Biometry authentication (Touch ID, Face ID, fingerprint) for Android and iOS from shared Kotlin Multiplatform code.

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Table of Contents

• Features
• Requirements
• Installation
• Usage
• Samples
• Permissions
• Building
• License

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Features

• Check availability — BiometryAuthenticator.isBiometryAvailable() returns BiometryAvailability (supported type, error message).
• Authenticate — BiometryAuthenticator.authenticate() shows the system dialog and returns BiometryResult (Success / Cancelled / Error).
• Shared models — BiometryResult, BiometryAvailability, BiometryType in commonMain.
• Android — BiometricManager + BiometricPrompt (runs on main thread).
• iOS — LocalAuthentication framework (Touch ID / Face ID).

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Requirements

Gradle	8.0+
Kotlin	2.0+
Android	minSdk 23+, compileSdk 34
iOS	11.0+

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Installation

Repositories (root settings.gradle.kts or build.gradle.kts):

repositories {
    mavenCentral()
    google()
}

Dependency (your KMP module):

// commonMain
commonMain.dependencies {
    implementation("dev.enumset:biometry-auth:1.0.0")
}

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Usage

Common code

Use from a coroutine (recommended: Dispatchers.Main on Android for UI):

val authenticator = createBiometryAuthenticator()

// Check availability
val availability = authenticator.isBiometryAvailable()
if (!availability.isAvailable) {
    // availability.errorMessage, availability.biometryType
    return
}

// Authenticate
when (val result = authenticator.authenticate(
    title = "Sign in",
    subtitle = "Confirm your identity",
    negativeButtonText = "Cancel",
    allowDeviceCredentials = true
)) {
    is BiometryResult.Success -> { /* success */ }
    is BiometryResult.Cancelled -> { /* user cancelled */ }
    is BiometryResult.Error -> { /* result.message, result.code */ }
}

Android

1. Before using biometry, set the FragmentActivity (e.g. in onCreate):

import dev.enumset.biometry.setFragmentActivityForBiometry

// In your FragmentActivity
setFragmentActivityForBiometry(this)

2. Call from a coroutine with Dispatchers.Main (dialog must run on main thread):

lifecycleScope.launch(Dispatchers.Main) {
    val authenticator = createBiometryAuthenticator()
    val result = authenticator.authenticate(
        title = "Sign in",
        subtitle = "Confirm your identity",
        negativeButtonText = "Cancel",
        allowDeviceCredentials = true
    )
}

iOS

Use the same common API: createBiometryAuthenticator() and authenticate(). The actual implementation uses LocalAuthentication.

Add to your app Info.plist (required for Face ID):

<key>NSFaceIDUsageDescription</key>
<string>Authenticate with Face ID or Touch ID</string>

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Samples

Module	Description
sample/androidApp	Android app (availability check + auth).
sample/composeApp	Compose Multiplatform sample (Android + iOS).
sample/iosApp	Native iOS app + Xcode integration.

Run Android sample:

./gradlew :sample:androidApp:assembleDebug
./gradlew :sample:androidApp:installDebug

iOS: build the framework with ./gradlew :biometry:linkDebugFrameworkIosSimulatorArm64 and follow sample/iosApp/README.md for Xcode.

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Permissions

The library does not declare permissions. Your app must add them.

Android — in your app manifest:

• USE_BIOMETRIC (API 28+)
• USE_FINGERPRINT (API 23–27, deprecated in 28)

See Biometric authentication | Android Developers.

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Building

./gradlew :biometry:build

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License

Apache-2.0