Viewing file:  MontgomeryMult.php (2.95 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
<?php
/**
* PHP Montgomery Modular Exponentiation Engine with interleaved multiplication
*
* PHP version 5 and 7
*
* @category Math
* @package BigInteger
* @author Jim Wigginton <terrafrost@php.net>
* @copyright 2017 Jim Wigginton
* @license http://www.opensource.org/licenses/mit-license.html MIT License
* @link http://pear.php.net/package/Math_BigInteger
*/
namespace phpseclib3\Math\BigInteger\Engines\PHP\Reductions;
use phpseclib3\Math\BigInteger\Engines\PHP\Base;
/**
* PHP Montgomery Modular Exponentiation Engine with interleaved multiplication
*
* @package PHP
* @author Jim Wigginton <terrafrost@php.net>
* @access public
*/
abstract class MontgomeryMult extends Montgomery
{
/**
* Montgomery Multiply
*
* Interleaves the montgomery reduction and long multiplication algorithms together as described in
* {@link http://www.cacr.math.uwaterloo.ca/hac/about/chap14.pdf#page=13 HAC 14.36}
*
* @see self::_prepMontgomery()
* @see self::_montgomery()
* @access private
* @param array $x
* @param array $y
* @param array $m
* @param string $class
* @return array
*/
public static function multiplyReduce(array $x, array $y, array $m, $class)
{
// the following code, although not callable, can be run independently of the above code
// although the above code performed better in my benchmarks the following could might
// perform better under different circumstances. in lieu of deleting it it's just been
// made uncallable
static $cache = [
self::VARIABLE => [],
self::DATA => []
];
if (($key = array_search($m, $cache[self::VARIABLE])) === false) {
$key = count($cache[self::VARIABLE]);
$cache[self::VARIABLE][] = $m;
$cache[self::DATA][] = self::modInverse67108864($m, $class);
}
$n = max(count($x), count($y), count($m));
$x = array_pad($x, $n, 0);
$y = array_pad($y, $n, 0);
$m = array_pad($m, $n, 0);
$a = [self::VALUE => self::array_repeat(0, $n + 1)];
for ($i = 0; $i < $n; ++$i) {
$temp = $a[self::VALUE][0] + $x[$i] * $y[0];
$temp = $temp - $class::BASE_FULL * ($class::BASE === 26 ? intval($temp / 0x4000000) : ($temp >> 31));
$temp = $temp * $cache[self::DATA][$key];
$temp = $temp - $class::BASE_FULL * ($class::BASE === 26 ? intval($temp / 0x4000000) : ($temp >> 31));
$temp = $class::addHelper($class::regularMultiply([$x[$i]], $y), false, $class::regularMultiply([$temp], $m), false);
$a = $class::addHelper($a[self::VALUE], false, $temp[self::VALUE], false);
$a[self::VALUE] = array_slice($a[self::VALUE], 1);
}
if (self::compareHelper($a[self::VALUE], false, $m, false) >= 0) {
$a = $class::subtractHelper($a[self::VALUE], false, $m, false);
}
return $a[self::VALUE];
}
}
|