[118630] in Cypherpunks
Re: Unplugged! The biggest hack in history
daemon@ATHENA.MIT.EDU (Anonymous)
Mon Oct 4 13:54:32 1999
Date: Mon, 4 Oct 1999 19:32:06 +0200 (CEST)
Message-Id: <199910041732.TAA22459@mail.replay.com>
From: Anonymous <nobody@replay.com>
To: cypherpunks@cyberpass.net
Reply-To: Anonymous <nobody@replay.com>
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.
