[2991] in cryptography@c2.net mail archive
Re: Turing Bombe story
daemon@ATHENA.MIT.EDU (Arnold G. Reinhold)
Fri Jul 17 19:06:21 1998
In-Reply-To: <3.0.3.32.19980716224032.03242d98@pop3.clark.net>
Date: Fri, 17 Jul 1998 17:46:19 -0400
To: Carl Ellison <cme@acm.org>, "Marcus Leech" <Marcus.Leech.mleech@nt.com>
From: "Arnold G. Reinhold" <reinhold@world.std.com>
Cc: Carl Ellison <cme@acm.org>, "Scott G. Kelly" <skelly@redcreek.com>,
Steve Reid <sreid@alpha.sea-to-sky.net>,
"Marcus Leech" <Marcus.Leech.mleech@nt.com>, cryptography@c2.net
At 10:40 PM -0400 7/16/98, Carl Ellison wrote:
...
>
>The thing that made the Bombe so blazingly fast was that Turing (and the
>Poles before him) used voltage on a wire as a logical TRUE and used
>switches, with bi-directional voltage flooding. What would be the execution
>of many hundreds of lines of C happened at the speed of light, in this 1940
>machine. From the time the rotors were in a new position, the actual
>logical contradiction testing took just a few nanoseconds -- or effectively
>0, since it took so long to move the rotors.
While the output of such circuits is effectively instantaneous compared to
electro-mechanical rotor movement, actually getting an answer in a few
nanoseconds is not so trivial. The wires have distributed inductance and
capacitance and have to be treated as a network of transmission lines. You
also have to worry about the characteristics of the voltage sources that
are "flooding" the lines and how you get rid of the charges that were
placed on the lines during the previous cycle.
None of this detracts form the brilliance of the Bombe design, of course.
Arnold Reinhold
Got Crypto? http://ciphersaber.gurus.com
