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

namespace Des
{
    class Program
    {

        public static string Encode(string data, string Key) //加密
        {
            byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(Key);
            byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(Key);
            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, string Key) //解密
        {
            byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(Key);
            byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(Key);
            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();
        }
        static void Main(string[] args)
        {
            string ecode;
            string dcode;
            ecode = Encode("Hello word,this is a testing", "qwertyui");
            Console.Write(ecode);
            Console.Write("\r\n");
            dcode = Decode(ecode, "qwertyui");
            Console.Write(dcode);
            Console.Write("\r\n");
        }
    }
}


输出:

E:\C#\Des\Des\bin\Debug>Des.exe
Zz8EouQdHsvcw4oB4IdNV5QFIyyLbYd2PCX1k4kvod0=
Hello word,this is a testing