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Alan Turing

Click my apple, see what happens!

Relaxation at Bletchley ('rounders' is similar to baseball)
A Queer Sort of Genius

ALAN TURING WAS CONCEIVED in the autumn of 1911 near Madras in southern India, where his father Julius was a member of the Indian Civil Service. His parents were determined he should be born in Britain and so they returned to London, where Alan was born on 23 June 1912. His father returned to India soon afterwards and his mother Ethel followed just fifteen months later, leaving Alan in the care of nannies and friends until he was old enough to attend boarding school. He later went on to Sherbourne School in Dorset, where he gained a reputation as a shy, awkward boy who was only good at science. His school days were generally unhappy, except for his friendship with fellow science student Christopher Morcom with whom he fell in love, although Morcom seems to have been unaware of the depth of feeling Turing had for him. They would discuss the latest scientific news and conduct their own experiments. In his final year at Sherborne, Morcom, who seemed to be the more gifted of the two, won a scholarship to Cambridge University, but before he could take it up he died suddenly of tuberculosis. Turing was devastated by the loss of the only person he would ever truly love. He determined to remember and honour his friend by also winning a place at Cambridge, and make discoveries his friend would otherwise have made.
   Turing entered King's College, Cambridge in 1931, at a time when there was intense debate about the nature of mathematics and logic by the leading mathematicians of the day. Central to the argument was the issue of undecidability, the notion that there were some mathematical questions which were beyond logical proof, so-called undecidable questions. In his influential paper 'On Computable Numbers', published in 1937, Turing addressed this problem by describing an imaginary machine designed to perform a particular operation, such as multiplying two numbers. The numbers could be fed into the machine via a paper tape, like the punched sheets used to feed a tune into a pianola. The answer could be output via another paper tape. Turing imagined a whole series of these so-called Turing machines, each specially designed to perform a certain mathematical function. He then took a more radical step. He imagined a machine whose internal workings could be altered to perform all the functions of all conceivable Turing machines. He called this device a universal machine (later to become known as a 'universal Turing machine'), because it would be capable of answering any question that could logically be answered. As it turned out, even this hypothetical device was unable to identify every undecidable question, because it is not always logically possible to answer a question about the undecidability of another question. The important thing however was that with his universal machine, Turing had given the world the blueprint for the modern programmable computer. The technology did not yet exist to build one, but the solid theoretical basis was there.
   His time at Cambridge was a happy one for Turing. He became a fellow of King's College at the age of 22, and led the life of a typical don. He achieved success in his work, and could be open about his sexuality in an environment that tolerated homosexual relationships. He had time for more trivial activities too. In 1938 he made a point of seeing the film Snow White and the Seven Dwarfs, containing the memorable scene where the Wicked Witch dunks an apple in poison. Afterwards his colleagues heard Turing continually repeating the macabre chant, "Dip the apple in the brew, Let the sleeping death seep through".

All this came to an end when, at the outbreak of war, Turing was invited to work as a cryptanalyst at Bletchley. He quickly gained a reputation as a bit of an eccentric, mainly for such things as cycling to work wearing a gas mask in spring and summer (he suffered from hay fever), and chaining his tea mug to the radiator in his hut to prevent it being stolen. He had trouble relating to people, especially women, but was strangely (for those times) open about his homosexuality. The latter didn't prevent him becoming engaged, although briefly, to Joan Clarke in 1941; she was one of the cleverest cryptographers working in the Naval Enigma codebreaking section at Bletchley Park. Turing broke it off after a couple of months, apparently because he had a dream in which his mother disapproved of his girlfriend.
    It could be that Turing had a mild form of autism, possibly Asperger Syndrome (otherwise known as high grade autism), which Isaac Newton is thought to have had. People with this disorder frequently come up with brilliant ideas which no normal person could have thought of. At the same time they have no idea how to relate to people, and cannot understand what others will think of their behaviour. They also tend to be loners and obsessive about their work.
   Whatever he may have been suffering from, there was no doubting Turing's brilliance and originality of thought. He was put to work on exploring what would happen if the German military changed its system of exchanging message-keys. Bletchley's early successes relied on Rejewski's work, which exploited the fact that Enigma operators encrypted each message-key twice. It was felt it wouldn't be long before the Germans noticed that this repetition was compromising the security of Enigma, and changed the procedure, thus confounding Bletchley's current codebreaking techniques. It was Turing's job to find an alternative way of attacking Enigma, one that did not rely on a repeated message-key.

