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bluesky - Re: how to do censorship resistance (Re: Grapevine Technical Overview)

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Subject: Global-Scale Distributed Storage Systems

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  • From: Bram Cohen <bram AT bitconjurer.org>
  • To: Global-Scale Distributed Storage Systems <bluesky AT franklin.oit.unc.edu>
  • Subject: Re: how to do censorship resistance (Re: Grapevine Technical Overview)
  • Date: Mon, 27 May 2002 19:42:53 -0700 (PDT)


Stephen Blackheath wrote:

> Another good thing about toroidal space is that you never have to
> traverse more than half of space, because if you did, you'd be better
> off going in the opposite direction.

That's cute, but a bit of a non-issue I think, since a factor of 2 doesn't
change the asymptotic any.

It occurs to me that if you generalize from 6-space to n-space, and
simplify so that each peer is at position 0 or 1 instead of a floating
point, then you wind up with something very similar to kademlia's xor
metric.

Each peer has an id which is 160 bits. The distance between peer A and B
is the number of 1 bits in the xor of A and B's ids.

You can read about kademlia at http://kademlia.scs.cs.nyu.edu/ It's metric
differs from the one I just gave in that it's a tree instead of a mesh.

You can probably do a good job of pruning peers by having each peer find
out about all of it's peers's peers (by querying it's immediate peers) and
having a policy that if it's peer A and it has peers B and C and the
distance between A and C is greater than both the distance between A and B
and B and C (each, not their sum) then it forgets about C.

Note that kademlia does this for robustness, rather than anonymity
purposes, so the way it uses peers is very different from grapevine.

-Bram





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