Re: Brin: Quantum Cryptography Outperformed By Thermodynamics

> The idea is straightforward. Alice wants to send Bob a message via an
> ordinary wire. At each end of the wire, there are two different
> resistors that correspond to a 0 or 1. Alice encodes her message by
> connecting these two resistors to the wire in the required sequence.
> Bob, on the other hand, connects his resistors to the wire at
> random. The crucial part of this set up is that the actual current
> and voltage through the wire is random, ideally Johnson noise. The
> essential features of this noise are determined by the combination of
> resistors at each end. This noise is public--anybody can see or
> measure it. Now here's the clever bit. Bob knows which resistor he
> connected to the wire and so can work out which resistor Alice must
> have connected. But Eve, who is listening in to the publicly
> available noise, does not know which resistor was connected at each
> end and cannot work it out either because the laws of thermodynamics
> prevent the extraction of this information from this kind of signal.

So why isn't this susceptible to a simple man in the middle attack?:

Eve cuts the wire between Alice and Bob (AB line) and insert her own 
node that connects to Alice (AE line) and Bob (BE Line) individually. 
Alice can't tell the difference between the AB line or the AE Line and 
sets her resisters.  Eve sets her resisters connected on the AE line to 
random and deciphers the sequence that Alice used.  Eve then Uses that 
sequence on the BE Line.  Bob can't tell the difference between the AB 
line and the BE line, sets his resisters randomly and decodes the 
message.  (Eve can even send Bob a False message).

Seems like this method requires a 100% secure land line, which is 
impractical.


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"It’s cheap to maintain Lies and expensive to maintain Trvth."
--KZK's Maxim