10

我有一个使用 JCE 算法“PBEWithSHA256And256BitAES-CBC-BC”创建的密文块。提供者是 BouncyCastle。我想做的是使用 BouncyCastle 轻量级 API 解密这个密文。我不想使用 JCE，因为这需要安装 Unlimited Strength Jurisdiction Policy Files。

在将 BC 与 PBE 和 AES 结合使用时，文档似乎很少。

这是我到目前为止所拥有的。解密代码无异常运行，但返回垃圾。

加密代码，

String password = "qwerty";
String plainText = "hello world";

byte[] salt = generateSalt();
byte[] cipherText = encrypt(plainText, password.toCharArray(), salt);

private static byte[] generateSalt() throws NoSuchAlgorithmException {
    byte salt[] = new byte[8];
    SecureRandom saltGen = SecureRandom.getInstance("SHA1PRNG");
    saltGen.nextBytes(salt);
    return salt;
}

private static byte[] encrypt(String plainText, char[] password, byte[] salt) throws NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException, InvalidKeyException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException {
    Security.addProvider(new BouncyCastleProvider());

    PBEParameterSpec pbeParamSpec = new PBEParameterSpec(salt, 20);

    PBEKeySpec pbeKeySpec = new PBEKeySpec(password);
    SecretKeyFactory keyFac = SecretKeyFactory.getInstance("PBEWithSHA256And256BitAES-CBC-BC");
    SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);

    Cipher encryptionCipher = Cipher.getInstance("PBEWithSHA256And256BitAES-CBC-BC");
    encryptionCipher.init(Cipher.ENCRYPT_MODE, pbeKey, pbeParamSpec);

    return encryptionCipher.doFinal(plainText.getBytes());
}

解密代码，

byte[] decryptedText = decrypt(cipherText, password.getBytes(), salt);

private static byte[] decrypt(byte[] cipherText, byte[] password, byte[] salt) throws DataLengthException, IllegalStateException, InvalidCipherTextException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException {
    BlockCipher engine = new AESEngine();
    CBCBlockCipher cipher = new CBCBlockCipher(engine);

    PKCS5S1ParametersGenerator keyGenerator = new PKCS5S1ParametersGenerator(new SHA256Digest());
    keyGenerator.init(password, salt, 20);

    CipherParameters keyParams = keyGenerator.generateDerivedParameters(256);
    cipher.init(false, keyParams);

    byte[] decryptedBytes = new byte[cipherText.length];
    int numBytesCopied = cipher.processBlock(cipherText, 0, decryptedBytes, 0);

    return decryptedBytes;
}
4

4 回答 4

11

我试过这个，它似乎工作。从 BC 类大量借来的org.bouncycastle.jce.provider.test.PBETest 

private byte[] decryptWithLWCrypto(byte[] cipher, String password, byte[] salt, final  int iterationCount)
        throws Exception
{
    PKCS12ParametersGenerator pGen = new PKCS12ParametersGenerator(new SHA256Digest());
    char[] passwordChars = password.toCharArray();
    final byte[] pkcs12PasswordBytes = PBEParametersGenerator
            .PKCS12PasswordToBytes(passwordChars);
    pGen.init(pkcs12PasswordBytes, salt, iterationCount);
    CBCBlockCipher aesCBC = new CBCBlockCipher(new AESEngine());
    ParametersWithIV aesCBCParams = (ParametersWithIV) pGen.generateDerivedParameters(256, 128);
    aesCBC.init(false, aesCBCParams);
    PaddedBufferedBlockCipher aesCipher = new PaddedBufferedBlockCipher(aesCBC,
            new PKCS7Padding());
    byte[] plainTemp = new byte[aesCipher.getOutputSize(cipher.length)];
    int offset = aesCipher.processBytes(cipher, 0, cipher.length, plainTemp, 0);
    int last = aesCipher.doFinal(plainTemp, offset);
    final byte[] plain = new byte[offset + last];
    System.arraycopy(plainTemp, 0, plain, 0, plain.length);
    return plain;
}
于 2010-06-02T20:05:11.320 回答
9

您的解密方法存在一些问题：

private static byte[] decrypt(final byte[] bytes, final char[] password, final byte[] salt) throws DataLengthException, IllegalStateException, InvalidCipherTextException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException {

    final PBEParametersGenerator keyGenerator = new PKCS12ParametersGenerator(new SHA256Digest());
    keyGenerator.init(PKCS12ParametersGenerator.PKCS12PasswordToBytes(password), salt, 20);
    final CipherParameters keyParams = keyGenerator.generateDerivedParameters(256, 128);

    final BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(new AESEngine()), new PKCS7Padding());
    cipher.init(false, keyParams);

    final byte[] processed = new byte[cipher.getOutputSize(bytes.length)];
    int outputLength = cipher.processBytes(bytes, 0, bytes.length, processed, 0);
    outputLength += cipher.doFinal(processed, outputLength);

    final byte[] results = new byte[outputLength];
    System.arraycopy(processed, 0, results, 0, outputLength);
    return results;
}

主要问题是您在不使用分组密码的情况下执行解密的方式以及该generateDerivedParameters方法缺少 IV 大小。我很快就看到了第一个问题，第二个问题就不那么明显了。我只是通过查看名为PBETest的 Bouncy Castle 测试才发现的。

于 2010-06-03T04:13:21.007 回答
1

生成与 JCE 对应项完全相同的密钥并非易事。我只是简要浏览了您的代码。发现至少一处不一致。JCE 使用 PKCS12 生成器，但您使用 PKCS5S1。

如果还有其他差异，我并不感到惊讶。您需要将您的代码与 BC 源代码进行比较。

于 2010-06-02T13:22:49.743 回答
0

我注意到您的加密方法接受密码作为字符数组，但解密接受密码作为字节。在 Java 中，字符是 16 位的，而字节是 8 位的。这可能会导致加密/解密的密钥不同，并可能解释乱码解密结果的问题？

于 2012-09-12T03:18:57.383 回答