On 6/15/2012 2:37 AM, KZK wrote:
> 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.
>
David Hobby Fri, 15 Jun 2012 06:31:29 -0700:
I believe that Alice and Bob are doing the resistor thing for each
bit simultaneously, and sharing their measurements over a separate
open channel.
And so Eve man-in-the-middles the second connection too. So all of
Alice and Bob's communications are with eve, so that (Eve and Alice) And
(Eve and Bob) are doing the resistor thing for each bit simultaneously
(but not Alice and Bob, they have no connection with each other), and
(Eve and Alice) And (Eve and Bob) are sharing their measurements over
the separate lines (but not Alice and Bob, they have no connection with
each other). Bob still can't tell the difference between Eve and Alice
and Alice can't tell the difference between Eve and Bob.
(The paper says the voltage/current data on the noisy
channel is "public".) Furthermore, they're tossing all the trials
where those data show they both picked the "high" resistors or both
picked the "low". So all Eve can usefully look at are data for
essentially identical trials, each one with the noise characteristic
of one high and one low resistor on the channel. Eve is free to relay
noise between the two lines in your example, but that won't help
her.
Doesn't matter, so long as Eve is between all communications channels.
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