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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: net.crypt
Subject: Re: Code Breaking
Message-ID: <600@brl-smoke.ARPA>
Date: Tue, 6-May-86 15:48:29 EDT
Article-I.D.: brl-smok.600
Posted: Tue May  6 15:48:29 1986
Date-Received: Thu, 8-May-86 20:26:24 EDT
References: <113@radha.UUCP> <331@brl-smoke.ARPA> <6649@utzoo.UUCP>
Reply-To: gwyn@brl.ARPA
Organization: Ballistic Research Lab (BRL)
Lines: 9

In article <6649@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes:
>They actually aren't bad if the bad guy has *no* *idea* that you might
>be using such a scheme.  If he once suspects it -- either from hearing
>about your scheme, or from breaking part of a message and noting the
>self-similarity -- it's all over.

As Henry probably knows, in practical cryptography the conservative
assumption is that the "enemy" knows or can find out the general
encryption system used; therefore, all security resides in the key.