493 lines
14 KiB
PHP
493 lines
14 KiB
PHP
<?php
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/* vim: set expandtab tabstop=4 shiftwidth=4 softtabstop=4: */
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/**
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* Pure-PHP implementation of RC4.
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*
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* Uses mcrypt, if available, and an internal implementation, otherwise.
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*
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* PHP versions 4 and 5
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*
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* Useful resources are as follows:
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*
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* - {@link http://www.mozilla.org/projects/security/pki/nss/draft-kaukonen-cipher-arcfour-03.txt ARCFOUR Algorithm}
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* - {@link http://en.wikipedia.org/wiki/RC4 - Wikipedia: RC4}
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*
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* RC4 is also known as ARCFOUR or ARC4. The reason is elaborated upon at Wikipedia. This class is named RC4 and not
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* ARCFOUR or ARC4 because RC4 is how it is refered to in the SSH1 specification.
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*
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* Here's a short example of how to use this library:
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* <code>
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* <?php
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* include('Crypt/RC4.php');
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*
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* $rc4 = new Crypt_RC4();
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*
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* $rc4->setKey('abcdefgh');
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*
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* $size = 10 * 1024;
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* $plaintext = '';
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* for ($i = 0; $i < $size; $i++) {
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* $plaintext.= 'a';
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* }
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*
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* echo $rc4->decrypt($rc4->encrypt($plaintext));
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* ?>
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* </code>
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*
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* LICENSE: This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*
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* @category Crypt
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* @package Crypt_RC4
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* @author Jim Wigginton <terrafrost@php.net>
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* @copyright MMVII Jim Wigginton
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* @license http://www.gnu.org/licenses/lgpl.txt
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* @version $Id$
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* @link http://phpseclib.sourceforge.net
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*/
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/**#@+
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* @access private
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* @see Crypt_RC4::Crypt_RC4()
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*/
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/**
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* Toggles the internal implementation
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*/
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define('CRYPT_RC4_MODE_INTERNAL', 1);
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/**
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* Toggles the mcrypt implementation
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*/
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define('CRYPT_RC4_MODE_MCRYPT', 2);
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/**#@-*/
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/**#@+
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* @access private
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* @see Crypt_RC4::_crypt()
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*/
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define('CRYPT_RC4_ENCRYPT', 0);
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define('CRYPT_RC4_DECRYPT', 1);
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/**#@-*/
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/**
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* Pure-PHP implementation of RC4.
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*
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* @author Jim Wigginton <terrafrost@php.net>
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* @version 0.1.0
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* @access public
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* @package Crypt_RC4
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*/
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class Crypt_RC4 {
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/**
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* The Key
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*
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* @see Crypt_RC4::setKey()
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* @var String
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* @access private
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*/
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var $key = "\0";
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/**
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* The Key Stream for encryption
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*
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* If CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT, this will be equal to the mcrypt object
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*
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* @see Crypt_RC4::setKey()
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* @var Array
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* @access private
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*/
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var $encryptStream = false;
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/**
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* The Key Stream for decryption
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*
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* If CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT, this will be equal to the mcrypt object
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*
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* @see Crypt_RC4::setKey()
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* @var Array
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* @access private
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*/
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var $decryptStream = false;
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/**
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* The $i and $j indexes for encryption
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*
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* @see Crypt_RC4::_crypt()
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* @var Integer
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* @access private
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*/
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var $encryptIndex = 0;
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/**
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* The $i and $j indexes for decryption
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*
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* @see Crypt_RC4::_crypt()
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* @var Integer
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* @access private
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*/
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var $decryptIndex = 0;
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/**
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* MCrypt parameters
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*
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* @see Crypt_RC4::setMCrypt()
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* @var Array
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* @access private
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*/
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var $mcrypt = array('', '');
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/**
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* The Encryption Algorithm
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*
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* Only used if CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT. Only possible values are MCRYPT_RC4 or MCRYPT_ARCFOUR.
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*
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* @see Crypt_RC4::Crypt_RC4()
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* @var Integer
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* @access private
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*/
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var $mode;
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/**
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* Default Constructor.
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*
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* Determines whether or not the mcrypt extension should be used.
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*
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* @param optional Integer $mode
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* @return Crypt_RC4
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* @access public
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*/
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function Crypt_RC4()
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{
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if ( !defined('CRYPT_RC4_MODE') ) {
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switch (true) {
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case extension_loaded('mcrypt') && (defined('MCRYPT_ARCFOUR') || defined('MCRYPT_RC4')):
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// i'd check to see if rc4 was supported, by doing in_array('arcfour', mcrypt_list_algorithms('')),
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// but since that can be changed after the object has been created, there doesn't seem to be
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// a lot of point...
