php DES加密算法实例分析

?php
/**
 *@see Yii CSecurityManager;
 */
class Des{
 public static function encrypt($data,$key){
   $module=mcrypt_module_open('des','', MCRYPT_MODE_CBC,'');
   $key=substr(md5($key),0,mcrypt_enc_get_key_size($module));
   srand();
   $iv=mcrypt_create_iv(mcrypt_enc_get_iv_size($module), MCRYPT_RAND);
   mcrypt_generic_init($module,$key,$iv);
   $encrypted=$iv.mcrypt_generic($module,$data);
   mcrypt_generic_deinit($module);
   mcrypt_module_close($module);
   return md5($data).'_'.base64_encode($encrypted);
 }
 public static function decrypt($data,$key){  
   $_data = explode('_',$data,2);
   if(count($_data)2){
    return false;
   }
   $data = base64_decode($_data[1]);   
   $module=mcrypt_module_open('des','', MCRYPT_MODE_CBC,'');
   $key=substr(md5($key),0,mcrypt_enc_get_key_size($module));
   $ivSize=mcrypt_enc_get_iv_size($module);
   $iv=substr($data,0,$ivSize);
   mcrypt_generic_init($module,$key,$iv);
   $decrypted=mdecrypt_generic($module,substr($data,$ivSize,strlen($data)));
   mcrypt_generic_deinit($module);
   mcrypt_module_close($module);
   $decrypted = rtrim($decrypted,"\0");    
   if($_data[0]!=md5($decrypted)){
    return false;
   }
   return $decrypted;
 }
}

?php
class STD3Des
{
  private $key = "";
  private $iv = "";
  /**
  * 构造，传递二个已经进行base64_encode的KEY与IV
  *
  * @param string $key
  * @param string $iv
  */
  function __construct ($key, $iv)
  {
    if (empty($key) || empty($iv)) {
      echo 'key and iv is not valid';
      exit();
    }
    $this->key = $key;
    $this->iv = $iv;
  }
  /**
  *加密
  * @param type> $value
  * @return type>
  */
  public function encrypt ($value)
  {
    $td = mcrypt_module_open(MCRYPT_3DES, '', MCRYPT_MODE_CBC, '');
    $iv = base64_decode($this->iv);
    $value = $this->PaddingPKCS7($value);
    $key = base64_decode($this->key);
    mcrypt_generic_init($td, $key, $iv);
    $ret = base64_encode(mcrypt_generic($td, $value));
    mcrypt_generic_deinit($td);
    mcrypt_module_close($td);
    return $ret;
  }
  /**
  *解密
  * @param type> $value
  * @return type>
  */
  public function decrypt ($value)
  {
    $td = mcrypt_module_open(MCRYPT_3DES, '', MCRYPT_MODE_CBC, '');
    $iv = base64_decode($this->iv);
    $key = base64_decode($this->key);
    mcrypt_generic_init($td, $key, $iv);
    $ret = trim(mdecrypt_generic($td, base64_decode($value)));
    $ret = $this->UnPaddingPKCS7($ret);
    mcrypt_generic_deinit($td);
    mcrypt_module_close($td);
    return $ret;
  }
  private function PaddingPKCS7 ($data)
  {
    $block_size = mcrypt_get_block_size('tripledes', 'cbc');
    $padding_char = $block_size - (strlen($data) % $block_size);
    $data .= str_repeat(chr($padding_char), $padding_char);
    return $data;
  }
  private function UnPaddingPKCS7($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);
  }
}
?>