[tor-bugs] #13021 [Tor Browser]: Review Canvas APIs for fingerprintability

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#13021: Review Canvas APIs for fingerprintability
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     Reporter:           |      Owner:  brade
  mikeperry              |     Status:  assigned
         Type:  task     |  Milestone:
     Priority:  major    |    Version:
    Component:  Tor      |   Keywords:  ff31-esr, tbb-fingerprinting,
  Browser                |  TorBrowserTeam201409
   Resolution:           |  Parent ID:
Actual Points:           |
       Points:           |
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Comment (by dcf):

 Replying to [comment:2 gacar]:
 > I checked https://bugzilla.mozilla.org/show_bug.cgi?id=884226: This
 brings a new canvas context property (`willReadFrequently`) that enables
 reading from a software backend instead of a hardware "accelerated" one,
 which turns out to be super-slow for some cases.

 If a browser has both accelerated and non-accelerated canvases, they
 probably don't render things identically. You could draw the same
 fingerprinting issue in both and hash them together, and thereby get more
 discriminating power than one canvas alone.

 I agree that willReadFrequently doesn't add any new fingerprinting power,
 because in its absence you just have to game whatever heuristic decides
 whether you get an accelerated or non-accelerated canvas.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13021#comment:3>
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