Confidence and Trustworthiness in Peer-to-Peer Overlay Networks

Abstract

P2P systems are in nature fully distributed with no centralized coordinator and objects are autonomously distributed to peers in P2P overlay networks. Hence, each peer has to obtain service information on objects by itself through communicating with its acquaintance peers. An acquaintance might hold obsolete, even incorrect information on objects due to the propagation delay of changed information on the objects and faults of peers. Hence, a peer has to collect correct object information only from trustworthy acquaintances which are considered to hold correct information. We discuss subjective and objective types of trustworthiness of an acquaintance to measure how much the peer can trust the acquaintance. The subjective trustworthiness of an acquaintance shows how much the peer trusts the acquaintance by itself through directly interacting with the acquaintance. On the other hand, the objective trustworthiness of an acquaintance indicates how much other peers trust the acquaintance, which is obtained by collecting the subjective trustworthiness of the acquaintance from other peers. The types of trustworthiness may not be similar. If a peer is confident of its own subjective trustworthiness, the peer takes the subjective trustworthiness. Otherwise, the peer rather takes the objective one. We discuss what type of trustworthiness a peer uses to measure the trustworthiness of an acquaintance based on the confidence. We evaluate how the objective trustworthiness changes in change of satisfiablity of an acquaintance.