GSM gets new security algorithm

5 Jul 2002 at 08:55 GMT Marc van Impe

A new security algorithm, known as A5/3, will provide users of GSM mobile phones with a higher level of protection against eavesdropping. With new encryption a prospective attacker, if he manages to pull a GSM phone call out of the radio waves, will be completely unable to make sense of it, even if he throws massive computing resources at the task.

A5/3 has been developed by a joint between the GSM Association Security Group and the 3rd Generation Partnership Project (3GPP), for use in GSM systems. It will also be useable with GPRS as GEA3, and also with HSCSD and EDGE.

The A5/3 encryption algorithm specifically supplies signalling protection, so that sensitive information such as telephone numbers is protected over the radio path, and user data protection, to protect voice calls and other user generated data passing over the radio path. The algorthm joins an existing family of GSM A5 algorithms, which was developed in 1987. The A5 has been blamed in the past for being weak against powerful computers.

The new algorithm was designed by the Security Algorithms Group of Experts (SAGE) of the European Telecommunications Standards Institute (ETSI), based on a requirements by 3GPP's Working Group SA3. The development was supported by the GSM Association, 3GPP and the United States' T1 Standards Committee, sponsored by the Alliance for Telecommunications Industry Solutions (ATIS).

A5/3 is based on the Kasumi algorithm, whic is to used also in 3rd Generation mobile systems as the core of confidentiality and integrity algorithms. Kasumi in turn was derived from the MISTY algorithm, created by Mitsubishi. The defining specifications are publicly available on the 3GPP web site.

It is expected that the algorithm will be publicly available from the third quarter of 2002 and will then be progressively implemented in mobile systems.