How to ensure secure access to the authorization token for another application?

Most secure methods:

• Using AccountManager. It allows centralized management of accounts and tokens. Only your application and authorized other applications can access the token after user confirmation.
• Using ContentProvider with appropriate permissions. You provide access to the token through ContentProvider, controlling who is allowed to read the data.
• Using IPC (Binder) with signature verification. You implement your own service that provides the token, but the service checks that the calling application is signed with the same key as yours.

<!-- Example permission for ContentProvider -->
<permission
    android:name="com.example.myapp.READ_TOKEN"
    android:protectionLevel="signature"/>

<provider
    android:name=".TokenProvider"
    android:authorities="com.example.myapp.tokenprovider"
    android:readPermission="com.example.myapp.READ_TOKEN"
    android:exported="true"/>

Unsafe methods (to avoid):

• Storing the token in SharedPreferences without encryption.
• Transmitting the token via intents without sender verification.
• Storing the token in files in a public directory.