Alan Turing, Bletchley Park and the Enigma

Alan Turing

Everybody (maybe even the dog 1) is speaking of the 2014 movie called “The Imitation Game” with Benjamin Cumberbatch starring as Alan Turing but how many really know him?

For many people, Alan Turing is one of the fathers of the modern computer (along with John Von Neumann) and rightfully so. What they need to know and what the movie is trying to do (I have yet to see it) is to show how influential he was.

Alan Turing

Bletchley Park

Alan Turing was one of the hundreds of people working at Bletchley Park, a secret facility created by GCHQ to break the German cipher machine called the Enigma during World War II. He helped improve the Polish electrical machine called the Bombe, designed to rapidly explore the different possibilities of daily encryption keys used by the Germans and find the rotor’s wirings.

Enigma machine

During his time at Bletchley Park, he also designed the first real computer, Colossus which was used to break another German cipher, the Lorenz ciphermachine.

I had the pleasure to visit Bletchley Park in 2012 during a FreeBSD developers’ summit. On our last day, we took the bus from Cambridge and got to BP. What a wonderful day!

Here are some pictures of Bletchley Park with the Enigma, the Colossus and the Park itself.

Bletchley Park

David Kahn wrote a lot about the Enigma in “The Codebreakers” and more specifically in “Seizing the Enigma”, although I think that some GCHQ information was still classified when he wrote the former in 1967.

The Turing Test

Alan Turing is also known for the Turing Test, an experiment to determine the capability of a machine to have intelligent behavior, like or close enough to a human’s, as part of his ongoing work on Artificial Intelligence. The well-known computer program called ELIZA was specifically created to pass the Turing test for example.


Alas, even with all his famous works and fabulous mind, he was caught by one of the twists Fate is known for: Turing was gay at a moment when it was still illegal to be so in the United Kingdom. He was given the choice of prison or probation, provided that he undergo chimical treatment. He also was thrown out of any work for GCHQ and even denied visit in the USA 2.

Alan Turing, one of our last geniuses, died in 1954, apparently from suicide, killed by stupidity of the worst kind.

The world had to wait a long time to see him officially pardonned by Her Majesty the Queen in Dec. 2013.


I will go see the movie of course, it just came out here in France. There have been several movies already both on the Enigma and the War but also on Turing himself. It will be interesting to see I think.

As some of you know, cryptography is one of my main hobbies and the Enigma, being a complex cipher, is really interesting, especially in the light of its vulnerabilities. Bletchley Park’s methods of breaking it along with William Friedman’s for breaking the Japanese cipher machine called Purple form the basis of many current attack on modern cryptosystems.




Pictures from Wikipedia Commons and me.


  1. Old joke that goes generally as “Everybody and his dog…”

  2. Remember this was during the “Cold War” and people were paranoid about Russia and spies. Such “immorality” could be used to force people to spy…