<?php /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ /* AES counter (CTR) mode 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 AesCtr extends Aes { /** * Encrypt a text using AES encryption in Counter mode of operation * - see * * 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) * @param keep keep 1:each not change 0:each change(default) * @return encrypted text */ public static function encrypt($plaintext, $password, $nBits, $keep=0) { $blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES if (!($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 $counterBlock = array(); if($keep==0){ $nonce = floor(microtime(true)*1000); // timestamp: milliseconds since 1-Jan-1970 $nonceMs = $nonce%1000; $nonceSec = floor($nonce/1000); $nonceRnd = floor(rand(0, 0xffff)); }else{ $nonce = 10000; $nonceMs = $nonce%1000; $nonceSec = floor($nonce/1000); $nonceRnd = 10000; } for ($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; } } ?>
Demo实例程序如下：