<?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;
   }
  }
 }
}