INTRODUCTION With GSM, systems for mobile communication reached a global scale. In the western world, it seems everyone has their own mobile phone, and GSM has taken more and more of the market. GSM allows users to roam seamlessly between networks, and separate the user identity from the phone equipment. In addition the GSM system provides the functional basis for the 3rd generation mobile system, UMTS.
Protection of the network against unauthorized use
Create a session key
Subscriber identification: IMSI or TMSI
Challenge-Response authentication of the subscriber by the operator
Authentication and Encryption Scheme A3 Mobile Station Radio Link GSM Operator A8 A5 A3 A8 A5 K i K c K c SIM Authentication: are SRES values equal? Challenge RAND m i Encrypted Data m i Signed response (SRES) SRES SRES F n F n