GSM

The goal of GSM is to provide a mobile phone System that allows user to roam throughout and provide voice services compatible to ISDN and PSTN.GSM stands for Global System for Mobile communications, originally from Groupe Special Mobile, used in 190 countries. GSM allows the integration of voice and data services and also the internetworking with the existing networks. The three types of services offered by GSM are Bearer Services, Tele Services and Supplementary services. GSM was designed with a moderate level of security. The system was designed to authenticate the subscriber using a pre-shared key and challenge-response.it also supports multiple algorithms so operators may replace that cipher with a stronger one.