Re: Chaos harnessed for encryption / Fluctuations and Or

[collins@newton.apple.com (Scott Collins)]

  >[...] that can synchronize without publishing their states.
  >If this could be done with strong PRNGs, you'd have something.

Here is a related article

  Article = "Secret Key Agreement by Public Discussion from Common Information"
  Author  = Ueli M. Maurer
  Publication = IEEE Transactions on Information Theory, Vol 39, No. 3
  Date    = May 1993

--Abstract--
The problem of generating a shared secret key S by two parties knowing
dependent random variables X and Y, respectively, but not sharing a secret
key initially, is considered.  An enemy who knows the random variable Z,
jointly distributed with X and Y according to some probability distribution
Pxyz, can also receive all messages exchanged by the two parties over a
public channel.  The goal of a protocol is that the enemy obtains at most a
negligible amount of information about S.  Upper bounds on H(S) as a
function of Pxyz are presented.  Lower bounds on the rate H(S)/N (as
N-->infinity) are derived for the case where X = [X1, ..., Xn], Y = [Y1,
..., Yn], and Z = [Z1, ..., Zn] result from N independent executions of a
random experiment generating Xi, Yi and Zi for i=1, ..., N.  In particular,
it is shown that such secret key agreement is possible for a scenario where
all three parties receive the output of a binary symmetric source over
independent binary symmetric channels, even when the enemy's channel is
superior to the other two channels.  The results suggest how to build
cryptographic systems that are provably secure against enemies with
unlimited computing power under realistic assumptions about the partial
independence of the noise on the involved communications channels.
--end of Abstract--

Hope you like it,

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