Turing bombe - front view

Turing bombe - rear view, case open

WREN checking a Turing bombe

Four rotor naval Enigma

HMS Tartar crew board the weathership Lauenburg

Unsuccessful sortie on the U-744

The second bombe

THE ANSWER LAY in the rapidly-accumulating library of old decrypted messages. Turing picked up on the fact that emanating as they did from military sources, many of the messages conformed to a rigid structure and contained the same or similar words and phrases in the same places. An example might be a daily weather report, sent from the same station at the same time each day. Located somewhere within the message would be the time, the location, and the German word 'wetter', meaning 'weather'. By looking at previously-decoded messages for that station, Turing could determine where these words should be, and compare them to the ciphertext. When a piece of plaintext can be associated with a piece of ciphertext, this combination is known as a 'crib'.
    However, he still had the problem of identifying the correct machine setting from the billions available. He decided to adopt Rejewski's approach of separating the scrambler settings from the plugboard settings. If he could find something in the crib which had nothing to do with the plugboard cablings, it was then feasible to check each of the remaining 1,054,560 possible scrambler combinations (60 arrangements x 17,576 orientations). Having found the correct scrambler settings, he could then deduce the plugboard cablings. Eventually he hit upon the idea of a particular type of crib which contained internal loops, similar to the chains exploited by Rejewski. Unlike Rejewski's work, which focused on the repeated message-key, Turing's loops connected certain plaintext and ciphertext letters within a crib. He then imagined an electro-mechanical machine which replicated having three Enigma machines connected together, such that the output of one was fed into the input of the next, and so on, simulating the letters in the loop. In this way he nullified the effect of the plugboard. The machine would then test each of the 17,576 orientations in turn, stopping when a possible orientation was found which would produce the loop in the crib. Once the correct setting was known, it was a relatively simple matter to figure out the plugboard connections. The only problem was picking which set of scramblers to use; if all 17,576 orientations had been checked without a result, then the rest of the sixty possible scrambler arrangements had to be tried one by one. Alternatively, the cryptanalyst could theoretically have sixty sets of three Enigmas running in parallel.

Turing's genius lay in turning his theoretical design of the electro-mechanical machine outlined above into a working reality. He finalised his design at the beginning of 1940, and the job of construction was given to the British Tabulating Machinery factory at Letchworth.
    The finished machine consisted of twelve sets of three electrically-linked Enigma machines (i.e. it had 12 x 3 x 3 = 108 wheels with each wheel wired up to represent a scrambler), and stood about two metres tall by two metres long and a metre wide (6' x 6' x 3'). It was called a bombe because it superficially resembled the Polish bomby. The first prototype, christened Victory, was put into operation on 14 March 1940 but proved to be disappointingly slow. It would take up to a week to find a particular key. With the help of a suggestion for improvement from Gordon Welchman a modified design was hastily drawn up, and the second bombe, christened Agnus Dei or Agnes for short, went into action five months later on 8 August 1940. Agnes fulfilled all expectations, which was just as well because on 10 May 1940 the long-awaited event happened—the Germans stopped repeating the message-key. For three months there was a virtual information blackout until Agnes came on line. Within eighteen months there were fifteen more bombes in operation, each one 'clattering like a million knitting needles'; by the end of 1942 there were 49, and by 1944, at least 200 in various locations around the countryside. To start a run, the cryptanalysts first had to produce a 'menu', which specified how to set up the wheels' initial positions and also how to connect up the masses of cabling behind each machine. The setting up was done by Wrens (Women's Royal Naval Service), who with the help of BTM factory staff also noted at what settings the machines stopped (signalling a possible 'match' with the key) then restarted them again, plus they had to inspect all the wheels to ensure their copper brushes were trimmed correctly and placed at the correct angle to make good electrical contact. Add in the deafening noise, stifling heat, oil leaks and occasional electrical shock produced by the machines in their stuffy, badly-ventilated building, and it's no wonder the Wrens dubbed it 'the hell-hole'.

