[tor-bugs] #22422 [Core Tor/Tor]: Add noise to PaddingStatistics

Tor Bug Tracker & Wiki blackhole at torproject.org
Wed Jun 21 19:04:00 UTC 2017


#22422: Add noise to PaddingStatistics
--------------------------+------------------------------------
 Reporter:  teor          |          Owner:
     Type:  defect        |         Status:  new
 Priority:  High          |      Milestone:  Tor: 0.3.1.x-final
Component:  Core Tor/Tor  |        Version:  Tor: 0.3.1.1-alpha
 Severity:  Normal        |     Resolution:
 Keywords:  privcount     |  Actual Points:
Parent ID:                |         Points:  0.5
 Reviewer:                |        Sponsor:
--------------------------+------------------------------------

Comment (by mikeperry):

 Replying to [comment:7 teor]:
 > Replying to [comment:6 mikeperry]:
 > > To know how many padding cells to expect for a client, we need
 information on how long an average client's connection lasts,
 >
 > Using closed connections to count clients (and also not quite the time
 interval you're after):
 > "Tor has about 700 thousand unique clients connecting to the network
 during an average 10-minute interval."

 This doesn't tell us how long a *single* client remains connected on
 average.

 > > how often they make connections during a 24 hour interval,
 >
 > "Compared to Tor’s own estimate of about 1.75 million clients per day in
 May 2016..., this suggests that the client population turns over about 2.5
 times a day."

 This doesn't tell us how many connections a *single* makes in a day.

 > > and what percentage of the time those connections are idle. Do we have
 this data?
 >
 > "Somewhat surprisingly, we found that about 130 thousand clients have
 in-
 > active circuits during an average 10 minutes."
 >
 > (That is, closed connections with no circuits with more than 8 cells
 either sent or received.)

 This doesn't tell us how *long* a single connection remains idle, on
 average.

 > > Also, is there a good example of where we add noise in a way
 successfully calculates how to hide a single client's activity? It would
 be helpful to have a reference to work off of.
 >
 > Pages 7-8 of the PrivCount paper give the theory behind differential
 noise.
 > I am not sure where to find anything similar in the tor code.
 > When we add noise, we've done it inconsistently and arbitrarily in the
 past.

 Right now, it looks like this is where we're headed here, too.

 > Perhaps Rob or Aaron can help?

 I'm hoping Karsten can as well.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22422#comment:9>
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