Java 中的 Bouncy Castle 加密 .Net 中的解密答案

【问题标题】：Bouncy Castle Encrypt in Java Decrypt in .NetJava 中的 Bouncy Castle 加密 .Net 中的解密
【发布时间】：2021-08-03 04:03:29
【问题描述】：

我使用以下方法使用密码加密字符串

    static String algorithm = "PBEWITHSHA256AND128BITAES-CBC-BC";
static byte[] salt = "b9v4n38s".getBytes(StandardCharsets.UTF_8);
static int derivedKeyLength = 128;
static int iterations = 20000;

public static byte[] encrypt(String plainText, String password) throws NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException, InvalidKeySpecException, NoSuchAlgorithmException {
    Security.addProvider(new BouncyCastleProvider());
    KeySpec spec = new PBEKeySpec(password.toCharArray(), salt, iterations, derivedKeyLength);
    SecretKeyFactory f = SecretKeyFactory.getInstance(algorithm);
    SecretKey key = f.generateSecret(spec);
    Cipher cipher = Cipher.getInstance(algorithm);
    cipher.init(Cipher.ENCRYPT_MODE, key);   
    byte[] text = plainText.getBytes(StandardCharsets.UTF_8);         
    byte[] encrypted = cipher.doFinal(text);
    return encrypted;
}

结果是 base64 编码并作为 arg[0] 发送到 .Net（arg[1] 是相同的密码）。现在我正在尝试使用此代码在 .Net 中解密该字符串

    private static string Decrypt(string[] args)
    {
        int derivedKeyLength = 128;
        int iterations = 20000;
        string algorithm = "PBEWITHSHA256AND128BITAES-CBC-BC";
        byte[] salt = Encoding.UTF8.GetBytes("b9v4n38s");

        PbeParametersGenerator pGen = new Pkcs12ParametersGenerator(new Sha256Digest());
        pGen.Init(Encoding.UTF8.GetBytes(args[1]), salt, iterations);
        ICipherParameters par = pGen.GenerateDerivedParameters("AES256", derivedKeyLength);
        IBufferedCipher c = CipherUtilities.GetCipher(algorithm);
        c.Init(false, par);
        var input = Convert.FromBase64String(args[0]);
        byte[] enc = c.DoFinal(input);
        var decoded = Encoding.UTF8.GetString(enc);
        return decoded;
    }

不幸的是，它在 DoFinal 上失败并显示消息 Org.BouncyCastle.Crypto.InvalidCipherTextException: 'pad block corrupted'

SecretKeyFactory.getInstance(algorithm) 使用与 java 中的 Cipher.getInstance(algorithm) 相同的算法字符串，但如果我在 .Net 中尝试 pGen.GenerateDerivedParameters(algorithm, derivedKeyLength); 它会抛出 Org.BouncyCastle.Security.SecurityUtilityException: 'Algorithm PBEWITHSHA256AND128BITAES-CBC-BC not recognised.'

我没有设置这个算法，只是在寻找一种在Java中加密字符串并在.Net中解密的方法。

【问题讨论】：

标签： java c# encryption bouncycastle

【解决方案1】：

用于解密使用发布的 Java 代码生成的密文的可能 C#/BC 代码是：

using System;
using System.Text;
using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Security;
...
private static string algorithm = "PBEWITHSHA256AND128BITAES-CBC-BC";
private static byte[] salt = Encoding.UTF8.GetBytes("b9v4n38s");
private static int iterations = 20000;

public static string Decrypt(string ciphertextB64, string password)
{
    IBufferedCipher cipher = CipherUtilities.GetCipher(algorithm);
    Asn1Encodable algParams = PbeUtilities.GenerateAlgorithmParameters(algorithm, salt, iterations);
    ICipherParameters cipherParams = PbeUtilities.GenerateCipherParameters(algorithm, password.ToCharArray(), algParams);
    cipher.Init(false, cipherParams);

    byte[] cipherBytes = Convert.FromBase64String(ciphertextB64);
    byte[] decrypted = cipher.DoFinal(cipherBytes);

    return Encoding.UTF8.GetString(decrypted);
}

测试：

string decrypted = Decrypt("mBy4YwAvUpvoSJhzBnpOCJw2kCayvdYfLJ/12x0BgUKh5m5bvArSheMMs2U5rYyE", "MyPassword");
Console.WriteLine(decrypted); // The quick brown fox jumps over the lazy dog

其中密文是使用密码 MyPassword 使用 Java 代码生成的。

请注意，静态盐通常是不安全的（当然测试目的除外）。

【讨论】：