A Flutter plugin to detect changes in biometric authentication status on Android and iOS.
This package is inspired by discussions and issues from:
Detecting biometric changes depends on the platform, and local_auth does not provide a direct way to check for biometric updates. Neither iOS nor Android exposes this functionality through existing Flutter plugins, meaning developers must implement native code themselves using platform channels. This package simplifies that process by providing a unified solution for both platforms.
On Android, when creating a cryptographic key, you can specify that it should be invalidated if new fingerprints are enrolled using KeyGenParameterSpec.Builder.setInvalidatedByBiometricEnrollment(true). However, this only works with keys requiring active authentication. The only way to check if a key is invalidated is by attempting authentication, which may trigger the authentication dialog.
On iOS, biometric changes can be detected using the evaluatedPolicyDomainState property of LAContext. By comparing the current domain state with a previously stored state, we can determine if biometric data has changed.
Neither of these APIs are directly exposed through existing Flutter plugins. This package provides a Flutter-friendly API by leveraging platform channels with native Swift and Kotlin implementations.
Add the dependency to your pubspec.yaml:
flutter_biometric_change_detector: ^1.0.1Import the package:
import 'package:flutter_biometric_change_detector/flutter_biometric_change_detector.dart';Call detectBiometricChange to check if biometric authentication has changed:
final hasChanged = await FlutterBiometricChangeDetector.detectBiometricChange();Note: Store the initial detectBiometricChange return value in local storage or use it to manage the authentication flow. Once a biometric change is detected, the app will return false in subsequent checks unless you track the previous state manually.
// Enum representing biometric authentication status
enum AuthChangeStatus {
VALID, // Authentication is valid and unchanged
CHANGED, // Biometric authentication has changed
INVALID, // Authentication is invalid
UNKNOWN // Status is unknown
}
// Checks biometric authentication status on iOS
Future<AuthChangeStatus?> checkBiometricIOS();
// Checks biometric authentication status on Android
Future<AuthChangeStatus?> checkBiometricAndroid();
// Detects any biometric changes
Future<AuthChangeStatus?> detectBiometricChange();Issues and pull requests are welcome!
- GitHub: flutter_biometric_change_detector
- Me: Nabraj Khadka
MIT License