使用Android指纹时出现问题:解密时需要IV.使用IvParameterSpec或AlgorithmParameters来提供它

Question

我正在关注Google提供的ConfirmCredential Android示例,但它只显示了如何加密数据.当我尝试解密它时,我得到例外:

java.security.InvalidKeyException: IV required when decrypting. Use IvParameterSpec or AlgorithmParameters to provide it.

我使用以下代码:

String transforation = KeyProperties.KEY_ALGORITHM_AES + "/" + KeyProperties.BLOCK_MODE_CBC + "/" + KeyProperties.ENCRYPTION_PADDING_PKCS7;

KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
keyStore.load(null);
SecretKey secretKey = (SecretKey) keyStore.getKey(KEY_NAME, null);

// encrypt
Cipher cipher = Cipher.getInstance(transforation);
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
String encriptedPassword = cipher.doFinal("Some Password".getBytes("UTF-8"));

// decrypt
cipher = Cipher.getInstance(transforation);
cipher.init(Cipher.DECRYPT_MODE, secretKey);
String password = new String(cipher.doFinal(encriptedPassword), "UTF-8"));

在行中抛出异常:

cipher.init(Cipher.DECRYPT_MODE, secretKey);

在这种情况下,任何关于解密的正确方法的想法？

Answer 1

基本上,您必须为解密模式传递IvParameterSpec,而不应手动将其设置为加密模式.

所以这就是我所做的,它运作良好:

private initCipher(int mode) {
    try {
        byte[] iv;
        mCipher = Cipher.getInstance(KeyProperties.KEY_ALGORITHM_AES + "/"
                + KeyProperties.BLOCK_MODE_CBC + "/"
                + KeyProperties.ENCRYPTION_PADDING_PKCS7);
        IvParameterSpec ivParams;
        if(mode == Cipher.ENCRYPT_MODE) {
            mCipher.init(mode, generateKey());
            ivParams = mCipher.getParameters().getParameterSpec(IvParameterSpec.class);
            iv = ivParams.getIV();
            fos = getContext().openFileOutput(IV_FILE, Context.MODE_PRIVATE);
            fos.write(iv);
            fos.close();
        }
        else {
            key = (SecretKey)keyStore.getKey(KEY_NAME, null);
            File file = new File(getContext().getFilesDir()+"/"+IV_FILE);
            int fileSize = (int)file.length();
            iv = new byte[fileSize];
            FileInputStream fis = getContext().openFileInput(IV_FILE);
            fis.read(iv, 0, fileSize);
            fis.close();
            ivParams = new IvParameterSpec(iv);
            mCipher.init(mode, key, ivParams);
        }
        mCryptoObject = new FingerprintManager.CryptoObject(mCipher);
    } catch(....)
}

您还可以使用Base64对IV数据进行编码,并将其保存在共享首选项下,而不是将其保存在文件下.

在这两种情况下,如果你采用版本的Android M的新的全备份功能,请记住,这个数据应该不被允许备份/恢复,因为当用户重新安装应用程序或其他设备上安装应用程序是无效的.