function _decryptBlock($in)
{
static $invtables;
if (empty($invtables)) {
$invtables =& $this->_getInvTables();
}
$dt0 = $invtables[0];
$dt1 = $invtables[1];
$dt2 = $invtables[2];
$dt3 = $invtables[3];
$isbox = $invtables[4];
$state = array();
$words = unpack('N*', $in);
$c = $this->c;
$dw = $this->dw;
$Nb = $this->Nb;
$Nr = $this->Nr;
// addRoundKey
$wc = $Nb - 1;
foreach ($words as $word) {
$state[] = $word ^ $dw[++$wc];
}
$temp = array();
for ($round = $Nr - 1; $round > 0; --$round) {
$i = 0;
// $c[0] == 0
$j = $Nb - $c[1];
$k = $Nb - $c[2];
$l = $Nb - $c[3];
while ($i < $Nb) {
$temp[$i] = $dt0[$state[$i] >> 24 & 0xff] ^ $dt1[$state[$j] >> 16 & 0xff] ^ $dt2[$state[$k] >> 8 & 0xff] ^ $dt3[$state[$l] & 0xff] ^ $dw[++$wc];
++$i;
$j = ($j + 1) % $Nb;
$k = ($k + 1) % $Nb;
$l = ($l + 1) % $Nb;
}
$state = $temp;
}
// invShiftRows + invSubWord + addRoundKey
$i = 0;
// $c[0] == 0
$j = $Nb - $c[1];
$k = $Nb - $c[2];
$l = $Nb - $c[3];
while ($i < $Nb) {
$word = $state[$i] & 0xff000000 | $state[$j] & 0xff0000 | $state[$k] & 0xff00 | $state[$l] & 0xff;
$temp[$i] = $dw[$i] ^ ($isbox[$word & 0xff] | $isbox[$word >> 8 & 0xff] << 8 | $isbox[$word >> 16 & 0xff] << 16 | $isbox[$word >> 24 & 0xff] << 24);
++$i;
$j = ($j + 1) % $Nb;
$k = ($k + 1) % $Nb;
$l = ($l + 1) % $Nb;
}
switch ($Nb) {
case 8:
return pack('N*', $temp[0], $temp[1], $temp[2], $temp[3], $temp[4], $temp[5], $temp[6], $temp[7]);
case 7:
return pack('N*', $temp[0], $temp[1], $temp[2], $temp[3], $temp[4], $temp[5], $temp[6]);
case 6:
return pack('N*', $temp[0], $temp[1], $temp[2], $temp[3], $temp[4], $temp[5]);
case 5:
return pack('N*', $temp[0], $temp[1], $temp[2], $temp[3], $temp[4]);
default:
return pack('N*', $temp[0], $temp[1], $temp[2], $temp[3]);
}
}