Abstract: The present reserch investigated the existing authentication mechanisms for mobile communications and analyses these mechanisms as a step to propose enhancement to authentication. Specifically, the authentication signalling in GSM and UMTS mobile networks is minimized and consequently the bottleneck at authentication centre is avoided, by reducing the number of messages between mobile and authentication centre (i.e., reducing the procedures of authentication) and then reducing the authentication times, setup time and data sizes. The replay attacks and guessing attack are infeasible because the subscriber uses different key to request for authentication.