Patent ID: 7280820

Claim:
A method, comprising: in a network terminal, using a subscriber identity module wherein a response is obtained as a result of a challenge given to the identity module as input, the method being used for authenticating an identity of a subscriber attached to a network; using a special security server in the network so that when a terminal attaches to the network, a message of a new user is transmitted to the security server; fetching subscriber authentication information corresponding to the new user from the mobile communications system to the network, the authentication information comprising at least a challenge and a response; and performing authentication based on the authentication information obtained from the mobile communications system by transmitting the challenge to the terminal through the network for storage on the terminal to ensure by the terminal that the challenge is used once, by checking at the terminal that the challenging is unique from challenges used in previous authentication exchanges wherein the terminal only responds to the challenge if the challenge had not been previously transmitted to the terminal, by generating, if the challenge is unique, a response from the challenge in the identity module of the terminal and by comparing the generated response with the response received from the mobile communications system.