Patent ID: 7526273

Claim:
A method for authentication in a mobile communication system having a mobile communication network and mobile stations, comprising: providing a service, by the network, to one of the mobile stations after authentication of the mobile station, wherein the mobile station comprises a portable module and mobile equipment configured to communicate with the mobile communication network and configured to communicate with the portable module; sending, by the network, random data to the mobile station; calculating, via the network, response data and key data from at least one of random data and a key stored in the network; calculating, via the portable module of the mobile station, response data and key data from at least one of random data and a key stored in the portable module, wherein the portable module stores the calculated key data; transmitting, via the portable module, the response data to the mobile equipment which sends the response data to the network; calculating, via the portable module, further key data from at least one of random data and the calculated key data; transmitting, from the portable module, the further key data to the mobile equipment to enable communication between the mobile equipment and the network for providing a service to the mobile station; calculating, in the network, further key data from at least one of random data and the calculated key data to enable communication between the network for providing a service to the mobile station and the mobile equipment; comparing via the network at least the response data from the mobile equipment and the response data calculated in the network during the authentication procedure, wherein a second authentication procedure is executed after authentication of the mobile station for checking whether the portable module is connected to the mobile equipment; sending, from the network, random data to the mobile station; calculating, via the portable module, new further key data from at least one of the random data and the stored key data that was calculated during authentication of the mobile station, wherein the network also calculates the new further key data from at least one of the random data and the stored key data that was calculated during authentication of the mobile station, wherein the new further key data is used for communication between the mobile equipment and the network.