Hi Gunes, Thanks a lot for the feedback! On 03/16/2016 03:30 PM, gunes acar wrote: > Hi Pierre, > > Thanks for the very well thought proposal! > > I'm curious about your ideas on the "returning device problem." EFF's > Panopticlick and AmIUnique.org use a combination of cookies and IP > address to recognize returning users - so that their fingerprints are > not "double-counted." > > Since these signals will not available anymore (unless the user opt-ins > to retain the cookie), I wonder what'd be your ideas to address this issue. This one is a really interesting question but a tricky one because we can't really rely on the cookies+IP combination with the Tor browser. My answer here is simple: it all depends on the goal we set for the website. Do we want to learn how many different values there are for a specific test so that we can reduce diversity among Tor users? In that case, the site would not store duplicated fingerprints or it could be finer-grained and not store duplicated values for each test. Or do we want to go further and know the actual distribution of values among Tor users so that it may guide the development of a potential defense? In this case, the site must identify returning users and it is a lot harder to do here. The only method that comes to mind and that would be accurate enough to work in this situation would be to put the test suite behind some kind of registration system. The problem is that a mandatory registration goes in the complete opposite direction of what Tor is about and it would greatly limit the number of participating users (or even render the site useless before it is even launched). A solution in the middle would be not to store duplicated fingerprints but I really don't know how much it would affect the statistics in the long run. Would it be marginal and affect like 2/3/4% of collected fingerprints or would it be a lot more and go above 20% or else? Finally, I thought about using additional means of identification like canvas fingerprinting but I don't think there would be enough diversity here to identify a browser. > > Please find other responses below. > > Best, > Gunes > > On 2016-03-15 04:46, Pierre Laperdrix wrote: >> Hi Tor Community, >> .... >> - How closed/private/transparent should the website be about its tests >> and the results? Should every tests be clearly indicated on the webpage >> with their own description? or should some tests stay hidden to prevent >> spreading usable tests to fingerprint Tor users? > > I think the site should be transparent about the tests it runs. Perhaps > the majority of the fingerprinting tests/code will run on the client > side and can be easily captured by anyone with necessary skills (even if > you obfuscate them). > You are right on that. It makes sense to be transparent since obfuscated JS code can be deciphered by someone with the necessary skills. Also, if tests are hidden, most Tor users would rightfully be wary on what is exactly being executed in their browser and they would simply not take the test. In that case, the impact of the website would be greatly limited. Being transparent really seems to be the right way to go here. >> - Should a statistics page exist? Should we give a read access to the >> database to every user (like in the form of a REST API or other solutions)? > > I think aggregate statistics should be available publicly but exposing > individual fingerprints publicly may not be necessary. > Like you said, aggregate statistics seem to be the best solution here. Then, I'm wondering if it would be possible to offer the complete list of values for each attribute separately from others. Then, my concern is how easy it would be to correlate separate attributes to recreate fingerprints, even partial ones. Regards, Pierre
Attachment:
signature.asc
Description: OpenPGP digital signature
_______________________________________________ tor-dev mailing list tor-dev@xxxxxxxxxxxxxxxxxxxx https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev