/**
* Key expansion for Rijndael Cipher(): performs key expansion on cipher key
* to generate a key schedule
*
* @param key cipher key byte-array (16 bytes)
* @return key schedule as 2D byte-array (Nr+1 x Nb bytes)
*/
function KeyExpansion($key)
{
// generate Key Schedule from Cipher Key [§5.2]
global $Rcon;
// PHP needs explicit declaration to access global variables!
$Nb = 4;
// block size (in words): no of columns in state (fixed at 4 for AES)
$Nk = count($key) / 4;
// key length (in words): 4/6/8 for 128/192/256-bit keys
$Nr = $Nk + 6;
// no of rounds: 10/12/14 for 128/192/256-bit keys
$w = array();
$temp = array();
for ($i = 0; $i < $Nk; $i++) {
$r = array($key[4 * $i], $key[4 * $i + 1], $key[4 * $i + 2], $key[4 * $i + 3]);
$w[$i] = $r;
}
for ($i = $Nk; $i < $Nb * ($Nr + 1); $i++) {
$w[$i] = array();
for ($t = 0; $t < 4; $t++) {
$temp[$t] = $w[$i - 1][$t];
}
if ($i % $Nk == 0) {
$temp = SubWord(RotWord($temp));
for ($t = 0; $t < 4; $t++) {
$temp[$t] ^= $Rcon[$i / $Nk][$t];
}
} else {
if ($Nk > 6 && $i % $Nk == 4) {
$temp = SubWord($temp);
}
}
for ($t = 0; $t < 4; $t++) {
$w[$i][$t] = $w[$i - $Nk][$t] ^ $temp[$t];
}
}
return $w;
}
function KeyExpansion($key)
{
global $Rcon;
$Nb = 4;
// block size (in words): no of columns in state (fixed at 4 for AES)
$Nk = count($key) / 4;
// key length (in words): 4/6/8 for 128/192/256-bit keys
$Nr = $Nk + 6;
// no of rounds: 10/12/14 for 128/192/256-bit keys
$w = array($Nb * ($Nr + 1));
setLength($temp, 4);
for ($i = 0; $i < $Nk; $i++) {
$r = array($key[4 * $i], $key[4 * $i + 1], $key[4 * $i + 2], $key[4 * $i + 3]);
$w[$i] = $r;
}
for ($i = $Nk; $i < $Nb * ($Nr + 1); $i++) {
$w[$i] = array();
for ($t = 0; $t < 4; $t++) {
$temp[$t] = $w[$i - 1][$t];
}
if ($i % $Nk == 0) {
$temp = SubWord(RotWord($temp));
for ($t = 0; $t < 4; $t++) {
$temp[$t] ^= $Rcon[$i / $Nk][$t];
}
} elseif ($Nk > 6 && $i % $Nk == 4) {
$temp = SubWord($temp);
}
for ($t = 0; $t < 4; $t++) {
$w[$i][$t] = $w[$i - $Nk][$t] ^ $temp[$t];
}
}
return $w;
}