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<?php
/**
* The Horde_Cipher_BlockMode_cfb64:: This class implements the
* Horde_Cipher_BlockMode using a 64 bit cipher feedback. This can
* used to encypt any length string and the encrypted version will be
* the same length.
*
* $Horde: horde/lib/Cipher/BlockMode/cfb64.php,v 1.2.2.4 2003/04/12 20:50:41 slusarz Exp $
*
* Copyright 2002-2003 Mike Cochrane <mike@graftonhall.co.nz>
*
* See the enclosed file COPYING for license information (LGPL). If you
* did not receive this file, see http://www.fsf.org/copyleft/lgpl.html.
*
* @author Mike Cochrane <mike@graftonhall.co.nz>
* @version $Revision: 1.2.2.4 $
* @since Horde 2.2
* @package horde.cipher
*/
class Horde_Cipher_BlockMode_cfb64 extends Horde_Cipher_BlockMode {
function encrypt(&$cipher, $plaintext)
{
$encrypted = '';
$n = 0;
$jMax = strlen($plaintext);
for ($j = 0; $j < $jMax; $j++) {
if ($n == 0) {
$this->_iv = $cipher->encryptBlock($this->_iv);
}
$c = $plaintext[$j] ^ $this->_iv[$n];
$this->_iv = substr($this->_iv, 0, $n) . $c . substr($this->_iv, $n + 1);
$encrypted .= $c;
$n = (++$n) & 0x07;
}
return $encrypted;
}
function decrypt(&$cipher, $ciphertext)
{
$decrypted = '';
$n = 0;
$jMax = strlen($ciphertext);
for ($j = 0; $j < $jMax; $j++) {
if ($n == 0) {
$this->_iv = $cipher->encryptBlock($this->_iv);
}
$c = $ciphertext[$j] ^ $this->_iv[$n];
$this->_iv = substr($this->_iv, 0, $n) . substr($ciphertext, $j, 1) . substr($this->_iv, $n + 1);
$decrypted .= $c;
$n = (++$n) & 0x07;
}
// Remove trailing \0's used to pad the last block
while (substr($decrypted, -1, 1) == "\0") {
$decrypted = substr($decrypted, 0, -1);
}
return $decrypted;
}
}
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