c# 加密解密算法

 #region DES 加密解密
       /// <summary>
       /// DES 加密(数据加密标准，速度较快，适用于加密大量数据的场合)
       /// </summary>
       /// <param name="EncryptString">待加密的密文</param>
       /// <param name="EncryptKey">加密的密钥</param>
       /// <returns>returns</returns>
       public  string DESEncrypt(string EncryptString, string EncryptKey)
       {
           if (string.IsNullOrEmpty(EncryptString)) { throw (new Exception("密文不得为空")); }
           if (string.IsNullOrEmpty(EncryptKey)) { throw (new Exception("密钥不得为空")); }
           if (EncryptKey.Length != 8) { throw (new Exception("密钥必须为8位")); }
           byte[] m_btIV = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
           string m_strEncrypt = "";
           DESCryptoServiceProvider m_DESProvider = new DESCryptoServiceProvider();
           try
           {
               byte[] m_btEncryptString = Encoding.Default.GetBytes(EncryptString);
               MemoryStream m_stream = new MemoryStream();
               CryptoStream m_cstream = new CryptoStream(m_stream, m_DESProvider.CreateEncryptor(Encoding.Default.GetBytes(EncryptKey), m_btIV), CryptoStreamMode.Write);
               m_cstream.Write(m_btEncryptString, 0, m_btEncryptString.Length);
               m_cstream.FlushFinalBlock();
               m_strEncrypt = Convert.ToBase64String(m_stream.ToArray());
               m_stream.Close(); m_stream.Dispose();
               m_cstream.Close(); m_cstream.Dispose();
           }
           catch (IOException ex) { throw ex; }
           catch (CryptographicException ex) { throw ex; }
           catch (ArgumentException ex) { throw ex; }
           catch (Exception ex) { throw ex; }
           finally { m_DESProvider.Clear(); }

           return m_strEncrypt;
       }
       /// <summary>
       /// DES 解密(数据加密标准，速度较快，适用于加密大量数据的场合)
       /// </summary>
       /// <param name="DecryptString">待解密的密文</param>
       /// <param name="DecryptKey">解密的密钥</param>
       /// <returns>returns</returns>
       public  string DESDecrypt(string DecryptString, string DecryptKey)
       {
           if (string.IsNullOrEmpty(DecryptString)) { throw (new Exception("密文不得为空")); }
           if (string.IsNullOrEmpty(DecryptKey)) { throw (new Exception("密钥不得为空")); }
           if (DecryptKey.Length != 8) { throw (new Exception("密钥必须为8位")); }
           byte[] m_btIV = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
           string m_strDecrypt = "";
           DESCryptoServiceProvider m_DESProvider = new DESCryptoServiceProvider();
           try
           {
               byte[] m_btDecryptString = Convert.FromBase64String(DecryptString);
               MemoryStream m_stream = new MemoryStream();
               CryptoStream m_cstream = new CryptoStream(m_stream, m_DESProvider.CreateDecryptor(Encoding.Default.GetBytes(DecryptKey), m_btIV), CryptoStreamMode.Write);
               m_cstream.Write(m_btDecryptString, 0, m_btDecryptString.Length);
               m_cstream.FlushFinalBlock();
               m_strDecrypt = Encoding.Default.GetString(m_stream.ToArray());
               m_stream.Close(); m_stream.Dispose();
               m_cstream.Close(); m_cstream.Dispose();
           }
           catch (IOException ex) { throw ex; }
           catch (CryptographicException ex) { throw ex; }
           catch (ArgumentException ex) { throw ex; }
           catch (Exception ex) { throw ex; }
           finally { m_DESProvider.Clear(); }

           return m_strDecrypt;
       }
       #endregion