More on Cribs—and Pinches

IF ALL WENT WELL the bombes might find a key within an hour. It was then a comparatively easy matter to deduce the other settings and hence find the day-key. Once that was known, all the other messages sent that day with that day-key could be deciphered. But the bombes couldn't operate without a menu, and a menu couldn't be written without a crib. And sometimes, even though a cryptanalyst might be sure he had the correct plaintext for the crib, he might not be certain exactly where it fitted within the ciphertext. There was however a way to check this, and it exploited the flaw in the Enigma machine mentioned earlier: no letter ever encrypts as itself. So all the codebreaker had to do was line up the ciphertext and plaintext one above the other, and slide one of them along until no letter is paired with itself. The following example illustrates this.

w e t t e r n u l l s e c h s

Notice that the first e in wetter is matched with an E in the ciphertext. The crib must therefore be misaligned. If we shift the plaintext one place to the left, the match still fails because this time the first s in sechs in matched with S in the ciphertext. However, if we shift the plaintext one place to the right there are no matches, and the crib is likely to be in the right place.

Whilst the codebreakers at Bletchley were having considerable success with the German Army and Airforce Enigma traffic, the same could not be said of the Naval or Kreigsmarine traffic. There were several reasons for this. Better training and stricter procedures meant the operators didn't send stereotypical messages, thereby depriving Bletchley of cribs. They had a more secure system for selecting and transmitting message-keys. And they had eight scramblers to choose from, not just five, which meant there were six times as many keys to check.
    Even worse than that, in the Atlantic the U-boat fleet under Admiral Dönitz had its own radio 'net' and used its own version of the Enigma machine, with four scramblers instead of the usual three. Bletchley's codename for this net was Shark, and the difficulty in breaking the Shark traffic was reflected in the huge amount of Allied shipping sunk by U-boat action during 1940 and 1941. The situation was becoming desperate as the U-boat wolf packs hunted down badly needed merchant convoys, seemingly at will. The ten month intelligence blackout caused by the inability to decrypt the German Naval Enigma caused a lot of friction between Bletchley Park and elements of the Royal Navy establishment. Finally, drawing on the Polish experience once again (and the Schmidt episode in particular), it became apparent that if cribs weren't available, the only other way in was to steal or copy codebooks from the enemy, hopefully without arousing suspicion back at German HQ.
    One particularly inventive scheme to accomplish a 'pinch' was thought up in September 1940 by a Lieutenant-Commander in Naval Intelligence. His idea was to take an air-worthy captured German bomber from the Air Ministry, dress up a crew of five tough men (one of whom had to speak German perfectly) in German Air Force uniforms and blood-soaked bandages, and crash the plane in the English Channel near a German ship, sending out an uncoded SOS message in plain German as they did so. Once on board the rescue ship the airmen would shoot the German crew, dump them overboard, and sail the ship plus its all-important codebooks back to an English port. The scheme (codenamed Operation Ruthless) quickly received the official go-ahead, but had to be postponed and eventually abandoned due to a lack of suitable German shipping operating at night. It should come as no surprise that the name of the Lt-Commander who thought up the scheme was Ian Fleming, who later went on to become famous as the author of the James Bond novels.
    Better success was had starting in May 1941, when a series of daring raids was carried out on isolated weatherships and the occasional stricken U-boat, resulting in codebooks being 'pinched'. To hide the fact the monthly codebooks were now in British hands, the raided boats were sunk, leading the Germans to believe the codebooks had sunk with them. From that point on the Shark traffic was broken virtually on a daily basis, allowing U-boat positions to be pin-pointed and conveys to be routed around them.

