<?php
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/* AES implementation in PHP (c) Chris Veness 2005-2011. Right of free use is granted for all */
/* commercial or non-commercial use under CC-BY licence. No warranty of any form is offered. */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
class Aes {
/**
* AES Cipher function: encrypt 'input' with Rijndael algorithm
*
* @param input message as byte-array (16 bytes)
* @param w key schedule as 2D byte-array (Nr+1 x Nb bytes) -
* generated from the cipher key by keyExpansion()
* @return ciphertext as byte-array (16 bytes)
*/
public static function cipher($input, $w) { // main cipher function [§5.1]
$Nb = 4; // block size (in words): no of columns in state (fixed at 4 for AES)
$Nr = count($w)/$Nb - 1; // no of rounds: 10/12/14 for 128/192/256-bit keys
$state = array(); // initialise 4xNb byte-array 'state' with input [§3.4]
for ($i=0; $i<4*$Nb; $i++) $state[$i%4][floor($i/4)] = $input[$i];
$state = self::addRoundKey($state, $w, 0, $Nb);
for ($round=1; $round<$Nr; $round++) { // apply Nr rounds
$state = self::subBytes($state, $Nb);
$state = self::shiftRows($state, $Nb);
$state = self::mixColumns($state, $Nb);
$state = self::addRoundKey($state, $w, $round, $Nb);
}
$state = self::subBytes($state, $Nb);
$state = self::shiftRows($state, $Nb);
$state = self::addRoundKey($state, $w, $Nr, $Nb);
$output = array(4*$Nb); // convert state to 1-d array before returning [§3.4]
for ($i=0; $i<4*$Nb; $i++) $output[$i] = $state[$i%4][floor($i/4)];
return $output;
}
private static function addRoundKey($state, $w, $rnd, $Nb) { // xor Round Key into state S [§5.1.4]
for ($r=0; $r<4; $r++) {
for ($c=0; $c<$Nb; $c++) $state[$r][$c] ^= $w[$rnd*4+$c][$r];
}
return $state;
}
private static function subBytes($s, $Nb) { // apply SBox to state S [§5.1.1]
for ($r=0; $r<4; $r++) {
for ($c=0; $c<$Nb; $c++) $s[$r][$c] = self::$sBox[$s[$r][$c]];
}
return $s;
}
private static function shiftRows($s, $Nb) { // shift row r of state S left by r bytes [§5.1.2]
$t = array(4);
for ($r=1; $r<4; $r++) {
for ($c=0; $c<4; $c++) $t[$c] = $s[$r][($c+$r)%$Nb]; // shift into temp copy
for ($c=0; $c<4; $c++) $s[$r][$c] = $t[$c]; // and copy back
} // note that this will work for Nb=4,5,6, but not 7,8 (always 4 for AES):
return $s; // see fp.gladman.plus.com/cryptography_technology/rijndael/aes.spec.311.pdf
}
private static function mixColumns($s, $Nb) { // combine bytes of each col of state S [§5.1.3]
for ($c=0; $c<4; $c++) {
$a = array(4); // 'a' is a copy of the current column from 's'
$b = array(4); // 'b' is a•{02} in GF(2^8)
for ($i=0; $i<4; $i++) {
$a[$i] = $s[$i][$c];
$b[$i] = $s[$i][$c]&0x80 ? $s[$i][$c]<<1 ^ 0x011b : $s[$i][$c]<<1;
}
// a[n] ^ b[n] is a•{03} in GF(2^8)
$s[0][$c] = $b[0] ^ $a[1] ^ $b[1] ^ $a[2] ^ $a[3]; // 2*a0 + 3*a1 + a2 + a3
$s[1][$c] = $a[0] ^ $b[1] ^ $a[2] ^ $b[2] ^ $a[3]; // a0 * 2*a1 + 3*a2 + a3
$s[2][$c] = $a[0] ^ $a[1] ^ $b[2] ^ $a[3] ^ $b[3]; // a0 + a1 + 2*a2 + 3*a3
$s[3][$c] = $a[0] ^ $b[0] ^ $a[1] ^ $a[2] ^ $b[3]; // 3*a0 + a1 + a2 + 2*a3
}
return $s;
}
/**
* Key expansion for Rijndael cipher(): performs key expansion on cipher key
* to generate a key schedule
*
* @param key cipher key byte-array (16 bytes)
* @return key schedule as 2D byte-array (Nr+1 x Nb bytes)
*/
public static function keyExpansion($key) { // generate Key Schedule from Cipher Key [§5.2]
$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) {
$temp = self::subWord(self::rotWord($temp));
for ($t=0; $t<4; $t++) $temp[$t] ^= self::$rCon[$i/$Nk][$t];
} else if ($Nk > 6 && $i%$Nk == 4) {
$temp = self::subWord($temp);
}
for ($t=0; $t<4; $t++) $w[$i][$t] = $w[$i-$Nk][$t] ^ $temp[$t];
}
return $w;
}
private static function subWord($w) { // apply SBox to 4-byte word w
for ($i=0; $i<4; $i++) $w[$i] = self::$sBox[$w[$i]];
return $w;
}
private static function rotWord($w) { // rotate 4-byte word w left by one byte
$tmp = $w[0];
for ($i=0; $i<3; $i++) $w[$i] = $w[$i+1];
$w[3] = $tmp;
return $w;
}
// sBox is pre-computed multiplicative inverse in GF(2^8) used in subBytes and keyExpansion [§5.1.1]
private static $sBox = array(
0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16);
// rCon is Round Constant used for the Key Expansion [1st col is 2^(r-1) in GF(2^8)] [§5.2]
private static $rCon = array(
array(0x00, 0x00, 0x00, 0x00),
array(0x01, 0x00, 0x00, 0x00),
array(0x02, 0x00, 0x00, 0x00),
array(0x04, 0x00, 0x00, 0x00),
array(0x08, 0x00, 0x00, 0x00),
array(0x10, 0x00, 0x00, 0x00),
array(0x20, 0x00, 0x00, 0x00),
array(0x40, 0x00, 0x00, 0x00),
array(0x80, 0x00, 0x00, 0x00),
array(0x1b, 0x00, 0x00, 0x00),
array(0x36, 0x00, 0x00, 0x00) );
}
?>
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