunkIds(chunk1))
+            .addMediaFiles(BackupMediaFile.newBuilder().addChunkIds(chunk2))
+            .addDocumentFiles(BackupDocumentFile.newBuilder().addChunkIds(chunk1))
+            .build()
+        val snapshot2 = BackupSnapshot.newBuilder()
+            .setTimeStart(Random.nextLong())
+            .addMediaFiles(BackupMediaFile.newBuilder().addChunkIds(chunk1))
+            .addMediaFiles(BackupMediaFile.newBuilder().addChunkIds(chunk2))
+            .addDocumentFiles(BackupDocumentFile.newBuilder().addChunkIds(chunk4))
+            .addDocumentFiles(BackupDocumentFile.newBuilder().addChunkIds(chunk5))
+            .build()
+        val storedSnapshot1 = StoredSnapshot("foo", snapshot1.timeStart)
+        val storedSnapshot2 = StoredSnapshot("bar", snapshot2.timeStart)
+        val storedSnapshots = listOf(storedSnapshot1, storedSnapshot2)
+        val cachedChunks = listOf(
+            CachedChunk(chunk1, 2, 0),
+            CachedChunk(chunk2, 2, 0),
+            CachedChunk(chunk4, 1, 0),
+        ) // chunk3 is not referenced and should get deleted
+        val cachedChunksSlot = slot<Collection<CachedChunk>>()
+
+        coEvery { plugin.getCurrentBackupSnapshots() } returns storedSnapshots
+        coEvery {
+            snapshotRetriever.getSnapshot(streamKey, storedSnapshot1)
+        } returns snapshot1
+        coEvery {
+            snapshotRetriever.getSnapshot(streamKey, storedSnapshot2)
+        } returns snapshot2
+        every { chunksCache.clearAndRepopulate(db, capture(cachedChunksSlot)) } just Runs
+        coEvery { plugin.deleteChunks(listOf(chunk3)) } just Runs
+
+        cacheRepopulater.repopulate(streamKey, availableChunkIds)
+
+        assertTrue(cachedChunksSlot.isCaptured)
+        assertEquals(cachedChunks.toSet(), cachedChunksSlot.captured.toSet())
+
+        coVerify { plugin.deleteChunks(listOf(chunk3)) }
+    }
+
+}
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/backup/SmallFileBackupTest.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/backup/SmallFileBackupTest.kt
new file mode 100644
index 00000000..cf5832c5
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/backup/SmallFileBackupTest.kt
@@ -0,0 +1,213 @@
+package org.calyxos.backup.storage.backup
+
+import android.content.ContentResolver
+import io.mockk.Runs
+import io.mockk.every
+import io.mockk.just
+import io.mockk.mockk
+import kotlinx.coroutines.runBlocking
+import org.calyxos.backup.storage.content.ContentFile
+import org.calyxos.backup.storage.content.DocFile
+import org.calyxos.backup.storage.db.CachedFile
+import org.calyxos.backup.storage.db.FilesCache
+import org.calyxos.backup.storage.getRandomDocFile
+import org.calyxos.backup.storage.getRandomString
+import org.calyxos.backup.storage.mockLog
+import org.calyxos.backup.storage.sameCachedFile
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import java.io.IOException
+import java.io.InputStream
+import kotlin.random.Random
+
+internal class SmallFileBackupTest {
+
+    private val contentResolver: ContentResolver = mockk()
+    private val filesCache: FilesCache = mockk()
+    private val zipChunker: ZipChunker = mockk()
+
+    private val smallFileBackup = SmallFileBackup(contentResolver, filesCache, zipChunker, true)
+
+    private val fileInputStream: InputStream = mockk()
+
+    init {
+        mockLog()
+    }
+
+    @Test
+    fun `unchanged file doesn't get backed up`(): Unit = runBlocking {
+        val files = listOf(getRandomDocFile())
+        val availableChunkIds = hashSetOf(getRandomString(6), getRandomString(6))
+        val cachedFile = files[0].toCachedFile(listOf(availableChunkIds.iterator().next()), 1)
+        val backupFile = files[0].toBackupFile(cachedFile.chunks, cachedFile.zipIndex)
+
+        every { filesCache.getByUri(files[0].uri) } returns cachedFile
+
+        val result = smallFileBackup.backupFiles(files, availableChunkIds, null)
+        assertEquals(cachedFile.chunks.toSet(), result.chunkIds)
+        assertEquals(1, result.backupDocumentFiles.size)
+        assertEquals(backupFile, result.backupDocumentFiles[0])
+        assertEquals(0, result.backupMediaFiles.size)
+    }
+
+    @Test
+    fun `changed file gets backed up`(): Unit = runBlocking {
+        val file = getRandomDocFile()
