CryptLib/Random/AbstractMixer.php

   1 <?php
   2 /**
   3  * An abstract mixer to implement a common mixing strategy
   4  *
   5  * PHP version 5.3
   6  *
   7  * @category  PHPCryptLib
   8  * @package   Random
   9  * @author    Anthony Ferrara <ircmaxell@ircmaxell.com>
  10  * @copyright 2011 The Authors
  11  * @license    http://www.opensource.org/licenses/mit-license.html  MIT License
  12  * @version   Build @@version@@
  13  */
  14
  15 namespace CryptLib\Random;
  16
  17 /**
  18  * An abstract mixer to implement a common mixing strategy
  19  *
  20  * @see      http://tools.ietf.org/html/rfc4086#section-5.2
  21  * @category PHPCryptLib
  22  * @package  Random
  23  * @author   Anthony Ferrara <ircmaxell@ircmaxell.com>
  24  */
  25 abstract class AbstractMixer implements \CryptLib\Random\Mixer {
  26
  27     /**
  28      * Get the block size (the size of the individual blocks used for the mixing)
  29      *
  30      * @return int The block size
  31      */
  32     abstract protected function getPartSize();
  33
  34     /**
  35      * Mix 2 parts together using one method
  36      *
  37      * @param string $part1 The first part to mix
  38      * @param string $part2 The second part to mix
  39      *
  40      * @return string The mixed data
  41      */
  42     abstract protected function mixParts1($part1, $part2);
  43
  44     /**
  45      * Mix 2 parts together using another different method
  46      *
  47      * @param string $part1 The first part to mix
  48      * @param string $part2 The second part to mix
  49      *
  50      * @return string The mixed data
  51      */
  52     abstract protected function mixParts2($part1, $part2);
  53
  54     /**
  55      * Mix the provided array of strings into a single output of the same size
  56      *
  57      * All elements of the array should be the same size.
  58      *
  59      * @param array $parts The parts to be mixed
  60      *
  61      * @return string The mixed result
  62      */
  63     public function mix(array $parts) {
  64         if (empty($parts)) {
  65             return '';
  66         }
  67         $len        = strlen($parts[0]);
  68         $parts      = $this->normalizeParts($parts);
  69         $stringSize = count($parts[0]);
  70         $partsSize  = count($parts);
  71         $result     = '';
  72         $offset     = 0;
  73         for ($i = 0; $i < $stringSize; $i++) {
  74             $stub = $parts[$offset][$i];
  75             for ($j = 1; $j < $partsSize; $j++) {
  76                 $newKey = $parts[($j + $offset) % $partsSize][$i];
  77                 //Alternately mix the output for each source
  78                 if ($j % 2 == 1) {
  79                     $stub ^= $this->mixParts1($stub, $newKey);
  80                 } else {
  81                     $stub ^= $this->mixParts2($stub, $newKey);
  82                 }
  83             }
  84             $result .= $stub;
  85             $offset  = ($offset + 1) % $partsSize;
  86         }
  87         return substr($result, 0, $len);
  88     }
  89
  90     /**
  91      * Normalize the part array and split it block part size.
  92      *
  93      * This will make all parts the same length and a multiple
  94      * of the part size
  95      *
  96      * @param array $parts The parts to normalize
  97      *
  98      * @return array The normalized and split parts
  99      */
 100     protected function normalizeParts(array $parts) {
 101         $blockSize = $this->getPartSize();
 102         $callback  = function($value) {
 103             return strlen($value);
 104         };
 105         $maxSize = max(array_map($callback, $parts));
 106         if ($maxSize % $blockSize != 0) {
 107             $maxSize += $blockSize - ($maxSize % $blockSize);
 108         }
 109         foreach ($parts as &$part) {
 110             $part = str_pad($part, $maxSize, chr(0));
 111             $part = str_split($part, $blockSize);
 112         }
 113         return $parts;
 114     }
 115 }