The Imitation Game

The Imitation Game

The release of the film "The Imitation Game" - starring Benedict "Sherlock Holmes" Cumberbatch and Keira Knightley - rekindled interest in the figure of Alan Turing. The film is based in parts on the life of the English mathematician, codebreaker, and father of computer science. Like a number of British chessplayers Turing, who because of his great mathematical talent was recruited by the British Secret Service, played a crucial role in cracking the code of the "Enigma", the machine the German army used during World War II to code their messages. Turing also formulated the theoretical basis for computer science („On Computable Numbers, with an Application to the Entscheidungsproblem“, 1936), and wrote the very first chess program. He put the sequence of commands for the imaginary machine - computers did not yet exist - on paper and that's why this program was called "Paper Engine".

Benedict Cumberbatch as Alan Turing

Keira Knightley as Joan Clarke

The movie reiterates a number of well-worn myths about the enigma and how it was deciphered, but is often historically inaccurate. Still, it was nominated for no less than eight oscars.

One dramatically motivated invention of the film is the connection between Alan Turing and John Cairncross, who was working as a Soviet spy. During and before the war Soviet intelligence services had recruited many sympathizers of communism as agents, particularly in England and the US, who subsequently infiltated British and US services, and sometimes managed to climb far up in government. Later, in the course of the VENONA project, a number of Soviet spies were exposed. Cairncross belonged to the so-called "Cambridge Five", a group of five British agents who were working for the Soviets. But while Cairncross was part of the British code-breaking team in Bletchley Park there is no confirmed connection to Turing.

The enigma is the best known of several cipher machines and was used by the German "Wehrmacht" to code and decode messages by a machine, and not by humans.

A set of rotating disks, called "rotors", converted the letters of messages to other letters. When decoding these messages the receiver had to know the original position of the rotors to re-translate the message. No easy task because the settings of the machine were changed daily.

Puzzling

Before WWII a group of Polish mathematicians around Jerzy Rozycki, Henryk Zygalski and Marian Rejewski had done groundbreaking work to understand how the enigma worked. Moreover, the patent of the machine was available in a number of patent offices and just needed to be read. But the fact that the code was changed daily made it difficult to decipher the messages properly. And even if the English had established the daily code of the Germans, they still had to decipher the many messages they got hold of - an enormous amount of work.

Bletchley Park

Among the English chessplayers in Bletchley Park were Hugh Alexander, Stuart Milner-Barry and Harry Golombek. All of them were part of the English National team at that time.

Matthew William Goode as Hugh Alexander

Milner-Barry later occupied a high post in English ministeries, Golombek worked as chess publisher and arbiter, while Alexander became director of the MI5 encryption department. This stopped him from playing any tournaments in the Eastern bloc and thus presumably robbed him of a chance to get the GM title.

The German secret service was aware that the enigma was not absolutely safe, but could not imagine that their opponents would invest the enormous amount of work necessary to crack the codes. But that is just what the British did and this proved to be particular useful in the African campaign because the decoded messages helped the British to cut off almost all ordnance from the German Africa corps. When the German navy realized that their codes had been cracked they put an additional disk into their navy enigmas, which made it significantly harder to decode the messages.

After the war Turing continued to work on the development of computers but because the Secret Service considered his homosexuality - a that time an offence - to be a safety risk he was forced to undergo hormonal treatment. In 1954 he committed suicide, probably by eating a poisoned apple. Two years ago Turing was rehabilitated by the Queen through the "Royal Pardon".
 

Trailer

Links:

Kasparov on Alan Turing and his 'Paper Machine'

Wikipedia article about Alan Turing

Wikipedia article about Bletchley Park

Wikipedia article about the Venona project