C#版QQTea加密

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace WindowsFormsApplication1
{
    /// <summary>
    /// 加密解密QQ消息包的工具类.
    /// </summary>
    public static class QQCrypter
    {
        private static void code(byte[] In, int inOffset, int inPos, byte[] Out, int outOffset, int outPos, byte[] key)
        {
            if (outPos > )
            {
                for (int i = ; i < ; i++)
                {
                    In[outOffset + outPos + i] = (byte)(In[inOffset + inPos + i] ^ Out[outOffset + outPos + i - ]);
                }
            }
            uint[] formattedKey = FormatKey(key);
            uint y = ConvertByteArrayToUInt(In, outOffset + outPos);
            uint z = ConvertByteArrayToUInt(In, outOffset + outPos + );
            uint sum = ;
            uint delta = 0x9e3779b9;
            uint n = ;

            while (n-- > )
            {
                sum += delta;
                y += ((z << ) + formattedKey[]) ^ (z + sum) ^ ((z >> ) + formattedKey[]);
                z += ((y << ) + formattedKey[]) ^ (y + sum) ^ ((y >> ) + formattedKey[]);
            }
            Array.Copy(ConvertUIntToByteArray(y), , Out, outOffset + outPos, );
            Array.Copy(ConvertUIntToByteArray(z), , Out, outOffset + outPos + , );
            if (inPos > )
            {
                for (int i = ; i < ; i++)
                {
                    Out[outOffset + outPos + i] = (byte)(Out[outOffset + outPos + i] ^ In[inOffset + inPos + i - ]);
                }
            }
        }

        private static void decode(byte[] In, int inOffset, int inPos, byte[] Out, int outOffset, int outPos, byte[] key)
        {
            if (outPos > )
            {
                for (int i = ; i < ; i++)
                {
                    Out[outOffset + outPos + i] = (byte)(In[inOffset + inPos + i] ^ Out[outOffset + outPos + i - ]);
                }
            }
            else
            {
                Array.Copy(In, inOffset, Out, outOffset, );
            }
            uint[] formattedKey = FormatKey(key);
            uint y = ConvertByteArrayToUInt(Out, outOffset + outPos);
            uint z = ConvertByteArrayToUInt(Out, outOffset + outPos + );
            uint sum = 0xE3779B90;
            uint delta = 0x9e3779b9;
            uint n = ;

            while (n-- > )
            {
                z -= ((y << ) + formattedKey[]) ^ (y + sum) ^ ((y >> ) + formattedKey[]);
                y -= ((z << ) + formattedKey[]) ^ (z + sum) ^ ((z >> ) + formattedKey[]);
                sum -= delta;
            }
            Array.Copy(ConvertUIntToByteArray(y), , Out, outOffset + outPos, );
            Array.Copy(ConvertUIntToByteArray(z), , Out, outOffset + outPos + , );
        }

        /**/
        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="In">密文</param>
        /// <param name="offset">密文开始的位置</param>
        /// <param name="len">密文长度</param>
        /// <param name="key">密钥</param>
        /// <returns>返回明文</returns>
        public static byte[] Decrypt(byte[] In, int offset, int len, byte[] key)
        {
            // 因为QQ消息加密之后至少是16字节，并且肯定是8的倍数，这里检查这种情况
            if ((len %  != ) || (len < ))
            {
                return null;
            }
            byte[] Out = new byte[len];
            for (int i = ; i < len; i += )
            {
                decode(In, offset, i, Out, , i, key);
            }
            for (int i = ; i < len; i++)
            {
                Out[i] = (byte)(Out[i] ^ In[offset + i - ]);
            }
            int pos = Out[] & 0x07;
            len = len - pos - ;
            byte[] res = new byte[len];
            Array.Copy(Out, pos + , res, , len);
            return res;
        }

        public static byte[] Encrypt(byte[] In, int offset, int len, byte[] key)
        {
            // 计算头部填充字节数
            int pos = (len + ) % ;
            if (pos != )
            {
                pos =  - pos;
            }
            byte[] plain = new byte[len + pos + ];
            Random Rnd = new Random();
            plain[] = (byte)((Rnd.Next() & 0xF8) | pos);
            for (int i = ; i < pos + ; i++)
            {
                plain[i] = (byte)(Rnd.Next() & 0xFF);
            }
            Array.Copy(In, , plain, pos + , len);
            for (int i = pos +  + len; i < plain.Length; i++)
            {
                plain[i] = 0x0;
            }
            // 定义输出流
            byte[] outer = new byte[len + pos + ];
            for (int i = ; i < outer.Length; i += )
            {
                code(plain, , i, outer, , i, key);
            }
            return outer;
        }

        private static uint[] FormatKey(byte[] key)
        {
            if (key.Length == )
            {
                throw new ArgumentException("Key must be between 1 and 16 characters in length");
            }
            byte[] refineKey = new byte[];
            if (key.Length < )
            {
                Array.Copy(key, , refineKey, , key.Length);
                for (int k = key.Length; k < ; k++)
                {
                    refineKey[k] = 0x20;
                }
            }
            else
            {
                Array.Copy(key, , refineKey, , );
            }
            uint[] formattedKey = new uint[];
            int j = ;
            for (int i = ; i < refineKey.Length; i += )
            {
                formattedKey[j++] = ConvertByteArrayToUInt(refineKey, i);
            }
            return formattedKey;
        }

        private static byte[] ConvertUIntToByteArray(uint v)
        {
            byte[] result = new byte[];
            result[] = (byte)((v >> ) & 0xFF);
            result[] = (byte)((v >> ) & 0xFF);
            result[] = (byte)((v >> ) & 0xFF);
            result[] = (byte)((v >> ) & 0xFF);
            return result;
        }

        private static uint ConvertByteArrayToUInt(byte[] v, int offset)
        {
            if (offset +  > v.Length)
            {
                return ;
            }
            uint output;
            output = (uint)(v[offset] << );
            output |= (uint)(v[offset + ] << );
            output |= (uint)(v[offset + ] << );
            output |= (uint)(v[offset + ] << );
            return output;
        }
    }

}