Encryption WWII style

At the end of WWI, a German Engineer by the name of Arthur Scherbius invented an electro-mechanical rotor cipher machine which came to be called 'Enigma'. Initially used for a variety of commercial and diplomatic communications it became most widely and famously used by the German military machine throughout World War II.

Enigma looks like a typewriter but with two sets of keys. The bottom set was used to enter the plain text and by using a mixture of electrical and mechanical processes this letter was encrypted into another letter which lit up one of the top keys. It was an ingenious system using 3 rotor plates and a reflector; the first plate would rotate after each letter was encrypted thus producing a different result even if the same letter was pressed on the bottom keyboard again. Once the first rotor had made one full rotation the second rotor would move forwards one stop and likewise when this second rotor had made one full rotation the third rotor would move forwards one stop. This meant that there were over 17000 different combinations before the 3 rotor plates came back to their effective start. As the lights lit up in turn the plain text was encrypted into cypher text and another enigma machine set up correctly (you needed to know the starting positions of each rotor and the order of the 3 rotor plates) would then decrypt the message at the other end.

In the early 1930s Polish deciphers had some success decoding the encrypted messages with the help of a French spy in who had access to a German post in September and October 1932. However, by the onset of WWII in September 1939 the Germans had continued to refine Enigma (with 5 rotor plates) and there were now 159 million million million combinations - 159,000,000,000,000,000,000 - this number is so huge that if one combination was tried every second there hasn't been enough time since the Big Bang to have tried all the combinations once yet. The Germans were resetting the machine at midnight Berlin time and they believed that Enigma was unbreakable! This set the allies a formidable task .

A British WWI codebreaker Dilly Knox, set up an Enigma research station at Bletchley Park, England and a crack team of gifted mathematicians and engineers including Tony Kendrick, Peter Twinn, Alan Turing and Gordon Welchman set about breaking Enigma. The task was immense but after 9 months they had build the first "Bombe" to decrypt the secret Enigma messages.

The Bombe itself was also incredibly complex and the knowledge of how to build one was shared with the Americans, thereby starting a very close relationship between the American and British secret services.

It is thought that the diligent and excellent work of those at Bletchley Park shortened WWII by 2 years and probably saved many millions of lives. The unsung heroes were sworn to secrecy and at the end of the war Churchill ordered that Bletchley park be decommissioned and all the decoding machines be broken up. This was the public cover story but we now know that a few of the 'Bombes' were moved to GCHQ (the central intelligence of the British Secret Services).

The Soviet front advanced across Eastern Europe at the end of the war and as they moved west they came across numerous Enigma machines which had been used by the Nazis and their allies. The Soviets had heard much about the Enigma machines and were somewhat in awe of them. Thinking that Enigma remained unbroken the Soviet and Eastern Block countries continued to use the Enigma machines for military and diplomatic communications for another 20 years into the early 1960's through the Cold War, little did they know that the British and Americans were listening in!

Eventually developing technologies led to widespread decline in the use of Enigma machines. Today, Bletchley Park is run by the Bletchley Park Trust as a museum telling the story of the breaking of the Enigma Code on the original site. The Bombe on display is a full-size working replica which has been put to the test no less than 17 times!

Of course the Enigma story has been retold in the blockbuster, 'The Imitation Game', although they didn't quite get everything right in the film as Turing himself didn't build the Bombe, that was done by Gordon Welchman but there is no doubt that Turing was instrumental in working out the complexity of Enigma and cracking the code.

I have the privilege to live 6 miles from Bletchley Park and the photos in this post were all taken on my iPhone 6s plus. It is a fabulous museum and I would encourage any of you to visit if you get the chance.

https://bletchleypark.org.uk