This dissertation characterizes the space of trust metrics, under both
the scalar assumption where each assertion is evaluated independently,
and the group assumption where a group of assertions are evaluated in
tandem. We present a quantitative framework for evaluating the attack
resistance of trust metrics, and give examples of trust metrics that
are within a small factor of optimum compared to theoretical upper
bounds. We discuss experiences with a real-world deployment of a group
trust metric, the Advogato website. Finally, we explore possible
applications of attack resistant trust metrics, including using it as
to build a distributed name server, verifying metadata in peer-to-peer
networks such as music sharing systems, and a proposal for highly spam
resistant e-mail delivery.