[tor-bugs] #11565 [Tor]: Make it clear if circ_id for create cell can be zero with non zero MSB

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#11565: Make it clear if circ_id for create cell can be zero with non zero MSB
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     Reporter:  cypherpunks  |      Owner:
         Type:  defect       |     Status:  new
     Priority:  normal       |  Milestone:  Tor: 0.2.5.x-final
    Component:  Tor          |    Version:
   Resolution:               |   Keywords:
Actual Points:               |  Parent ID:
       Points:               |
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Comment (by nickm):

 I don't see how you can leak information with that; if you managed to fill
 up the circID space between A and B, *and* get an exact count of circuits,
 you could learn whether A or B was the connection initiator... but to fill
 up the space in v4 link protocol, you would need to make 2 billion
 circuits, and to get an exact count, you would need to be sure that nobody
 else is making circuits too.  Even if you succeeded, it's not clear to me
 what good it would do to know whether A or B is the initiator.

 At least, that's what I think now.  Is there an attack here that I'm
 missing?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/11565#comment:4>
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