[tor-dev] (Draft) Proposal 224: Next-Generation Hidden Services in Tor

Michael Rogers michael at briarproject.org
Thu May 28 10:59:48 UTC 2015

On 28/05/15 11:28, Jeff Burdges wrote:
>> One small problem with this suggestion (hopefully fixable) is that 
>> there's no single "current consensus" that the client and IP are 
>> guaranteed to share:
>> https://lists.torproject.org/pipermail/tor-dev/2014-September/007571.html
> If I understand, you’re saying the set of candidate RPs is larger
> than the set of candidate IPs which is larger than the set of
> candidate HSDirs, so disagreements about the consensus matter
> progressively more.  Alright, fair enough.

I wasn't thinking about the sizes of the sets so much as the probability
of overlap. If the client picks n HSDirs or IPs from the 1:00 consensus
and the service picks n HSDirs or IPs from the 2:00 consensus, and the
set of candidates is fairly stable between consensuses, and the ordering
is consistent, we can adjust n to get an acceptable probability of
overlap. But if the client and service (or client and IP) are picking a
single RP, there's no slack - they have to pick exactly the same one.

> An IP is quite long lived already, yes?  There is no route for the HS
> to tell the client its consensus time, but the client could share its
> consensus time, assuming that information is not sensitive elsewhere,
> so the HS could exclude nodes not considered by the client.  It's
> quite complicated though, so maybe not the best approach.

Even if the service knows what consensus the client is using, the
service may not have a copy of that consensus (and may not ever have had

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