Abstract: In wireless sensor networks,it is difficult to take from the rate of trust risk. This paper used the concept or cloud theory to estimate dynamic context and consequently presented the definition of risk signal,and a cloud trust model based on risk evaluation for wireless sensor networks was proposed in this paper to solve this problem, in which the uncertainty between dynamic context relationships is considered. The risk was evaluated using cloud theory, quantified using risk and trust uncertainty degree presented in a uniform form. The simulation results show that the proposed trust model based on risk evaluation can efficiently express uncertainty of risk and trust, and decrease trust risk of nodes. And so this trust model also can evidently take from the rate of trust risk, and enhance successful cooperation ratio of system.

Key words: Trust model,Risk,Cloud model