<?php

      //------------------------------------------------------------------------------------
      function evalCrossTotal($strMD5)
      {
          $intTotal = 0;
          $arrMD5Chars = str_split($strMD5, 1);
          foreach ($arrMD5Chars as $value)
          {
              $intTotal += '0x0'.$value;
          }
          return $intTotal;
      }//-----------------------------------------------------------------------------------



      //------------------------------------------------------------------------------------
      function encryptString($strString, $strPassword)
      {
          // $strString is the content of the entire file with serials
          $strPasswordMD5 = md5($strPassword);
          $intMD5Total = evalCrossTotal($strPasswordMD5);
          $arrEncryptedValues = array();
          $intStrlen = strlen($strString);
          for ($i=0; $i<$intStrlen; $i++)
          {
              $arrEncryptedValues[] =  ord(substr($strString, $i, 1))
                                       +  ('0x0' . substr($strPasswordMD5, $i%32, 1))
                                       -  $intMD5Total;
              $intMD5Total = evalCrossTotal(substr(md5(substr($strString,0,$i+1)), 0, 16)
                                       .  substr(md5($intMD5Total), 0, 16));
          }
          return implode(' ' , $arrEncryptedValues);
      }//-----------------------------------------------------------------------------------

    ?>