We owe a lot to this giant.
I was vaguely aware that Alan Turing laid the mathematical foundations for computing and was a leader in the wartime breaking of the German Enigma code by the English. Then in the 1980s I read Andrew Hodges’ biography of Turing, titled The Enigma, which helped sharpen my image of Alan Turing. Born in 1912, he thought of numbers as mere symbols, which led to his becoming a powerhouse in number theory. Before World War 2, number theory was a quiet corner of mathematics of seemingly no practical use. Before the war, Alan studied at Cambridge and Princeton, and in a famous paper, proposed a “universal machine”, which he proved mathematically could perform the functions of any other machine. Then Germany attacked England and used Enigma machines to encrypt its military messages . . .
The stack of rotors inside an Enigma machine, consisting of three rotors and Umkehrwalze-B (the reflector).
The story of the decoding of German encrypted messages deserves at least several books. The Wikipedia article entitled Cryptanalysis of the Enigma is excellent. There were multiple generations of Enigma machines, whose encrypted messages became increasingly difficult to crack. Each German service employed different Enigma operating protocols, from weak to robust. Turing’s number theory work led to the development of the bombe, a machine that was used to decode Enigma encrypted messages. From June 1941, the Brits routinely decoded German U-boat messages, which brought the sinking of supply ships to a halt. England would not be starved to death.
The Germans subsequently deployed the Lorenz teleprinter machine, whose encrypted messages were eventually decrypted by a massive electromechanical machine with vacuum tube “valves” the Brits called Colossus.
After the war, Turing worked on the design and development of digital milestones, including the ACE and Manchester Mark 1 computers. He pioneered Artificial Intelligence and used mathematics to model and predict biological behavior. He died in 1954 at age 42. He’s believed to have poisoned himself with cyanide, but there’s evidence that his death may have been accidental.
The biography The Enigma is complete — maybe too complete, but the central character remains fascinating. From a book review on Amazon by Thomas D. Jennings:
“. . . Turing was a difficult person: an unapologetic homosexual in post-Victorian England; ground-breaking mathematician; utterly indifferent to social conventions; arrogantly original (working from first principles, ignoring precedents); with no respect for professional boundaries (a ‘pure’ mathematician who taught himself engineering and electronics).”
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