[118657] in Cypherpunks
Re: Unplugged! The biggest hack in history
daemon@ATHENA.MIT.EDU (Jonathan Wienke)
Mon Oct 4 23:07:44 1999
Message-Id: <3.0.6.32.19991004193903.007da7a0@mail.itiaccess.com>
Date: Mon, 04 Oct 1999 19:39:03 -0700
To: cypherpunks@cyberpass.net
From: Jonathan Wienke <mis@itiaccess.com>
In-Reply-To: <199910041732.TAA22459@mail.replay.com>
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Reply-To: Jonathan Wienke <mis@itiaccess.com>
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At 07:32 PM 10/4/99 +0200, Anonymous wrote:
>Bill Stewart writes:
>> It's not just that the eavesdropper has a hard time figuring out
>> what Alice and Bob's modems negotiated - it's that the negotiation
>> determines the correct voltage/power/etc levels for each frequency
>> to cram the most possible bits through the connection between
>> those two endpoints given their actual analog characteristics,
>> and Eve's modem is on a different hunk of wire so it needs
>> different levels to optimally transmit data to it.
>
>This is also the basis for some of the methods of secure cryptography
>which don't depend on computational assumptions. Ueli Maurer has
been
>one of the main researchers on this.
>
>If two people are separated by a wire with some inherent amount of
>noise which affects the eavesdropper differently than the two people,
>they can set up a secure channel even without any preshared secrets.
>Basically they exchange a lot of random data and consolidate it in
such
>a way that the eavesdropper ends up seeing mostly noise, producing a
>shared secret key that the eavesdropper doesn't know.
>
>You can also do Oblivious Transfer with a noisy channel and from this
>you can build up much the same technology as PK crypto.
>
>The problem is that you have to estimate your noise levels, which
>basically means estimating how much money your attacker can spend to
>eliminate noise. Then if you're wrong and he spends more, you may be
>vulnerable.
Noise elimination (at least for constant noise like tape hiss) is
cheap. There is an excellent shareware audio editing program
available called Cool Edit
(http://www.syntrillium.com/cooledit/index.html#rm) which includes a
noise filter. You set up the filter by selecting a portion of the
sound file containing only noise and letting the filter create a
profile if the noise characteristics. You then run the filter on the
entire file, and all noise matching the profile is eliminated. I have
used it to make a cheap tape sound like a cheap CD.
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Jonathan
