**2.9. Related work**

246 Wireless Sensor Networks – Technology and Protocols

**2.8. Reputation systems** 

about each other[5,60].

reputation.

themselves.

forwarding attacks. This leads to the demand of increasing the number of sensors or changing the node deployment to return network connectivity. This is very expensive,

Network resources are also affected by misbehaving nodes. For example, Denial of service attacks affect resource availability, whether we consider an offended node as a resource for routing or we consider the availability of data itself. Also, this attack forces offended nodes

As we can see, the information value and the network performance are directly affected by

A reputation system is a type of cooperative filtering algorithm which attempts to determine ratings for a collection of entities that belong to the same community. Every entity rates other entities of interest based on a given collection of opinions that those entities hold

Reputation systems have recently received considerable attention in different fields such as distributed artificial intelligence, economics, evolutionary biology, etc. Most of the concepts in reputation systems depend on social networks analogy. As expected, reputation systems are complex in the sense that they do not have a single notion, but a single system will consist of multiple parts of notions. Thus, comparing reputation systems is, in fact, a very difficult problem. All known trials on such problem were based on qualitative approach. The work in [61] proposes an attempt on comparing reputation systems quantitatively based on game theory. The authors, thus, identify different notions of reputation systems like, contextualization, personalization, individual and group reputation, and direct and indirect

Reputation systems are often useful in large online communities in which users may frequently have the opportunity to interact with users with whom they have no prior experience. Such cases are clearly applicable to e-commerce applications and on line auctioning sites like eBay[62] and Epinions[63]. Another important field that derives the same concept of enforced interaction among entities that lack priori experience on each other is the field of ad hoc and wireless sensor network. This is because nodes in such networks need to route each others' packets. Thus, a trust relation should exist among

In the context of MANET and WSN [5, 11, 64], the reputation of a node is the amount of trust the other nodes grant to it regarding its cooperation and participation in forwarding packets. Hence, each node keeps track of each other's reputation according to the behavior it observes, and the reputation information may be exchanged between nodes to help each other to infer the accurate values. There is a trade-off between efficiency in using available information and robustness against misinformation. If ratings made by others are considered, the reputation system can be vulnerable to false accusations or false praise.

the security level provided by trust awareness of the routing operation in WSN.

however, can be avoided if a good secure routing solution is adopted.

to consume unnecessary energy on packet reception and processing.
