[tor-bugs] #13193 [Tor]: Tag circuits locally by exit vs hidden-service, for stats

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#13193: Tag circuits locally by exit vs hidden-service, for stats
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 Reporter:  arma                 |          Owner:
     Type:  enhancement          |         Status:  new
 Priority:  normal               |      Milestone:  Tor: 0.2.???
Component:  Tor                  |        Version:
 Keywords:  SponsorR, tor-relay  |  Actual Points:
Parent ID:  #13192               |         Points:
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 If we as a relay see a begin cell on a circuit, we know it's for exiting.

 And if we see one of the various hidden service related cells on it, we
 know it's for hidden services.

 And if we see an extend cell, we're a middle (i.e intermediary) hop in a
 circuit that terminates somewhere else. (assuming nobody uses the leaky
 pipe topology design, where you can exit from intermediary hops).

 How many of each type of circuit do relays of various types handle?

 And finally, what privacy risks are there to publishing aggregate ("total
 over past n seconds") statistics? for various values of n?

 One approach to ameliorating the privacy question could be to discard
 circuits where the previous hop isn't a known relay. I think that's relays
 in the guard position, and relays in the middle-hop position for users who
 use bridges.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13193>
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