Mobile phones are rapidly becoming one of the most popular tools for communication. The rapid growth of wireless technology and the increasing use of such technologies in coordination with the internet require a very careful look at the issue of security. Security, Authentication, Encryption and Access Control are vital features that must be present in any communication network. In our paper we will investigate 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 UNITS 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.
