用C＃实现Des加密和解密

using System;
using System.IO;
using System.Security.Cryptography;

namespace Vavic
{
 /// <summary>
 /// Security 的摘要说明。
 /// </summary>
 public class Security
 {
  const string KEY_64 = "VavicApp";
  const string IV_64 = "VavicApp"; //注意了，是8个字符，64位

  public Security()
  {
   //
   // TODO: 在此处添加构造函数逻辑
   //
  }

  public static string Encode(string data)
  {
   byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64);
   byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64);

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

  public static string Decode(string data)
  {   
   byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64);
   byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64);

   byte[] byEnc;
   try
   {
    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();
  }
 }
}