问题描述

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.

I have a block of ciphertext that was created using the JCE algorithim "PBEWithSHA256And256BitAES-CBC-BC". The provider is BouncyCastle. What I'd like to do it decrypt this ciphertext using the BouncyCastle lightweight API. I don't want to use JCE because that requires installing the Unlimited Strength Jurisdiction Policy Files.

在将 BC 与 PBE 和 AES 结合使用时，文档似乎很少.

Documentation seems to be thin on the ground when it comes to using BC with PBE and AES.

这是我目前所拥有的.解密代码运行无异常但返回垃圾.

Here's what I have so far. The decryption code runs without exception but returns rubbish.

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;
}

推荐答案

我试过这个，它似乎工作.大量借鉴了 BC 类 org.bouncycastle.jce.provider.test.PBETest

I tried this and it seemed to work. Borrowed heavily from the BC class 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;
}

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