auth_grace library

Smart biometric authentication with automatic grace period.

auth_grace provides a simple API for biometric authentication that skips the prompt if the user's phone was recently unlocked — exactly like Google Pay.

Key Features:

• Automatic grace period after unlock (configurable, default 30 seconds)
• Skips biometric prompt during grace period
• Supports strict mode for sensitive operations (payments, transfers)
• Hardware-backed keystore on Android, Keychain on iOS
• Handles key invalidation on biometric change
• Graceful fallback on unsupported devices

Quick Start:

final auth = AuthGrace(
  options: AuthGraceOptions(
    gracePeriodSeconds: 30,
    reason: 'Authenticate to open',
  ),
);

await auth.init();
final result = await auth.authenticate();

if (result.isSuccess) {
  // User authenticated or grace period active
}

For Payment Flows (strict mode):

final strictAuth = AuthGrace(
  options: AuthGraceOptions(alwaysRequire: true),
);
await strictAuth.authenticate();

Lifecycle Management:

Call AuthGrace.init once at app startup to set up the keystore/keychain. Call AuthGrace.reset on logout or user account switch to clear the grace period. Call AuthGrace.authenticate when you need to verify user identity.

See also:

• AuthGrace - main class for authentication
• AuthGraceOptions - configuration options
• AuthResult - authentication result with status and method

Classes

AuthGrace

Smart biometric authentication with an automatic grace period.

AuthGraceOptions

Configuration options for AuthGrace.

AuthResult

The result returned by AuthGrace.authenticate.

Enums

AuthMethod

The mechanism that produced the AuthResult.

AuthStatus

The high-level outcome of an AuthGrace.authenticate call.