C# RSA加密与PHP解密跨平台实现指南

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using System.Xml.Serialization;

namespace TEST
{
    public class RSAEncrypter
    {
        private RSACryptoServiceProvider _rsa;
        private RSAParameters _privateKey;
        private RSAParameters _publicKey;

        /// <summary>
        /// 构造函数，生成2048位的RSA密钥对。
        /// </summary>
        public RSAEncrypter()
        {
            _rsa = new RSACryptoServiceProvider(2048); // 建议使用2048位或更高
            _privateKey = _rsa.ExportParameters(true);  // 导出包含私钥的参数
            _publicKey = _rsa.ExportParameters(false); // 导出仅包含公钥的参数
        }

        /// <summary>
        /// 使用指定的公钥加密明文。
        /// </summary>
        /// <param name="plainText">待加密的明文。</param>
        /// <param name="publicKeyXml">XML格式的公钥字符串。</param>
        /// <returns>Base64编码的密文。</returns>
        public string Encrypt(string plainText, string publicKeyXml)
        {
            // 导入XML格式的公钥
            _rsa.FromXmlString(publicKeyXml);
            // 重新导入公钥参数，确保当前RSA实例使用正确的公钥
            // 注意：这里publicKeyXml通常应包含Modulus和Exponent
            // _publicKey = _rsa.ExportParameters(false); // 这一行在FromXmlString后通常不需要
            // _rsa.ImportParameters(_publicKey); // 这一行在FromXmlString后通常不需要

            var data = Encoding.Unicode.GetBytes(plainText); // 使用Unicode编码
            // RSA加密，第二个参数为false表示使用PKCS#1 v1.5填充
            var cypher = _rsa.Encrypt(data, false); 
            return Convert.ToBase64String(cypher); // 将密文转换为Base64字符串以便传输
        }

        /// <summary>
        /// 获取XML格式的私钥字符串。
        /// </summary>
        /// <returns>XML格式的私钥字符串。</returns>
        public string PrivateKeyString()
        {
            var sw = new StringWriter();
            var xs = new XmlSerializer(typeof(RSAParameters));
            xs.Serialize(sw, _privateKey);
            return sw.ToString();
        }

        /// <summary>
        /// 获取XML格式的公钥字符串。
        /// </summary>
        /// <returns>XML格式的公钥字符串。</returns>
        public string PublicKeyString()
        {
            var sw = new StringWriter();
            var xs = new XmlSerializer(typeof(RSAParameters));
            xs.Serialize(sw, _publicKey);
            return sw.ToString();
        }
    }
}

<?php

// 从C#加密端获取的Base64编码密文
$encryptedData = '
b9+nktWSdlYQWiuswcT49JJdt1mmZj87Gwwydkpiu2Xbf3n1Nc+xE5whSzgfTIIthQEVssCUk/UfNsyN2iC37nkxcQe4Xu6KsiWFYvCRZmxww24p/qi43isd1ijCS6wajrJbrpq2tvLzBZ7KhrYkEt3qPbanRRslJauzaCW8MT42HotFl7mVKJjj5p+U6p5dklkm0Uxn36a9eB8+Nt8kSum1YcUbkrS0TRhmorQxifNY99yEju3KeISq5+946tKpW+Efau0CvUF/V5mKn203T5MdO8x5z7VFejHW6dB6oDxTh9EeEyEAPPRBz734wtZxCOVODd39Ttnk6FfnnWat8w==
';

// 经过转换后的PEM格式私钥字符串
// 确保这个私钥与C#加密时使用的公钥是配对的
$private_key = '
-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----
';

$decriptedData = ''; // 用于存储解密后的数据

// 1. 对Base64编码的密文进行解码
$decodedEncryptedData = base64_decode($encryptedData);

// 2. 使用openssl_private_decrypt进行解密
// 第一个参数是解码后的密文
// 第二个参数是用于存储解密结果的变量
// 第三个参数是PEM格式的私钥
// 第四个参数指定填充模式，与C#加密时使用的PKCS#1 v1.5填充对应
$success = openssl_private_decrypt(
    $decodedEncryptedData