- In the paper, we propose an efficient two-factor localized authentication scheme suitable for WLAN roaming. The proposed authentication scheme can greatly improve the security compared with the previously reported counterparts, where two independent factors, such as “what you know” and “what you have”, are utilized in the authentication process for a mobile user (MU). Some important issues specific to the wireless environment are considered in the design of the scheme, such as limited computation power, memory space, and battery capacity of mobile stations (MSs), and ping-pong movement problem when roaming across WLANs. The detailed implementation of the proposed scheme is presented, where some of the key performance measures and security are analyzed. Numerical results demonstrate that the proposed scheme can significantly outperform the legacy authentication schemes in terms of signaling overhead, power consumption, and authentication latency without losing the capability o...