DES加密、解密

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

    /// <summary>
    /// SymmetricMethod 的摘要说明。
    /// 对称算法加密类，提供系统默认密钥，与用户密码两种方式
    /// </summary>
public class SymmetricMethod
{
    #region DES加密、解密
    private static TripleDES mydes = new TripleDESCryptoServiceProvider();
    public const string IV = "DSi5F:8y#s^:4>Ea";
    public const string KEY = "$fH5#$DFs9khg6#>z[5lkd3&@u3{P[.e";

    /**/
    /// <summary>
    /// 获得密钥
    /// </summary>
    /// <returns>密钥</returns>
    private static byte[] GetLegalKey()
    {
        string sTemp = KEY;
        mydes.GenerateKey();
        byte[] bytTemp = mydes.Key;
        int KeyLength = bytTemp.Length;
        if (sTemp.Length > KeyLength)
            sTemp = sTemp.Substring(0, KeyLength);
        else if (sTemp.Length < KeyLength)
            sTemp = sTemp.PadRight(KeyLength, ' ');
        return ASCIIEncoding.ASCII.GetBytes(sTemp);
    }
    /**/
    /// <summary>
    /// 获得初始向量IV
    /// </summary>
    /// <returns>初试向量IV</returns>
    private static byte[] GetLegalIV()
    {
        string sTemp = IV;
        mydes.GenerateIV();
        byte[] bytTemp = mydes.IV;
        int IVLength = bytTemp.Length;
        if (sTemp.Length > IVLength)
            sTemp = sTemp.Substring(0, IVLength);
        else if (sTemp.Length < IVLength)
            sTemp = sTemp.PadRight(IVLength, ' ');
        return ASCIIEncoding.ASCII.GetBytes(sTemp);
    }
    /**/
    /// <summary>
    /// 加密方法
    /// </summary>
    /// <param name="Source">待加密的串</param>
    /// <returns>经过加密的串</returns>
    public static string DESEncrypt(string Source)
    {
        try
        {
            byte[] bytIn = UTF8Encoding.UTF8.GetBytes(Source);
            MemoryStream ms = new MemoryStream();
            mydes.Key = GetLegalKey();
            mydes.IV = GetLegalIV();
            ICryptoTransform encrypto = mydes.CreateEncryptor();
            CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write);
            cs.Write(bytIn, 0, bytIn.Length);
            cs.FlushFinalBlock();
            ms.Close();
            byte[] bytOut = ms.ToArray();
            return Convert.ToBase64String(bytOut);
        }
        catch (Exception ex)
        {
            return string.Empty;
        }
    }
    /**/
    /// <summary>
    /// 解密方法
    /// </summary>
    /// <param name="Source">待解密的串</param>
    /// <returns>经过解密的串</returns>
    public static string DESDecrypt(string Source)
    {
        try
        {
            byte[] bytIn = Convert.FromBase64String(Source);
            MemoryStream ms = new MemoryStream(bytIn, 0, bytIn.Length);
            mydes.Key = GetLegalKey();
            mydes.IV = GetLegalIV();
            ICryptoTransform encrypto = mydes.CreateDecryptor();
            CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read);
            StreamReader sr = new StreamReader(cs);
            return sr.ReadToEnd();
        }
        catch
        {
            return string.Empty;
        }
    }
    #endregion
}