Who is Alan Turing? Let’e break the enigma.

Alan Turing, a British mathematician, cryptologist and the founder of modern computing has been lately celebrated in the film “The Imitation Game”; its fragility and arrogance have been brilliantly interpreted by Benedict Cumberbatch, who showed again his artistry to play the role of the unappreciated genius. As Mr. Cumberbatch alias Alan’s would say “Sometimes it is the people no one imagines anything of, who do the things that no one can imagine” and yet he proved that the unbreakable Enigma code could be decrypted.

The Enigma machine was developed after the treaty of Versailles in 1919 by Arthur Scherbius and implemented by the Nazi Germany during the Second World War. The machine was similar to an electric typewriter and it was used to create encrypted messages, which were communicated through a Morse-coded radio. Given the number of infinite variables, Enigma could generate 186 million, million, million code systems. The settings were changed everyday making the machine immune to frequency analysis. 

In the late 1932 Enigma saw its first enemy in Rejewski: having secretly procured two pages of the Enigma daily keys, the Polish mathematician exploited the power of permutations and groups to breakthrough the Enigma mechanism. But it is the creation of the British Bombe nurtured by Alan Turing and the Bletchley Park team, which had a major impact on the unfolding of the war.

As the German U-boats were becoming more and more of a peril for the Allies, the British Intelligence realised that the only way to win the war of the Atlantic was to create a machine able to defeat Enigma. By eliminating thousands of permutations, as Enigma could not encrypt a letter as itself, Turing developed the idea of a crib, an educated guess of what a message might have said. The first breakthrough was given by the weather reports which were communicated every day in a standardize way. For example, the crib used was:

WETTERVORHERSAGEBISKAYA (weather forecast of the Biscay Gulf)

and the corresponding encrypted message was:

…QFZWRWIVTYRESXBFOGKUHQBAISEZ…

The encrypted message was slid along the crib until there was no correspondence between the letters. The drums of the Bombe were then set with the crib found and the machine was put into action to find the settings of Enigma.

The truth behind the Bombe has been kept secret for 30 years until the mid 70s when the Germans were acknowledged that the unbreakable Enigma machine had been broken. It is estimated that the first mover advantage that the Allies acquired by capturing the German’s strategy had been determinant in the outcome of the war: 4 millions of lives have been saved and the war has been shortened by 2 years.

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Rebecca Marocco

Rebecca Marocco

Third Year student in Economics and Management at Royal Holloway, University of London. Eclectic writer, passionate leader and sports lover.