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Up Close and Personal with an Enigma Machine

Wednesday, 15 November 2017

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Year 7 girls at Bolton School Girls’ Division enjoyed a fascinating morning with Dr James Grime, Mathematician and lecturer, who spoke to them about cryptography - the science and mathematics of codes and code breaking – including a demonstration of a genuine WWII enigma machine!

The whole year group was given a potted history of codes and code breaking from the Spartans who would tattoo messages onto slaves’ heads and wear special coded belts, to the invention of the Caesar Shift code by Julius Caesar to the deciphering of Mary Queen of Scots’ secret code to Babington which revealed her plotting the demise of Elizabeth I and led to her own gruesome beheading. They also learnt about al-Kindi, the original codebreaker. The General Substitution Cipher gives 400 million billion billion coding options, which would take the world population of 7 billion people, 2 billion years to decode!  However, al-Kindi of Baghdad in 900 AD worked out how decipher such codes by working out which letters are most commonly used in words; he realised that “e” is the most popular letter, followed by “t”, then “a”, then “o”, then “I” and so forth. This made cracking codes considerably easier.

The entertaining talk built up towards a demonstration of the 81 year old enigma machine that Dr Grime had with him. He explained that it is the only remaining travelling enigma machine and belongs to his friend and author Simon Singh, who bought it from an American who picked it up in a French field at the end of the Second World War and took it away with him as a souvenir!

The enigma machine was invented by a German and used during the last world war. The girls got to get up close and some were allowed to touch it even though it is an antique! Once the wooden box was opened, they saw what looks like 2 typewriters on top of each other. The keys are not quite laid out in the same way as a British typewriter as it was designed for the German language. Dr Grime explained how you enter your message into one of the typewriters and this illuminates other letters on the other keyboard which gives you a code that you then need to send to colleagues elsewhere for deciphering at their end on their own enigma machine. There does not seem to be any link between the codes generated by the typewriter and the same word can have a different code each time you type it in, for example a simple word like “HI” could, in code, be “QQ” and then, next time around, “XV” or some such. The reason for this, the girls learnt, is because each time a code word is inputted it drives a mechanism underneath that spins three rotors (one that moves quickly, one that moves only when the other rotor has done a full circuit and then a third rotor which moves even slower and only rotates when the second rotor has made a full circuit) which then connects wires underneath and lights up different letters each time. The starting point of the rotors - and hence the code - would be changed every day. To decipher a code, there needed to be a machine set up in exactly the same way at the receiving end of the message.

Year 7 learnt that it was actually three Polish scientists that first reconstructed an earlier version of the German machine before the Second World War began and they did this without actually seeing an enigma machine! During the Second World War, Alan Turing worked at the Government Code and Cipher School at Bletchley Park – the forerunner of GCHQ – where he devised the techniques which cracked the now very advanced German enigma code. As a result of the information gained through this device, it has been claimed, hostilities between Germany and the Allied forces were curtailed by two years.

After the presentation, classes enjoyed workshops in which they got to be the codebreakers. Through a series of clues, words were deduced and finally rearranged into a meaningful sentence.

Post-event, Dr James Grime said: “As someone fascinated by Mathematics and codes, it is such fun and a privilege to exhibit this enigma machine. Code breaking always fascinates young people and they are always very impressed that this is an actual piece of living history from World War II.”

Mr Stephen Wrigley, a Maths Teacher in Bolton School Girls’ Division who organised the event, said: “My hope is to show students how Maths can be applied to different situations - in this case, code breaking. Dr Grime’s talk also shows how code breaking has its place in history, exemplified by the foiling of the Babington Plot of 1586 which aimed at assassinating Queen Elizabeth I, and the breaking of the enigma code in the Second World War, both of which had huge implications.”

Year 7 pupil Harriet said: “I gained confidence in code breaking and learnt how I could be a code breaker for MI5 or MI6 when I grow up. I have also gained experience in code breaking which could help me when I grow up.” Classmate Tanya added: “I really enjoyed the morning and learnt all about the German’s enigma machine and how the Poles and then the British cracked the code. You obviously had to be good at Maths to work out these codes. The workshop was fun too where we got to do our own codes; we gave out clues and others had to guess. The different words put together spelt out a sentence in the end.”

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