加密與解密

using System;
using System.Collections.Generic;
using System.Text;
using System.Security.Cryptography;
using System.IO;

    /// <summary>
    /// 加密字符
    /// </summary>
    /// <param name=pToEncrypt>加密字符串</param>
    /// <param name=skey>加密密鑰</param>
    /// <returns>返回加密</returns>
   public  class DescMD5
    {
       public static  string skey = "abcdefgh";

        public string Skey
        {
            get { return skey; }
            set { skey = value; }
        }


       /// <summary>
       /// 加密函數
       /// </summary>
       /// <param name="pToEncrypt"></param>
       /// <returns></returns>
       public  string EnCrypt(string pToEncrypt)
       {
           //訪問數據加密標準(DES)算法的加密服務提供程序 (CSP) 版本的包裝對象
           DESCryptoServiceProvider des = new DESCryptoServiceProvider();
           des.Key = System.Text.ASCIIEncoding.ASCII.GetBytes(skey);//建立加密對象的密鑰和偏移量
           des.IV = ASCIIEncoding.ASCII.GetBytes(skey); //原文使用ASCIIEncoding.ASCII方法的GetBytes方法
           byte[] inputbyteArray = Encoding.Default.GetBytes(pToEncrypt);//把字符串放到byte數組中
           MemoryStream ms = new MemoryStream();//創建其支持存儲區爲內存的流　
         
           CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
           cs.Write(inputbyteArray, 0, inputbyteArray.Length);
           cs.FlushFinalBlock();//上面已經完成了把加密後的結果放到內存中去


           StringBuilder ret = new StringBuilder();
           foreach (byte b in ms.ToArray())
           {
               ret.AppendFormat("{0:X2}", b);
           
          
           }
           return ret.ToString();



       }
      
           

       /// <summary>
       /// 解密ESC函數
       /// </summary>
       /// <param name="pToDecrypt">被解密的字符串</param>
       /// <param name="sKey">密鑰（只支持8個字節的密鑰，同前面的加密密鑰相同）</param>
       /// <returns>返回被解密的字符串</returns>

       public  string DeCrypt(string pToDecrypt)
       {

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

               inputbyteArray[i] = (byte)x;
          
           }
           des.Key = ASCIIEncoding.ASCII.GetBytes(skey);
           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();


           return System.Text.Encoding.Default.GetString(ms.ToArray());

       }

       public DescMD5() { }



    }