如何在 android 中使用 aes-256-gcm 加密带重音的文本

Question

我尝试用重音加密文本，但节点 js 服务器无法解密我收到响应“错误：不支持的状态或无法验证数据”。我该怎么办？

这里是 Android 用于加密文本的文件。

public static String encrypt(String text, String masterKey) throws InvalidKeySpecException, NoSuchAlgorithmException, IOException, IllegalBlockSizeException, InvalidKeyException, BadPaddingException, InvalidAlgorithmParameterException, NoSuchPaddingException {
    byte[] iv = generateIv(16);
    byte[] salt = generateIv(64);
    SecretKey key = getKeyFromPassword(masterKey, salt);
    byte[] cipher = encryptHelper("AES/GCM/NoPadding", text, key,  new GCMParameterSpec(GCM_TAG_LENGTH * 8, iv));
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    byte[] ciphertext = Arrays.copyOfRange(cipher, 0, text.length());
    byte[] tag = Arrays.copyOfRange(cipher, text.length(), cipher.length);
    outputStream.write(salt);
    outputStream.write(iv);
    outputStream.write(tag);
    outputStream.write(ciphertext);
    String base64Encrypted;
    if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        base64Encrypted = Base64.getEncoder().encodeToString(outputStream.toByteArray());
    }else{
        base64Encrypted = android.util.Base64.encodeToString(outputStream.toByteArray(), android.util.Base64.DEFAULT);
    }
    return base64Encrypted;
}
public static byte[] encryptHelper(String algorithm, String input, SecretKey key,
                                   GCMParameterSpec gcmParameterSpec) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {

    Cipher cipher = Cipher.getInstance(algorithm);
    cipher.init(Cipher.ENCRYPT_MODE, key, gcmParameterSpec);
    return cipher.doFinal(input.getBytes(StandardCharsets.UTF_8));
}

这里是解密文本的节点js文件。

function decryptDataTestWork(encdata, masterkey) {
// body...
// base64 decoding
const bData = Buffer.from(encdata, 'base64');

// convert data to buffers
const salt = bData.slice(0, 64);
const iv = bData.slice(64, 80);
const tag = bData.slice(80, 96);
const text = bData.slice(96);

/*console.log(salt);
console.log(iv);
console.log(tag);
console.log(text);*/

// derive key using; 32 byte key length
const key = crypto.pbkdf2Sync(masterkey, salt, 2145, 32, 'sha512');

// AES 256 GCM Mode
const decipher = crypto.createDecipheriv('aes-256-gcm', key, iv);
decipher.setAuthTag(tag);

// encrypt the given text
return decipher.update(text, 'binary', 'utf8') + decipher.final('utf8');
};

我收到了这个回复

Error: Unsupported state or unable to authenticate data

这是文本和密钥

"description":"Désolé"
"key":"tIJg9tyj2setkg7gknVreP5PXzRQV5J3"

请问我该怎么办？谢谢！

Answer 1

问题出在Java代码和密文与标签的错误分隔上。

您根据明文大小确定密文大小（由于缺少填充，这对于 GCM 是可能的），但随后假设字符串 text 与字节数组 text.getBytes(StandardCharsets.UTF_8)]，如果文本字符的编码超过一个字节，则通常不会出现这种情况。

以下实现使用标记大小来分隔两个部分：

byte[] ciphertext = Arrays.copyOfRange(cipher, 0, cipher.length - GCM_TAG_LENGTH);
byte[] tag = Arrays.copyOfRange(cipher, cipher.length - GCM_TAG_LENGTH, cipher.length);

通过此更改，假定使用相同的密钥，在我的机器上使用 NodeJS 代码解密是成功的（请注意，无法检查密钥派生，因为 Java 端缺少 getKeyFromPassword()）。

Answer 2

修复后建议代码工作正常

public static String encrypt(String text, String masterKey) throws InvalidKeySpecException, NoSuchAlgorithmException, IOException, IllegalBlockSizeException, InvalidKeyException, BadPaddingException, InvalidAlgorithmParameterException, NoSuchPaddingException {
    byte[] iv = generateIv(16);
    byte[] salt = generateIv(64);
    SecretKey key = getKeyFromPassword(masterKey, salt);
    byte[] cipher = encryptHelper("AES/GCM/NoPadding", text, key,  new GCMParameterSpec(GCM_TAG_LENGTH * 8, iv));
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    byte[] ciphertext = Arrays.copyOfRange(cipher, 0, cipher.length - GCM_TAG_LENGTH);
    byte[] tag = Arrays.copyOfRange(cipher, cipher.length - GCM_TAG_LENGTH, cipher.length);
    outputStream.write(salt);
    outputStream.write(iv);
    outputStream.write(tag);
    outputStream.write(ciphertext);
    String base64Encrypted;
    if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        base64Encrypted = Base64.getEncoder().encodeToString(outputStream.toByteArray());
    }else{
        base64Encrypted = android.util.Base64.encodeToString(outputStream.toByteArray(), android.util.Base64.DEFAULT);
    }
    return base64Encrypted;
}
public static SecretKey getKeyFromPassword(String masterKey, byte[] salt) throws NoSuchAlgorithmException, InvalidKeySpecException {

    SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA512");
    KeySpec spec = new PBEKeySpec(masterKey.toCharArray(), salt, 2145, 256);
    return new SecretKeySpec(factory.generateSecret(spec).getEncoded(), "AES");
}
public static byte[] encryptHelper(String algorithm, String input, SecretKey key,
                                   GCMParameterSpec gcmParameterSpec) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {

    Cipher cipher = Cipher.getInstance(algorithm);
    cipher.init(Cipher.ENCRYPT_MODE, key, gcmParameterSpec);
    return cipher.doFinal(input.getBytes(StandardCharsets.UTF_8));
}
public static byte[] generateIv(int N) {
    byte[] iv = new byte[N];
    new SecureRandom().nextBytes(iv);
    return iv;
}

谢谢@Topaco！你救了我！

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