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

/// <summary>
/// Des 的摘要说明
/// </summary>
public class Des
{
    public Des()
    {        
    }

    public static string Encrypt(string stringToEncrypt, string sKey)
    {
        DESCryptoServiceProvider des = new DESCryptoServiceProvider();
        byte[] inputByteArray = Encoding.GetEncoding("UTF-8").GetBytes(stringToEncrypt);
        des.Key = ASCIIEncoding.UTF8.GetBytes(sKey);
        des.IV = ASCIIEncoding.UTF8.GetBytes(sKey);
        MemoryStream ms = new MemoryStream();
        CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
        cs.Write(inputByteArray, 0, inputByteArray.Length);
        cs.FlushFinalBlock();
        StringBuilder ret = new StringBuilder();
        foreach (byte b in ms.ToArray())
        {
            ret.AppendFormat("{0:X2}", b);
        }
        ret.ToString();
        return ret.ToString();
    }


    public static string Decrypt(string stringToDecrypt, string sKey)
    {
        DESCryptoServiceProvider des = new DESCryptoServiceProvider();
        byte[] inputByteArray = new byte[stringToDecrypt.Length / 2];
        for (int x = 0; x < stringToDecrypt.Length / 2; x++)
        {
            int i = (Convert.ToInt32(stringToDecrypt.Substring(x * 2, 2), 16));
            inputByteArray[x] = (byte)i;
        }
        des.Key = ASCIIEncoding.UTF8.GetBytes(sKey);
        des.IV = ASCIIEncoding.UTF8.GetBytes(sKey);
        MemoryStream ms = new MemoryStream();
        CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);
        cs.Write(inputByteArray, 0, inputByteArray.Length);
        cs.FlushFinalBlock();
        StringBuilder ret = new StringBuilder();
        return System.Text.Encoding.Default.GetString(ms.ToArray());
    }
}

        string key = "cba1238b";

        string abc= Des.Encrypt("abc", key);
        Response.Write(abc);
        Response.Write("<hr>");
        string abc2 = Des.Decrypt(abc, key);
        Response.Write(abc2);