In tactical IoT networks, tactical IoT sensors are increasingly expected to be exploited for information collection in battlefields or dangerous areas on behalf of soldiers. The main function of these networks is to use sensors to measure radiation, nuclear, and biochemical values for the safety of allies and also to monitor and reconnaissance enemies. These tactical IoT sensors require a network traffic flow that sends various types of measured information to the gateway, which needs high reliability. To ensure reliability, it must be able to detect malicious nodes that perform packet-dropping attacks to disrupt the network traffic flow, and energy-constrained tactical IoT sensors require energy-efficient methods to detect them. Therefore, in this paper, we propose an energy efficient hybrid trust evaluation scheme for locating malicious nodes that perform packet-dropping attacks in a tree-based IoT network. Tactical IoT sensors send a query to the gateway by observing the traffic patterns of their child nodes. Moreover, depending on the situation, the gateway detects malicious nodes by choosing between gateway-assisted trust evaluation and gateway-independent trust evaluation. We implemented and evaluated the proposed scheme with the OPNET simulator, and the result showed that a higher packet delivery ratio can be achieved with significantly lower energy consumption.
