Key to breaking Nazi code was in the patent office

William Knowles wk at
Sat Apr 21 04:10:35 EDT 2001

By Michael Smith
Friday 20 April 2001

BRITAIN'S wartime codebreakers could have cracked the German Enigma
cipher machine much earlier if they had followed a diagram for the
commercial version lodged with the British Patent Office in the
mid-1920s, documents released to the Public Record Office show.

But the codebreakers did not believe that the German army would have
been so stupid as to use the same simple wiring system as the widely
available commercial machine for their military equivalents. The Code
and Cypher School, commonly known by its wartime home at Bletchley
Park, was fully aware of how the commercial machine worked in the

Chiffriermaschinen Aktiengesellschaft, the German company that
manufactured it, had offered the British Government commercial Enigma
machines at a price of $190 each in June 1924. Britain declined to
take up the offer, waiting for the Germans to register it with the
British Patent Office.

Then they obtained the description of how it worked from the patent
officials, including detailed plans of the make-up of the commercial
machine.The files show that, contrary to what had previously been
thought, British codebreakers were working on the Enigma machine
during the 1920s and 1930s.

But they did not manage to break the military variant until early 1940
after gaining vital help from the Poles. The Enigma machine looked
like a typewriter. Pressing the keys sent an electrical impulse
through a series of circuits wired through rotors that moved with each
tap of the key, constantly varying the cipher.

British codebreakers had made a good deal of progress in breaking the
military version but were held up because they could not work out the
order in which the typewriter keys were wired into the internal
circuits. "The Germans weren't idiots," said Peter Twinn, one of those
who broke Enigma. "When they had a perfect opportunity to introduce a
safeguard to their machine by jumbling it up, that would be a sensible
thing to do."

It was not until July 1939, when they met their Polish equivalents who
had broken early versions of the machine, that they found out that it
was wired alphabetically, A to the first contact, B to the second
contact and so on. This was the same as in the diagram attached to the
patent application but was so obvious that the codebreakers never even
considered it as a possibility.

Six months later, codebreakers made their first break into Enigma,
something they could have done far earlier if they had only tried the
alphabetical system in the patent application."It was such an obvious
thing to do, really a silly thing to do, that nobody ever thought it
worthwhile trying it," said Mr Twinn.

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