AuthGrace class

Smart biometric authentication with an automatic grace period.

AuthGrace wraps local_auth and adds a grace window — if the device was unlocked recently the biometric prompt is skipped entirely, giving the same frictionless experience as Google Pay.

Typical lifecycle

// 1. Create once (e.g. in a singleton or provider)
final auth = AuthGrace(
  options: const AuthGraceOptions(gracePeriodSeconds: 30),
);

// 2. Initialise at app startup — generates the Keystore/Keychain key
await auth.init();

// 3. Authenticate whenever the app moves to the foreground
final result = await auth.authenticate();
if (result.isSuccess) {
  // allow access
}

// 4. Reset on logout or account switch
await auth.reset();

Platform notes

• Android — grace period is enforced by the Android Keystore at the hardware (TEE) level using a time-bound AES key. The key validity window is set via AuthGraceOptions.gracePeriodSeconds.
• iOS — grace period is approximated by recording a Keychain timestamp after every successful local_auth prompt and comparing it on the next call. This is not hardware-enforced like the Android implementation.

Constructors

AuthGrace({AuthGraceOptions? options})

Creates an AuthGrace instance.

Properties

hashCode → int

The hash code for this object.

no setter, inherited

options → AuthGraceOptions

The options controlling grace period behaviour.

final

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

authenticate() → Future<AuthResult>

Authenticates the user, honouring the configured grace period.

init() → Future<void>

Initialises the plugin.

isAvailable() → Future<bool>

Returns true if the device supports biometric or device-credential authentication.

isHardwareBacked() → Future<bool>

Returns true if the device has a hardware-backed secure element (TEE on Android, Secure Enclave on iOS).

isWithinGracePeriod() → Future<bool>

Returns true if the device was unlocked within the grace window, without showing any authentication prompt.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

reset() → Future<void>

Deletes the Keystore key (Android) and Keychain timestamp (iOS), ending the current grace window immediately.

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited