This is a PHP version of AES (Advanced Encryption Standard). I created this PHP version as a server-side complement to my JavaScript AES implementation.
This version directly mirrors the JavaScript version; it differs in that PHP has Base64 encoding and UTF-8 encoding built-in, and has no unsigned-right-shift operator(!), but is otherwise a straightforward port, with syntactic differences and differently-named library functions. It is quite simple to compare the two versions side-by-side.
An explanation of the operation of the algorithm is given with the JavaScript version.
Note that these scripts are intended to assist in studying the algorithms, not for production use. With security applications especially, standard libraries are always to be preferred over bespoke solutions. However, if interoperability between browser and PHP is required and standard libraries cannot be used, this provides a way to achieve that.
See below for the source code of the PHP implementation. §ection numbers relate the code back to sections in the standard.
I
offer these formulæ & scripts for free use and adaptation as my contribution to the open-source
info-sphere from which I have received so much. You are welcome to re-use these scripts [under a simple attribution license or a GPL licence,
without any warranty express or implied] provided solely that you retain my copyright notice and a
link to this page.
If you would like to show your appreciation and support continued development of these scripts,
I would most gratefully accept donations.
If you have any queries or find any problems, contact me at ku.oc.epyt-elbavom@cne-stpircs.
© 2005-2017 Chris Veness
<?php
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/* AES implementation in PHP */
/* (c) Chris Veness 2005-2014 www.movable-type.co.uk/scripts */
/* 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 [§5.1]: 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)
{
$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 $output;
}
/**
* Xor Round Key into state S [§5.1.4].
*/
private static function addRoundKey($state, $w, $rnd, $Nb)
{
for ($r = 0; $r < 4; $r++) {
for ($c = 0; $c < $Nb; $c++) $state[$r][$c] ^= $w[$rnd * 4 + $c][$r];
}
return $state;
}
/**
* Apply SBox to state S [§5.1.1].
*/
private static function subBytes($s, $Nb)
{
for ($r = 0; $r < 4; $r++) {
for ($c = 0; $c < $Nb; $c++) $s[$r][$c] = self::$sBox[$s[$r][$c]];
}
return $s;
}
/**
* Shift row r of state S left by r bytes [§5.1.2].
*/
private static function shiftRows($s, $Nb)
{
$t = array(4);
for ($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 $s; // see fp.gladman.plus.com/cryptography_technology/rijndael/aes.spec.311.pdf
}
/**
* Combine bytes of each col of state S [§5.1.3].
*/
private static function mixColumns($s, $Nb)
{
for ($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 $s;
}
/**
* Generate Key Schedule from Cipher Key [§5.2].
*
* Perform key expansion on cipher key to generate a key schedule.
*
* @param key cipher key byte-array (16 bytes).
* @return key schedule as 2D byte-array (Nr+1 x Nb bytes).
*/
public static function keyExpansion($key)
{
$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 $w;
}
/**
* Apply SBox to 4-byte word w.
*/
private static function subWord($w)
{
for ($i = 0; $i < 4; $i++) $w[$i] = self::$sBox[$w[$i]];
return $w;
}
/**
* Rotate 4-byte word w left by one byte.