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define('CRYPT_RC4_MODE', CRYPT_RC4_MODE_MCRYPT);
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break;
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default:
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define('CRYPT_RC4_MODE', CRYPT_RC4_MODE_INTERNAL);
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}
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}
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switch ( CRYPT_RC4_MODE ) {
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case CRYPT_RC4_MODE_MCRYPT:
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switch (true) {
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case defined('MCRYPT_ARCFOUR'):
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$this->mode = MCRYPT_ARCFOUR;
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break;
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case defined('MCRYPT_RC4');
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$this->mode = MCRYPT_RC4;
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}
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}
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}
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/**
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* Sets the key.
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*
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* Keys can be between 1 and 256 bytes long. If they are longer then 256 bytes, the first 256 bytes will
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* be used. If no key is explicitly set, it'll be assumed to be a single null byte.
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*
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* @access public
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* @param String $key
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*/
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function setKey($key)
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{
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$this->key = $key;
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if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT ) {
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return;
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}
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$keyLength = strlen($key);
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$keyStream = array();
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for ($i = 0; $i < 256; $i++) {
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$keyStream[$i] = $i;
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}
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$j = 0;
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for ($i = 0; $i < 256; $i++) {
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$j = ($j + $keyStream[$i] + ord($key[$i % $keyLength])) & 255;
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$temp = $keyStream[$i];
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$keyStream[$i] = $keyStream[$j];
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$keyStream[$j] = $temp;
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}
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$this->encryptIndex = $this->decryptIndex = array(0, 0);
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$this->encryptStream = $this->decryptStream = $keyStream;
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}
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/**
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* Dummy function.
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*
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* Some protocols, such as WEP, prepend an "initialization vector" to the key, effectively creating a new key [1].
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* If you need to use an initialization vector in this manner, feel free to prepend it to the key, yourself, before
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* calling setKey().
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*
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* [1] WEP's initialization vectors (IV's) are used in a somewhat insecure way. Since, in that protocol,
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* the IV's are relatively easy to predict, an attack described by
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* {@link http://www.drizzle.com/~aboba/IEEE/rc4_ksaproc.pdf Scott Fluhrer, Itsik Mantin, and Adi Shamir}
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* can be used to quickly guess at the rest of the key. The following links elaborate:
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*
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* {@link http://www.rsa.com/rsalabs/node.asp?id=2009 http://www.rsa.com/rsalabs/node.asp?id=2009}
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* {@link http://en.wikipedia.org/wiki/Related_key_attack http://en.wikipedia.org/wiki/Related_key_attack}
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*
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* @param String $iv
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* @see Crypt_RC4::setKey()
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* @access public
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*/
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function setIV($iv)
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{
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}
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/**
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* Sets MCrypt parameters. (optional)
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*
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* If MCrypt is being used, empty strings will be used, unless otherwise specified.
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*
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* @link http://php.net/function.mcrypt-module-open#function.mcrypt-module-open
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* @access public
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* @param optional Integer $algorithm_directory
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* @param optional Integer $mode_directory
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*/
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function setMCrypt($algorithm_directory = '', $mode_directory = '')
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{
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if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT ) {
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$this->mcrypt = array($algorithm_directory, $mode_directory);
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$this->_closeMCrypt();
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}
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}
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/**
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* Encrypts a message.
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*
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* @see Crypt_RC4::_crypt()
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* @access public
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* @param String $plaintext
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*/
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function encrypt($plaintext)
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{
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return $this->_crypt($plaintext, CRYPT_RC4_ENCRYPT);
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}
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/**
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* Decrypts a message.
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*
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* $this->decrypt($this->encrypt($plaintext)) == $this->encrypt($this->encrypt($plaintext)).
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* Atleast if the continuous buffer is disabled.
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*
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* @see Crypt_RC4::_crypt()
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* @access public
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* @param String $ciphertext
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*/
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function decrypt($ciphertext)
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{
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return $this->_crypt($ciphertext, CRYPT_RC4_DECRYPT);
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}
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/**
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* Encrypts or decrypts a message.
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*
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* @see Crypt_RC4::encrypt()
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* @see Crypt_RC4::decrypt()
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* @access private
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* @param String $text
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* @param Integer $mode
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*/
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function _crypt($text, $mode)
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{
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if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT ) {
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$keyStream = $mode == CRYPT_RC4_ENCRYPT ? 'encryptStream' : 'decryptStream';
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if ($this->$keyStream === false) {
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$this->$keyStream = mcrypt_module_open($this->mode, $this->mcrypt[0], MCRYPT_MODE_STREAM, $this->mcrypt[1]);
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mcrypt_generic_init($this->$keyStream, $this->key, '');
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} else if (!$this->continuousBuffer) {
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mcrypt_generic_init($this->$keyStream, $this->key, '');
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}
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$newText = mcrypt_generic($this->$keyStream, $text);
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if (!$this->continuousBuffer) {
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mcrypt_generic_deinit($this->$keyStream);
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}
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return $newText;
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}
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if ($this->encryptStream === false) {
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$this->setKey($this->key);
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}
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switch ($mode) {
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case CRYPT_RC4_ENCRYPT:
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$keyStream = $this->encryptStream;
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list($i, $j) = $this->encryptIndex;
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break;
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case CRYPT_RC4_DECRYPT:
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$keyStream = $this->decryptStream;
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list($i, $j) = $this->decryptIndex;
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}
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$newText = '';
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for ($k = 0; $k < strlen($text); $k++) {
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$i = ($i + 1) & 255;
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$j = ($j + $keyStream[$i]) & 255;
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$temp = $keyStream[$i];
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$keyStream[$i] = $keyStream[$j];
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$keyStream[$j] = $temp;
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$temp = $keyStream[($keyStream[$i] + $keyStream[$j]) & 255];
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$newText.= chr(ord($text[$k]) ^ $temp);
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}
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if ($this->continuousBuffer) {
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switch ($mode) {
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case CRYPT_RC4_ENCRYPT:
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$this->encryptStream = $keyStream;
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$this->encryptIndex = array($i, $j);
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break;
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case CRYPT_RC4_DECRYPT:
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$this->decryptStream = $keyStream;
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$this->decryptIndex = array($i, $j);
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}
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}
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return $newText;
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}
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/**
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* Treat consecutive "packets" as if they are a continuous buffer.
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*
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* Say you have a 16-byte plaintext $plaintext. Using the default behavior, the two following code snippets
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* will yield different outputs:
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*
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* <code>
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* echo $rc4->encrypt(substr($plaintext, 0, 8));
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* echo $rc4->encrypt(substr($plaintext, 8, 8));
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* </code>
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* <code>
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* echo $rc4->encrypt($plaintext);
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* </code>
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*
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* The solution is to enable the continuous buffer. Although this will resolve the above discrepancy, it creates
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* another, as demonstrated with the following:
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*
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* <code>
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* $rc4->encrypt(substr($plaintext, 0, 8));
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* echo $rc4->decrypt($des->encrypt(substr($plaintext, 8, 8)));
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* </code>
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* <code>
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* echo $rc4->decrypt($des->encrypt(substr($plaintext, 8, 8)));
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* </code>
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*
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* With the continuous buffer disabled, these would yield the same output. With it enabled, they yield different
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* outputs. The reason is due to the fact that the initialization vector's change after every encryption /
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* decryption round when the continuous buffer is enabled. When it's disabled, they remain constant.
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*
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* Put another way, when the continuous buffer is enabled, the state of the Crypt_DES() object changes after each
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* encryption / decryption round, whereas otherwise, it'd remain constant. For this reason, it's recommended that
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* continuous buffers not be used. They do offer better security and are, in fact, sometimes required (SSH uses them),
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* however, they are also less intuitive and more likely to cause you problems.
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*
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* @see Crypt_RC4::disableContinuousBuffer()
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* @access public
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*/
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function enableContinuousBuffer()
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{
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$this->continuousBuffer = true;
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}
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/**
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* Treat consecutive packets as if they are a discontinuous buffer.
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*
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* The default behavior.
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*
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* @see Crypt_RC4::enableContinuousBuffer()
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* @access public
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*/
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function disableContinuousBuffer()
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{
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if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_INTERNAL ) {
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$this->encryptIndex = $this->decryptIndex = array(0, 0);
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$this->setKey($this->key);
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}
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$this->continuousBuffer = false;
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}
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/**
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* Dummy function.
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*
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* Since RC4 is a stream cipher and not a block cipher, no padding is necessary. The only reason this function is
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* included is so that you can switch between a block cipher and a stream cipher transparently.
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*
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* @see Crypt_RC4::disablePadding()
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* @access public
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*/
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function enablePadding()
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{
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}
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/**
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* Dummy function.
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*
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* @see Crypt_RC4::enablePadding()
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* @access public
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*/
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function disablePadding()
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{
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}
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/**
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* Class destructor.
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*
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* Will be called, automatically, if you're using PHP5. If you're using PHP4, call it yourself. Only really
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* needs to be called if mcrypt is being used.
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*
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* @access public
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*/
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function __destruct()
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{
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if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT ) {
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$this->_closeMCrypt();
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}
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}
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/**
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* Properly close the MCrypt objects.
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*
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* @access prviate
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*/
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function _closeMCrypt()
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{
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if ( $this->encryptStream !== false ) {
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if ( $this->continuousBuffer ) {
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mcrypt_generic_deinit($this->encryptStream);
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}
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mcrypt_module_close($this->encryptStream);
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$this->encryptStream = false;
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}
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if ( $this->decryptStream !== false ) {
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if ( $this->continuousBuffer ) {
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mcrypt_generic_deinit($this->decryptStream);
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}
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mcrypt_module_close($this->decryptStream);
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$this->decryptStream = false;
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}
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}
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} |