<?php
namespace Mdanter\Ecc\Random;
use Mdanter\Ecc\Math\GmpMathInterface;
use Mdanter\Ecc\Util\NumberSize;
class RandomNumberGenerator implements RandomNumberGeneratorInterface
{
/**
* @var GmpMathInterface
*/
private $adapter;
/**
* RandomNumberGenerator constructor.
* @param GmpMathInterface $adapter
*/
public function __construct(GmpMathInterface $adapter)
{
$this->adapter = $adapter;
}
/**
* @param \GMP $max
* @return \GMP
*/
public function generate(\GMP $max)
{
$numBits = NumberSize::bnNumBits($this->adapter, $max);
$numBytes = ceil($numBits / 8);
// Generate an integer of size >= $numBits
$bytes = random_bytes($numBytes);
$value = $this->adapter->stringToInt($bytes);
$mask = gmp_sub(gmp_pow(2, $numBits), 1);
$integer = gmp_and($value, $mask);
return $integer;
}
}