Decrypt super secret message with authentication.

AesDecryptWithAuth.java

try {
    KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
    keyStore.load(null);

    SecretKey secretKey = 
        (SecretKey) keyStore.getKey(SecurityConstants.KEY_AES, null);
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");

    // The next line may throw a UserNotAuthenticatedException and
    // we need to prompt the user to authenticate again
    cipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));
    byte[] decryptedBytes = cipher.doFinal(cipherBytes);

} catch (UserNotAuthenticatedException e) {
    // User is not authenticated, let's authenticate with
    // device credentials!
    showAuthenticationScreen();
    return;
} catch { … }