Proposal for Anti-Keystroke Fingerprinting at the Display Server Level

[bancfc at openmailbox.org]

On 2016-03-24 12:45, Pekka Paalanen wrote:
> 
> Hi,
> 
> that's interesting. Sounds like you are looking for volunteers to
> implement what you want, right?

Yes please. Unfortunately I don't know C or have the skill to code 
something like this myself.

> 
> I skimmed through [3], and I got the impression that what the software
> does is to round key press and release times to the nearest multiple of
> 50ms or something along those lines.
> 
> I can immediately see one problem with that approach: key repeat.
> 
> Key repeat is based on a timer. On Wayland, that timer is currently in
> the application, not in the kernel nor even in the display server. If
> you skew the timings, you may screw up the repeats. For the record, it
> seems the default repeat on Weston is 40 Hz, which means 25 ms period.
> Rounding to nearest 50 ms sounds like a pretty big difference.

I originally proposed this on the QEMU/Libvirt lists and we reached the 
conclusion that the Display-server or kernel is the best place for this 
to benefit as many people as possible.

Someone replied with ideas about what an implementation would look like 
and he covers some of the problems you bring up:
https://lists.nongnu.org/archive/html/qemu-discuss/2016-03/msg00024.html

> 
> Another issue are gamers, who are going to hate you for messing up
> their key timings, so this system must be user-controlled.

Yes having this as an option people can change for specific usecases is 
the way to go. Per app or a global setting - which ever possible could 
work here.

> 
> I suppose there is also a practical issue of synchronizing key events
> to other input events. E.g. if you want to ctrl+click something, you
> have to synchronize multiple input event streams under the same timing
> fudging system to avoid the case where sometimes the key is not
> accounted for when clicking.
> 
> All that makes me wonder if the kernel is a sensible place for this.
> For a machine specifically built to be more secure at the expence of
> usability by ignoring all the above issues, then perhaps.
> 

I posted on lkml but no one seems to show interest and within a few 
hours my message is already buried.

> 
> Thanks,
> pq
> 
>> 
>> [1]
>> http://arstechnica.com/security/2015/07/how-the-way-you-type-can-shatter-anonymity-even-on-tor/
>> 
>> [2] http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=7358795
>> 
>> [3] https://archive.is/vCvWb
>> 
>> [4]
>> https://www.lightbluetouchpaper.org/2015/07/30/double-bill-password-hashing-competition-keyboardprivacy/#comment-1288166
>> 
>> [5] https://trac.torproject.org/projects/tor/ticket/16110
>> 
>> [6] https://trac.torproject.org/projects/tor/ticket/1517
>> 
>> 
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