CryptLib/Encryption/PackingMode/ANSIx923.php

   1 <?php
   2 /**
   3  * A packing mode implementation for ASNIx923 padding
   4  *
   5  * PHP version 5.3
   6  *
   7  * @category   PHPCryptLib
   8  * @package    Encryption
   9  * @subpackage PackingMode
  10  * @author     Anthony Ferrara <ircmaxell@ircmaxell.com>
  11  * @copyright  2011 The Authors
  12  * @license    http://www.opensource.org/licenses/mit-license.html  MIT License
  13  * @version    Build @@version@@
  14  */
  15
  16 namespace CryptLib\Encryption\PackingMode;
  17
  18 /**
  19  * A packing mode implementation for ASNIx923 padding
  20  *
  21  * @category   PHPCryptLib
  22  * @package    Encryption
  23  * @subpackage PackingMode
  24  * @author     Anthony Ferrara <ircmaxell@ircmaxell.com>
  25  */
  26 class ANSIx923 implements \CryptLib\Encryption\PackingMode {
  27
  28     /**
  29      * Pad the string to the specified size
  30      *
  31      * @param string $string    The string to pad
  32      * @param int    $blockSize The size to pad to
  33      *
  34      * @return string The padded string
  35      */
  36     public function pad($string, $blockSize = 32) {
  37         $pad = $blockSize - (strlen($string) % $blockSize);
  38         return $string . str_repeat(chr(0), $pad - 1) . chr($pad);
  39     }
  40
  41     /**
  42      * Strip the padding from the supplied string
  43      *
  44      * @param string $string The string to trim
  45      *
  46      * @return string The unpadded string
  47      */
  48     public function strip($string) {
  49         $end = ord(substr($string, -1));
  50         $len = strlen($string) - $end;
  51         $tmp = str_repeat(chr(0), $end - 1) . chr($end);
  52         if (substr($string, $len) == $tmp) {
  53             return substr($string, 0, $len);
  54         }
  55         return false;
  56     }
  57
  58 }