<?php
class DES
{
    var $key;
    var $iv; //偏移量
   
    function DES($key = '11001100', $iv=0 ) {
    //key长度8例如:1234abcd
        $this->key = $key;
        if( $iv == 0 ) {
            $this->iv = $key; //默认以$key 作为 iv
        } else {
            $this->iv = $iv; //mcrypt_create_iv ( mcrypt_get_block_size (MCRYPT_DES, MCRYPT_MODE_CBC), MCRYPT_DEV_RANDOM );
        }
    }
   
    function encrypt($str) {
    //加密，返回大写十六进制字符串
        $size = mcrypt_get_block_size ( MCRYPT_DES, MCRYPT_MODE_CBC );
        $str = $this->pkcs5Pad ( $str, $size );
        return strtoupper( bin2hex( mcrypt_cbc(MCRYPT_DES, $this->key, $str, MCRYPT_ENCRYPT, $this->iv ) ) );
    }
   
    function decrypt($str) {
    //解密
        $strBin = $this->hex2bin( strtolower( $str ) );
        $str = mcrypt_cbc( MCRYPT_DES, $this->key, $strBin, MCRYPT_DECRYPT, $this->iv );
        $str = $this->pkcs5Unpad( $str );
        return $str;
    }
   
    function hex2bin($hexData) {
        $binData = "";
        for($i = 0; $i < strlen ( $hexData ); $i += 2) {
            $binData .= chr ( hexdec ( substr ( $hexData, $i, 2 ) ) );
        }
        return $binData;
    }

    function pkcs5Pad($text, $blocksize) {
        $pad = $blocksize - (strlen ( $text ) % $blocksize);
        return $text . str_repeat ( chr ( $pad ), $pad );
    }
   
    function pkcs5Unpad($text) {
        $pad = ord ( $text {strlen ( $text ) - 1} );
        if ($pad > strlen ( $text ))
            return false;
        if (strspn ( $text, chr ( $pad ), strlen ( $text ) - $pad ) != $pad)
            return false;
        return substr ( $text, 0, - 1 * $pad );
    }
   
}
?>

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

namespace WindowsFormsApplication1
{
    /// <summary>
    /// DES加密解密字符串
    /// </summary>
    public class DesEncryption
    {
        /// <summary>
        /// DES加密字符串
        /// </summary>
        /// <param name="encryptString">待加密的字符串</param>
        /// <param name="encryptKey">加密密钥,要求为8位</param>
        /// <returns>加密成功返回加密后的字符串，失败返回null</returns>
        public static string EncryptDES(string encryptString, string encryptKey = "11001100")
        {
            try
            {
                byte[] rgbKey = ASCIIEncoding.ASCII.GetBytes(encryptKey.Substring(0, 8));
                byte[] rgbIV = rgbKey;
                byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptString);
                DESCryptoServiceProvider dCSP = new DESCryptoServiceProvider();
                MemoryStream mStream = new MemoryStream();
                CryptoStream cStream = new CryptoStream(mStream, dCSP.CreateEncryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
                cStream.Write(inputByteArray, 0, inputByteArray.Length);
                cStream.FlushFinalBlock();
                StringBuilder ret = new StringBuilder();
                foreach (byte b in mStream.ToArray())
                {
                    ret.AppendFormat("{0:X2}", b);
                }
                ret.ToString();
                return ret.ToString();
            }
            catch
            {
                return null;
            }
        }

        /// <summary>
        /// DES解密字符串
        /// </summary>
        /// <param name="decryptString">待解密的字符串</param>
        /// <param name="decryptKey">解密密钥,要求为8位,和加密密钥相同</param>
        /// <returns>解密成功返回解密后的字符串，失败返回null</returns>
        public static string DecryptDES(string decryptString, string decryptKey = "11001100")
        {
            try
            {
                byte[] rgbKey = ASCIIEncoding.ASCII.GetBytes(decryptKey);
                byte[] rgbIV = rgbKey;
                byte[] inputByteArray = new byte[decryptString.Length / 2];
                for (int x = 0; x < decryptString.Length / 2; x++)
                {
                    int i = (Convert.ToInt32(decryptString.Substring(x * 2, 2), 16));
                    inputByteArray[x] = (byte)i;
                }           
                DESCryptoServiceProvider DCSP = new DESCryptoServiceProvider();
                MemoryStream mStream = new MemoryStream();
                CryptoStream cStream = new CryptoStream(mStream, DCSP.CreateDecryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
                cStream.Write(inputByteArray, 0, inputByteArray.Length);
                cStream.FlushFinalBlock();
                return Encoding.UTF8.GetString(mStream.ToArray());
            }
            catch
            {
                return null;
            }
        }
    }
}