Secure location information management in cellular radio systems

To ensure reachability of mobile subscribers, cellular radio networks (GSM, IS-41) store location information usually in a home location register (HLR) and in a visitor location register (VLR). To trace mobile users, the network operator just has then to read in these registers. This is considered as a violation of the data security requirement confidentiality. Neither potential communication partners nor third parties should be able to record moving tracks of users without their explicit consent. We propose two new methods that allow the storing of subscribers' exact location information in central databases but still guarantee their privacy. These methods are the "anonymous-subscriber" strategy (AS) and the "anonymity classes" strategy (AC). AS and AC methods protect the subscriber's location information and do not neglect performance considerations. The basic idea of these new strategies is to permit entries of exact location information only if the subscriber remains anonymous. We show that the new procedures can be realized as extensions to the GSM-system. For this purpose they have been specified according to the GSM recommendations methodology and a simulation program using the OPNET Tool, has been developed. Finally, we discuss the influence of the new methods on the network performances.