[tor-bugs] #16824 [Tor]: coexistence of client and relay processing on same thread poses traffic confirmation risk

[Tor Bug Tracker & Wiki]

#16824: coexistence of client and relay processing on same thread poses traffic
confirmation risk
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     Reporter:  starlight  |      Owner:
         Type:  defect     |     Status:  new
     Priority:  normal     |  Milestone:  Tor: 0.2.7.x-final
    Component:  Tor        |    Version:  Tor: 0.2.6.10
   Resolution:             |   Keywords:  PostFreeze027
Actual Points:             |  Parent ID:
       Points:             |
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Comment (by s7r):

 @mikeperry is right. Regardless if the same Tor instance runs a client
 only or a client and a relay, an active observer can distinguish the
 client traffic mixed with the relayed traffic using the timing method
 described by you. But, running a relay and a client (even on the same
 instance) provides you security against other attacks, which are not
 active, so this x2 option (be a client and a relay, even on the same Tor
 instance) is at least equally anonymous, if not (as I see it is) more
 anonymous.

 Adding a warning here will confuse users. How can we explain this well
 enough in a single log line? Saying that it's not safe would be false,
 saying it is less anonymous would be false, saying the client traffic is
 compromised would be false (the traffic is not compromised, just worst
 case distinguished from the relayed traffic, running the client in a
 separate instance would not mitigate this).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16824#comment:8>
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