From: Jim Gillogly <jim@acm.org>
Date: Wed, 8 Feb 95 14:11:36 PST
To: kkirksey@world.std.com (Ken Kirksey)
Subject: Re: Jefferson Wheel Cypher
In-Reply-To: <199502082012.AA18336@world.std.com>
Message-ID: <199502082211.OAA21023@mycroft.rand.org>
MIME-Version: 1.0
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Isn't that the same as Bazeries' Cylinder Cipher, where you have a bunch of
disks with mixed alphabets around the edges, you put them on a rod in some
order, set the plaintext along a row, then read the ciphertext off any
other row?  If so, a short paper of mine was just printed in "The
Cryptogram" (JF95 issue) about cryptanalyzing it.  A US military field
cipher was based on the Jefferson version; I handled a copy (with metal
disks) in the National Cryptologic Museum just outside Ft. Meade last
summer.  There may even be an Aegean Park Press publication on it.  The
servicemen hated it -- fiddling with all the disks in the heat of battle
made it cumbersome for tactical use.

If it's as I describe, I'd call it a multiple-key polyalphabetic: keyed
alphabets, keyed order, and (potentially ambiguous) offset key for
deciding how far around the cylinder to go.  The period is how many disks
you have, since they stay in the same order (but with different relative
offset) for the whole message.  It's not really an autokey under the
Meaning of the Act, since there's no feed-forward from one letter to the next.

I'm sure Kahn's "The Codebreakers" will have more info.

	Jim Gillogly
	Highday, 18 Solmath S.R. 1995, 21:59