Support Direct Boot mode

Android 7.0 runs in a secure, Direct Boot mode when the device has been powered on but the user hasn't unlocked the device. To support this, the system provides two storage locations for data:

Credential encrypted storage, which is the default storage location and only available after the user has unlocked the device.
Device encrypted storage, which is a storage location available both during Direct Boot mode and after the user has unlocked the device.

By default, apps don't run during Direct Boot mode. If your app needs to take action during Direct Boot mode, you can register app components to be run during this mode. Some common use cases for apps needing to run during Direct Boot mode include:

Apps that have scheduled notifications, such as alarm clock apps.
Apps that provide important user notifications, like SMS apps.
Apps that provide accessibility services, like Talkback.

If your app needs to access data while running in Direct Boot mode, use device encrypted storage. Device encrypted storage contains data encrypted with a key that is only available after a device has performed a successful verified boot.

For data that must be encrypted with a key associated with user credentials, such as a PIN or password, use credential encrypted storage. Credential encrypted storage is available after the user has successfully unlocked the device and until the user restarts the device. If the user enables the lock screen after unlocking the device, credential encrypted storage remains available.

Request access to run during Direct Boot

Apps must register their components with the system before they can run during Direct Boot mode or access device encrypted storage. Apps register with the system by marking components as encryption aware. To mark your component as encryption aware, set the android:directBootAware attribute to true in your manifest.

Encryption aware components can register to receive an ACTION_LOCKED_BOOT_COMPLETED broadcast message from the system when the device has been restarted. At this point device encrypted storage is available, and your component can execute tasks that need to be run during Direct Boot mode, such as triggering a scheduled alarm.

The following code snippet is an example of how to register a BroadcastReceiver as encryption aware, and add an intent filter for ACTION_LOCKED_BOOT_COMPLETED, in the app manifest:

<receiver
  android:directBootAware="true" >
  ...
  <intent-filter>
    <action android:name="android.intent.action.LOCKED_BOOT_COMPLETED" />
  </intent-filter>
</receiver>

Once the user has unlocked the device, all components can access both the device encrypted storage as well as credential encrypted storage.

Access device encrypted storage

To access device encrypted storage, create a second Context instance by calling Context.createDeviceProtectedStorageContext(). All storage API calls made using this context access the device encrypted storage. The following example accesses the device encrypted storage and opens an existing app data file:

Kotlin

val directBootContext: Context = appContext.createDeviceProtectedStorageContext()
// Access appDataFilename that lives in device encrypted storage
val inStream: InputStream = directBootContext.openFileInput(appDataFilename)
// Use inStream to read content...

Java

Context directBootContext = appContext.createDeviceProtectedStorageContext();
// Access appDataFilename that lives in device encrypted storage
FileInputStream inStream = directBootContext.openFileInput(appDataFilename);
// Use inStream to read content...

Use device encrypted storage only for information that must be accessible during Direct Boot mode. Don't use device encrypted storage as a general-purpose encrypted store. For private user information, or encrypted data that isn't needed during Direct Boot mode, use credential encrypted storage.

Get notified of user unlock

When the user unlocks the device after restart, your app can switch to accessing credential encrypted storage and use regular system services that depend on user credentials.

To get notified when the user unlocks the device after a reboot, register a BroadcastReceiver from a running component to listen for unlock notification messages. When the user unlocks the device after boot:

If your app has foreground processes that need immediate notification, listen for the ACTION_USER_UNLOCKED message.
If your app only uses background processes that can act on a delayed notification, listen for the ACTION_BOOT_COMPLETED message.

If the user has unlocked the device, you can find out by calling UserManager.isUserUnlocked().

Migrate existing data

If a user updates their device to use Direct Boot mode, you might have existing data that needs to get migrated to device encrypted storage. Use Context.moveSharedPreferencesFrom() and Context.moveDatabaseFrom(), with the destination context as the method caller and the source context as the argument, to migrate preference and database data between credential encrypted storage and device encrypted storage.

Don't migrate private user information, such as passwords or authorization tokens, from credential encrypted storage to device encrypted storage. Use your best judgment when deciding what other data to migrate to device encrypted storage. In some scenarios, you might need to manage separate sets of data in the two encrypted stores.

Test your encryption aware app

Test your encryption aware app with Direct Boot mode enabled.

Most devices running recent versions of Android enable Direct Boot mode whenever a lockscreen credential (PIN, pattern, or password) has been set. Specifically, this is the case on all devices that use file-based encryption. To check whether a device uses file-based encryption, run the following shell command:

adb shell getprop ro.crypto.type

If the output is file, then the device has file-based encryption enabled.

On devices that don't use file-based encryption by default, there might be other options for testing Direct Boot mode:

Some devices that use full-disk encryption (ro.crypto.type=block) and are running Android 7.0 through Android 12 can be converted to file-based encryption. There are two ways to do this:
- On the device, enable Developer options if you haven't already by going to Settings > About phone and tapping Build number seven times. Then go to Settings > Developer options and select Convert to file encryption.
- Alternatively, run the following shell commands:
```
adb reboot-bootloader
fastboot --wipe-and-use-fbe
```
Devices running Android 13 or lower support an "emulated" Direct Boot mode that uses file permissions to simulate the effects of encrypted files being locked and unlocked. Only use emulated mode during development; it can cause data loss. To enable emulated Direct Boot mode, set a lock pattern on the device, choose "No thanks" if prompted for a secure start-up screen when setting a lock pattern, and then run the following shell command:
```
adb shell sm set-emulate-fbe true
```
To turn off emulated Direct Boot mode, run the following shell command:
```
adb shell sm set-emulate-fbe false
```
Running either of these commands causes the device to reboot.

Check device policy encryption status

Device administration apps can use DevicePolicyManager.getStorageEncryptionStatus() to check the current encryption status of the device.

If your app targets an API level lower than Android 7.0 (API 24), getStorageEncryptionStatus() returns ENCRYPTION_STATUS_ACTIVE if the device is using either full-disk encryption or file-based encryption with Direct Boot. In both of these cases, data is always stored encrypted at rest.

If your app is targets Android 7.0 (API 24) or higher, getStorageEncryptionStatus() returns ENCRYPTION_STATUS_ACTIVE if the device is using full-disk encryption. It returns ENCRYPTION_STATUS_ACTIVE_PER_USER if the device is using file-based encryption with Direct Boot.

If you build a device administration app that targets Android 7.0, make sure to check for both ENCRYPTION_STATUS_ACTIVE and ENCRYPTION_STATUS_ACTIVE_PER_USER to determine whether the device is encrypted.

Additional code samples

The DirectBoot sample further demonstrates the use of the APIs covered on this page.