public function start($user, $password) {
        $conn = MySQL::getInstance()->getConnector();
        $DAO = new DAO();
        $user = new StringExpression($user);
        $password = new StringExpression($password);

        if($flood = Cookie::getInstance()->get('flooding')){
            $this->last_message = 'Acesso bloqueado por 5 minutos!';
            $this->notify();
            header('Location: '.URL_ROOT.'login.php');
            return  false;
        }

        $DAO->select()->table('users')->where("user_name = {$user->interpret($conn)} AND user_pswd = MD5({$password->interpret($conn)})");
        if($result = $DAO->fetchOne()){
            Session::getInstance()->set('uid', $result['uid']);
            $this->last_message = null;
            $this->notify();
            header('Location: '.URL_ROOT);
        } else {
            $this->last_message = 'Usuário e/ou senha incorretos!';
            $this->notify();
            header('Location: '.URL_ROOT.'login.php');
        }
    }