From: "James A. Donald" <jamesd@echeque.com>
Date: Wed, 20 Sep 95 23:39:58 PDT
To: David Van Wie <cypherpunks@toad.com>
Subject: Re: Entropy vs Random Bits
Message-ID: <199509210639.XAA15833@blob.best.net>
MIME-Version: 1.0
Content-Type: text/plain


At 11:51 PM 9/20/95 P, David Van Wie wrote:
> This is odd.  The term entropy describes an aspect of thermodynamic 
> equlibrium in physical systems.  Although sometimes used as a synonym for 
>"random," that definition is vernacular, not technical.  In fact, there is 
> no meaningful relationship between "entropy" and random data of the type 
> described in the postings related to seed values.  In the presense of a 
> perfectly suitable and precise mathematical term (i.e. random),

Your use of the word random is incorrect:  The throw of a dice is 
random, but only contains 2.6 bits of entropy.

The windows VDT counter is very far from being random, but 
contains roughly sixteen bits of entropy.

> why invent new terms?  Why use them to mean at least two different things?

This is old term of the art, a term of information theory:  We use 
the same word because entropy in information theory has the same 
measure as entropy in thermodynamics.

In both cases the entropy, measured in bits, of an ensemble of 
possible states is sum of  - P(i) * lg[P(i)] over all the possible states.


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