Patent ID: 8576751

Claim:
A method of operation in a mobile communication system comprising the steps of: A mobile station receiving a certified service record from its home network and storing the certified service record, the certified service record including a service record and a certificate code, the service record indicating, as determined by the home network, types of communications services permitted to be provided to the mobile station by a visited network when the mobile station roams to a visited network, and the certificate code being a code generated by a calculation procedure applied to a contents of the service record using an authentication key and used for authenticating the service record; and the authentication key is being retrieved from a key issuing terminal; the mobile station roaming from its home network to a first visited network and sending to the first visited network the certified service record so that the visited network may know the types of communication services it is permitted to provide to the mobile station, the visited network determining if the service record provided by the mobile station is authentic by: separately calculating an authentication code for the service record received from the mobile station using the authentication key obtained by the visited network from the key issuing terminal; the visited network authenticating the received service record by determining whether the separately calculated authentication code matches the certificate code received from the mobile station; and if the visited network determines that the service record is authentic, the visited network providing communication services to the mobile station as a function of the types of communication services in the service record.