Abstract: The present invention relates to an authorized domain including a plurality of Authorized Domain Managers (ADMs). The plurality of ADMs contrary to a single ADM solution enables portable ADMs, that do not have to be continuously connected to the AD. The invention provides a solution for keeping the ADMs synchronized. For this purpose, inter alia, each ADM is provided with a map, which comprises an identifier area for containing identifiers corresponding to other devices, and at least one property area for containing properties of the identifiers. The property area is mapped on the identifier area. The properties are arranged to provide information about updates thereof. By obtaining map contents of another ADM, and comparing the contents of the own map with the map contents of the other ADM, it is possible for an ADM to determine whether to perform any updates of the own map.