The master codebreaker: the incredible legacy of Alan Turing

Alan Turing was an English computer scientist, mathematician, logician and cryptanalyst whose work has led him to be considered the father of theoretical computer science and artificial intelligence. Born on June 23, 1912, in London, Turing played a key role in the Allied victory over the Axis powers in World War II — recently depicted in the Oscar-nominated film The Imitation Game (2014).

According to Winston Churchill, Turing made "the single greatest contribution to the Allied forces victory in the Second World War." He was even made an Officer of the Most Excellent Order of the British Empire (OBE) by King George VI in 1946 for his wartime services. But despite this, Turing did not receive the commendation and respect he deserved while he was alive.

In 1952, the English government, unaware of his classified code-breaking efforts during the war, prosecuted him for being a homosexual and chemically castrated him. On June 7, 1954, Turing was found dead in his house and cyanide poisoning was confirmed to be the cause of death. Even though the investigation stated it to be a suicide, Turing experts have ruled it to be an accident.

There has never been a speck of doubt about his contribution to computer science, and in 1966 the 'Turing Award' was established— the highest accolade in the computing industry. However, it wasn't until the 1990s when Turing's war contributions at Bletchley Park were fully realised (two of his code-breaking theories were released as late as 2012). He has since become a cult hero and was even granted a posthumous pardon by Queen Elizabeth II in 2013 for his criminal conviction for homosexuality. Today, on Alan Turing's 105th birthday, we pay tribute to the man who changed the course of history by recounting his three greatest achievements:

Breaking the Enigma

Despite his varied achievements, Alan Turing is most famous for cracking the 'Enigma' code. The Enigma was an enciphering machine used by the German armed forces to send secure messages. After Polish mathematicians worked out how to read Enigma messages and shared the information with British intelligence, the Germans increased its security during the Second World War by changing the cipher daily. This is where Alan Turing, already working part-time for the British Government’s Code and Cypher School, was roped in to work full-time at Bletchley Park in Buckinghamshire.

Turing, along with fellow code-breaker Gordon Welchman, then created a machine called the 'Bombe'. Capable of decrypting Enigma messages with remarkable ease, the Bombe allowed Allied Forces to read German Air Force communications and alter their strategies to gain the upper hand.

Turing's other wartime achievements also included developing two more complex code-breaking techniques called 'Banburismus' and 'Turingery'. The first allowed Allied intelligence to decrypt complex German naval communications and avoid their dreaded U-Boats. While the second allowed them to read crucial messages sent by the German Army High Command using the 'Lorenz' high-security teleprinter cipher machine. Turing also created a speech scrambling device he called 'Delilah'.

The idea of software

Turing made his most significant contribution to the age of computers before the outbreak of World War II. In 1936, Turing wrote a paper titled “On Computable Numbers, with an Application to the Entscheidungsproblem [decision problem]” which went on to become one of the founding elements of the digital revolution that continues to gain momentum even today. The paper was a theoretical breakthrough which spawned the idea that a machine could be used to compute anything that a human mind could — and this abstract computer was called the 'universal Turing machine', established the fundamental logical principles of the modern digital computer.

What Turing probably didn't realise at the time was that he had just invented the idea of software — something that would enable computers to surpass a human's computing prowess rather than augment it. His theoretical model of a universal Turing machine was subsequently used by engineers at the University of Manchester to build the world’s first working electronic stored-program digital computer in June 1948.

Conceptualising artificial intelligence

The rise of artificial intelligence is the latest development in the digital revolution. Despite it becoming a key area of study only in the past few years, Alan Turing envisaged its possibility way back in 1950 — which is why he's called the 'father of artificial intelligence'. In a paper titled "Computing Machinery and Intelligence", Turing tackled the question 'can machines think?' by drawing comparisons between a computing machine and the human brain. He theorised that the brain is essentially an 'unorganised machine' that transforms into a powerful 'universal machine' through constant 'training'. If this was true, Turing wondered, could a digital machine be taught how to think on its own? To this end, he proposed an experiment called 'The Imitation Game'. The experiment, which is now known as the 'Turing Test', "requires that a human being should be unable to distinguish the machine from another human being by using the replies to questions put to both."

Computer science was not the only scientific field that interested Turing. He also dabbled in physics, biology, chemistry and neurology. In fact, his ground-breaking work on morphogenisis — a mathematical explanation of how things grow — in 1952 eventually spawned a completely new field of mathematical biology.

Alan Turing was a man far ahead of his time: he theorised and invented things which others in that era could scarcely dream of. And for that, he deserves to be considered among the greatest minds of human history.