If I was given this job, not knowing anything about typewriters or spying, my first plan would be to modify all typewriters regularly by switching parts around

If I was given this job, not knowing anything about typewriters or spying, my first plan would be to modify all typewriters regularly by switching parts around according to a random draw, and also by rejigging any calibration settings (individual letter height, etc). This would modify both the sound of the typewriters and the fingerprints of the actual typed output [1]. This way, there would never be a per-typewriter profile, because all machines are randomised every week. Obviously, I'd also have a white-room analysis team checking whether the scheme works. Maybe someone who knows more about typewriters could tell me whether this would work at all, or there is a fatal flaw. [1] http://scholar.google.com.au/scholar?q=%22typewriter+identification%22&btnG=&hl=en&as_sdt=0%2C5 http://scholar.google.com.au/scholar?q=%22typewriter+identif...