C#加密与解密

        /// <summary>
        ///  DEC   加密过程  
        /// </summary>
        /// <param name="pToEncrypt">要加密的字符串</param>
        /// <param name="sKey">密匙</param>
        /// <returns></returns>  
        public static 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);

            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();
        }

        /// <summary>
        /// DEC   解密过程  
        /// </summary>
        /// <param name="pToDecrypt">要解密的字符串</param>
        /// <param name="sKey">密匙</param>
        /// <returns></returns>
        public static string Decrypt(string pToDecrypt, string sKey)
        {
            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);

            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());
        }