[tor-bugs] #10969 [Tor]: Set of guard nodes can act as a linkability fingerprint

[Tor Bug Tracker & Wiki]

#10969: Set of guard nodes can act as a linkability fingerprint
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 Reporter:  asn                                  |          Owner:
     Type:  defect                               |  mikeperry
 Priority:  Medium                               |         Status:
Component:  Tor                                  |  assigned
 Severity:  Normal                               |      Milestone:  Tor:
 Keywords:  tor-client, tor-guard,               |  0.2.8.x-final
  026-triaged-1, XKEYSCORE                       |        Version:
Parent ID:  #11480                               |     Resolution:
  Sponsor:                                       |  Actual Points:
                                                 |         Points:  large
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Comment (by isis):

 Replying to [comment:19 cypherpunks]:
 > Is this really a worthwhile problem to solve? If there there is any non-
 Tor network traffic, it likely contains some unique identifier anyway
 (cookies, session ids, unique ids in update checks; the set of update
 checks is likely unique; standard browsers likely have a unique
 fingerprint that is probed by ad networks).
 >
 > Users who are not able to set guard nodes manually, will more than
 likely run into one of the things mentioned above.

 '''Yes. It is very important.'''

 It's important because one of the major use cases for Tor is for people
 who have been (or are) in abusive relationships, or people who have
 stalkers.  All such an abuser/stalker would need to do to find the
 person's physical location is wardrive around while running wireshark —
 any relatively unskilled person could do this.

 A bigger problem is that this allows adversaries with more observational
 capabilities (e.g. NSA, GCHQ, BND, perhaps some ISPs) to track Tor users'
 movements and store that data forever.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/10969#comment:20>
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