function _encryptBlock($in)
{
static $tables;
if (empty($tables)) {
$tables =& $this->_getTables();
}
$t0 = $tables[0];
$t1 = $tables[1];
$t2 = $tables[2];
$t3 = $tables[3];
$sbox = $tables[4];
$state = array();
$words = unpack('N*', $in);
$c = $this->c;
$w = $this->w;
$Nb = $this->Nb;
$Nr = $this->Nr;
// addRoundKey
$wc = $Nb - 1;
foreach ($words as $word) {
$state[] = $word ^ $w[++$wc];
}
// fips-197.pdf#page=19, "Figure 5. Pseudo Code for the Cipher", states that this loop has four components -
// subBytes, shiftRows, mixColumns, and addRoundKey. fips-197.pdf#page=30, "Implementation Suggestions Regarding
// Various Platforms" suggests that performs enhanced implementations are described in Rijndael-ammended.pdf.
// Rijndael-ammended.pdf#page=20, "Implementation aspects / 32-bit processor", discusses such an optimization.
// Unfortunately, the description given there is not quite correct. Per aes.spec.v316.pdf#page=19 [1],
// equation (7.4.7) is supposed to use addition instead of subtraction, so we'll do that here, as well.
// [1] http://fp.gladman.plus.com/cryptography_technology/rijndael/aes.spec.v316.pdf
$temp = array();
for ($round = 1; $round < $Nr; ++$round) {
$i = 0;
// $c[0] == 0
$j = $c[1];
$k = $c[2];
$l = $c[3];
while ($i < $Nb) {
$temp[$i] = $t0[$state[$i] >> 24 & 0xff] ^ $t1[$state[$j] >> 16 & 0xff] ^ $t2[$state[$k] >> 8 & 0xff] ^ $t3[$state[$l] & 0xff] ^ $w[++$wc];
++$i;
$j = ($j + 1) % $Nb;
$k = ($k + 1) % $Nb;
$l = ($l + 1) % $Nb;
}
$state = $temp;
}
// subWord
for ($i = 0; $i < $Nb; ++$i) {
$state[$i] = $sbox[$state[$i] & 0xff] | $sbox[$state[$i] >> 8 & 0xff] << 8 | $sbox[$state[$i] >> 16 & 0xff] << 16 | $sbox[$state[$i] >> 24 & 0xff] << 24;
}
// shiftRows + addRoundKey
$i = 0;
// $c[0] == 0
$j = $c[1];
$k = $c[2];
$l = $c[3];
while ($i < $Nb) {
$temp[$i] = $state[$i] & 0xff000000 ^ $state[$j] & 0xff0000 ^ $state[$k] & 0xff00 ^ $state[$l] & 0xff ^ $w[$i];
++$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]);
}
}
