05/12/2021

009 – Ciphers and fish – 1936

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…he must aim at becoming educated.  If he is to be solely a scientific specialist,
[then] he is wasting his time at a Public School.”  Turing’s headmaster on his focus on mathematics.

While in his early twenties Alan Turing defined many concepts in computing and algorithms that would become fundamental to computer science.  November 1936, he wrote ‘On Computable Numbers’ outlining his thoughts for a ‘universal computer’, aka the ‘Turing machine’.

Turing became head of Hut 8 at the WWII Government Code & Cipher School at Bletchley Park, putting theoretical thinking into practice decoding German naval encrypted signals.

Before the war the Poles had captured a German Enigma machine and cryptoanalysts had developed the ‘Bomba’ to decode the German field and theatre message.  Turing’s team developed the ‘Bombe’, its own device built by BTM.  This worked on iteration and elimination, disproving incorrect settings rather than forecasting the correct one.

At Letchworth BTM linked four Bombes creating the Giant.  Whenever a decoding was completed, a message to Bletchley would advise, ‘The Giant has caught a whale.’

Max Newman, Turing’s mathematics lecturer at Cambridge, joined him at Bletchley Park to work on decrypting a German teleprinter cipher.  From late 1942 in what was called the Newmanry section he concentrated on an automated system for decoding.  The Wrens called his device ‘Heath Robinson’ after the cartoonist who depicted eccentric machines; it proved none too accurate.

In 1941 the German High Command introduced Lorenz, a more complex system for high-level messages.  Without a captured device or details of its structure the codebreakers had to wait for human error to come to their aid.

In August 1942 a German operator, finding a Lorenz message sent from Athens to Vienna had not been received, sent it again and failed to reset the device; he also used an abbreviation.  This gave insight into decoding messages and the machine’s structure.

Turing and Newman developed a device to decode the Lorenz cipher.  Tommy Flowers wss recruited from the Post Office Research Station.  He proposed a device using 1,500 thermionic valves, they called it Colossus – its accuracy was greater than  the Heath Robinson and it ran at five times its speed.

Colossus II with 2,500 valves followed in June 1944 and proved invaluable when it revealed that Hitler overruled his generals, believing the Allied misinformation about the D-day landings.

Post WWII Turing declared he was ‘busy ‘building a brain’ – the universal Turing machine from his 1936 paper.  An offer to assist in its building persuaded him to join The National Physical Laboratory.

1946 Turing designed the ACE, Advanced Computing Engine, at a budget of £11,200!  Protracted delays frustrated Turing, he took a sabbatical year then Newman lured him to Manchester University.  1950 NPL produced Pilot ACE, a reduced version of the ACE, which was then the fastest computer in the world.

1952 While in Manchester Turing picked up a nineteen-year-old man who later broke into his home.  Turing called the police, which proved a big mistake when he later confessed to a sexual relationship.  Homosexuality was illegal in the UK and he was convicted of indecency, losing his security clearance.

Opting for chemical castration rather than jail, he could not cope when he developed breasts from the oestrogen.  Sadly in 1954 he took his own life by eating a poisoned apple.

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