[2989] in cryptography@c2.net mail archive
Re: Turing Bombe story
daemon@ATHENA.MIT.EDU (Carl Ellison)
Fri Jul 17 13:27:55 1998
Date: Fri, 17 Jul 1998 01:53:06 -0400
To: Steve Bellovin <smb@research.att.com>
From: Carl Ellison <cme@acm.org>
Cc: cryptography@c2.net
In-Reply-To: <199807170514.BAA17275@postal.research.att.com>
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At 01:14 AM 7/17/98 -0400, Steve Bellovin wrote:
>There were many different elements that entered into an Enigma key
>setting. First, there was the choice of three rotors, from a set
>that was (I think) as high as seven. On some machines, there was
>a choice of reflectors. On each of the rotors, there was the
>ring setting. Then there was the 3-letter per-message setting,
>and the plugboard.
The Bombe ignored the ring setting. If a crib happened to cross a wheel
turnover, they were screwed. This is why they preferred to find two cribs,
each in a different disjoint contiguous span of 13 letters -- so that if one
of the cribs had a turnover, the other didn't.
- Carl
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|Carl M. Ellison cme@acm.org http://www.pobox.com/~cme |
| PGP: 08FF BA05 599B 49D2 23C6 6FFD 36BA D342 |
+-Officer, officer, arrest that man. He's whistling a dirty song.--+
