Proposal for Anti-Keystroke Fingerprinting at the Input Driver Level
Date: Wed Mar 23 2016 - 18:50:40 EST
== Attack Description ==
Keystroke fingerprinting works by measuring how long keys are pressed
and the time between presses. Its very high accuracy poses a serious
threat to anonymous users.
This tracking technology has been deployed by major advertisers (Google,
Facebook), banks and massive online courses. Its also happening at a
massive scale because just using a JS application (or SSH in interactive
mode) in presence of a network adversary that records all traffic allows
them to construct biometric models for virtually everyone (think Google
suggestions) even if the website does not record these biometric stats
itself. They have this data from everyone's clearnet browsing and by
comparing this to data exiting the Tor network they will unmask users.
== Current Measures and Threat Model ==
While the Tor Browser team is aware of the problem and working on a
solution, current measures  are not enough. 
It's very useful to have it fixed on the OS level so even compromised
VMs could not perform keystroke fingerprinting. Another reason is, that
other applications (chat clients come to mind) and others that implement
fixed in Tor Browser is nice but non-ideal.
This is valid for systems running in VMs or on bare metal such as the
TAILS Anonymous distro.
== Existing Work on Countermeasures ==
As a countermeasure security researcher Paul Moore created a prototype
Chrome plugin known as KeyboardPrivacy. It works by caching keystrokes
and introducing a random delay before passing them on to a webpage.
Unfortunately there is no source code available for the add-on and the
planned Firefox version has not surfaced so far. There are hints that
the author wants to create a closed hardware USB device that implements
this which does not help our cause.
GenodeOS a security centric microkernel OS has already implemented a
QubesOS a security centric OS based on Xen will add a fix to deal with
A widely deployed Linux version only makes sense and would have the
greatest impact for security of most free/open systems out there.
== Proposal for a System-wide Solution ==
A very much needed project would be to write a program that mimics the
functionality of the this add-on but on the kernel level. Implementing
it in the kernel ensures absolutely everything consuming input events on
a workstation is protected.