  Studies on the large scale peer-to-peer (P2P) network like Gnutella have
shown the presence of large number of free riders. Moreover, the open and
decentralized nature of P2P network is exploited by malicious users who
distribute unauthentic or harmful contents. Despite the existence of a number
of trust management schemes in the literature for combating against free riding
and distribution of malicious files, these mechanisms are not scalable due to
their high computational, communication and storage overhead. These schemes
also do not consider effect of trust management on quality-of-service (QoS) of
the search. This paper presents a trust management scheme for P2P networks that
minimizes distribution of spurious files by a novel technique called topology
adaptation. It also reduces search time since most of the queries are resolved
within the community of trustworthy peers. Simulation results indicate that the
trust management overhead due to the pr oposed mechanism decreases considerably
as the network topology stabilizes. The mechanism is also found to be robust
even in presence of a large percentage of malicious peers.
