GSM: Security, Services, and the SIM

Abstract

Security requirements and services of a mobile communication system differ, due to the radio communication between the user and the base station, extensively from those of a fixed network. There is no physical link in the form of a (fixed) telephone line between the user and the local exchange, which could serve to “identify” the user for routing and charging purposes. Authentication by means of cryptographic procedures is thus required to stop impostors from taking on the identity of somebody else and “transferring” calls and charges. Eavesdropping on the radio path, intercepting data or tracing the whereabouts of a user by listening to signalling data are other serious threats. This paper discusses countermeasures designed into the Global System for Mobile communications, the rÔle of the Subscriber Identity Module as a security device and security aspects related to the management of the secret authentication keys.