A WAVE operating the NCR bombe

Rotor and Commutator - note the use of numbers instead of letters

Front of US bombe

Rear of US bombe
The Two-Edged Sword

BEING ABLE TO LISTEN IN on the enemy's intentions almost throughout the whole of the war gave the Allies an enormous advantage. However, to ensure they continued to have that advantage, absolute secrecy about the source of the intelligence was essential. If the Germans ever suspected Enigma was being broken, they would have taken steps to either increase security still further, or stopped using it altogether. As it happened, the Germans did continually make changes to security procedures and the actual hardware at intervals, which forced the Bletchley Park cryptanalysts into a game of catch-up. There were occasional investigations by the Germans into whether the Allies were breaking Enigma traffic (Dönitz in particular was suspicious of this), but each time the conclusion was negative. Enigma was thought to be impregnable.
    The true source of the Enigma and Ultra material was known only to a handful of people. To disguise the source, Churchill let it be known that the intelligence came from 'Boniface', a fictitious MI6 operative. Special liaison teams were set up to distribute the information to commanders in the field. The trouble was, the commanders themselves weren't told of the source, and being inherently distrustful of MI6 information, they initially failed to take advantage of it. Eventually though they came to trust it, and it allowed them to be more assured in their decision-making. Indeed, the intelligence provided by Ultra proved to be invaluable in battlefronts all over the world: the North Africa campaign, the Mediterranean, the Atlantic, the Pacific and in the Allied invasion of Europe (the D-Day landings).
    So tight was the security surrounding Enigma, that even in Bletchley Park the occupants of one hut didn't know what was going on in the others, unless their work was directly related. They couldn't tell anyone anything about the nature of the work—not even their parents. Some of the people who worked there tell stories of being ostracised or even ridiculed for "not being in uniform and fighting at the Front". They couldn't tell their detractors that if it wasn't for them and their colleagues at BP, a lot more of the men and women "in uniform and fighting at the Front" would be dead or wounded. Considering that towards the end of the war there were 12,000 people working at Bletchley (over three 8-hour shifts per day), the fact that nothing leaked out is a remarkable achievement.
    The Royal Navy, too, did its bit in not divulging to the enemy that Enigma messages were being broken. For example, sometimes U-boats were deliberately allowed to escape even though their positions had been identified through message decrypts. In one instance the exact location of a group of nine ships, German tankers and supply vessels, was identified. The Admiralty informed Royal Navy destroyer captains of the whereabouts of only seven of the ships, lest the sinking of all nine should arouse German suspicions that their communications were compromised. The seven were duly sunk, but then the destroyers accidently came across the other two ships, and sank them as well. The destroyer captains knew nothing about Enigma or the policy of not arousing suspicion—they just thought they were doing their duty. However, German suspicions were aroused, and an investigation was launched into this and other similar attacks, exploring the possibility Enigma had been broken. The report concluded that the numerous losses were either due to natural misfortune, or a British spy who had infiltrated the Kreigsmarine. The breaking of Enigma was considered impossible and inconceivable.

