[Sommaire] [Imprimer]

   1  <?php
   2  /**
   3   * The Horde_Cipher_BlockMode_cfb64:: This class implements the
   4   * Horde_Cipher_BlockMode using a 64 bit cipher feedback.
   5   *
   6   * This can be used to encrypt any length string and the encrypted
   7   * version will be the same length.
   8   *
   9   * $Horde: framework/Cipher/Cipher/BlockMode/cfb64.php,v 1.7.12.5 2006/01/01 21:28:11 jan Exp $
  10   *
  11   * Copyright 2002-2006 Mike Cochrane <mike@graftonhall.co.nz>
  12   *
  13   * See the enclosed file COPYING for license information (LGPL). If you
  14   * did not receive this file, see http://www.fsf.org/copyleft/lgpl.html.
  15   *
  16   * @author  Mike Cochrane <mike@graftonhall.co.nz>
  17   * @since   Horde 2.2
  18   * @package Horde_Cipher
  19   */
  20  class Horde_Cipher_BlockMode_cfb64 extends Horde_Cipher_BlockMode {
  21  
  22      /**
  23       * Encrypt a string.
  24       *
  25       * @param Horde_Cipher $cipher  Cipher algorithm to use for
  26       *                              encryption.
  27       * @param string $plaintext     The data to encrypt.
  28       *
  29       * @return  The encrypted data.
  30       */
  31      function encrypt(&$cipher, $plaintext)
  32      {
  33          $encrypted = '';
  34  
  35          $n = 0;
  36          $jMax = strlen($plaintext);
  37          for ($j = 0; $j < $jMax; $j++) {
  38              if ($n == 0) {
  39                  $this->_iv = $cipher->encryptBlock($this->_iv);
  40              }
  41  
  42              $c = $plaintext[$j] ^ $this->_iv[$n];
  43              $this->_iv = substr($this->_iv, 0, $n) . $c . substr($this->_iv, $n + 1);
  44              $encrypted .= $c;
  45  
  46              $n = (++$n) & 0x07;
  47          }
  48  
  49          return $encrypted;
  50      }
  51  
  52      /**
  53       * Decrypt a string.
  54       *
  55       * @param Horde_Cipher $cipher  Cipher algorithm to use for
  56       *                              decryption.
  57       * @param string $ciphertext    The data to decrypt.
  58       *
  59       * @return  The decrypted data.
  60       */
  61      function decrypt(&$cipher, $ciphertext)
  62      {
  63          $decrypted = '';
  64  
  65          $n = 0;
  66          $jMax = strlen($ciphertext);
  67          for ($j = 0; $j < $jMax; $j++) {
  68              if ($n == 0) {
  69                  $this->_iv = $cipher->encryptBlock($this->_iv);
  70              }
  71  
  72              $c = $ciphertext[$j] ^ $this->_iv[$n];
  73              $this->_iv = substr($this->_iv, 0, $n) . substr($ciphertext, $j, 1) . substr($this->_iv, $n + 1);
  74              $decrypted .= $c;
  75  
  76              $n = (++$n) & 0x07;
  77          }
  78  
  79          // Remove trailing \0's used to pad the last block.
  80          while (substr($decrypted, -1, 1) == "\0") {
  81              $decrypted = substr($decrypted, 0, -1);
  82          }
  83  
  84          return $decrypted;
  85      }
  86  
  87  }