Patent ID: 7366303

Claim:
A network system comprising: a network control element and a communication device associated to a subscriber, wherein the communication device is configured to send a registration message including subscriber information to be protected and an integrity code, to the network control element, wherein the communication device is configured to calculate the integrity code by using a part or whole of the registration message including the subscriber information to be protected, and the network element is configured to verify the integrity code included in the registration message, wherein the network element is configured to perform an authentication of the subscriber by using the integrity code, wherein the network control element is configured to control a first network, and the network system comprises an additional network control element configured to control a second network, said additional network control element being further configured to perform an additional authentication, wherein the communication device is configured to calculate a result from a predetermined number supplied by the additional network control element, wherein the result is used by the additional network control element for performing the additional authentication, wherein the communication device is configured to send a message including algorithm capability information to the network control element, and wherein the network control element is configured to choose which algorithm is to be used for calculating the integrity code and to forward a message including information about the chosen algorithm to the communication device.