(Back)Hands Across the Sea—the American Contribution

TOWARDS THE END OF 1940 (i.e. about a year before America entered the war), discussions were held about an Anglo-American exchange of cryptographic secrets. Despite reservations in some British quarters about the ability of the Americans to keep classified information secure (which in hindsight is rather ironic when you consider the damage done later to British Intelligence by Philby, Maclean, Burgess and Blunt), the first American codebreaking liaison team arrived in Britain in February 1941. In return for explaining how the Americans had broken the Japanese machine code known as 'Purple', they were to be told all about British progress on German ciphers. However the British, whilst appearing to be cooperative, endeavoured to give the Americans as little as possible. They did not, for example, allow the Americans access to Enigma intercepts on a day-to-day basis. This continued until the Shark Enigma traffic was blacked out on 1 February 1942. With U-boats now playing havoc with shipping along the east coast of America, the Americans demanded to know why they were no longer receiving Enigma information, and started making noises about trying to break Enigma themselves. This was something the British did not want. After some to-ing and fro-ing, it was agreed that Bletchley would send over a British bombe within four months, to allow the Americans to carry out their own research on Enigma-breaking machines. For one reason or another the bombe was never delivered. The Americans, concerned that new British bombes capable of dealing with the Naval four-wheel Enigma traffic would not be ready for at least six months, and scared that a well-aimed series of bombing raids on Bletchley Park could wipe out all Enigma codebreaking, determined to develop their own Enigma-breaking resources, including high-speed bombes.
    Eventually, bowing to the inevitable, the British agreed to allow American cryptographers to be sent to England, and to be equipped with British bombes so they could help directly in the decrypting of Enigma messages. Intelligence gleaned from the messages could be sent to Washington. The Americans were even allowed to set up their own intercept stations in England. In the meantime, work was proceeding at the National Cash Register complex in Dayton, Ohio to produce the US Navy-designed ultimate bombe—an all-electronic machine, 100 times faster than anything in use at the time, and powered by tens of thousands of fast-pulsing miniature gas tubes. In charge of production at NCR was 35-year-old Joe Desch, an electrical engineer who had designed the miniature gas tube before the war. Desch soon realised that due to overheating and reliability issues the Navy's all-electronic design was impractical, and he sought and received permission to build an electro-mechanical machine instead. It would look similar to but operate 30% faster than the proposed British high-speed bombe, and would incorporate electronic technology so that when a 'hit' was made, it would allow the machine to brake at high speeds and reverse itself to the exact sequence of rotor positions that had broken the code, and print them out. The reversing and noting was something that had to be done by hand for the British bombes.
    In December 1942, Alan Turing visited NCR to offer advice and also report on progress. Whilst he himself was polite and charming to his hosts, his report was quite scathing about most aspects of the machine's design, but was especially so about the auto-reverse feature.
"They say the whole machine is being built sufficiently strong to withstand such strain," Turing wrote. "Possibly the real objection to this method is that the time taken over each stop is fairly considerable . . . 15 seconds, and of course it seems a pity for them to go out of their way to build the machine to do all this stopping if it is not necessary." Turing's report was not shown to Desch in case it demoralised him.

24 May 1943 — In a secured inner room in NCR's Building 26, not long after lunch, Phil Bochicchio (floor manager for the project) was conducting a test run on 'Adam'—one of two prototype bombes— when its high pitched whine suddenly died and the machine shut off. At first, he thought it was just one more electrical short in the temperamental device. But then, as it was designed to do, the bombe came back to life and began slowly to rewind. That could mean only one thing: it had scored a 'hit' on part of an Enigma message fed into the machine. When a hit occurred, a complete circuit surged through all 64 of the bombe's fast spinning "commutator" wheels—possible only if it had arrived at the positions of all four rotors on the Enigma machine that may have created the message. The surge set off a braking mechanism that stopped the bombe's wheels within four to five revolutions, then rewound them back to their hit positions and printed out the rotor sequence. That's exactly what happened, but Bochicchio was still skeptical. He had a fellow engineer run the same encrypted message through 'Eve', the other prototype. It shut off in precisely the same rotor positions.
    Although NCR had now proved the feasibility of the machine, there was still the problem of reliability to address. Each machine simulated the action of sixteen four-wheel Enigma machines. The main bakelite wheels spun at 3,600 rpm, which made them overheat, distort, crack and produce faulty electrical signals. The machines leaked oil. The Navy again wanted to change the design, to one with even greater wheel speeds. Desch again successfully argued against change, and reduced the main wheel speeds to 1,750 rpm to stop them distorting. Eventually even the oil leaks were brought under control. By December 1943 NCR had produced 121 of the bombes, which after a bedding-in period gained a reputation for great reliability. All the modifications made to the original specification throughout the project were now paying off. Consider that in June 1943, when the first machines were under development, it took an average of 600 hours to decrypt an Enigma Naval message. From December 1943 until the end of the war, when all 121 machines came on line, it took an average of just 18 hours. Even the British had to grudgingly admit the US bombes worked and worked well, and eventually they left most of the Atlantic Enigma codebreaking effort to the Americans.

