[network-health] ASMap Work for Sybil Resistance in Bitcoin Core

[Roger Dingledine]

On Fri, Jan 31, 2020 at 05:48:19PM -0500, Matt Corallo wrote:
> Still, relying on the dirauths as they exist today is not perfect. While it may, in principle, be ok that OVH has a preponderance of Tor relays, it wouldn???t be ok to build a path through only OVH relays (even if they are in different countries). In theory ASMap could address exactly that.

Hi Matt!

The real fun begins when you think not just about the locations of the
relays, but about the locations that the traffic goes through, when it's
transiting between relays.

That is, yes you should worry about whether all your relays are in
buildings owned by OVH. But you should also worry about whether the
traffic between the relays transits a single (the same) telephone company
at each hop. And for the Tor case (I don't know about your case), what
matters most to us is the internet path between the client and the first
relay, and the internet path between the last relay and the destination.

Many papers have been written about the topic, from measuring how bad
it is:
https://www.freehaven.net/anonbib/#feamster:wpes2004
https://www.freehaven.net/anonbib/#DBLP:conf:ccs:EdmanS09
https://www.freehaven.net/anonbib/#ccs2013-usersrouted
https://www.freehaven.net/anonbib/#trustrep-pets2015
https://www.freehaven.net/anonbib/#tortraceroutes-pets2015

to designing alternate path selection mechanisms to avoid trust
bottlenecks:
https://www.freehaven.net/anonbib/#ccs2011-trust
https://www.freehaven.net/anonbib/#ASlevel-ndss2016
https://www.freehaven.net/anonbib/#taps-ndss2017
https://www.freehaven.net/anonbib/#counter-raptor
https://www.freehaven.net/anonbib/#placement-pets2019

And those are just a few of them. To start reading, I would suggest
these three:
https://blog.torproject.org/improving-tors-anonymity-changing-guard-parameters
https://www.freehaven.net/anonbib/#ccs2013-usersrouted
https://www.freehaven.net/anonbib/#placement-pets2019

Hope this helps,
--Roger