A Trust Evaluation Model for Wireless Sensor Networks
4. Overview of the Efficient Dynamic Trust Evaluation Model
To efficiently compute the trust values on sensor nodes, we first need a clear understanding of the trust model process. The DTEM runs at the middleware of every sensor node. Every node maintains the trust value about other nodes; there is no central repository for storing trust values of every entity in the system. The process of DTEM is shown in Figure 1; the direction of the arrow represents the flow of information between them. And the specific process is as follows.
(1) Information gathering: we use watchdog mechanism to monitor neighboring nodes' activities periodically as RFSN to collect evidence information. The available neighbor nodes' information is stored in the routing table of the node.
(2) Trust value calculation: in the proposed trust models, when a subject node wants to obtain the trust value of an object, it first checks its recorded list of neighbor nodes. The direct trust and recommendation are used to evaluate the trustworthiness of sensor nodes based on the recorded list. The direct trust is directly calculated based on the communication, data consistency, and energy. However, due to malicious attacks, using only direct trust to evaluate sensor nodes is not accurate. Thus, the recommendation from other sensor nodes is needed to improve the trust evaluation. Due to the dynamic behavior of WSNs and the impact of some special malicious attacks like on-off attack, the calculation of trust value should be based upon history interaction records and updated periodically.
(3) Trust value integration: to ensure that the trust model makes a decision more scientifically, dynamically, and adaptively, we define a dynamic balance weight factor to realize the integration trust value of direct trust and indirect trust.
