Big hype on small worlds. (was Re: Dijjer and Freenet (RE: [p2p-hackers] clustering))

[Alen Peacock]

On 3/22/06, Oskar Sandberg <ossa at math.chalmers.se> wrote:
>
> But you cannot discount churn from this equation - this is a distributed
> P2P scenario, nobody is up 24/7. And, on the flipside, never changing
> neighbors will means that once an attacker is in, he can do a lot of
> damage without being replaced.

Churn rate will be specific to the application running on top of the
DHT, but yes, if churn is high and *no one* stays on 24/7, my argument
goes away to a large extent.


> I don't think a trust system can do much at all. Because the graph in
> the DHT (however you do it) prescribes at least a distribution regarding
> who should be linking whom (based on ID),

Nodes in kademlia do have some freedom of choice.  They can certainly
choose to reject adding blacklisted nodes to their own routing tables.
 Nodes are rejected if they are unreachable due to non-transitivity,
for example.  Adding other criteria for rejection is likewise okay,
because the core algorithm's parallel query strategy is resilient to
errors -- in the case of trust, if your closest neighbors don't trust
you, then more distant neighbors certainly shouldn't either, so the
fact that they don't route to you is beneficial.

Of course, trust doesn't protect as well against nodes that behave
kindly to all near neighbors, but maliciously to those more distant. 
To start to deal with that you'd need to extend from purely local
trust to some sort of reputation system.

Alen