From: "Perry E. Metzger" <perry@piermont.com>
Date: Thu, 19 Sep 1996 08:09:34 +0800
To: sjohnson@packetengines.com (stuart johnson)
Subject: Re: a simple cypher scheme
In-Reply-To: <9609180005.AA14720@ns.tsinet.com>
Message-ID: <199609181641.MAA14118@jekyll.piermont.com>
MIME-Version: 1.0
Content-Type: text/plain



stuart johnson writes:
> a co-worker here has
> come up with a 'cypher' scheme that he would like to use to send code to our
> clients.  the scheme is this : he would take the file of code and pad all
> lines to the length of the longest line, he would then preform column swaps,
> and then row swaps, to 'mix up' the file. the person receiving the file
> would then preform the opposite functions to recover the file.  it seems so
> simple that it can't be good. i've convenced him to use pgp, but i would
> like some input if possible on why his cypher scheme is not a good one.

This is a variant on a scheme called a transposition cipher. It was
okay, but not very good, technology in the Civil War, when it was last
seriously used. It can be broken with a technique called multiple
anagramming.

Perry