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();
        }
    }
}