The names of Alan Turing and the Enigma encryption machine have grown inextricably linked over the years, owing to Turing's contribution to British decryption efforts during World War II. It's fitting, therefore, to see one of the few surviving Enigma machines from that era on show during a celebration of Turing's legacy in 2012, the 100th year after his birth. The University of Kent, hosting the 64th British Mathematical Colloquium at its School of Mathematics, Statistics and Actuarial Science, was the stage for the demonstration of an original German Enigma machine from 1936.
Enigma was the brand of an enciphering machine invented at the tail end of the Great War, in 1918, which was employed by the German military and other nations starting in the 1920s. Though it's popularly associated with use by Nazi Germany, it's worth noting that it was a method for encrypting confidential communications before Hitler's rise to power and remained in use after the conclusion of WWII.
The breadbox-sized machines rely on a combination of rudimentary electronics, basic mechanics, and some clever mathematics. A circuit is created between a battery and a set of lamps, the latter forming a lightboard beneath a panel inscribed with the 26 letters in the Latin alphabet. You connect the circuit by pressing any of the keys on the keyboard installed below the lightboard, which — depending on the present configuration — gives you the appropriate cipher for your "plain text" input. Once you press a key, one of the three rotors above the lightboard rolls over, and the next time you push the same letter you're given a different response, as the rotor movement alters the circuit. In addition to that automatic realigning, there's a plugboard at the front of the Enigma machine, which allows the operator to tweak the precise encryption system further.
All told, with a three-rotor encryption machine such as the one I saw today, the number of cipher permutations you could churn out is said to be in excess of 1023. That should give you an idea of how torrid a task Allied code crackers would have had during the war. The amusing thing is that the machine itself hardly feels like the sort of life-altering invention that it was. It's built in a utilitarian fashion, with its solid wood case punctuated only by a closing latch and a metal handle. Inside, the top lid is dedicated to yet more basic necessities: there's a row of spare light bulbs, a pair of spare wires for the plugboard, and a lengthy instruction sheet detailing the proper cleaning methodology. It's about as glamorous as a night out in Hanover.
Of course, there's no communication hardware of any kind on board. The Enigma machine was used strictly to encrypt messages (kept intentionally short, so as to minimize the chances of hostile decryption), with the coded text string then being passed along via Morse code to the intended recipient, who in turn would have the same cryptography key on his Enigma machine and would use it to decode the message.
Although Alan Turing can't — and wouldn't want to — lay claim to singlehandedly defeating the highly sophisticated Enigma encryption, he was instrumental in bringing down the time it took to crack intercepted communications from days and weeks down to mere hours. He built on breakthroughs made by Polish cryptographers and engineered massive decryption machines he called superbombes, which were used in this effort. Today's demonstration of the 1936 Enigma machine — discovered by a US serviceman after the war, purchased by Simon Singh, and now part of Cambridge University's Millenium Mathematics Project — was accompanied by a public lecture by Andrew Hodges, Dean at Wadham College at the University of Oxford, who authored the biography titled Alan Turing: The Enigma. Hodges closed his lecture with a touching quote from Turing that I would like to echo here:
"The isolated man does not develop any intellectual power. It is necessary for him to be immersed in an environment of other men, whose techniques he absorbs during the first twenty years of his life. He may then perhaps do a little research of his own and make a very few discoveries which are passed on to other men ... the search for new techniques must be regarded as carried out by the human community as a whole, rather than by individuals."