用C＃實現Des加密和解密

using System;
using System.IO;
using System.Security.Cryptography;
namespace Vavic
{
/// <summary>
/// Security 的摘要說明。
/// </summary>
public class Security
{
const string KEY_64 = "VavicApp";
const string IV_64 = "VavicApp"; //注意了，是8個字元，64位
public Security()
{
//
// TODO: 在此處添加建構函式邏輯
//
}
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();
}
}
}