CryptLib/Random/Source/MTRand.php

   1 <?php
   2 /**
   3  * The MTRand Random Number Source
   4  *
   5  * This source generates low strength random numbers by using the internal
   6  * mt_rand() function.  By itself it is quite weak.  However when combined with
   7  * other sources it does provide significant benefit.
   8  *
   9  * PHP version 5.3
  10  *
  11  * @category   PHPCryptLib
  12  * @package    Random
  13  * @subpackage Source
  14  * @author     Anthony Ferrara <ircmaxell@ircmaxell.com>
  15  * @copyright  2011 The Authors
  16  * @license    http://www.opensource.org/licenses/mit-license.html  MIT License
  17  * @version    Build @@version@@
  18  */
  19
  20 namespace CryptLib\Random\Source;
  21
  22 use CryptLib\Core\Strength;
  23
  24 /**
  25  * The MTRand Random Number Source
  26  *
  27  * This source generates low strength random numbers by using the internal
  28  * mt_rand() function.  By itself it is quite weak.  However when combined with
  29  * other sources it does provide significant benefit.
  30  *
  31  * @category   PHPCryptLib
  32  * @package    Random
  33  * @subpackage Source
  34  * @author     Anthony Ferrara <ircmaxell@ircmaxell.com>
  35  * @codeCoverageIgnore
  36  */
  37 class MTRand implements \CryptLib\Random\Source {
  38
  39     /**
  40      * Return an instance of Strength indicating the strength of the source
  41      *
  42      * @return Strength An instance of one of the strength classes
  43      */
  44     public static function getStrength() {
  45         // Detect if Suhosin Hardened PHP patch is applied
  46         if (defined('S_ALL')) {
  47             return new Strength(Strength::MEDIUM);
  48         } else {
  49             return new Strength(Strength::LOW);
  50         }
  51     }
  52
  53     /**
  54      * Generate a random string of the specified size
  55      *
  56      * @param int $size The size of the requested random string
  57      *
  58      * @return string A string of the requested size
  59      */
  60     public function generate($size) {
  61         $result = '';
  62         for ($i = 0; $i < $size; $i++) {
  63             $result .= chr((mt_rand() ^ mt_rand()) % 256);
  64         }
  65         return $result;
  66     }
  67
  68 }