Filtering SPAM in P2PSIP Communities with Web of Trust

Spam is a dominant problem on email systems today. One of the reasons is the lack of infrastructure for security and trust. As Voice over IP (VoIP) communication becomes increasingly popular, proliferation of spam calls is only a matter of time. As SIP identity scheme is practically similar to email, those share the same threats. We utilized Host Identity Protocol (HIP) to provide basic security, such as end-toend encryption. To provide call filtering, however, other tools are needed. In this paper, we suggest applying trust paths familiar from the PGP web of trust to prevent unwanted communication in P2PSIP communities. The goal is to provide trust visibility beyond the first hop without requiring people to openly share private data such as contact lists. Since our distributed environment limits global solutions, our proposal bases on scale-free distributed nodes which provide service to the social trust neighborhood. We have implemented the service as a freely deployable stand-alone HTTP server, which can be either independent or a part of the P2P overlay. We have evaluated the performance of the path finding algorithm using the social network data from the PGP web of trust.