Code Breakers Remembered

By Mike Green, EPN -- Electronic News, 5/22/2003

Earlier this month the Institute of Electrical and Electronics Engineers (IEEE) presented a milestone award commemorating the technological advances performed at Bletchley Park, England, to aid the allied forces during World War II. Led by Alan Turing, the team successfully cracked the codes of the Japanese, Italian, and German military, including the notorious Enigma code.
The Enigma Machine

First created at the end of the First World War by Arthur Scherbius in Berlin, this rotary electromechanical enciphering device was used by the German armed forces and secret service throughout the1920’s and 30’s. Its basic principle was that letters would be substituted for others via the machine’ electrical connections, and this was followed by shifts in the alphabet and further substitutions. The added complexity that Willi Korn endowed to the device in the 1940’s meant that the total of seven substitutions took place in all, this translated to 17,576 different possible alphabets being available.

The machine itself consisted of 26 keys, a plug board (with which the substitutions were performed), and 5 rotors (which set the alphabet shifts). The total number of possible states of the machine was 10²³. This made a huge number of possible settings for any one day, and left the Allies with an almost impossible task. The Germans were confident that above all -- the code was unbreakable.

However, there were two small but fatal flaws. Firstly the system would not encipher a letter as itself. Secondly the code was reciprocal (i.e. if it substituted a for x, it would likewise substitute x for a. This gave the Germans an advantage as the machine didn’t have to be set differently to receive or send code, but it was also to prove their undoing, as it made the signals easier to unravel.

Alan Turing - An Accidental Hero

Born in 1912, in Paddington, London, Alan Mathison Turing was the son of a civil servant, who worked for the British Government in India. His parents continued to live on the sub-continent so Alan and his brother were passed from pillar to post, fostered in various households, before he received a place in place in Sherborne public school. He went on to study Quantum Physics at Kings College Cambridge, and was given a first class degree in 1934, fellowship of the college in 1935, and the Smith’s prize for his work on probability theory in 1936.

All this seemed to be the beginning of a very promising academic career, but Turing was not destined to be another stuffy professor. He had already started to tackle some of the underling questions that characterised the latter stages of the 20th century - those that would form the of computer science. His concept of a universal machine that could be programmed to do any systematic process (known as the Turing machine) became the basis of the modern theory of computation. In his work he managed to bridge the gap between human abstract thought and digital operations.

He returned from Princeton University in 1938, after completing a PhD in Logic and Number Theory, to take up a position at the British Government’s Code and Cipher School. With the threat of war looming, the government were putting a great deal of their intelligence resources into fathoming German communications. They enlisted the help of Polish code breakers who had spent many years trying to unlock the secrets of Enigma, and had some limited success. When war broke, Turing took up full-time work on the project, and was put in charge of the Cryptanalytic Head Quarters at Bletchley Park, Buckinghamshire (the centre for Allied code breaking during the conflict - referred to as ‘Station X’). The Polls progress was based on being able to decode Nazi signals under certain conditions, and Turing and his team were set the task of expanding the scope of their ‘Bomba’ device. Together, he and Gordon Welchman designed the Enigma Bombe machine, which would be able to fully decode the German signals. Once Station X had intercepted enough signals that day they could construct a menu to run on the Bombe that would then calculate the enigma base settings for that day. The information gleaned from the deciphered code (known as ultra) was then used to foil German battle tactics, and was particularly effective in defending the Atlantic convoys against U Boat attack. This was followed by the Colossus, which was used to decipher the ‘Sturgeon’ and ‘Tunny’ codes. Arguably this could be referred to as the first electronic computer, although it was only capable of a specific task not following different programs it was set.

Turing’s Rise & Fall

Turing received the OBE for his contribution to the war effort, and went on to be appointed principal scientific officer at the National Physical Laboratories (NPL), where he was put in charge of a team to work on creating an electronic computing device (in direct competition with work already in progress across the Atlantic on the ENIAC). The principle of the ACE (Automatic Computing Engine) was to create a universal machine through programming (rather than having to create a series of machines for different tasks, made up of different components). Turing’s ideas on using an abbreviated code of instructions pre-empted the concept of a programming language. But although his thinking was making great leaps towards what we now recognise as modern computing, NPL’s construction of the hardware to back this up was floundering. Due to the lack of engineering support that Turing received, ACE never got off the ground.

He then took on the role of Deputy Director of the Computational Laboratories in Manchester University, and his paper on the philosophy of machine and mind - “computing machinery & intelligence” again showed his grasp of ideas way beyond the capacity of his peers. In this work he predicted the development of artificial intelligence, decades before it would become a reality.

He was elected to the Fellowship of the Royal Society in 1951, and continued to work with GCHQ (the British Intelligence Service’s monitoring facility set up after the war). However his long hours of toil deciphering the Nazi codes, and his ground breaking research into computer technology were soon to be forgotten. Alan Turing’s image was suddenly turned from one of hero to villain. In 1952 he was arrested for his homosexual activities, which at this time it was still a very serious crime in England. Rather than face a prison sentence he was forced to agree to a year long series of oestrogen injections, designed to reduce his sexual urges (scarcely kind treatment for a man who had helped save thousands of lives only a few years before). Also his security clearance was revoked (as homosexuals were seen as a high risk), and this proved to have a profound effect on his mental state. Turing was found dead from cyanide poisoning in 1954 (he was 42 years old) -- the coroner’s verdict was suicide.

Gone but not forgotten

Although his genius may have not been fully appreciated while he was still alive, Turing has been the subject of several books and plays. His likeness is captured in a sculpture to be found in Sackville Park Manchester, and there is a plaque at his birthplace in London. In 1991 Bletchley Park was saved from demolition, and now houses a museum retelling the story of the men and women who helped bring the Second World War to an end.