+        val files = listOf(file)
+        val availableChunkIds = hashSetOf(getRandomString(6))
+        val cachedFile =
+            file.toCachedFile(availableChunkIds.toList(), 5).copy(size = Random.nextLong())
+
+        singleFileBackup(files, cachedFile, availableChunkIds)
+    }
+
+    @Test
+    fun `new file gets backed up`(): Unit = runBlocking {
+        val file = getRandomDocFile()
+        val files = listOf(file)
+        val availableChunkIds = hashSetOf(getRandomString(6))
+
+        singleFileBackup(files, null, availableChunkIds)
+    }
+
+    @Test
+    fun `unchanged file recovers missing chunks`(): Unit = runBlocking {
+        val file = getRandomDocFile()
+        val files = listOf(file)
+        val missingChunk = getRandomString(6)
+        val cachedFile = file.toCachedFile(listOf(missingChunk), 5)
+        val availableChunkIds = hashSetOf(getRandomString(6))
+
+        singleFileBackup(files, cachedFile, availableChunkIds)
+    }
+
+    private suspend fun singleFileBackup(
+        files: List<DocFile>,
+        cachedFile: CachedFile?,
+        availableChunkIds: HashSet<String>
+    ) {
+        val file = files[0]
+        val zipChunk = ZipChunk(getRandomString(6), listOf(file), Random.nextLong(), true)
+        val newCachedFile = file.toCachedFile(listOf(zipChunk.id), 1)
+        val backupFile = file.toBackupFile(newCachedFile.chunks, newCachedFile.zipIndex)
+        val missingChunks =
+            if (cachedFile == null) emptyList() else cachedFile.chunks - availableChunkIds
+
+        addFile(file, cachedFile)
+        every { zipChunker.finalizeAndReset(missingChunks) } returns zipChunk
+        every { filesCache.upsert(sameCachedFile(newCachedFile)) } just Runs
+
+        val result = smallFileBackup.backupFiles(files, availableChunkIds, null)
+        assertEquals(newCachedFile.chunks.toSet(), result.chunkIds)
+        assertEquals(1, result.backupDocumentFiles.size)
+        assertEquals(backupFile, result.backupDocumentFiles[0])
+        assertEquals(0, result.backupMediaFiles.size)
+    }
+
+    @Test
+    fun `first of two new files throws and gets ignored`(): Unit = runBlocking {
+        val file1 = getRandomDocFile()
+        val file2 = getRandomDocFile()
+        val files = listOf(file1, file2)
+        val availableChunkIds = hashSetOf(getRandomString(6))
+
+        val zipChunk = ZipChunk(getRandomString(6), listOf(file2), Random.nextLong(), true)
+        val cachedFile2 = file2.toCachedFile(listOf(zipChunk.id), 1)
+        val backupFile = file2.toBackupFile(cachedFile2.chunks, cachedFile2.zipIndex)
+
+        every { filesCache.getByUri(file1.uri) } returns null
+        every { contentResolver.openInputStream(file1.uri) } throws IOException()
+        addFile(file2)
+        every { zipChunker.finalizeAndReset(emptyList()) } returns zipChunk
+        every { filesCache.upsert(sameCachedFile(cachedFile2)) } just Runs
+
+        val result = smallFileBackup.backupFiles(files, availableChunkIds, null)
+        assertEquals(cachedFile2.chunks.toSet(), result.chunkIds)
+        assertEquals(1, result.backupDocumentFiles.size)
+        assertEquals(backupFile, result.backupDocumentFiles[0])
+        assertEquals(0, result.backupMediaFiles.size)
+    }
+
+    @Test
+    fun `two files get put into two chunks if they are too big`(): Unit = runBlocking {
+        val file1 = getRandomDocFile()
+        val file2 = getRandomDocFile()
+        val files = listOf(file1, file2)
+
+        val zipChunk1 = ZipChunk(getRandomString(6), listOf(file1), Random.nextLong(), true)
+        val zipChunk2 = ZipChunk(getRandomString(6), listOf(file2), Random.nextLong(), true)
+        val cachedFile1 = file1.toCachedFile(listOf(zipChunk1.id), 1)
+        val cachedFile2 = file2.toCachedFile(listOf(zipChunk2.id), 1)
+        val backupFile1 = file1.toBackupFile(cachedFile1.chunks, cachedFile1.zipIndex)
+        val backupFile2 = file2.toBackupFile(cachedFile2.chunks, cachedFile2.zipIndex)
+
+        addFile(file1)
+        every { zipChunker.fitsFile(file2) } returns false
+        every { zipChunker.finalizeAndReset(emptyList()) } returns zipChunk1 andThen zipChunk2
+        every { filesCache.upsert(sameCachedFile(cachedFile1)) } just Runs
+        addFile(file2)
