哈哈，接着上面的《RC4加密算法在C++中的实现》。

不用想，没错，我就是用C＋＋做客户端，用C＃做服务端的，所以，服务端一样得有RC4的算法实现。

这次的RC4有个基类CryptoBase，这个基类，是为了为多种加密算法提供统一接口而设计的，我这里实现了RC4、DES、RSA三种算法。和C＋＋中一样，C＃这里也要有一个十六进制字符串转换函数来编码解码。

经过测试，客户端C＋＋的RC4能够很好的和服务端C＃中的RC4结合工作，也就是说，一端加密的数据，另一端完全可以解密。很遗憾，实在找不到能和C＃中的RSA算法对应的C＋＋实现的RSA算法，希望得到高人指点……

代码文件有两个：

CryptoBase.cs文件：

以下是代码片段： using System; using System.Collections.Generic; using System.Text; namespace NewLife.Cryptography {     /// <summary>     /// 加密类基类     /// </summary>     public class CryptoBase     {         /// <summary>         /// 编码转换器，用于字节码和字符串之间的转换，默认为本机编码         /// </summary>         static public Encoding Encode = Encoding.Default;         public enum EncoderMode { Base64Encoder, HexEncoder };         /// <summary>         /// 带编码模式的字符串加密         /// </summary>         /// <param name="data">要加密的数据</param>         /// <param name="pass">密码</param>         /// <param name="em">编码模式</param>         /// <returns>加密后经过编码的字符串</returns>         public String Encrypt(String data, String pass, CryptoBase.EncoderMode em)         {             if (data == null || pass == null) return null;             if (em == EncoderMode.Base64Encoder)                 return Convert.ToBase64String(EncryptEx(Encode.GetBytes(data), pass));             else                 return ByteToHex(EncryptEx(Encode.GetBytes(data), pass));         }         /// <summary>         /// 带编码模式的字符串解密         /// </summary>         /// <param name="data">要解密的数据</param>         /// <param name="pass">密码</param>         /// <param name="em">编码模式</param>         /// <returns>明文</returns>         public String Decrypt(String data, String pass, CryptoBase.EncoderMode em)         {             if (data == null || pass == null) return null;             if (em == EncoderMode.Base64Encoder)                 return Encode.GetString(DecryptEx(Convert.FromBase64String(data), pass));             else                 return Encode.GetString(DecryptEx(HexToByte(data), pass));         }         /// <summary>         /// 加密         /// </summary>         /// <param name="data">要加密的数据</param>         /// <param name="pass">密码</param>         /// <returns>加密后经过默认编码的字符串</returns>         public String Encrypt(String data, String pass)         {             return Encrypt(data, pass, EncoderMode.Base64Encoder);         }         /// <summary>         /// 解密         /// </summary>         /// <param name="data">要解密的经过编码的数据</param>         /// <param name="pass">密码</param>         /// <returns>明文</returns>         public String Decrypt(String data, String pass)         {             return Decrypt(data, pass, EncoderMode.Base64Encoder);         }         /// <summary>         /// 加密         /// </summary>         /// <param name="data">要加密的数据</param>         /// <param name="pass">密钥</param>         /// <returns>密文</returns>         virtual public Byte[] EncryptEx(Byte[] data, String pass) { return null; }         /// <summary>         /// 解密         /// </summary>         /// <param name="data">要解密的数据</param>         /// <param name="pass">密码</param>         /// <returns>明文</returns>         virtual public Byte[] DecryptEx(Byte[] data, String pass) { return null; }         static public Byte[] HexToByte(String szHex)         {             // 两个十六进制代表一个字节             Int32 iLen = szHex.Length;             if (iLen <= 0 || 0 != iLen % 2)             {                 return null;             }             Int32 dwCount = iLen / 2;             UInt32 tmp1, tmp2;             Byte[] pbBuffer = new Byte[dwCount];             for (Int32 i = 0; i < dwCount; i++)             {                 tmp1 = (UInt32)szHex[i * 2] - (((UInt32)szHex[i * 2] >= (UInt32)'A') ? (UInt32)'A' - 10 : (UInt32)'0');                 if (tmp1 >= 16) return null;                 tmp2 = (UInt32)szHex[i * 2 + 1] - (((UInt32)szHex[i * 2 + 1] >= (UInt32)'A') ? (UInt32)'A' - 10 : (UInt32)'0');                 if (tmp2 >= 16) return null;                 pbBuffer[i] = (Byte)(tmp1 * 16 + tmp2);             }             return pbBuffer;         }         static public String ByteToHex(Byte[] vByte)         {             if (vByte == null || vByte.Length < 1) return null;             StringBuilder sb = new StringBuilder(vByte.Length * 2);             for (int i = 0; i < vByte.Length; i++)             {                 if ((UInt32)vByte[i] < 0) return null;                 UInt32 k = (UInt32)vByte[i] / 16;                 sb.Append((Char)(k + ((k > 9) ? 'A' - 10 : '0')));                 k = (UInt32)vByte[i] % 16;                 sb.Append((Char)(k + ((k > 9) ? 'A' - 10 : '0')));             }             return sb.ToString();         }     }     interface ICrypto     {         /// <summary>         /// 加密         /// </summary>         /// <param name="data">要加密的数据</param>         /// <param name="pass">密钥</param>         /// <returns>密文</returns>         Byte[] EncryptEx(Byte[] data, String pass);         /// <summary>         /// 解密         /// </summary>         /// <param name="data">要解密的数据</param>         /// <param name="pass">密码</param>         /// <returns>明文</returns>         Byte[] DecryptEx(Byte[] data, String pass);     } }

RC4.cs文件：

以下是代码片段： using System; using System.Collections.Generic; using System.Text; namespace NewLife.Cryptography {     public class RC4Crypto : CryptoBase     {         static public RC4Crypto RC4 = new RC4Crypto();         public override Byte[] EncryptEx(Byte[] data, String pass)         {             if (data == null || pass == null) return null;             Byte[] output = new Byte[data.Length];             Int64 i = 0;             Int64 j = 0;             Byte[] mBox = GetKey(Encode.GetBytes(pass), 256);             // 加密             for (Int64 offset = 0; offset < data.Length; offset++)             {                 i = (i + 1) % mBox.Length;                 j = (j + mBox[i]) % mBox.Length;                 Byte temp = mBox[i];                 mBox[i] = mBox[j];                 mBox[j] = temp;                 Byte a = data[offset];                 //Byte b = mBox[(mBox[i] + mBox[j] % mBox.Length) % mBox.Length];                 // mBox[j] 一定比 mBox.Length 小，不需要在取模                 Byte b = mBox[(mBox[i] + mBox[j]) % mBox.Length];                 output[offset] = (Byte)((Int32)a ^ (Int32)b);             }             return output;         }         public override Byte[] DecryptEx(Byte[] data, String pass)         {             return EncryptEx(data, pass);         }         /// <summary>         /// 打乱密码         /// </summary>         /// <param name="pass">密码</param>         /// <param name="kLen">密码箱长度</param>         /// <returns>打乱后的密码</returns>         static private Byte[] GetKey(Byte[] pass, Int32 kLen)         {             Byte[] mBox = new Byte[kLen];             for (Int64 i = 0; i < kLen; i++)             {                 mBox[i] = (Byte)i;             }             Int64 j = 0;             for (Int64 i = 0; i < kLen; i++)             {                 j = (j + mBox[i] + pass[i % pass.Length]) % kLen;                 Byte temp = mBox[i];                 mBox[i] = mBox[j];                 mBox[j] = temp;             }             return mBox;         }     } }