protected static function mintRand(): string
    {
        $uuid = static::randomBytes(16);
        // set variant
        $uuid[8] = \chr(\ord($uuid[8]) & static::CLEAR_VAR | static::VAR_RFC);
        // set version
        $uuid[6] = \chr(\ord($uuid[6]) & static::CLEAR_VER | static::VERSION_4);

        return $uuid;
    }