Re: [tor-talk] Making TBB undetectable!

[Ben Tasker <ben@xxxxxxxxxxxxxxx>]

> False! A unique Tor exit IP that visits site1.com then site2.com won't
> compromise same person visited those sites or tow different person who
> used same Tor exit IP at the same time did that, thus anonymity
> remains true.

But if one has one fingerprint (the default TBB) and the other an
'undetectable' one, then you can easily differentiate that they are two
different users. They both came from Tor exits, so you "know" they're TOR
users, but one user changing TBB's signature means they no longer appear as
close to identical as possible.

> TBB because when a natural fingerprint is used once then there will be
> no enough information available for data miners to link pseudonyms for
> deanonymization,

Used once, sure. But over time, it's likely going to get used more than
once, unless you're planning on inserting some sort of randomisation to try
and prevent that (by making some aspect different each session), but that
randomisation then becomes a potential means to identify users who are
using "UnidentifiableMode"

> Undetectability is a crucial requirement for privacy protection tools
> and unfortunately seems that Tor developers don't wanna put their time
> on this issue. I hope other folks take this problem serious and do
> something quickly.

I don't _know_ but I suspect it's actually the opposite - thought has
previously been put into the feasibility and risk and it's been decided
that the current approach should be safer. Making something "Undetectable"
is very, very hard as your margin for error is 0 (because 0.01 gives
something that someone could use to make it identifiable). Making something
common so you can blend into the crowd makes it easier to avoid
(potentially) costly mistakes.

Remember that those who are _really_ interested in de-anonymising via
fingerprinting are _very_ good at finding means to differentiate between
requests, one tiny slip-up is all it would take to make your
"Unidentifiable" browser extremely identifiable. You'd then (potentially)
be the only client with fingerprint a, coming from a Tor exit.

Even if you didn't slip up, let's say you make your requests look almost
exactly like vanilla firefox. If you're the only user using that mode at a
given time, every request coming from an exit with your fingerprint is an
opportunity to correlate that traffic back to you. There's no immediate
proof that all that traffic is you, but volumes would be low enough that
you could then start examining requests with an aim to trying to prove it's
all one user.

Blending into the crowd is not without it's value.

On Thu, Oct 1, 2015 at 12:09 PM, behnaz Shirazi <skorpino789263@xxxxxxxxx>
wrote:

> On Sat, Sep 26, 2015 at 7:44 PM, Jeremy Rand <biolizard89@xxxxxxxxx>
> wrote:
> >Maybe I'm not understanding you, but given that all TBB users are
> >already distinguishable from other users since their IP address is a
> >Tor exit, I'm not seeing how TorBrowser having a different fingerprint
> >from other browsers is a problem.  The important thing is that
> >TorBrowser users have the same fingerprint as each other, which the
> >TorBrowser devs seem to be doing a good job on.
>
> False! A unique Tor exit IP that visits site1.com then site2.com won't
> compromise same person visited those sites or tow different person who
> used same Tor exit IP at the same time did that, thus anonymity
> remains true.
>
> On Sun, Sep 27, 2015 at 7:40 AM, Dave Warren <davew@xxxxxxxxxxxx> wrote:
> >No, you can't just patch in a hardcoded window and screen size unless it
> reflects the actual >viewport size.
> >JavaScript is often used to position elements using relatively absolute
> positioning based on >the viewport that it understands is correct, this
> will fail if the viewport vs reported size isn't >accurate. More
> importantly, it won't even work, JavaScript can detect where wrapping
> >happens, and some creative 1 pixel tall transparent images could detect
> the actual horizontal >width by using varying widths.
>
> Browser Add-ons can change actual view size to anything we plan.
>
> On Mon, Sep 28, 2015 at 4:23 PM, AMuse <tor-amuse@xxxxxxxxxx> wrote:
> >Having a unique, or unique enough browser fingerprint would allow
> >website owners and content network providers to track a TOR user across
> >nodes and/or sessions. With a large enough CDN (facebook, etc) you could
> >reasonably de-anonymize a user.
>
> That is correct. But a Tor user who temporarily use a natural
> fingerprint to become undetectable for a while won't deanonymize
> itself nor the rest of other Tor users who use a detectable version of
> TBB because when a natural fingerprint is used once then there will be
> no enough information available for data miners to link pseudonyms for
> deanonymization, and for sure Tor users who need undetectability won't
> use the undetectablizer Add-on all the time hence detectable TBB users
> won't become unique.
>
> Undetectability is a crucial requirement for privacy protection tools
> and unfortunately seems that Tor developers don't wanna put their time
> on this issue. I hope other folks take this problem serious and do
> something quickly.
> --
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-- 
Ben Tasker
https://www.bentasker.co.uk
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