[3038] in cryptography@c2.net mail archive
Re: Turing Bombe story
daemon@ATHENA.MIT.EDU (Clive D.W. Feather)
Wed Jul 22 13:21:08 1998
Date: Wed, 22 Jul 1998 17:28:07 +0100
To: cryptography@c2.net
From: "Clive D.W. Feather" <clive@on-the-train.demon.co.uk>
Reply-To: "Clive D.W. Feather" <clive@linx.org>
In-Reply-To: <3.0.3.32.19980716174533.032b5358@pop3.clark.net>
In article <3.0.3.32.19980716174533.032b5358@pop3.clark.net>, Carl Ellison
<cme@acm.org> writes
>The brilliance of the Bombe was that it needed to test only for
>the non-plugboard elements: (26^3)*P(5,3) = 1054560 possibilities,
>or half that to the expected break. This comes out to about an hour
>and a half, for a single Bombe, if it runs at 10 msec per rotor
>position.
A single Bombe unit tested one rotor order. It took about 12 minutes to
run through the 26^3 combinations.
A Bombe (the physical machine that's being rebuilt) consisted of three
units stacked vertically, plus on some machines 4 extra wheels that were
used for testing a possible "drop".
To test a crib, 20 Bombes (60 units) were all wired up identically and set
running. Hopefully one of the 20 would find the answer.
>As for a modern Pentium beating the Bombe, maybe -- but the Bombe did an
>incredible number of LIPS.
A few weeks ago I was looking at the BP web site. Following some links, I
fairly soon came across a Bombe simulator which I downloaded, but forgot
where I got it from. Here's the documentation that came with it:
sbgen.c sbgen.exe & sb.h
This is a program that simulates how the Turing Bombe worked but
with a few small improvements that were not present in the origional
machine. The program sbgen is used to build a bombe program which
is then compiled and run. It is used as follows:
supergen <plain-text> <cipher-text> >super.c
cl /O2 /Ox /Gr /G5 /Fc super.c
super
It will cycle through all 60 rotor possibilities and print out all the
settings that it calculates are the Enigma settings along with the
known plug board configuration. This process should not take more than
eight minutes on a 100 Mhz Pentium.
Nik Shaylor (nshaylor@tcp.co.uk)
Hopefully something like AltaVista can find it for you.
--
Clive D.W. Feather | Regulation Officer, LINX | Work: <clive@linx.org>
Tel: +44 1733 705000 | (on secondment from | Home: <cdwf@i.am>
Fax: +44 1733 353929 | Demon Internet) | <http://i.am/davros>
Written on my laptop; please observe the Reply-To address
