使用 BouncyCastle 的分组密码加密/解密字节数组的最简单方法是什么？

Question

如果我有一个BlockCipher 和一个byte[] 是从包含秘密消息的String 获得的，那么获取加密消息的byte[] 的最简单方法是什么？

在普通的Java API中，我可以只做cipher.doFinal(secretMessage)，但这里似乎没有类似的东西，它只处理块。

我知道我可以使用BufferedBlockCipher，但这仍然不能显着简化事情。使用此密码最简单的高级方法是什么？

Answer 1

好的，所以使用轻量级 API 和计数器模式，这是您将获得的最简单和现代的模式之一：

public class BouncyEncrypt {

    private static final int IV_SIZE = 16;

    public static void main(String[] args) throws Exception {
        // key should really consist of 16 random bytes
        byte[] keyData = new byte[256 / Byte.SIZE];
        KeyParameter key = new KeyParameter(keyData);

        byte[] ciphertext = encryptWithAES_CTR(key, "owlstead");
        System.out.println(decryptWithAES_CTR(key, ciphertext));
    }

    private static byte[] encryptWithAES_CTR(KeyParameter key, String in)
            throws IllegalArgumentException, UnsupportedEncodingException,
            DataLengthException {
        // iv should be unique for each encryption with the same key
        byte[] ivData = new byte[IV_SIZE];
        SecureRandom rng = new SecureRandom();
        rng.nextBytes(ivData);
        ParametersWithIV iv = new ParametersWithIV(key, ivData);

        SICBlockCipher aesCTR = new SICBlockCipher(new AESFastEngine());

        aesCTR.init(true, iv);
        byte[] plaintext = in.getBytes("UTF-8");
        byte[] ciphertext = new byte[ivData.length + plaintext.length];
        System.arraycopy(ivData, 0, ciphertext, 0, IV_SIZE);
        aesCTR.processBytes(plaintext, 0, plaintext.length, ciphertext, IV_SIZE);
        return ciphertext;
    }

    private static String decryptWithAES_CTR(KeyParameter key, byte[] ciphertext)
            throws IllegalArgumentException, UnsupportedEncodingException,
            DataLengthException {
        if (ciphertext.length < IV_SIZE) {
            throw new IllegalArgumentException("Ciphertext too short to contain IV");
        }

        ParametersWithIV iv = new ParametersWithIV(key, ciphertext, 0, IV_SIZE);

        SICBlockCipher aesCTR = new SICBlockCipher(new AESFastEngine());
        aesCTR.init(true, iv);
        byte[] plaintext = new byte[ciphertext.length - IV_SIZE];
        aesCTR.processBytes(ciphertext, IV_SIZE, plaintext.length, plaintext, 0);
        return new String(plaintext, "UTF-8");
    }
}

计数器模式不需要填充并且完全在线，因此您只需致电processBytes。对于 CBC 模式，您应该查看 PaddedBufferedBlockCipher。在解密过程中，您仍然需要处理少量的缓冲区：在解密之前，您不知道存在的填充量。

您可以删除 IV 代码和 UTF-8 字符解码 + 异常处理，但您会不安全并且可能不兼容。此代码将 IV 作为密文的前缀。

Answer 2

BouncyCastle 实现了“普通 Java API”，因此您可以使用 Cipher.doFinal(String.getBytes())，您只需在获取 Cipher 时指定提供者“BC”：Cipher.getInstance("YourTransformation", "BC")

Answer 3

使用 Bouncy Castle 的 CipherOutputStream。它是最接近 Java API 的东西。

static final BouncyCastleProvider PROVIDER = new BouncyCastleProvider();

public static void main(String[] args) throws Exception {
    KeyGenerator kg = KeyGenerator.getInstance("Threefish-1024", PROVIDER);
    kg.init(1024);
    KeyParameter key = new KeyParameter(kg.generateKey().getEncoded());
    byte[] tweak = new byte[16];
    TweakableBlockCipherParameters params = new TweakableBlockCipherParameters(key, tweak);

    byte[] plaintext = "Hi! I'm cat!".getBytes();
    byte[] ciphertext = encrypt(params, plaintext);
    System.out.println(new String(decrypt(params, ciphertext)));
    // prints "Hi! I'm cat!"
}

static byte[] encrypt(TweakableBlockCipherParameters params, byte[] plaintext) throws Exception {
    return encryptOrDecrypt(true, params, plaintext);
}

static byte[] decrypt(TweakableBlockCipherParameters params, byte[] ciphertext) throws Exception {
    return encryptOrDecrypt(false, params, ciphertext);
}

static byte[] encryptOrDecrypt(boolean encrypt, TweakableBlockCipherParameters params, byte[] bytes) throws Exception {
    PaddedBufferedBlockCipher cipher = new PaddedBufferedBlockCipher(
            new CBCBlockCipher(
                    new ThreefishEngine(ThreefishEngine.BLOCKSIZE_1024)), new PKCS7Padding());
    cipher.init(encrypt, params);
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    CipherOutputStream cos = new CipherOutputStream(baos, cipher);
    cos.write(bytes);
    // calling CipherOutputStream.close is mandatory
    // it acts like Cipher.doFinal
    cos.close();
    return baos.toByteArray();
}

_{Link to my answer to a similar and related question.}