/**
* Decrypts the ciphertext using Blowfish with the given key.
*
* @param string $ciphertext the encrypted string
* @param string $key the encryption key
* @param int $mode one of BLOWFISH_MODE_CBC, BLOWFISH_MODE_EBC. BLOWFISH_MODE_CBC is recommened
* @param int $padding one of BLOWFISH_PADDING_NONE, BLOWFISH_PADDING_RFC, BLOWFISH_PADDING_ZERO. BLOWFISH_PADDING_RFC is recommened
* @param int $iv the initialisation vector. Required when using CBC mode.
* @return string Returns the plaintext string.
* @author Matt Harris
**/
public function decrypt($ciphertext, $key, $mode = Blowfish::BLOWFISH_MODE_CBC, $padding = Blowfish::BLOWFISH_PADDING_RFC, $iv = NULL)
{
if ($mode == Blowfish::BLOWFISH_MODE_CBC and empty($iv)) {
throw new Exception('CBC Mode requires an IV key');
return;
}
$plaintext = '';
$fish = new Blowfish($key, $mode, $padding, $iv);
$block =& $fish->blockSize;
$len = strlen($ciphertext);
# encrypt in 1 byte intervals
for ($i = 0; $i < $len; $i += $block) {
list(, $xL, $xR) = unpack('N2', substr($ciphertext, $i, $block));
$fish->_decipher($xL, $xR);
if ($mode == Blowfish::BLOWFISH_MODE_CBC) {
$chain = $i == 0 ? $fish->IV : substr($ciphertext, $i - $block, $block);
$plaintext .= pack('N2', $xL, $xR) ^ $chain;
} else {
$plaintext .= pack('N2', $xL, $xR);
}
}
$plaintext = $fish->_unpad($plaintext);
unset($fish);
return $plaintext;
}
