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 p_s 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 st_st on an acquaintance p_t shows how much the peer p_s trusts the acquaintance p_t. The objective trustworthiness ot_st on an acquaintance p_t indicates how much other peers trust the acquaintance p_t. In this paper, we discuss three algorithms OT1, OT2, and OT3 for a peer p_s to obtain the objective trustworthiness ot_st on the acquaintance p_t. A peer p_s collects subjective trustworthiness on an acquaintance p_t from peers and obtain the average value as the objective trustworthiness. In the algorithm OT1, a peer p_s tries to find every acquaintance of a target acquaintance p_t in a type of flooding algorithm. Here, it takes time and more number of messages are transmitted. On the other hand, the peer p_s 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 p_s can trust are considered. We evaluate the algorithms in terms of how correct objective trustworthiness can be obtained.