+        // zipChunker.finalizeAndReset defined above for both files
+        every { filesCache.upsert(sameCachedFile(cachedFile2)) } just Runs
+
+        val result = smallFileBackup.backupFiles(files, hashSetOf(), null)
+        assertEquals(listOf(zipChunk1.id, zipChunk2.id).toSet(), result.chunkIds)
+        assertEquals(
+            listOf(backupFile1, backupFile2).sortedBy { it.name },
+            result.backupDocumentFiles.sortedBy { it.name }
+        )
+        assertEquals(0, result.backupMediaFiles.size)
+    }
+
+    @Test
+    fun `two files get put into into the same chunk if they fit`(): Unit = runBlocking {
+        val file1 = getRandomDocFile()
+        val file2 = getRandomDocFile()
+        val files = listOf(file1, file2)
+
+        val zipChunk = ZipChunk(getRandomString(6), listOf(file1, file2), Random.nextLong(), true)
+        val cachedFile1 = file1.toCachedFile(listOf(zipChunk.id), 1)
+        val cachedFile2 = file2.toCachedFile(listOf(zipChunk.id), 2)
+        val backupFile1 = file1.toBackupFile(cachedFile1.chunks, cachedFile1.zipIndex)
+        val backupFile2 = file2.toBackupFile(cachedFile2.chunks, cachedFile2.zipIndex)
+
+        addFile(file1)
+        every { zipChunker.fitsFile(file2) } returns true
+        addFile(file2)
+        every { zipChunker.finalizeAndReset(emptyList()) } returns zipChunk
+        every { filesCache.upsert(sameCachedFile(cachedFile1)) } just Runs
+        every { filesCache.upsert(sameCachedFile(cachedFile2)) } just Runs
+
+        val result = smallFileBackup.backupFiles(files, hashSetOf(), null)
+        assertEquals(listOf(zipChunk.id).toSet(), result.chunkIds)
+        assertEquals(
+            listOf(backupFile1, backupFile2).sortedBy { it.name },
+            result.backupDocumentFiles.sortedBy { it.name }
+        )
+        assertEquals(0, result.backupMediaFiles.size)
+    }
+
+    @Test
+    fun `two files don't get backed up when finalize throws`(): Unit = runBlocking {
+        val file1 = getRandomDocFile()
+        val file2 = getRandomDocFile()
+        val files = listOf(file1, file2)
+
+        addFile(file1)
+        every { zipChunker.fitsFile(file2) } returns true
+        addFile(file2)
+        every { zipChunker.finalizeAndReset(emptyList()) } throws IOException()
+
+        val result = smallFileBackup.backupFiles(files, hashSetOf(), null)
+        assertEquals(emptySet<String>(), result.chunkIds)
+        assertEquals(0, result.backupDocumentFiles.size)
+        assertEquals(0, result.backupMediaFiles.size)
+    }
+
+    private fun addFile(file: ContentFile, cachedFile: CachedFile? = null) {
+        every { filesCache.getByUri(file.uri) } returns cachedFile
+        every { contentResolver.openInputStream(file.uri) } returns fileInputStream
+        every { zipChunker.addFile(file, fileInputStream) } just Runs
+        every { fileInputStream.close() } just Runs
+    }
+
+}
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ZipChunkerTest.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ZipChunkerTest.kt
new file mode 100644
index 00000000..c88f4450
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/backup/ZipChunkerTest.kt
@@ -0,0 +1,127 @@
+package org.calyxos.backup.storage.backup
+
+import io.mockk.Runs
+import io.mockk.every
+import io.mockk.just
+import io.mockk.mockk
+import org.calyxos.backup.storage.getRandomDocFile
+import org.calyxos.backup.storage.getRandomString
+import org.calyxos.backup.storage.toHexString
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import java.io.IOException
+import java.io.InputStream
+import javax.crypto.Mac
+import kotlin.random.Random
+import kotlin.test.assertFailsWith
+
+internal class ZipChunkerTest {
+
+    private val mac: Mac = mockk()
+    private val chunkWriter: ChunkWriter = mockk()
+    private val fileInputStream: InputStream = mockk()
+
+    private val zipChunker = ZipChunker(mac, chunkWriter, 42)
+
+    @Test
+    fun fitsFile() {
+        val zipChunker = ZipChunker(mac, chunkWriter, 10)
+        for (i in (0L..10L)) {
+            assertTrue(zipChunker.fitsFile(getRandomDocFile(i)))
+        }
+        assertFalse(zipChunker.fitsFile(getRandomDocFile(11)))
+    }
+
+    @Test
+    fun addFile() {
+        val file1 = getRandomDocFile()
