On Fri, 12 Jan 2001, John Young wrote:

>Wright also describes the use of supersensitive microphones
>to pick up the daily setting of rotors on cryptomachines of the 
>time, in particular the Hagelins made by CryptoAG.

Hmmm.  That sounds like a trick that could be brought up to 
date.  If you get two sensitive microphones in a room, you 
should be able to do interferometry to get the exact locations 
on a keyboard of keystrokes from the sound of someone typing.  
I guess three would be better, but with some reasonable 
assumptions about keys being coplanar or on a surface of known 
curvature, two would do it.  Interesting possibilities.


[A quick contemplation of the wavelength of the sounds in question
would put an end to that speculation I suspect. --Perry]

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