Файл: classes/aesctr.class.php
Строк: 272
<?php
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/* AES counter (CTR) mode implementation in PHP */
/* (c) Chris Veness 2005-2011 www.movable-type.co.uk/scripts */
/* Right of free use is granted for all commercial or non-commercial use providing this */
/* copyright notice is retainded. 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;
}
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
?>