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From: biep@cs.vu.nl (J. A. "Biep" Durieux)
Newsgroups: sci.math,sci.crypt
Subject: Re: Encryption of Hoffman coded text
Message-ID: <851@klipper.cs.vu.nl>
Date: Wed, 12-Aug-87 07:14:18 EDT
Article-I.D.: klipper.851
Posted: Wed Aug 12 07:14:18 1987
Date-Received: Fri, 14-Aug-87 04:44:46 EDT
References: <10489@linus.UUCP] <7876@mimsy.UUCP> <10604@linus.UUCP> <1227@hropus.UUCP> <1034@faline.bellcore.com>
Reply-To: biep@cs.vu.nl (J. A. "Biep" Durieux)
Organization: VU Informatica, Amsterdam
Lines: 19
Xref: mnetor sci.math:1854 sci.crypt:521

In article <1034@faline.bellcore.com> karn@faline.bellcore.com (Phil R. Karn) writes:
>> Is decryption more difficult if you use Hoffman coding..?
>
>Yes, it is well known that increasing the entropy ("randomness") of the
>plaintext before encryption is an excellent way to thwart cryptanalysis.
>I've heard it from someone that should know that "knowing when you've found
>the answer" is indeed perhaps THE hardest part of cryptanalysis.

That sounds as if true, but I don't think Huffman encoding will make that
so difficult (that is, Huffman encoding on a letter-by-letter basis), since
English is also rather easily recognisable (from random bits) by it's inter-
character statistics, i.e. the relative frequencies of groups of letters.
It will be a bit more work, through, and a *real good* compress algorithm
will take advantage of these regularities too (if it's there for multiple
uses. Otherwise telling the recipient how to decode might be more work than
sending the plaintext).
-- 
						Biep.  (biep@cs.vu.nl via mcvax)
	To be the question or not to be the question, that is.