这个C#类封装的DES加密解密，可以使用默认秘钥进行加密、解密，也可以自定义秘钥进行加密、解密，调用简单方便。

using System;
using System.Security.Cryptography; 
using System.Text;
namespace DotNet.Utilities
{
    /// <summary>
    /// DES加密/解密类。
    /// </summary>
    public class DESEncrypt
    {
        public DESEncrypt()
        {          
        }
 
        #region ========加密========
  
        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="Text"></param>
        /// <returns></returns>
        public static string Encrypt(string Text)
        {
            return Encrypt(Text,"sharejs.com");
        }
        /// <summary>
        /// 加密数据
        /// </summary>
        /// <param name="Text"></param>
        /// <param name="sKey"></param>
        /// <returns></returns>
        public static string Encrypt(string Text,string sKey)
        {
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            byte[] inputByteArray;
            inputByteArray=Encoding.Default.GetBytes(Text);
            des.Key = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8));
            des.IV = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8));
            System.IO.MemoryStream ms=new System.IO.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);
            }
            return ret.ToString();
        }
 
        #endregion
         
        #region ========解密========
    
  
        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="Text"></param>
        /// <returns></returns>
        public static string Decrypt(string Text)
        {
            return Decrypt(Text,"sharejs.com");
        }
        /// <summary>
        /// 解密数据
        /// </summary>
        /// <param name="Text"></param>
        /// <param name="sKey"></param>
        /// <returns></returns>
        public static string Decrypt(string Text,string sKey)
        {
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            int len;
            len=Text.Length/2;
            byte[] inputByteArray = new byte[len];
            int x,i;
            for(x=0;x<len;x++)
            {
                i = Convert.ToInt32(Text.Substring(x * 2, 2), 16);
                inputByteArray[x]=(byte)i;
            }
            des.Key = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8));
            des.IV = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8));
            System.IO.MemoryStream ms=new System.IO.MemoryStream();
            CryptoStream cs=new CryptoStream(ms,des.CreateDecryptor(),CryptoStreamMode.Write);
            cs.Write(inputByteArray,0,inputByteArray.Length);
            cs.FlushFinalBlock();
            return Encoding.Default.GetString(ms.ToArray());
        }
  
        #endregion
 
 
    }
}