C# 基于密码的AES加解密算法转Java实现，相关方法替代咨询

现有Java代码问题梳理 #

• 密钥衍生逻辑错误：C#中Rfc2898DeriveBytes仅生成128位AES密钥，IV是独立生成的随机值，现有Java代码从PBKDF2输出结果中截取IV，和C#逻辑完全不匹配
• 密文结构错误：C#最终返回的Base64密文是「16字节盐 + 16字节随机IV + 实际密文」的拼接结果，现有Java代码仅返回了实际密文，缺失前两段数据
• PBKDF2参数错误：现有代码申请了384位衍生结果，实际只需要128位密钥即可

对应C#类的Java完整实现 #

import javax.crypto.Cipher;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;
import java.util.Base64;

public class StringCipher {
    // 对应C#的密钥长度配置，单位为比特
    private static final int KEY_SIZE = 128;
    // 和C#的迭代次数保持一致
    private static final int DERIVATION_ITERATIONS = 1000;
    // 128比特对应16字节
    private static final int BLOCK_SIZE = KEY_SIZE / 8;

    private static byte[] generate128BitsOfRandomEntropy() {
        byte[] randomBytes = new byte[BLOCK_SIZE];
        new SecureRandom().nextBytes(randomBytes);
        return randomBytes;
    }

    // 加密方法和C#逻辑完全对齐
    public static String encrypt(String plainText, String passPhrase) throws Exception {
        byte[] salt = generate128BitsOfRandomEntropy();
        byte[] iv = generate128BitsOfRandomEntropy();
        byte[] plainTextBytes = plainText.getBytes(java.nio.charset.StandardCharsets.UTF_8);

        // 对应C#的Rfc2898DeriveBytes，默认PBKDF2WithHmacSHA1算法和C#完全一致
        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        PBEKeySpec spec = new PBEKeySpec(passPhrase.toCharArray(), salt, DERIVATION_ITERATIONS, KEY_SIZE);
        byte[] keyBytes = factory.generateSecret(spec).getEncoded();
        SecretKeySpec secretKey = new SecretKeySpec(keyBytes, "AES");

        // 对应C# RijndaelManaged配置，AES是Rijndael块大小固定128位的标准实现，PKCS5Padding和C#的PKCS7Padding兼容
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secretKey, new IvParameterSpec(iv));
        byte[] cipherTextBytes = cipher.doFinal(plainTextBytes);

        // 拼接盐、IV、密文，和C#输出结构完全一致
        byte[] result = new byte[BLOCK_SIZE * 2 + cipherTextBytes.length];
        System.arraycopy(salt, 0, result, 0, BLOCK_SIZE);
        System.arraycopy(iv, 0, result, BLOCK_SIZE, BLOCK_SIZE);
        System.arraycopy(cipherTextBytes, 0, result, BLOCK_SIZE * 2, cipherTextBytes.length);

        return Base64.getEncoder().encodeToString(result);
    }

    // 解密方法和C#逻辑完全对齐
    public static String decrypt(String cipherText, String passPhrase) throws Exception {
        byte[] cipherDataWithSaltIv = Base64.getDecoder().decode(cipherText);
        // 提取前16字节盐
        byte[] salt = new byte[BLOCK_SIZE];
        System.arraycopy(cipherDataWithSaltIv, 0, salt, 0, BLOCK_SIZE);
        // 提取16-32字节作为IV
        byte[] iv = new byte[BLOCK_SIZE];
        System.arraycopy(cipherDataWithSaltIv, BLOCK_SIZE, iv, 0, BLOCK_SIZE);
        // 提取剩余部分为实际密文
        byte[] cipherTextBytes = new byte[cipherDataWithSaltIv.length - BLOCK_SIZE * 2];
        System.arraycopy(cipherDataWithSaltIv, BLOCK_SIZE * 2, cipherTextBytes, 0, cipherTextBytes.length);

        // 生成匹配的密钥
        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        PBEKeySpec spec = new PBEKeySpec(passPhrase.toCharArray(), salt, DERIVATION_ITERATIONS, KEY_SIZE);
        byte[] keyBytes = factory.generateSecret(spec).getEncoded();
        SecretKeySpec secretKey = new SecretKeySpec(keyBytes, "AES");

        // 执行解密
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));
        byte[] plainTextBytes = cipher.doFinal(cipherTextBytes);

        return new String(plainTextBytes, java.nio.charset.StandardCharsets.UTF_8);
    }
}

适配说明 #

• C#的RijndaelManaged当块大小设置为128时就是标准AES算法，Java的AES算法实现完全兼容
• C#的PaddingMode.PKCS7和Java的PKCS5Padding在块大小为8的倍数时完全等价，AES块大小固定为16字节，无需额外适配
• 本实现和原版C#代码完全互通，C#加密的密文可以直接用Java解密，反之亦然

内容的提问来源于stack exchange，提问作者bjalexmdd