On the establishment of distinct identifies in overlay networks

We study ways to restrict or prevent the damage that can be caused in a peer-to-peer network by corrupt entities creating multiple pseudonyms. We show that it is possible to remotely issue certificates that can be used to test the distinctness of identities. To our knowledge, this is the first work that shows that remote anonymous certification of identity is possible under adversarial conditions. Our certification protocols are based on geometric techniques that establish location information in a fault-tolerant and distributed fashion. They do not rely on a centralized certifying authority or infrastructure that has direct knowledge of entities in the system, and work in Euclidean or spherical geometry of arbitrary dimension. Our protocols tolerate corrupt entities, including corrupt certifiers as well as collusion by certification applicants and certifiers. We consider both broadcast and point-to-point message passing models.