*/
private static function rotWord($w)
{
$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 $rCon = array(
array(0x00, 0x00, 0x00, 0x00),
array(0x01, 0x00, 0x00, 0x00),
array(0x02, 0x00, 0x00, 0x00),
array(0x04, 0x00, 0x00, 0x00),
array(0x08, 0x00, 0x00, 0x00),
array(0x10, 0x00, 0x00, 0x00),
array(0x20, 0x00, 0x00, 0x00),
array(0x40, 0x00, 0x00, 0x00),
array(0x80, 0x00, 0x00, 0x00),
array(0x1b, 0x00, 0x00, 0x00),
array(0x36, 0x00, 0x00, 0x00));
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
<?php
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/* AES counter (CTR) mode implementation in PHP */
/* (c) Chris Veness 2005-2014 www.movable-type.co.uk/scripts */
/* Right of free use is granted for all commercial or non-commercial use under CC-BY licence. */
/* No warranty of any form is offered. */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
Class AesCtr extends Aes
{
/**
* Encrypt a text using AES encryption in Counter mode of operation
* - see http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf
*
* Unicode multi-byte character safe
*
* @param plaintext source text to be encrypted
* @param password the password to use to generate a key
* @param nBits number of bits to be used in the key (128, 192, or 256)
* @return encrypted text
*/
public static function encrypt($plaintext, $password, $nBits)
{
$blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
if (!($nBits == 128 || $nBits == 192 || $nBits == 256)) return ''; // standard allows 128/192/256 bit keys
// note PHP (5) gives us plaintext and password in UTF8 encoding!
// use AES itself to encrypt password to get cipher key (using plain password as source for
// key expansion) - gives us well encrypted key
$nBytes = $nBits / 8; // no bytes in key
$pwBytes = array();
for ($i = 0; $i < $nBytes; $i++) $pwBytes[$i] = ord(substr($password, $i, 1)) & 0xff;
$key = Aes::cipher($pwBytes, Aes::keyExpansion($pwBytes));
$key = array_merge($key, array_slice($key, 0, $nBytes - 16)); // expand key to 16/24/32 bytes long
// initialise 1st 8 bytes of counter block with nonce (NIST SP800-38A §B.2): [0-1] = millisec,
// [2-3] = random, [4-7] = seconds, giving guaranteed sub-ms uniqueness up to Feb 2106
$counterBlock = array();
$nonce = floor(microtime(true) * 1000); // timestamp: milliseconds since 1-Jan-1970
$nonceMs = $nonce % 1000;
$nonceSec = floor($nonce / 1000);
$nonceRnd = floor(rand(0, 0xffff));
for ($i = 0; $i < 2; $i++) $counterBlock[$i] = self::urs($nonceMs, $i * 8) & 0xff;
for ($i = 0; $i < 2; $i++) $counterBlock[$i + 2] = self::urs($nonceRnd, $i * 8) & 0xff;
for ($i = 0; $i < 4; $i++) $counterBlock[$i + 4] = self::urs($nonceSec, $i * 8) & 0xff;
// and convert it to a string to go on the front of the ciphertext
$ctrTxt = '';
for ($i = 0; $i < 8; $i++) $ctrTxt .= chr($counterBlock[$i]);
// generate key schedule - an expansion of the key into distinct Key Rounds for each round
$keySchedule = Aes::keyExpansion($key);
//print_r($keySchedule);
$blockCount = ceil(strlen($plaintext) / $blockSize);
$ciphertxt = array(); // ciphertext as array of strings
for ($b = 0; $b < $blockCount; $b++) {
// set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
// done in two stages for 32-bit ops: using two words allows us to go past 2^32 blocks (68GB)
for ($c = 0; $c < 4; $c++) $counterBlock[15 - $c] = self::urs($b, $c * 8) & 0xff;
for ($c = 0; $c < 4; $c++) $counterBlock[15 - $c - 4] = self::urs($b / 0x100000000, $c * 8);
$cipherCntr = Aes::cipher($counterBlock, $keySchedule); // -- encrypt counter block --
// block size is reduced on final block
$blockLength = $b < $blockCount - 1 ? $blockSize : (strlen($plaintext) - 1) % $blockSize + 1;
$cipherByte = array();
