Estoy creando una aplicación donde el usuario tiene dos opciones para desbloquear su aplicación, una está usando un pin y la otra está usando una huella digital. Para usar la huella digital, primero deben configurar un pin porque este pin es la clave de descifrado para obtener sus detalles cifradosSharedPreferences.

Así que he seguido este tutorial aquí:http://www.techotopia.com/index.php/An_Android_Fingerprint_Authentication_Tutorial#Accessing_the_Android_Keystore_and_KeyGenerator

He logrado que la aplicación lea una huella digital y diga si es válida o no. Pero cuando se autoriza la huella digital, no tengo idea de cómo sacar ese pin del almacén de claves de Android.

Aquí hay un código para demostrar:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    keyguardManager = (KeyguardManager) getSystemService(KEYGUARD_SERVICE);
    fingerprintManager = (FingerprintManager) getSystemService(FINGERPRINT_SERVICE);

    if (!keyguardManager.isKeyguardSecure()) {

        Toast.makeText(this, "Lock screen security not enabled in Settings", Toast.LENGTH_LONG).show();
        return;
    }

    if (ActivityCompat.checkSelfPermission(this,
            Manifest.permission.USE_FINGERPRINT) !=
            PackageManager.PERMISSION_GRANTED) {
        Toast.makeText(this, "Fingerprint authentication permission not enabled", Toast.LENGTH_LONG).show();

        return;
    }

    if (!fingerprintManager.hasEnrolledFingerprints()) {

        // This happens when no fingerprints are registered.
        Toast.makeText(this, "Register at least one fingerprint in Settings", Toast.LENGTH_LONG).show();
        return;
    }

    generateKey();

    if (cipherInit()) {
        cryptoObject = new FingerprintManager.CryptoObject(cipher);
        FingerprintHandler helper = new FingerprintHandler(this);

        helper.startAuth(fingerprintManager, cryptoObject);
    }

}

protected void generateKey() {
    try {
        keyStore = KeyStore.getInstance("AndroidKeyStore");
    } catch (Exception e) {
        e.printStackTrace();
    }

    try {
        keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, "AndroidKeyStore");
    } catch (NoSuchAlgorithmException |
            NoSuchProviderException e) {
        throw new RuntimeException("Failed to get KeyGenerator instance", e);
    }

    try {
        keyStore.load(null);
        keyGenerator.init(new
                KeyGenParameterSpec.Builder(KEY_NAME,
                KeyProperties.PURPOSE_ENCRYPT |
                        KeyProperties.PURPOSE_DECRYPT)
                .setBlockModes(KeyProperties.BLOCK_MODE_CBC)
                .setUserAuthenticationRequired(true)
                .setEncryptionPaddings(
                        KeyProperties.ENCRYPTION_PADDING_PKCS7)
                .build());
        keyGenerator.generateKey();
    } catch (NoSuchAlgorithmException |
            InvalidAlgorithmParameterException
            | CertificateException | IOException e) {
        throw new RuntimeException(e);
    }
}

public boolean cipherInit() {
    try {
        cipher = Cipher.getInstance(
                KeyProperties.KEY_ALGORITHM_AES + "/"
                        + KeyProperties.BLOCK_MODE_CBC + "/"
                        + KeyProperties.ENCRYPTION_PADDING_PKCS7);
    } catch (NoSuchAlgorithmException |
            NoSuchPaddingException e) {
        throw new RuntimeException("Failed to get Cipher", e);
    }

    try {
        keyStore.load(null);
        SecretKey key = (SecretKey) keyStore.getKey(KEY_NAME,
                null);

        cipher.init(Cipher.ENCRYPT_MODE, key);
        return true;
    } catch (KeyPermanentlyInvalidatedException e) {
        return false;
    } catch (KeyStoreException | CertificateException
            | UnrecoverableKeyException | IOException
            | NoSuchAlgorithmException | InvalidKeyException e) {
        throw new RuntimeException("Failed to init Cipher", e);
    }
}

KEY_NAME es la clave (pin) que estoy tratando de almacenar (creo).

Luego en elFingerprintHandler clase hay este método:

public void onAuthenticationSucceeded(
        FingerprintManager.AuthenticationResult result) {

    Toast.makeText(appContext,
            "Authentication succeeded.",
            Toast.LENGTH_LONG).show();

}

Pero, ¿cómo obtengo la clave que quiero delresult ¿como mucho?