[Sommaire] [Imprimer]

   1  <?php
   2  /**
   3   * The Horde_Cipher_BlockMode_cbc:: This class implements the
   4   * Horde_Cipher_BlockMode using the Cipher Block Chaining method of
   5   * encrypting blocks of data.
   6   *
   7   * $Horde: framework/Cipher/Cipher/BlockMode/cbc.php,v 1.7.12.5 2006/01/01 21:28:11 jan Exp $
   8   *
   9   * Copyright 2002-2006 Mike Cochrane <mike@graftonhall.co.nz>
  10   *
  11   * See the enclosed file COPYING for license information (LGPL). If you
  12   * did not receive this file, see http://www.fsf.org/copyleft/lgpl.html.
  13   *
  14   * @author  Mike Cochrane <mike@graftonhall.co.nz>
  15   * @since   Horde 2.2
  16   * @package Horde_Cipher
  17   */
  18  class Horde_Cipher_BlockMode_cbc extends Horde_Cipher_BlockMode {
  19  
  20      /**
  21       * Encrypt a string.
  22       *
  23       * @param Horde_Cipher $cipher  Cipher algorithm to use for
  24       *                              encryption.
  25       * @param string $plaintext     The data to encrypt.
  26       *
  27       * @return  The encrypted data.
  28       */
  29      function encrypt(&$cipher, $plaintext)
  30      {
  31          $encrypted = '';
  32  
  33          $blocksize = $cipher->getBlockSize();
  34          $previousCipher = $this->_iv;
  35  
  36          $jMax = strlen($plaintext);
  37          for ($j = 0; $j < $jMax; $j += $blocksize) {
  38              $plain = substr($plaintext, $j, $blocksize);
  39  
  40              if (strlen($plain) < $blocksize) {
  41                  // pad the block with \0's if it's not long enough
  42                  $plain = str_pad($plain, 8, "\0");
  43              }
  44  
  45              $plain = $plain ^ $previousCipher;
  46              $previousCipher = $cipher->encryptBlock($plain);
  47              $encrypted .= $previousCipher;
  48          }
  49  
  50          return $encrypted;
  51      }
  52  
  53      /**
  54       * Decrypt a string.
  55       *
  56       * @param Horde_Cipher $cipher  Cipher algorithm to use for
  57       *                              decryption.
  58       * @param string $ciphertext    The data to decrypt.
  59       *
  60       * @return  The decrypted data.
  61       */
  62      function decrypt(&$cipher, $ciphertext)
  63      {
  64          $decrypted = '';
  65  
  66          $blocksize = $cipher->getBlockSize();
  67          $previousCipher = $this->_iv;
  68  
  69          $jMax = strlen($ciphertext);
  70          for ($j = 0; $j < $jMax; $j += $blocksize) {
  71              $plain = substr($ciphertext, $j, $blocksize);
  72              $decrypted .= $cipher->decryptBlock($plain) ^ $previousCipher;
  73              $previousCipher = $plain;
  74          }
  75  
  76          // Remove trailing \0's used to pad the last block.
  77          while (substr($decrypted, -1, 1) == "\0") {
  78              $decrypted = substr($decrypted, 0, -1);
  79          }
  80  
  81          return $decrypted;
  82      }
  83  
  84  }