Trustworthiness-based Group Communication Protocols

In peer-to-peer (P2P) overlay networks, a group of multiple peers have to cooperate with each other. P2P systems are in nature scalable distributed systems, where there is no centralized coordinator. It is difficult, maybe impossible for each peer to communicate with every other peer in P2P overlay networks. An acquaintance peer of a peer is another peer with which the peer can directly communicate. Each peer has to obtain access and location information on resources like databases through communicating with acquaintance peers. It is critical to discuss how each peer can trust an acquaintance peer in P2P networks since acquaintance peers may have obsolete information and may be faulty. In this paper, we discuss subjective and objective types of trustworthiness of a peer on an acquaintance peer. A peer obtains the subjective trustworthiness on an acquaintance peer through directly communicating with the acquaintance peer. On the other hand, a peer obtains the objective trustworthiness on a target acquaintance peer through collecting subjective trustworthiness of other peers on the target acquaintance peer. In this paper, the trustworthiness is given based on the Fuzzy logics. There are cases the subjective and objective types of trustworthiness on an acquaintance peer are different. That is, other peers have different trustworthiness opinions on the target acquaintance peer. A peer decides on which type of trustworthiness to be taken based on the confidence. The confidence of a peer shows how much the peer is confident of its own trustworthiness opinion, i.e. subjective trustworthiness on the acquaintance peer. If a peer is confident of the trustworthiness opinion, i.e. the confidence is larger, the peer takes the subjective trustworthiness on the target acquaintance peer. Otherwise, the peer takes the objective trustworthiness.