On 09/18/2017 09:27 PM, jes...@gmail.com wrote:
> Thank you Micah and Michał, but I am not actually asking about a standard as 
> strong as 100% bulletproof anonymity or anything. I really am just concerned 
> about whether any of the methods on that list that I linked to would be 
> enough to leak cookie-like reference data between two separate Qubes security 
> domains.

Cookie-like reference data between two separate Qubes security domains
cannot happen. This would mean one VM is able to influence the hard disk
of another, which would be a vulnerability in Qubes.

> Being tracked as I browse around *in* a given security domain is entirely my 
> problem of course, and I understand that. My only concern is working to 
> ensure that to an outside observer such as webservers and ad networks nothing 
> short of the shared IP address (and via Tor or VPN or different IPs honestly 
> allocated to different domains perhaps not even that) can act as a reliable 
> indicator that web browsing activity in one Qubes security domain is "linked" 
> to activity from another security domain via any secretly stored cookie-like 
> reference identifiers that get somehow leaked across domains.

What can however happen is things like hardware fingerprinting through
the browser, like CPU frequency measurements.

Also, Qubes doesn't guarantee two VMs can't talk together, so if you
have at the same time a browser in two VMs in two websites they may be
able to talk together using such side channels (timing the cache,
ultra-low-level stuff like that).

So even though supercookies and the like aren't shared in Qubes, if you
use an insufficiently anonymising web browser, a web site may be able to
fingerprint your hardware through the browser (Qubes/Xen does nothing to
prevent that for performance reasons), and then to link your hardware to
different identities you used to browse different pages in different VMs.

I don't know of any website that would try to talk to others through
side-channels, but I seem to remember articles on hardware
fingerprinting (esp. the cpu frequency and drift, iirc) through JS from
a few years back, so I guess against state-of-the-art tracking systems
Qubes will not be enough.

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