**3.1. Reputation system framework**

The conceptual operation of the reputation system is based on building a trust relation between different members of the community as they learn about each other. Thus, irrespective of why a node needs to build such relations, any reputation system must have two basic components, i.e. monitoring component to allow nodes to learn about each other and rating component to build the trust relations among nodes. However, the purpose of these trust relations will determine the specifications of each component and may imply a new component responsible for further actions based on the trust relations.

Our reputation system is fully distributed in the sense that each node implements all modules with the full functionality. Moreover, at the initial deployment stage, all nodes start with default and equal reputation values. This implies that all nodes have the same trust relation among each other. However, these initial reputation values are not the ones that imply a full trust. This is because our system assumes an always-suspicious environment in which all nodes are always '*suspects*'. A node can increase its reputation by good behavior or, otherwise, it decreases.

Since the purpose of the reputation system in this work is to provide trust aware routing in WSN, there are three basic components in our system. They are as follows.
