Android Passkeys

[TheRealSenpai]

What are Passkeys?
- Passkeys replace passwords with cryptographic keys tied to your device and biometrics.
- They use a public/private key pair: the public key goes to the server, the private key stays on your device, protected by biometrics or PIN.
- When signing in, the server sends a challenge, which is signed using your private key. The server verifies it with your public key—you're authenticated, no password needed.

Advantages:
- Impossible to forget; always on your device.
- Resistant to phishing: Passkeys are domain-specific, so fakes don't work.
- More secure: even if the server is hacked, only public keys are leaked, which are useless without the matching private key.
- Improved user experience: quick biometric login, easy sync via Google Password Manager/iCloud Keychain, privacy (no need for "Login with Google/Facebook").

Core Tech:
- Passkeys leverage public-key cryptography (e.g., ECDSA, RSA, EdDSA).
- Registration and authentication rely on the FIDO2/WebAuthn standards; most Android APIs wrap these for developers.

Creating Passkeys (Kotlin Example):

Add dependencies:
 kotlin
dependencies { 
    implementation("androidx.credentials:credentials:1.2.0")
    implementation("androidx.credentials:credentials-play-services-auth:1.2.0") // Optional
}
 
Create a CredentialManager:
 kotlin
class AuthViewModel(application: Application): AndroidViewModel(application) {
    private val credentialManager = CredentialManager.create(application)
}
 

Registration:
 kotlin
suspend fun registerPasskey(username: String) {
    try {
        val registrationOptions = apiService.getRegistrationOptions(username)
        val request = CreatePublicKeyCredentialRequest(registrationOptions.toString(), null)
        val result = credentialManager.createCredential(getApplication(), request)
        val response = result.data as CreatePublicKeyCredentialResponse
        apiService.verifyRegistration(response.registrationResponseJson)
        // Success!
    } catch (e: Exception) {
        // Handle error
    }
}
 

Authentication:
 kotlin
suspend fun authenticateWithPasskey() {
    try {
        val authOptions = apiService.getAuthenticationOptions()
        val request = GetCredentialRequest(listOf(GetPublicKeyCredentialOption(authOptions.toString(), null)))
        val result = credentialManager.getCredential(getApplication(), request)
        val response = result.credential as PublicKeyCredential
        val token = apiService.verifyAuthentication(response.authenticationResponseJson)
        // Success!
    } catch (e: Exception) {
        // Handle error
    }
}
 

 Typical Backend: 
Node.js (SimpleWebAuthn example for registration options):
 javascript
app.post('/generate-registration-options', async (req, res) => {
    const { username } = req.body;
    let user = await User.findOne({ username });
    if (!user) user = await User.create({ username });
    const challenge = crypto.randomBytes(32).toString('base64url');
    req.session.challenge = challenge;
    req.session.userId = user.id;
    const options = generateRegistrationOptions({
        rpName: 'Your App',
        rpID: 'yourdomain.com',
        userID: user.id,
        userName: username,
        challenge,
    });
    res.json(options);
});
 

 Manifest & Setup: 
 xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.passkeydemo">
    <uses-permission android:name="android.permission.INTERNET" />
    <application
        ...>
        <meta-data
            android:name="android.credentials.provider"
            android:resource="@xml/credentials_rules" />
    </application>
</manifest>
 

`res/xml/credentials_rules.xml`:
 xml
<credentials-rules>
    <allow-provider packageName="com.google.android.gms"/>
</credentials-rules>

Tips & Best Practices:
- Always check if the device is secure (screen lock set).
- Support fallback (traditional auth) during migration.
- Cloud sync handled by Google/Apple—no extra code for you.
- Use strong randomness for challenges.
- Validate origins; defend against replay attacks.

Conclusion:
Passkeys provide a practical passwordless, phishing-resistant solution that improves UX, security, and is straightforward to implement for Android and backend.



For questions, feel free to message me privately. I am always open for technical insights. For android-based device hacking services, I offer quality services and pricing.