public class Security
  {
    string _QueryStringKey = "ABCDEFH"; //URL传输参数加密Key//ijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
    string _PasswordKey = "hgfedcba"; //Password加密Key//ZYXWVUTSRQPONMLKJIHGFEDCBAzyxwvutsrqponmlkji

    public Security()
    {
      //
      // TODO: 在此处添加构造函数逻辑
      //
    }
    public string EncryptQueryString(string QueryString)
    {
      return Encrypt(QueryString, _QueryStringKey);
    }    
    /// 解密URL传输的字符串
    public string DecryptQueryString(string QueryString)
    {
      return Decrypt(QueryString, _QueryStringKey);
    }    
    /// 加密帐号口令
    public string EncryptPassword(string Password)
    {
      return Encrypt(Password, _PasswordKey);
    }    
    /// 解密帐号口令
    public string DecryptPassword(string Password)
    {
      return Decrypt(Password, _PasswordKey);
    }    
    /// DEC 加密过程
    public string Encrypt(string pToEncrypt, string sKey)
    {
      DESCryptoServiceProvider des = new DESCryptoServiceProvider(); //把字符串放到byte数组中 

      byte[] inputByteArray = Encoding.Default.GetBytes(pToEncrypt);
      //byte[] inputByteArray=Encoding.Unicode.GetBytes(pToEncrypt); 

      des.Key = ASCIIEncoding.ASCII.GetBytes(sKey); //建立加密对象的密钥和偏移量      
      des.IV = ASCIIEncoding.ASCII.GetBytes(sKey); //原文使用ASCIIEncoding.ASCII方法的GetBytes方法       
      MemoryStream ms = new MemoryStream(); //使得输入密码必须输入英文文本
      CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);

      cs.Write(inputByteArray, 0, inputByteArray.Length);
      cs.FlushFinalBlock();

      StringBuilder ret = new StringBuilder();
      foreach (byte b in ms.ToArray())
      {
        ret.AppendFormat("{0:X2}", b);
      }
      ret.ToString();
      return ret.ToString();
    }    
    /// DEC 解密过程
    public string Decrypt(string pToDecrypt, string sKey)
    {
      try
      {
        DESCryptoServiceProvider des = new DESCryptoServiceProvider();

        byte[] inputByteArray = new byte[pToDecrypt.Length / 2];
        for (int x = 0; x < pToDecrypt.Length / 2; x++)
        {
          int i = (Convert.ToInt32(pToDecrypt.Substring(x * 2, 2), 16));
          inputByteArray[x] = (byte)i;
        }

        des.Key = ASCIIEncoding.ASCII.GetBytes(sKey); //建立加密对象的密钥和偏移量，此值重要，不能修改 
        des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
        MemoryStream ms = new MemoryStream();
        CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);

        //if (cs.Length > 0&&cs.Length!=null)
        //{
        cs.Write(inputByteArray, 0, inputByteArray.Length);
        cs.FlushFinalBlock();

        StringBuilder ret = new StringBuilder(); //建立StringBuild对象，CreateDecrypt使用的是流对象，必须把解密后的文本变成流对象 

        return System.Text.Encoding.Default.GetString(ms.ToArray());
      }
      catch
      {
        return "";
      }
     // }
     // else
      //{
        //return "";
      //}
    }    
    /// 检查己加密的字符串是否与原文相同
    public bool ValidateString(string EnString, string FoString, int Mode)
    {
      switch (Mode)
      {
        default:
        case 1:
          if (Decrypt(EnString, _QueryStringKey) == FoString.ToString())
          {
            return true;
          }
          else
          {
            return false;
          }
        case 2:
          if (Decrypt(EnString, _PasswordKey) == FoString.ToString())
          {
            return true;
          }
          else
          {
            return false;
          }
      }
    }
  }