The integration of the Internet of Things (IoT) with fog computing has significantly enhanced the capabilities of IoT applications y extending their reach and reducing latency. Fog nodes, being transient and authorized service providers, necessitate eauthentication of IoT end devices when contact is lost, requiring the device to connect to a new fog node. In this research, we propose an innovative security protocol designed to ensure seamless failover among fog nodes. This protocol facilitates quick and easy failover authentication among IoT devices and fognodes using the key agreement among fog nodes. LEFAM overcomes the requirement for the end device to communicate with the fog node atleast once to get the security token in order to execute failover authentication. This work proposes efficient, scalable and robust scheme required for fog-IoT environment to provide solution in case of failure of the primary fognodes. Our approach effectively mitigates various security threats, as demonstrated through informal analysis. Furthermore, simulation results obtained using the Scyther tool confirm the robustness of our protocol in terms of security. A formal analysis conducted using the RoR model further substantiates the reliability of our protocol. Notably, our protocol involves fewer message exchanges, indicating a lower communication overhead compared to other existing schemes. The key finding indicates that the LEFAM scheme offers an average improvement of ≈ 76% and 1188 bits for computation and communication overheads, respectively. Overall, our protocol not only enhances security but also offers superior performance relative to existing protocols.

Keywords：Authentication; Failover; IoT-fog; Key agreement; Scyther simulation