private static function getHash($H, $X)
    {
        $Y = [];
        $Y[0] = str_pad('', 16, "\0");
        $num_blocks = (int) (mb_strlen($X, '8bit') / 16);
        for ($i = 1; $i <= $num_blocks; $i++) {
            $Y[$i] = self::getProduct(self::getBitXor($Y[$i - 1], mb_substr($X, ($i - 1) * 16, 16, '8bit')), $H);
        }

        return $Y[$num_blocks];
    }
private static function getHash($H, $X)
    {
        $Y = [];
        $Y[0] = str_pad('', 16, "\0");
        $num_blocks = (int) (mb_strlen($X, '8bit') / 16);
        for ($i = 1; $i <= $num_blocks; $i++) {
            $Y[$i] = self::getProduct(self::getBitXor($Y[$i - 1], mb_substr($X, ($i - 1) * 16, 16, '8bit')), $H);
        }

        return $Y[$num_blocks];
    }
@param string $H
@param string $X

@return mixed