+        val file2 = getRandomDocFile()
+        val file3 = getRandomDocFile()
+
+        every { chunkWriter.writeNewZipEntry(any(), 1, fileInputStream) } just Runs
+        zipChunker.addFile(file1, fileInputStream)
+
+        every { chunkWriter.writeNewZipEntry(any(), 2, fileInputStream) } just Runs
+        zipChunker.addFile(file2, fileInputStream)
+
+        every { chunkWriter.writeNewZipEntry(any(), 3, fileInputStream) } just Runs
+        zipChunker.addFile(file3, fileInputStream)
+    }
+
+    @Test
+    fun `throwing in addFile does not modify counter`() {
+        val zipChunker = ZipChunker(mac, chunkWriter, 10)
+        val file1 = getRandomDocFile(5)
+        val file2 = getRandomDocFile(5)
+        val file3 = getRandomDocFile(5)
+
+        every { chunkWriter.writeNewZipEntry(any(), 1, fileInputStream) } just Runs
+        zipChunker.addFile(file1, fileInputStream)
+
+        every { chunkWriter.writeNewZipEntry(any(), 2, fileInputStream) } throws IOException()
+        assertFailsWith(IOException::class) {
+            zipChunker.addFile(file2, fileInputStream)
+        }
+
+        // uses counter 2 again
+        every { chunkWriter.writeNewZipEntry(any(), 2, fileInputStream) } just Runs
+        zipChunker.addFile(file3, fileInputStream)
+    }
+
+    @Test
+    fun `two files finalizeAndReset()`() {
+        val file1 = getRandomDocFile(4)
+        val file2 = getRandomDocFile(8)
+        val chunkIdBytes = Random.nextBytes(64)
+        val missingChunks = listOf(getRandomString(6), getRandomString(6))
+        val wasWritten = Random.nextBoolean()
+        val zipChunk = ZipChunk(chunkIdBytes.toHexString(), listOf(file1, file2), 22L)
+
+        every { chunkWriter.writeNewZipEntry(any(), 1, fileInputStream) } just Runs
+        zipChunker.addFile(file1, fileInputStream)
+        every { chunkWriter.writeNewZipEntry(any(), 2, fileInputStream) } just Runs
+        zipChunker.addFile(file2, fileInputStream)
+
+        every { mac.doFinal(any()) } returns chunkIdBytes
+        every { chunkWriter.writeZipChunk(zipChunk, any(), missingChunks) } returns wasWritten
+
+        assertEquals(
+            zipChunk.copy(wasUploaded = wasWritten),
+            zipChunker.finalizeAndReset(missingChunks)
+        )
+
+        // counter gets reset to 1
+        val file1a = getRandomDocFile(4)
+        every { chunkWriter.writeNewZipEntry(any(), 1, fileInputStream) } just Runs
+        zipChunker.addFile(file1a, fileInputStream)
+    }
+
+    @Test
+    fun `throwing in finalizeAndReset() resets counter`() {
+        val file1 = getRandomDocFile(4)
+        val file2 = getRandomDocFile(8)
+        val chunkIdBytes = Random.nextBytes(64)
+        val missingChunks = listOf(getRandomString(6), getRandomString(6))
+        val zipChunk = ZipChunk(chunkIdBytes.toHexString(), listOf(file1, file2), 22L)
+
+        every { chunkWriter.writeNewZipEntry(any(), 1, fileInputStream) } just Runs
+        zipChunker.addFile(file1, fileInputStream)
+        every { chunkWriter.writeNewZipEntry(any(), 2, fileInputStream) } just Runs
+        zipChunker.addFile(file2, fileInputStream)
+
+        every { mac.doFinal(any()) } returns chunkIdBytes
+        every { chunkWriter.writeZipChunk(zipChunk, any(), missingChunks) } throws IOException()
+
+        assertFailsWith(IOException::class) {
+            zipChunker.finalizeAndReset(missingChunks)
+        }
+
+        // counter still gets reset to 1 even though we had an exception
+        val file1a = getRandomDocFile(4)
+        every { chunkWriter.writeNewZipEntry(any(), 1, fileInputStream) } just Runs
+        zipChunker.addFile(file1a, fileInputStream)
+    }
+
+}
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/crypto/HkdfTest.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/crypto/HkdfTest.kt
new file mode 100644
index 00000000..632e386a
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/crypto/HkdfTest.kt
@@ -0,0 +1,77 @@
+package org.calyxos.backup.storage.crypto
+
+import org.junit.Assert.assertArrayEquals
+import org.junit.Test
+import javax.crypto.spec.SecretKeySpec
+
+internal class HkdfTest {
+
+    @Test
+    fun rfc5869testCase1() {
+        checkStep2(
+            "077709362c2e32df0ddc3f0dc47bba6390b6c73bb50f9c3122ec844ad7c2b3e5",
