DES加密 DES解密

        public static string _KEY = "HQDCKEY1";  //密钥  
        public static string _IV = "HQDCKEY2";   //向量  

        /// <summary>  
        /// DES加密  
        /// </summary>  
        /// <param name="data"></param>  
        /// <returns></returns>  
        public static string Encode(string data)
        {

            byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(_KEY);
            byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(_IV);

            DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
            int i = cryptoProvider.KeySize;
            MemoryStream ms = new MemoryStream();
            CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateEncryptor(byKey, byIV), CryptoStreamMode.Write);

            StreamWriter sw = new StreamWriter(cst);
            sw.Write(data);
            sw.Flush();
            cst.FlushFinalBlock();
            sw.Flush();

            string strRet = Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length);
            return strRet;
        }

        /// <summary>  
        /// DES解密  
        /// </summary>  
        /// <param name="data"></param>  
        /// <returns></returns>  
        public static string Decode(string data)
        {

            byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(_KEY);
            byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(_IV);

            byte[] byEnc;

            try
            {
                data.Replace("_%_", "/");
                data.Replace("-%-", "#");
                byEnc = Convert.FromBase64String(data);

            }
            catch
            {
                return null;
            }

            DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
            MemoryStream ms = new MemoryStream(byEnc);
            CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateDecryptor(byKey, byIV), CryptoStreamMode.Read);
            StreamReader sr = new StreamReader(cst);
            return sr.ReadToEnd();
        }