[8441] in cryptography@c2.net mail archive
Re: NONSTOP Crypto Query
daemon@ATHENA.MIT.EDU (Ray Dillinger)
Sat Jan 13 17:36:53 2001
Date: Sat, 13 Jan 2001 12:11:13 -0800 (PST)
From: Ray Dillinger <bear@sonic.net>
To: Ben Laurie <ben@algroup.co.uk>
Cc: John Young <jya@pipeline.com>, cryptography@c2.net
In-Reply-To: <3A5FAFB1.33FF89E2@algroup.co.uk>
Message-ID: <Pine.LNX.4.21.0101131154020.13365-100000@bolt.sonic.net>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
>Ray Dillinger wrote:
>>
>> 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.
>>
>> Bear
>>
>> [A quick contemplation of the wavelength of the sounds in question
>> would put an end to that speculation I suspect. --Perry]
We hear low-frequency sounds when we type. But have we ever checked
for high-frequency sounds outside of human hearing range? I'd bet
a keyboard has a number of squeaks and ticks and twangs up there.
I'd also bet that most of the keys, after a keyboard's broken in,
don't sound exactly alike -- wear and tear, typing patterns, etc.
You might be able to resolve ambiguities of interferometry by using
the sounds of the keys themselves.
Bear