+            "f0f1f2f3f4f5f6f7f8f9",
+            42,
+            "3cb25f25faacd57a90434f64d0362f2a2d2d0a90cf1a5a4c5db02d56ecc4c5bf34007208d5b887185865"
+        )
+    }
+
+    @Test
+    @Throws(Exception::class)
+    fun rfc5869testCase2() {
+        checkStep2(
+            "06a6b88c5853361a06104c9ceb35b45cef760014904671014a193f40c15fc244",
+            "b0b1b2b3b4b5b6b7b8b9babbbcbdbebfc0c1c2c3c4" +
+                "c5c6c7c8c9cacbcccdcecfd0d1d2d3d4d5d6d7d8d9" +
+                "dadbdcdddedfe0e1e2e3e4e5e6e7e8e9eaebecedeeeff0f1f2f3f4f5f6f7f8f9fafbfcfdfeff",
+            82,
+            "b11e398dc80327a1c8e7f78c596a49344f012eda2" +
+                "d4efad8a050cc4c19afa97c59045a99cac7827271c" +
+                "b41c65e590e09da3275600c2f09b8367793a9aca3db" +
+                "71cc30c58179ec3e87c14c01d5c1f3434f1d87"
+        )
+    }
+
+    @Test
+    @Throws(Exception::class)
+    fun rfc5869testCase3() {
+        checkStep2(
+            "19ef24a32c717b167f33a91d6f648bdf96596776afdb6377ac434c1c293ccb04",
+            "",
+            42,
+            "8da4e775a563c18f715f802a063c5a31b8a11f5c5ee1879ec3454e5f3c738d2d9d201395faa4b61a96c8"
+        )
+    }
+
+    @Throws(java.lang.Exception::class)
+    private fun checkStep2(prk: String, info: String, length: Int, okm: String) {
+        val seed = decodeHexString(prk)
+        val secretKey = SecretKeySpec(seed, 0, seed.size, "AES")
+        val currentOkm: ByteArray = Hkdf.expand(secretKey, decodeHexString(info), length)
+        assertArrayEquals(decodeHexString(okm), currentOkm)
+    }
+
+    private fun decodeHexString(hexString: String): ByteArray {
+        require(hexString.length % 2 != 1) { "Invalid hexadecimal String supplied." }
+        val bytes = ByteArray(hexString.length / 2)
+        var i = 0
+        while (i < hexString.length) {
+            bytes[i / 2] = hexToByte(hexString.substring(i, i + 2))
+            i += 2
+        }
+        return bytes
+    }
+
+    private fun hexToByte(hexString: String): Byte {
+        val firstDigit = toDigit(hexString[0])
+        val secondDigit = toDigit(hexString[1])
+        return ((firstDigit shl 4) + secondDigit).toByte()
+    }
+
+    private fun toDigit(hexChar: Char): Int {
+        val digit = Character.digit(hexChar, 16)
+        require(digit != -1) { "Invalid Hexadecimal Character: $hexChar" }
+        return digit
+    }
+
+}
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/prune/PrunerTest.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/prune/PrunerTest.kt
new file mode 100644
index 00000000..3c359cf6
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/prune/PrunerTest.kt
@@ -0,0 +1,102 @@
+package org.calyxos.backup.storage.prune
+
+import io.mockk.Runs
+import io.mockk.coEvery
+import io.mockk.every
+import io.mockk.just
+import io.mockk.mockk
+import io.mockk.slot
+import kotlinx.coroutines.runBlocking
+import org.calyxos.backup.storage.api.StoragePlugin
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.backup.BackupDocumentFile
+import org.calyxos.backup.storage.backup.BackupMediaFile
+import org.calyxos.backup.storage.backup.BackupSnapshot
+import org.calyxos.backup.storage.crypto.Hkdf.ALGORITHM_HMAC
+import org.calyxos.backup.storage.crypto.Hkdf.KEY_SIZE_BYTES
+import org.calyxos.backup.storage.crypto.StreamCrypto
+import org.calyxos.backup.storage.db.CachedChunk
+import org.calyxos.backup.storage.db.ChunksCache
+import org.calyxos.backup.storage.db.Db
+import org.calyxos.backup.storage.getRandomString
+import org.calyxos.backup.storage.mockLog
+import org.calyxos.backup.storage.plugin.SnapshotRetriever
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import javax.crypto.spec.SecretKeySpec
+import kotlin.random.Random
+
+@Suppress("BlockingMethodInNonBlockingContext")
+internal class PrunerTest {
+
+    private val db: Db = mockk()
+    private val chunksCache: ChunksCache = mockk()
+    private val plugin: StoragePlugin = mockk()
+    private val snapshotRetriever: SnapshotRetriever = mockk()
+    private val retentionManager: RetentionManager = mockk()
+    private val streamCrypto: StreamCrypto = mockk()
+    private val streamKey = "This is a backup key for testing".toByteArray()
