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<?php
/**
* PHP Power of Two Modular Exponentiation Engine
*
* PHP version 5 and 7
*
* @author Jim Wigginton <[email protected]>
* @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 Power Of Two Modular Exponentiation Engine
*
* @author Jim Wigginton <[email protected]>
*/
abstract class PowerOfTwo extends Base
{
/**
* Prepare a number for use in Montgomery Modular Reductions
*
* @param array $x
* @param array $n
* @param string $class
* @return array
*/
protected static function prepareReduce(array $x, array $n, $class)
{
return self::reduce($x, $n, $class);
}
/**
* Power Of Two Reduction
*
* @param array $x
* @param array $n
* @param string $class
* @return array
*/
protected static function reduce(array $x, array $n, $class)
{
$lhs = new $class();
$lhs->value = $x;
$rhs = new $class();
$rhs->value = $n;
$temp = new $class();
$temp->value = [1];
$result = $lhs->bitwise_and($rhs->subtract($temp));
return $result->value;
}
}
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