Systems using peer-to-peer (P2P) overlay networks are getting a central position in information systems. P2P systems are in nature fully distributed, with no centralized coordinator and each peer is autonomous. Each peer has to obtain information on resource objects like databases distributed in networks by itself through communicating with its acquaintance peers. Since the P2P system is scalable, it takes time to propagate information on objects to peers in the network. A peer might be faulty and a peer holding an object might lose the object. Thus, an acquaintance peer might hold obsolete, even incorrect information on objects. It is critical to discuss how a peer can trust each acquaintance peer. We discuss two types of trustworthiness, subjective and objective ones. The subjective trustworthiness on an acquaintance peer is obtained by directly interacting with the acquaintance peer. On the other hand, the objective trustworthiness on an acquaintance peer is obtained by collecting the subjective trustworthiness of other peers. The subjective and objective types of trustworthiness might be different. If a peer is confident of its trustworthiness opinion, the peer takes the subjective trustworthiness. Otherwise, the peer rather takes the objective one. We discuss what type of trustworthiness a peer uses on an acquaintance peer based on the confidence.