+    private val masterKey = SecretKeySpec(streamKey, 0, KEY_SIZE_BYTES, ALGORITHM_HMAC)
+
+    init {
+        mockLog(false)
+        every { db.getChunksCache() } returns chunksCache
+        every { plugin.getMasterKey() } returns masterKey
+        every { streamCrypto.deriveStreamKey(masterKey) } returns streamKey
+    }
+
+    private val pruner = Pruner(db, retentionManager, plugin, snapshotRetriever, streamCrypto)
+
+    @Test
+    fun test() = runBlocking {
+        val chunk1 = getRandomString(6)
+        val chunk2 = getRandomString(6)
+        val chunk3 = getRandomString(6)
+        val chunk4 = getRandomString(6)
+        val snapshot1 = BackupSnapshot.newBuilder()
+            .setTimeStart(Random.nextLong())
+            .addMediaFiles(BackupMediaFile.newBuilder().addChunkIds(chunk1))
+            .addMediaFiles(BackupMediaFile.newBuilder().addChunkIds(chunk2))
+            .addDocumentFiles(BackupDocumentFile.newBuilder().addChunkIds(chunk1))
+            .addDocumentFiles(BackupDocumentFile.newBuilder().addChunkIds(chunk3))
+            .build()
+        val snapshot2 = BackupSnapshot.newBuilder()
+            .setTimeStart(Random.nextLong())
+            .addMediaFiles(BackupMediaFile.newBuilder().addChunkIds(chunk1))
+            .addMediaFiles(BackupMediaFile.newBuilder().addChunkIds(chunk2))
+            .addDocumentFiles(BackupDocumentFile.newBuilder().addChunkIds(chunk4))
+            .build()
+        val storedSnapshot1 = StoredSnapshot("foo", snapshot1.timeStart)
+        val storedSnapshot2 = StoredSnapshot("bar", snapshot2.timeStart)
+        val storedSnapshots = listOf(storedSnapshot1, storedSnapshot2)
+        val expectedChunks = listOf(chunk1, chunk2, chunk3)
+        val actualChunks = slot<Collection<String>>()
+        val actualChunks2 = slot<Collection<String>>()
+        val cachedChunk3 = CachedChunk(chunk3, 0, 0)
+
+        coEvery { plugin.getCurrentBackupSnapshots() } returns storedSnapshots
+        every {
+            retentionManager.getSnapshotsToDelete(storedSnapshots)
+        } returns listOf(storedSnapshot1)
+        coEvery { snapshotRetriever.getSnapshot(streamKey, storedSnapshot1) } returns snapshot1
+        coEvery { plugin.deleteBackupSnapshot(storedSnapshot1) } just Runs
+        every {
+            db.applyInParts(capture(actualChunks), captureLambda())
+        } answers {
+            secondArg<(Collection<String>) -> Unit>().invoke(actualChunks.captured)
+        }
+        every { chunksCache.decrementRefCount(capture(actualChunks2)) } just Runs
+        every { chunksCache.getUnreferencedChunks() } returns listOf(cachedChunk3)
+        coEvery { plugin.deleteChunks(listOf(chunk3)) } just Runs
+        every { chunksCache.deleteChunks(listOf(cachedChunk3)) } just Runs
+
+        pruner.prune(null)
+
+        assertTrue(actualChunks.isCaptured)
+        assertTrue(actualChunks2.isCaptured)
+        assertEquals(expectedChunks.sorted(), actualChunks.captured.sorted())
+        assertEquals(expectedChunks.sorted(), actualChunks2.captured.sorted())
+    }
+
+}
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/prune/RetentionManagerTest.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/prune/RetentionManagerTest.kt
new file mode 100644
index 00000000..7c19d7e5
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/prune/RetentionManagerTest.kt
@@ -0,0 +1,142 @@
+package org.calyxos.backup.storage.prune
+
+import android.content.Context
+import android.content.SharedPreferences
+import io.mockk.every
+import io.mockk.mockk
+import org.calyxos.backup.storage.api.SnapshotRetention
+import org.calyxos.backup.storage.api.StoredSnapshot
+import org.calyxos.backup.storage.getRandomString
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import java.time.LocalDateTime
+import java.time.ZoneOffset.UTC
+
+internal class RetentionManagerTest {
+
+    private val context: Context = mockk()
+    private val prefs: SharedPreferences = mockk()
+
+    private val retention = RetentionManager(context)
+
+    private val userId = getRandomString()
+
+    @Test
+    fun testDailyRetention() {
+        expectGetRetention(SnapshotRetention(2, 0, 0, 0))
+        val storedSnapshots = listOf(
+            // 1577919600000
+            LocalDateTime.of(2020, 1, 1, 23, 0).toMillis(),
