protected function consistentResponseTime($startTime)
    {
        if (!Config::inst()->get('LDAPLoginForm', 'consistent_password_times')) {
            return;
        }

        $timeTaken = microtime(true) - $startTime;
        if ($timeTaken < self::RESPONSE_TIME) {
            $sleepTime = self::RESPONSE_TIME - $timeTaken;
            // usleep takes microseconds, so we times our sleep period by 1mil (1mil ms = 1s)
            usleep($sleepTime * 1000000);
        }

    }