for ($i = 0; $i < $blockLength; $i++) { // -- xor plaintext with ciphered counter byte-by-byte --
$cipherByte[$i] = $cipherCntr[$i] ^ ord(substr($plaintext, $b * $blockSize + $i, 1));
$cipherByte[$i] = chr($cipherByte[$i]);
}
$ciphertxt[$b] = implode('', $cipherByte); // escape troublesome characters in ciphertext
}
// implode is more efficient than repeated string concatenation
$ciphertext = $ctrTxt . implode('', $ciphertxt);
$ciphertext = base64_encode($ciphertext);
return $ciphertext;
}
/**
* Decrypt a text encrypted by AES in counter mode of operation
*
* @param ciphertext source text to be decrypted
* @param password the password to use to generate a key
* @param nBits number of bits to be used in the key (128, 192, or 256)
* @return decrypted text
*/
public static function decrypt($ciphertext, $password, $nBits)
{
$blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
if (!($nBits == 128 || $nBits == 192 || $nBits == 256)) return ''; // standard allows 128/192/256 bit keys
$ciphertext = base64_decode($ciphertext);
// use AES to encrypt password (mirroring encrypt routine)
$nBytes = $nBits / 8; // no bytes in key
$pwBytes = array();
for ($i = 0; $i < $nBytes; $i++) $pwBytes[$i] = ord(substr($password, $i, 1)) & 0xff;
$key = Aes::cipher($pwBytes, Aes::keyExpansion($pwBytes));
$key = array_merge($key, array_slice($key, 0, $nBytes - 16)); // expand key to 16/24/32 bytes long
// recover nonce from 1st element of ciphertext
$counterBlock = array();
$ctrTxt = substr($ciphertext, 0, 8);
for ($i = 0; $i < 8; $i++) $counterBlock[$i] = ord(substr($ctrTxt, $i, 1));
// generate key schedule
$keySchedule = Aes::keyExpansion($key);
// separate ciphertext into blocks (skipping past initial 8 bytes)
$nBlocks = ceil((strlen($ciphertext) - 8) / $blockSize);
$ct = array();
for ($b = 0; $b < $nBlocks; $b++) $ct[$b] = substr($ciphertext, 8 + $b * $blockSize, 16);
$ciphertext = $ct; // ciphertext is now array of block-length strings
// plaintext will get generated block-by-block into array of block-length strings
$plaintxt = array();
for ($b = 0; $b < $nBlocks; $b++) {
// set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
for ($c = 0; $c < 4; $c++) $counterBlock[15 - $c] = self::urs($b, $c * 8) & 0xff;
for ($c = 0; $c < 4; $c++) $counterBlock[15 - $c - 4] = self::urs(($b + 1) / 0x100000000 - 1, $c * 8) & 0xff;
$cipherCntr = Aes::cipher($counterBlock, $keySchedule); // encrypt counter block
$plaintxtByte = array();
for ($i = 0; $i < strlen($ciphertext[$b]); $i++) {
// -- xor plaintext with ciphered counter byte-by-byte --
$plaintxtByte[$i] = $cipherCntr[$i] ^ ord(substr($ciphertext[$b], $i, 1));
$plaintxtByte[$i] = chr($plaintxtByte[$i]);
}
$plaintxt[$b] = implode('', $plaintxtByte);
}
// join array of blocks into single plaintext string
$plaintext = implode('', $plaintxt);
return $plaintext;
}
/*
* Unsigned right shift function, since PHP has neither >>> operator nor unsigned ints
*
* @param a number to be shifted (32-bit integer)
* @param b number of bits to shift a to the right (0..31)
* @return a right-shifted and zero-filled by b bits
*/
private static function urs($a, $b)
{
$a &= 0xffffffff;
$b &= 0x1f; // (bounds check)
if ($a & 0x80000000 && $b > 0) { // if left-most bit set
$a = ($a >> 1) & 0x7fffffff; // right-shift one bit & clear left-most bit
$a = $a >> ($b - 1); // remaining right-shifts
} else { // otherwise
$a = ($a >> $b); // use normal right-shift
}
return $a;
}
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
The following Test Harness illustrates server-side encryption and decryption using the PHP AES script. Testing is simplified by temporarily setting the nonce to 0, so that the ciphertext is constant for a given plaintext.