+            // 1577872800000
+            LocalDateTime.of(2020, 1, 1, 10, 0).toMillis(),
+            // 1583276400000
+            LocalDateTime.of(2020, 3, 3, 23, 0).toMillis(),
+        ).map { StoredSnapshot(userId, it) }
+        val toDelete = retention.getSnapshotsToDelete(storedSnapshots)
+        assertEquals(listOf(1577872800000), toDelete.map { it.timestamp })
+    }
+
+    @Test
+    fun testWeeklyRetention() {
+        expectGetRetention(SnapshotRetention(0, 2, 0, 0))
+
+        val timestamps = listOf(
+            // 1583362800000
+            LocalDateTime.of(2020, 3, 4, 23, 0).toMillis(),
+            // 1608544800000
+            LocalDateTime.of(2020, 12, 21, 10, 0).toMillis(),
+            // 1608638400000
+            LocalDateTime.of(2020, 12, 22, 12, 0).toMillis(),
+            // 1608678000000
+            LocalDateTime.of(2020, 12, 22, 23, 0).toMillis(),
+        ).map { StoredSnapshot(userId, it) }
+        val toDelete = retention.getSnapshotsToDelete(timestamps)
+        assertEquals(listOf(1608544800000, 1608638400000), toDelete.map { it.timestamp })
+    }
+
+    @Test
+    fun testMonthlyRetention() {
+        expectGetRetention(SnapshotRetention(2, 0, 2, 0))
+
+        val timestamps = listOf(
+            // 1580857200000
+            LocalDateTime.of(2020, 2, 4, 23, 0).toMillis(),
+            // 1583362800000
+            LocalDateTime.of(2020, 3, 4, 23, 0).toMillis(),
+            // 1608544800000
+            LocalDateTime.of(2020, 12, 21, 10, 0).toMillis(),
+            // 1608678000000
+            LocalDateTime.of(2020, 12, 22, 23, 0).toMillis(),
+        ).map { StoredSnapshot(userId, it) }
+        val toDelete = retention.getSnapshotsToDelete(timestamps)
+        assertEquals(listOf(1580857200000), toDelete.map { it.timestamp })
+    }
+
+    @Test
+    fun testYearlyRetention() {
+        expectGetRetention(SnapshotRetention(0, 0, 0, 4))
+
+        val timestamps = listOf(
+            // 1515106800000
+            LocalDateTime.of(2018, 1, 4, 23, 0).toMillis(),
+            // 1549321200000
+            LocalDateTime.of(2019, 2, 4, 23, 0).toMillis(),
+            // 1551740400000
+            LocalDateTime.of(2019, 3, 4, 23, 0).toMillis(),
+            // 1608544800000
+            LocalDateTime.of(2020, 12, 21, 10, 0).toMillis(),
+            // 1608678000000
+            LocalDateTime.of(2020, 12, 22, 23, 0).toMillis(),
+        ).map { StoredSnapshot(userId, it) }
+        // keeps only the latest one for each year, so three in total, even though keep is four
+        val toDelete = retention.getSnapshotsToDelete(timestamps)
+        assertEquals(listOf(1549321200000, 1608544800000), toDelete.map { it.timestamp })
+    }
+
+    @Test
+    fun testDefaultRetention() {
+        expectGetRetention(
+            SnapshotRetention(
+                PREF_DEFAULT_DAILY,
+                PREF_DEFAULT_WEEKLY,
+                PREF_DEFAULT_MONTHLY,
+                PREF_DEFAULT_YEARLY
+            )
+        )
+        val timestamps = listOf(
+            // 1515106800000
+            LocalDateTime.of(2018, 1, 4, 23, 0).toMillis(),
+            // 1549321200000
+            LocalDateTime.of(2019, 2, 4, 23, 0).toMillis(),
+            // 1551740400000
+            LocalDateTime.of(2019, 3, 4, 23, 0).toMillis(),
+            // 1551441600000
+            LocalDateTime.of(2019, 3, 1, 12, 0).toMillis(),
+            // 1608044400000
+            LocalDateTime.of(2020, 12, 15, 15, 0).toMillis(),
+            // 1608544800000
+            LocalDateTime.of(2020, 12, 21, 10, 0).toMillis(),
+            // 1608678000000
+            LocalDateTime.of(2020, 12, 22, 23, 0).toMillis(),
+            // 1608638400000
+            LocalDateTime.of(2020, 12, 22, 12, 0).toMillis(),
+        ).map { StoredSnapshot(userId, it) }
+        val toDelete = retention.getSnapshotsToDelete(timestamps)
+        assertEquals(
+            listOf(1515106800000, 1549321200000, 1551441600000, 1608638400000),
+            toDelete.map { it.timestamp })
+    }
+
+    private fun expectGetRetention(snapshotRetention: SnapshotRetention) {
+        every { context.getSharedPreferences(PREFS, 0) } returns prefs
+        every { prefs.getInt(PREF_DAILY, any()) } returns snapshotRetention.daily
