Edge of Innovation

The Imitation Game and the debt we all owe to Alan Turing

Have you seen The Imitation Game yet? You should. This compelling techno-thriller tells the bittersweet story of British mathematician, cryptanalyst and computer scientist Alan Turing, played brilliantly by Sherlock actor Benedict Cumberbatch. Not only is Turing one of the men responsible for cracking the Enigma code in WW2, but he is widely considered as the father of computer science and artificial intelligence.

The computer, tablet or mobile phone that you’re reading these words on is a descendant of Turing’s idea of a computing machine.

Turing’s work at Bletchley Park

The Imitation Game focuses on the key moments in Turing’s life, notably his work at the Government Code and Cypher School (GC&CS) at Bletchley Park, where he and his fellow cryptanalysts had the seemingly impossible task of cracking Germany’s complex Enigma cipher. Watch The Imitation Game trailer below.

The typewriter-style Enigma machines used multiple rotor scramblers to substitute the letters of any typed text to produce a code. Each rotor had 26 alphabetical starting positions, so the original 3-rotor enigma machine could be set in 26 x 26 x 26 (17,576) ways. According to the Bletchley Park Trust, the Enigma cypher changed at least once per day, giving 159 million million million possible settings to choose from.

You can create your own Enigma codes here.

“The process of breaking Enigma was aided considerably by a complex electro-mechanical device, designed by Alan Turing and Gordon Welchman,” says the Bletchley Park Trust, which operates the old GC&CS building as a heritage and education site.

“The Bombe, as it was called, ran through all the possible Enigma wheel configurations in order to reduce the possible number of settings in use to a manageable number for further hand testing.”

Towards the end of the war, Turing’s machines were decoding over 3,000 Enigma-generated naval codes a day.

Designing the world’s first programmable computer

Turing’s computational work, particularly his use of probability in cryptanalysis, led to the design of Colossus, the world’s first programmable computer. Built to crack the Lorenz cipher that followed Enigma, it helped weaken the U-Boat threat, confuse the Germans as to the locations of the D-Day landings and shortened the war by as much as four years. Turing and the team at Bletchley Park arguably changed the course of the conflict and saved millions of lives.

So why is the film called The Imitation Game?

After the war ended, Turing proposed a computing challenge to measure machine intelligence. It considered the question: “Can machines think?”

Alan Turing
Alan Turing defined a test for machine intelligence. Photo courtesy of www.bletchleypark.org.uk.

Turing suggested an ‘imitation game’ in 1950. The game is played with three people – a man (A), a woman (B), and an interrogator (C), who may be of either sex. “The object of the game for the interrogator,” he wrote, “is to determine which of the other two is the man and which is the woman.”

Simple enough, perhaps. But Turing proposed a crucial change to the game. What would happen if a machine took the part of A? Could the interrogator tell which one was the computer and which one was the human being?

The Turing Test was born, a true test of artificial intelligence that has yet to be cracked. Find out more about The Imitation Game and the work of Alan Turing on the Bletchley Park website.



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