On 07/31/2014 11:44 AM, Joe Btfsplk wrote: > Wow, I'm surprised no one has questioned this before or has a reasonable > explanation. > Why Panopticlick's total estimated entropy, *reported in the sentence > _above_ their results table,* is much less than the sum of individual > parameters' entropies - shown in the table: > > "_Currently, we estimate that your browser has a fingerprint that > conveys *nn.nn bits* of identifying information_." > > To arrive at a total *"bits of identifying information"*, do they ignore > characteristics with entopies < certain values? > Because, in a typical test - w/ JS ENabled, the sentence may show total > entropy of *13.xx bits.* > In the same test, the sum of entropies from their included table may be > *34.xx* bits identifying information. > > Why is there such a huge difference? To arrive at their "total," what > do they ignore - and WHY? > Or, do they take the results in the table & apply additional > algorithms? If so, do they detail that? > Thanks.
I gather that entropy isn't always additive. I'd need to learn a lot before saying much more about that. There's probably something useful in https://panopticlick.eff.org/browser-uniqueness.pdf. Having Javascript blocked is itself information, but I don't think that Panopticlick is including that in the result. > On 7/30/2014 9:12 AM, Joe Btfsplk wrote: >> On 7/29/2014 4:35 PM, Ben Bailess wrote: >>> But here are some numbers that I just collected that >>> perhaps could be of use to you. This test was done with the latest TBB >>> (3.6.3) and Firefox versions on Linux (Fedora), with both JS on and off: >>> >>> FF (private browsing) / JS disabled = 16 bits (not "unique" - one in >>> 65,487) >>> FF (private browsing) / JS enabled = 22 bits ("unique" out of >4M >>> samples) >>> FF (normal browsing) / JS disabled = 15.98 bits (not "unique" - one in >>> 64,524) >>> FF (normal browsing) / JS enabled = 21.07 bits (not "unique" but one in >>> 2,193,824 [roughly 2 matching entries in the sample]... so the other >>> data >>> point may well have been me...) >>> TBB / JS enabled = 12.06 bits (not "unique" - one in 4,260) >>> TBB / JS disabled = 9.05 bits (not "unique" - one in 529 are same) >>> >> Thanks to all for your input. >> OK, I slept & revisited Panopticlick fingerprinting results >> https://panopticlick.eff.org. Silly me - I was looking at the values >> listed for each parameter, then assessing the total entropy for all >> parameters shown. >> Yes, if I look at the value they report *in a sentence* above the >> results table, that total is far < than the sum of "bits of identifying >> information" for all browser characteristics measured, as shown in their >> results table. >> >> For those that haven't looked at the site (or anything similar), the >> total entropy that Panopticlick arrives at is far < than the sum of >> individual values. >> ("The total is less than the sum of its parts" ??) >> Like when it says, >> "_Currently, we estimate that your browser has a fingerprint that >> conveys *13.72 bits* of identifying information_*,*" but the sum of all >> parameters in that same test is *far* > than 13.72 bits. >> >> Maybe someone more familiar w/ their algorithm to arrive at the grand >> total "*bits of identifying information," *(that they state in a >> sentence, above the results table) can explain why their stated total >> entropy for the browser tested is *so much lower* than the total of all >> parameters shown in the table of test results. >> >> I read their paper, https://panopticlick.eff.org/browser-uniqueness.pdf, >> but missed any explanation of why that is so. >> I have an idea why that may be true, but no (generic) mathematical >> explanation. > -- tor-talk mailing list - [email protected] To unsubscribe or change other settings go to https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk
