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493 lines
14 KiB
493 lines
14 KiB
<?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: RC4.php,v 1.8 2009/06/09 04:00:38 terrafrost Exp $ |
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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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} |