Two Types of Trustworthiness of Acquaintances in Peer-to-Peer (P2P) Overlay Networks

Peer-to-peer(P2P) systems are in nature fully distributed with no centralized coordinator. A peer ps has to collect correct object information from trustworthy acquaintances which are considered to hold correct information. We consider two types of trustworthiness. First, the subjective trustworthiness stst on an acquaintance pt shows how much the peer ps trusts the acquaintance pt. The objective trustworthiness otst on an acquaintance pt indicates how much other peers trust the acquaintance pt. In this paper, we discuss three algorithms OT1, OT2, and OT3 for a peer ps to obtain the objective trustworthiness otst on the acquaintance pt. A peer ps collects subjective trustworthiness on an acquaintance pt from peers and obtain the average value as the objective trustworthiness. In the algorithm OT1, a peer ps tries to find every acquaintance of a target acquaintance pt in a type of flooding algorithm. Here, it takes time and more number of messages are transmitted. On the other hand, the peer ps sends request messages only to the acquaintances to reduce the number of messages in the algorithms OT1 and OT2. In OT2, only acquaintances which the peer ps can trust are considered. We evaluate the algorithms in terms of how correct objective trustworthiness can be obtained.