GSM Security features, threats and solutions

GSM (group special mobile or general system for mobile communications) is the Pan-European standard for digital cellular communications. The Group Special Mobile was established in 1982 within the European Conference of Post and Telecommunication Administrations (CEPT). A Further important step in the history of GSM as a standard for a digital mobile cellular communications was the signing of a GSM Memorandum of Understanding (MoU) in 1987 in which 18 nations committed themselves to implement cellular networks based on the GSM specifications. In 1991 the first GSM based networks commenced operations. GSM provides enhanced features over older analog-based systems, which are summarized below:

Total Mobility: The subscriber has the advantage of a Pan-European system allowing him to communicate from everywhere and to be called in any area served by a GSM cellular network using the same assigned telephone number, even outside his home location. The calling party does not need to be informed about the called person's location because the GSM networks are responsible for the location tasks. With his personal chipcard he can use a telephone in a rental car, for example, even outside his home location. This mobility feature is preferred by many business people who constantly need to be in touch with their headquarters.

High Capacity and Optimal Spectrum Allocation: The former analog-based cellular networks had to combat capacity problems, particularly in metropolitan areas. Through a more efficient utilization of the assigned frequency bandwidth and smaller cell sizes, the GSM System is capable of serving a greater number of subscribers. The optimal use of the available spectrum is achieved through the application Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), efficient half-rate and full-rate speech coding, and the Gaussian Minimum Shift Keying (GMSK) modulation scheme.

Security: The security methods standardized for the GSM System make it the most secure cellular telecommunications standard currently available. Although the confidentiality of a call and anonymity of the GSM subscriber is only guaranteed on the radio channel, this is a major step in achieving end-to- end security. The subscriber’s anonymity is ensured through the use of temporary identification numbers. The confidentiality of the communication itself on the radio link is performed by the application of encryption algorithms and frequency hopping which could only be realized using digital systems and signaling.

Services: The list of services available to GSM subscribers typically includes the following: voice communication, facsimile, voice mail, short message transmission, data transmission and supplemental services such as call forwarding.