On 3/21/06, Oskar Sandberg <[EMAIL PROTECTED]> wrote: > > The kind of attack I > mean is wide scale sybil type attack with a user spawning millions of > fake identities for his node, giving nodes faulty neighbors and > misinforming them about the size of the network etc.
Isn't the sybil attack against kademlia mitigated by the fact that the routing table has a "LRU with live nodes never evicted from k-buckets" strategy? It seems to me that this preference for old contacts would make it unlikely that a sybil attack against an established kademlia DHT could have much success. Admittedly, churn rate comes into play here, but the fact that a sybil attack could *never* purge currently connected valid nodes from a peer's routing table means that such a peer would always have at least some valid contacts. And the fact that each peer has some valid contacts implies that a valid route can always resolve, doesn't it (admittedly, with some decrease in performance/efficiency)? > There are other > more devious attacks such as those attempting to upset just routes for > one particular key value as well. There are defenses against targetted key attacks (in addition to the old contacts preference). For example, make each node choose its own Ku/Kr pair before joining, with nodeID = H(Ku). A node would have to 'prove' its identity before any of its operations or results are accepted (through challenge/response or signatures). Under such a scheme, an adversary could still spawn millions of sybil identities, but it wouldn't be able to choose a specific ID space to target. The millions of nodes /could/ try to upset some specific route, but preference for old contacts still makes this rather difficult. If you wanted to get really paranoid, you could introduce a trust/reputation system on top of a strong ID system like that mentioned above. This would even further diminish the effectiveness of sybil attacks of this nature. I hope I'm not being naive or unimaginitive by proposing that these countermeasures make such attacks less effective. I'd love to see further discussion on why these are insufficient, as well as further discussion on attackability of DHTs. Alen _______________________________________________ p2p-hackers mailing list p2p-hackers@zgp.org http://zgp.org/mailman/listinfo/p2p-hackers _______________________________________________ Here is a web page listing P2P Conferences: http://www.neurogrid.net/twiki/bin/view/Main/PeerToPeerConferences
