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<?php
/**
* The Horde_Cipher_BlockMode_cbc:: This class implements the
* Horde_Cipher_BlockMode using the Cipher Block Chaininng method of
* encrypting blocks of data.
*
* $Horde: horde/lib/Cipher/BlockMode/cbc.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_cbc extends Horde_Cipher_BlockMode {
function encrypt(&$cipher, $plaintext)
{
$encrypted = '';
$blocksize = $cipher->getBlockSize();
$previousCipher = $this->_iv;
$jMax = strlen($plaintext);
for ($j = 0; $j < $jMax; $j += $blocksize) {
$plain = substr($plaintext, $j, $blocksize);
if (strlen($plain) < $blocksize) {
// pad the block with \0's if it's not long enough
$plain = str_pad($plain, 8, "\0");
}
$plain = $plain ^ $previousCipher;
$previousCipher = $cipher->encryptBlock($plain);
$encrypted .= $previousCipher;
}
return $encrypted;
}
function decrypt(&$cipher, $ciphertext)
{
$decrypted = '';
$blocksize = $cipher->getBlockSize();
$previousCipher = $this->_iv;
$jMax = strlen($ciphertext);
for ($j = 0; $j < $jMax; $j += $blocksize) {
$plain = substr($ciphertext, $j, $blocksize);
$decrypted .= $cipher->decryptBlock($plain) ^ $previousCipher;
$previousCipher = $plain;
}
// remove trailing \0's used to pad the last block
while (substr($decrypted, -1, 1) == "\0") {
$decrypted = substr($decrypted, 0, -1);
}
return $decrypted;
}
}
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