public static function anonymizeUserId($userId)
    {
        $trackerCache = Tracker\Cache::getCacheGeneral();
        $salt = '';
        if (!empty($trackerCache[PrivacyManager::OPTION_USERID_SALT])) {
            $salt = $trackerCache[PrivacyManager::OPTION_USERID_SALT];
        }
        if(empty($salt)) {
            return $userId;
        }
        return sha1($userId . $salt);
    }