It provides fields to enter the password and plaintext message, and then invokes itself to encrypt the plaintext and/or decrypt the ciphertext.
<?php
require 'aes.class.php'; // AES PHP implementation
require 'aesctr.class.php'; // AES Counter Mode implementation
$timer = microtime(true);
// initialise password & plaintext if not set in post array
$pw = empty($_POST['pw']) ? 'L0ck it up saf3' : $_POST['pw'];
$pt = empty($_POST['pt']) ? 'pssst ... đon’t tell anyøne!' : $_POST['pt'];
$cipher = empty($_POST['cipher']) ? '' : $_POST['cipher'];
$plain = empty($_POST['plain']) ? '' : $_POST['plain'];
// perform encryption/decryption as required
$encr = empty($_POST['encr']) ? $cipher : AesCtr::encrypt($pt, $pw, 256);
$decr = empty($_POST['decr']) ? $plain : AesCtr::decrypt($cipher, $pw, 256);
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>AES in PHP test harness</title>
</head>
<body>
<form method="post">
<table>
<tr>
<td>Password:</td>
<td><input type="text" name="pw" size="16" value="<?= $pw ?>"></td>
</tr>
<tr>
<td>Plaintext:</td>
<td><input type="text" name="pt" size="40" value="<?= htmlspecialchars($pt) ?>"></td>
</tr>
<tr>
<td><button type="submit" name="encr" value="Encrypt it">Encrypt it</button></td>
<td><input type="text" name="cipher" size="80" value="<?= $encr ?>"></td>
</tr>
<tr>
<td><button type="submit" name="decr" value="Decrypt it">Decrypt it</button></td>
<td><input type="text" name="plain" size="40" value="<?= htmlspecialchars($decr) ?>"></td>
</tr>
</table>
</form>
<p><?= round(microtime(true) - $timer, 3) ?>s</p>
</body>
</html>
The following Test Harness illustrates a possible way of integrating JavaScript encoding with PHP decoding. Testing is simplified by temporarily setting the nonce to 0, so that the ciphertext is constant for a given plaintext.
The HTML file presents fields to enter the plaintext message. It uses the JavaScript version to encrypt the message client-side, and invokes the PHP file passing the ciphertext in the POST array. The PHP script then uses the PHP version to decrypt the ciphertext passed in the POST array and display it.
Of course, any real application would use a more sophisticated approach to password management!
aes-js-php.html:
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>AES JavaScript+PHP test harness (client-side encrypt)</title>
<script defer src="aes.js">/* AES JavaScript implementation */</script>
<script defer src="aes-ctr.js">/* AES Counter Mode implementation */</script>
<script defer src="base64.js">/* Base64 encoding */</script>
<script defer src="utf8.js">/* UTF-8 encoding */</script>
</head>
<body>
<!-- encrypt the message before submitting the form -->
<form name="frm" id="frm" method="post" action="aes-js-php.php"
onsubmit="frm.message.value = Aes.Ctr.encrypt(frm.message.value, 'L0ck it up saf3', 256);">
<p>Message: <input type="text" name="message" id="message" size="40" value=""></p>
<p><input type="submit" value="Encrypt it:"></p>
</form>
</body>
</html>
aes-js-php.php:
<?php require 'aes.class.php'; // AES PHP implementation require 'aesctr.class.php'; // AES Counter Mode implementation ?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>AES JavaScript+PHP test harness (server-side decrypt)</title> </head> <body> <!-- output the post array received and dectypt the message --> <pre>$_POST: <?= print_r($_POST, true) ?></pre> <pre>Plaintext: <?= AesCtr::decrypt($_POST['message'], 'L0ck it up saf3', 256) ?></pre> </body> </html>
Note that these PHP scripts use ‘short open tags’ “<?” and “<?=”. If your server doesn’t have short tags enabled, use the full tags “<?php” and “<?php echo” instead (see short_open_tag directive and echo).