Just for reference, it is called pseudospoofing or, using a recent buzzword, Sybil attack. I think this problem is orthogonal to actual P2P protocols. It is ra

Just for reference, it is called pseudospoofing or, using a recent buzzword, Sybil attack. I think this problem is orthogonal to actual P2P protocols. It is rare that such protection is deeply integrated into the protocol itself, the most popular one is probably a GNUnet with its economic system. On the other hand, solution from Tor with its directory services and FreeNet with F2F mode can be adopted by any P2P network.