secure_biometric_storage

Fork of biometric_storage with focus on security

Encrypted file store, optionally secured by a biometric lock for Android and iOS.

Meant as a way to store small data in a hardware encrypted fashion. E.g. to store passwords, secret keys, etc. but not massive amounts of data.

Uses similar encryption mechanism as in flutter_secure_storage

• Android: Uses androidx with KeyStore.
• iOS: LocalAuthentication with KeyChain.

Security Enhancements:

• On both Android and iOS keys are invalidated if new fingerprint/face are added.
• Auth-per-use keys are used for storages secured by a biometric lock.
• BIOMETRIC_STRONG used on Android.

An auth-per-use key requires the user to present a biometric credential each time your app needs to access data that's guarded by that key. Auth-per-use keys can be useful for high-value transactions, such as making a large payment or updating a person's health records.

Getting Started

Android

• Requirements:

  • Android: API Level >= 23

  • MainActivity must extend FlutterFragmentActivity

  • Theme for the main activity must use Theme.AppCompat theme. (Otherwise there will be crashes on Android < 29) For example:

    AndroidManifest.xml:

    <activity
    android:name=".MainActivity"
    android:launchMode="singleTop"
    android:theme="@style/LaunchTheme"

    xml/styles.xml:

        <style name="LaunchTheme" parent="Theme.AppCompat.NoActionBar">
        <!-- Show a splash screen on the activity. Automatically removed when
             Flutter draws its first frame -->
        <item name="android:windowBackground">@drawable/launch_background</item>
    
        <item name="android:windowNoTitle">true</item>
        <item name="android:windowActionBar">false</item>
        <item name="android:windowFullscreen">true</item>
        <item name="android:windowContentOverlay">@null</item>
    </style>

iOS

https://developer.apple.com/documentation/localauthentication/logging_a_user_into_your_app_with_face_id_or_touch_id

• include the NSFaceIDUsageDescription key in your app’s Info.plist file
• Requires at least iOS 9

Resources

• https://developer.android.com/topic/security/data
• https://developer.android.com/topic/security/best-practices
• https://developer.android.com/training/sign-in/biometric-auth