From: fc@all.net (Dr. Frederick B. Cohen)
Date: Sun, 5 Nov 1995 12:41:59 +0800
To: cypherpunks@toad.com
Subject: Real randomness generators
Message-ID: <9511032132.AA00195@all.net>
MIME-Version: 1.0
Content-Type: text


Two points:

	1 - The noisiest thing on most lists is the noise about other
	peoples' noise.

	2 - Why not use the postings of people complaining about other
	peoples' posts as a source for noise.  Surely few things in the
	Universe are more random.

On the the subject at hand:

	There are two major technical issues I have encountered in using
EM waves (which is what video and radio noise are) for generating
randomness. 

	1 - They tend to be biased toward 1 or 0.  This can often be
	compensated for by (for example) xoring one bit stream from the
	same source with the inverse of another.  By doing this enough
	times, you can eliminate many of the characteristics of interest.

	2 - Noise tends to be characteristic for different media and noise
	causes.  This is a more difficult issue.  For example, certain
	types of media tend toward short noise bursts.  In these cases,
	you have to be quite careful to assure that the bit streams meet
	the randomness criteria of the application.

As a side issue, you may find that once you start sending enough
information with truly random characteristics, you will be visited by
people that don't want you sending it.  I know people who have
experienced these visitations and felt highly constrained as a result.

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