java 中的 TripleDES 加密，用于 C# 中的解密

Question

我有 C# 代码可以解密另一个应用程序传递的加密令牌。我不能改变这部分。现在我正在 java 中编写一个应用程序，它将加密我的令牌，然后将其传递给 C# 应用程序。

我无法将加密字符串与 java 代码匹配。任何帮助，将不胜感激。谢谢。

C# Code

public class Crypto
{
    private TripleDES DesInstance = null;

    public Crypto(string key)
    {
        byte[] password = Encoding.GetEncoding(1252).GetBytes(key);
        DesInstance = new System.Security.Cryptography.TripleDESCryptoServiceProvider();
        PasswordDeriveBytes pdb = new PasswordDeriveBytes(password, null);
        DesInstance.IV = new byte[8];
        DesInstance.Key = pdb.CryptDeriveKey("TripleDES", "SHA1", 192, DesInstance.IV);
    }

    public string Decrypt(string cipheredText)
    {
        byte[] cipherText = StringToByteArray(cipheredText);
        string plainText = null;

        ICryptoTransform transform = DesInstance.CreateDecryptor();

        MemoryStream memStreamEncryptedData = new MemoryStream(cipherText, 0, cipherText.Length - 1);
        CryptoStream encStream = new CryptoStream(memStreamEncryptedData, transform, CryptoStreamMode.Read);
        using (StreamReader srDecrypt = new StreamReader(encStream, Encoding.GetEncoding(1252)))
        {
            plainText = srDecrypt.ReadToEnd();
        }

        return plainText;
    }

    private byte[] StringToByteArray(string hex)
    {
        return Enumerable.Range(0, hex.Length)
                         .Where(x => x % 2 == 0)
                         .Select(x => Convert.ToByte(hex.Substring(x, 2), 16))
                         .ToArray();
    }
}

Java Code

public class TripleDes {

    private static final String UNICODE_FORMAT = "UTF-8";
    public static final String DESEDE_ENCRYPTION_SCHEME = "DESede";
    private KeySpec ks;
    private SecretKeyFactory skf;
    private Cipher cipher;
    byte[] arrayBytes;
    private String myEncryptionKey;
    private String myEncryptionScheme;
    SecretKey key;

    public TripleDes() throws Exception {
        myEncryptionKey = "045e466ccc34a1f1688640d0441601b7ae2c";
        myEncryptionScheme = DESEDE_ENCRYPTION_SCHEME;
        arrayBytes = myEncryptionKey.getBytes(UNICODE_FORMAT);
        ks = new DESedeKeySpec(arrayBytes);
        skf = SecretKeyFactory.getInstance(myEncryptionScheme);
        cipher = Cipher.getInstance(myEncryptionScheme);
        key = skf.generateSecret(ks);
    }

    public String encrypt(String unencryptedString) {
        String encryptedString = null;
        try {
            cipher.init(Cipher.ENCRYPT_MODE, key);
            byte[] plainText = unencryptedString.getBytes(UNICODE_FORMAT);
            byte[] encryptedText = cipher.doFinal(plainText);
            encryptedString = new String(Base64.encodeBase64(encryptedText));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return encryptedString;
    }

    public String decrypt(String encryptedString) {
        String decryptedText = null;
        try {
            cipher.init(Cipher.DECRYPT_MODE, key);
            byte[] encryptedText = Base64.decodeBase64(encryptedString);
            byte[] plainText = cipher.doFinal(encryptedText);
            decryptedText = new String(plainText);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return decryptedText;
    }
}

Answer 1

C# 代码使用 PasswordDeriveBytes#CryptDeriveKey() 作为密钥派生函数，它是 CAPI 的 CryptDeriveKey() 函数的包装器（参见 here）。 Java 代码中缺少此功能，这是不兼容的原因之一。

PasswordDeriveBytes#CryptDeriveKey() 不要与 PasswordDeriveBytes#GetBytes() 混淆。后者使用了评论中提到的PBKDF1算法的（by MS）扩展实现，此处不适用

CryptDeriveKey()算法描述here and an implementation can be found here:

public static byte[] CryptDeriveKey(byte[] hBaseData, String hashAlgorithm, int requiredLength) throws NoSuchAlgorithmException {
    int keyLength = hBaseData.length;
    byte[] derivedKey = new byte[requiredLength];
    if (keyLength >= requiredLength) {
        for (int i = 0; i < requiredLength; i++) {
            derivedKey[i] = hBaseData[i];
        }
        return derivedKey;
    }

    byte[] buff1 = new byte[64];
    byte[] buff2 = new byte[64];
    Arrays.fill(buff1, (byte) 0x36);
    Arrays.fill(buff2, (byte) 0x5C);
    for (int i = 0; i < keyLength; i++) {
        buff1[i] ^= hBaseData[i];
        buff2[i] ^= hBaseData[i];
    }

    MessageDigest md = MessageDigest.getInstance(hashAlgorithm);
    md.reset();
    byte[] result1 = md.digest(buff1);
    md.reset();
    byte[] result2 = md.digest(buff2);

    for (int i = 0; i < requiredLength; i++) {
        if (i < result1.length)
            derivedKey[i] = result1[i];
        else
            derivedKey[i] = result2[i - result1.length];
    }
    return derivedKey;
}

请注意，CryptDeriveKey() 不希望密码短语作为第一个参数，而是密码短语的哈希值。

用法示例：

String passphrase = "my passphrase";
String digestName = "SHA-1"; 
MessageDigest md = MessageDigest.getInstance(digestName);
byte[] hash = md.digest(passphrase.getBytes("Cp1252"));
byte[] key = CryptDeriveKey(hash, digestName, 24);
System.out.println(HexFormat.of().formatHex(key)); // 5de508082bfe0924356d881c8cde15a540c92f267ef5a416

请注意，在 DES 或 TripleDES 的情况下，不调整奇偶校验位。这隐含地发生在 SecretKeyFactory#generateSecret().

其他问题：除了密钥派生外，还需要在 Java 代码。由于 C# 代码出于未知原因删除了密文的最后一个字节，因此必须在 Java 代码中的密文末尾添加一个虚拟字节。

虽然无法根据描述更改C#代码，但以下是关于漏洞的说明：密钥推导较弱（这适用于CryptDeriveKey()和PBKDF1），应替换为专用的password-based 像 Argon2 或 PBKDF2 这样的密钥派生。静态 IV（如零 IV）也很弱。 TripleDES 已被弃用且速度较慢，应替换为 AES 等现代算法。

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