+        every { prefs.getInt(PREF_WEEKLY, any()) } returns snapshotRetention.weekly
+        every { prefs.getInt(PREF_MONTHLY, any()) } returns snapshotRetention.monthly
+        every { prefs.getInt(PREF_YEARLY, any()) } returns snapshotRetention.yearly
+    }
+
+    private fun LocalDateTime.toMillis(): Long {
+        return toInstant(UTC).toEpochMilli()
+    }
+
+}
diff --git a/storage/lib/src/test/java/org/calyxos/backup/storage/restore/FileSplitterTest.kt b/storage/lib/src/test/java/org/calyxos/backup/storage/restore/FileSplitterTest.kt
new file mode 100644
index 00000000..cfd1161f
--- /dev/null
+++ b/storage/lib/src/test/java/org/calyxos/backup/storage/restore/FileSplitterTest.kt
@@ -0,0 +1,79 @@
+package org.calyxos.backup.storage.restore
+
+import org.calyxos.backup.storage.backup.Backup
+import org.calyxos.backup.storage.backup.BackupMediaFile
+import org.calyxos.backup.storage.backup.BackupSnapshot
+import org.calyxos.backup.storage.getRandomString
+import org.calyxos.backup.storage.mockLog
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+internal class FileSplitterTest {
+
+    private val fileSplitter = FileSplitter
+
+    init {
+        mockLog()
+    }
+
+    @Test
+    fun testDuplicateZipChunks() {
+        val chunkId = getRandomString()
+        val mediaFiles = listOf(
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("1a").setZipIndex(1).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("2a").setZipIndex(2).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("1b").setZipIndex(1).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("2b").setZipIndex(2).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("1c").setZipIndex(1).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("2c").setZipIndex(2).build(),
+        )
+        val snapshot = BackupSnapshot.newBuilder()
+            .setVersion(Backup.VERSION.toInt())
+            .addAllMediaFiles(mediaFiles)
+            .build()
+        val result = fileSplitter.splitSnapshot(snapshot)
+
+        assertTrue(result.multiChunkFiles.isEmpty())
+        assertTrue(result.multiChunkMap.isEmpty())
+        assertTrue(result.singleChunks.isEmpty())
+
+        assertEquals(1, result.zipChunks.size)
+        val restorableChunk = result.zipChunks.iterator().next()
+        assertEquals(2, restorableChunk.files.size)
+        assertEquals("1a", restorableChunk.files[0].name)
+        assertEquals("2a", restorableChunk.files[1].name)
+    }
+
+    @Test
+    fun testDuplicateZipChunksWithGaps() {
+        val chunkId = getRandomString()
+        val mediaFiles = listOf(
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("3a").setZipIndex(7).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("1a").setZipIndex(2).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("2a").setZipIndex(6).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("4a").setZipIndex(9).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("1b").setZipIndex(2).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("2b").setZipIndex(6).build(),
+            BackupMediaFile.newBuilder().addChunkIds(chunkId).setName("4b").setZipIndex(9).build(),
+        )
+        val snapshot = BackupSnapshot.newBuilder()
+            .setVersion(Backup.VERSION.toInt())
+            .addAllMediaFiles(mediaFiles)
+            .build()
+        val result = fileSplitter.splitSnapshot(snapshot)
+
+        assertTrue(result.multiChunkFiles.isEmpty())
+        assertTrue(result.multiChunkMap.isEmpty())
+        assertTrue(result.singleChunks.isEmpty())
+
+        assertEquals(1, result.zipChunks.size)
+        val restorableChunk = result.zipChunks.iterator().next()
+        assertEquals(4, restorableChunk.files.size)
+        assertEquals("1a", restorableChunk.files[0].name)
+        assertEquals("2a", restorableChunk.files[1].name)
+        assertEquals("3a", restorableChunk.files[2].name)
+        assertEquals("4a", restorableChunk.files[3].name)
+    }
+
+}
diff --git a/storage/logcat-verbose.sh b/storage/logcat-verbose.sh
new file mode 100755
index 00000000..958b8d28
--- /dev/null
+++ b/storage/logcat-verbose.sh
@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+adb shell setprop log.tag.JobScheduler DEBUG
+adb shell setprop log.tag.JobScheduler.ContentObserver DEBUG