DES加密程序就解密方法。


namespace Encryption
{
    using System;
    using System.Text;    public static class DES
    {
        private const string DESKey = "e!f@b#o$";        public static string DESEncrypKey(string Src, string Key)
        {
            string CS$1$0000;
            try
            {
                byte[] b1 = Encoding.Default.GetBytes(Src);
                int KeyLen = Key.Length;
                if (KeyLen == 0)
                {
                    Key = "e!f@b#o$";
                }
                int KeyPos = -1;
                int SrcAsc = 0;
                int Range = 0x100;
                int offset = new Random().Next(0, Range);
                string dest = string.Format("{0:X2}", offset);
                foreach (byte b in b1)
                {
                    SrcAsc = (b + offset) % 0xff;
                    if (KeyPos < (KeyLen - 1))
                    {
                        KeyPos++;
                    }
                    else
                    {
                        KeyPos = 0;
                    }
                    SrcAsc ^= Convert.ToByte(Key[KeyPos]);
                    dest = dest + string.Format("{0:X2}", SrcAsc);
                    offset = SrcAsc;
                }
                CS$1$0000 = dest;
            }
            catch
            {
                throw new Exception("加密错误");
            }
            return CS$1$0000;
        }        public static string DESUncrypKey(string Src, string Key)
        {
            string CS$1$0000;
            try
            {
                int KeyLen = Key.Length;
                if (KeyLen == 0)
                {
                    Key = "e!f@b#o$";
                }
                int KeyPos = -1;
                int SrcAsc = 0;
                int offset = Convert.ToByte(Src.Substring(0, 2), 0x10);
                int SrcPos = 2;
                int i = 0;
                byte[] dest = new byte[(Src.Length / 2) - 1];
                while (SrcPos < Src.Length)
                {
                    SrcAsc = Convert.ToByte(Src.Substring(SrcPos, 2), 0x10);
                    if (KeyPos < (KeyLen - 1))
                    {
                        KeyPos++;
                    }
                    else
                    {
                        KeyPos = 0;
                    }
                    int TmpSrcAsc = SrcAsc ^ Convert.ToByte(Key[KeyPos]);
                    if (TmpSrcAsc <= offset)
                    {
                        TmpSrcAsc = (0xff + TmpSrcAsc) - offset;
                    }
                    else
                    {
                        TmpSrcAsc -= offset;
                    }
                    dest[i] = (byte) TmpSrcAsc;
                    offset = SrcAsc;
                    SrcPos += 2;
                    i++;
                }
                CS$1$0000 = Encoding.Default.GetString(dest);
            }
            catch
            {
                throw new Exception("解密错误");
            }
            return CS$1$0000;
        }        public static string StringToBytes(string Src)
        {
            string s = string.Empty;
            byte[] buffer = Encoding.Unicode.GetBytes(Src);
            foreach (byte b in buffer)
            {
                s = s + b.ToString();
            }
            return s;
        }        public static string StringToBytes(string src, Encoding encode)
        {
            byte[] buffer = encode.GetBytes(src);
            string strBuffer = string.Empty;
            foreach (byte b in buffer)
            {
                strBuffer = strBuffer + b.ToString();
            }
            return strBuffer;
        }
    }
}加密过后的密文是554A1B76C45E278DD4951984790A6B83这种格式的，求大牛帮忙写一个解密的程序。