Today, the most basic question concerning wireless sensor networks is designing a system that guarantees their security. One of the issues which has attracted extensive debate is developing a routing process which has the shortest distance and which uses the least amount of power so as the life span of the network can be increased. In this article we intend to create security in the network and also incorporate these two parameters. Therefore, by dividing the network in to clusters and by assigning the head cluster as the master agent, and through negotiations carried out between this agent and the other agents present in the network which function on the basis of multi-agent systems, and by making use of fuzzy decisions made by the master agent, we will deal with how much a node can trust other nodes; and finally, the enemy is identified when it passes through the expert system. Results obtained suggest that this system establishes a high level of security in the network.     

Key words: Fuzzy system, multi-agent system, node trust, wireless sensor network.