The photos on the left show the front and rear of the only remaining example of the wartime US Navy bombe. It is at NSA's National Cryptologic Museum at Ft. Meade, Maryland.

Lorenz SZ40



From Heath Robinson to Colossus

WHILST ENIGMA, if used properly, provided strong encryption, there was an even stronger machine cipher being used by the Germans. It was used by Hitler to communicate with his generals, and was produced by the Lorenz SZ40, a semi-automatic, multi-rotor machine even more complex than Enigma. BP codenamed the Lorenz traffic Tunny, and as D-Day approached, breaking it was to become increasingly important.
    John Tiltman and Bill Tutte, two of BP's codebreakers, discovered a weakness in the way the Lorenz cipher was used, and this enabled them to eventually crack the code. However, the subtleties of the Lorenz cipher meant that bombes were not flexible enough to assist in the breaking, so each message had to be painstakingly broken by hand over several weeks, by which time the information was largely out of date. A mechanised solution was desperately needed.
    Bletchley mathematician Max Newman became convinced that the answer lay in building a computing machine that could adapt itself to different problems, along the lines of the 'universal machine' described by Turing in his 1937 thesis. The first attempt, named 'Robinson' after the designer of cartoon contraptions Heath Robinson, was a partial success but had its practical drawbacks. It relied on two streams of punched paper tape being synchronised and driven at very high speed past an optical reader, which could read 5000 characters per second. The paper tape kept breaking. The Bletchley Park hierarchy deemed the idea of such a machine technically impossible, and shelved the project. Luckily, a Post Office engineer named Tommy Flowers, who had been involved in discussions about Newman's design, decided to ignore Bletchley's skepticism and build a machine using electronic valves to replicate what Robinson was supposed to do, only much faster and without the need to synchronise the paper tapes. He spent ten months at the Post Office's research station at Dollis Hill, North London, turning Newman's blueprint into the machine which became known as Colossus. It had 1500 electronic valves, and was delivered to Bletchley on 8 December 1943. Because it utilised electronic switching it was much faster than the old bombes, which used sluggish electromechanical relays. But even more important than its speed was the fact that Colossus was programmable, and it was thus the world's first programmable electronic computer.
    Following the success of Colossus Mark I, ten Mark II models (with 2400 valves) were built. They played a major role in intelligence operations supporting the Normandy landings. It should be noted here that Colossus was never used to break Enigma-enciphered messages, contrary to popular belief.
    After the war the Colossus machines (along with nearly everything else at Bletchley Park) were destroyed, and those who had worked on them were forbidden to talk about their experiences. Tommy Flowers was ordered to dispose of the blueprints, and he duly burned them. The plans for the world's first computer were lost for ever.

    [Update: According to a recent (2012) BBC documentary, not all the Colossus machines were destroyed at the end of the war. Churchill, in the interests of secrecy, did order that most of the machines were to be broken up "into pieces no bigger than a man's hand", but two of the Colossus machines were transferred to the Government Communications Headquarters (GCHQ) at Eastcote in 1946, and were further transferred to Cheltenham in the mid-1950s when GCHQ moved there. Both of the Colossus machines were eventually dismantled in 1959 and 1960 respectively.]

    The shroud of secrecy covering the work at Bletchley meant that J. Presper Eckert and John W. Mauchly of the University of Pennsylvania received the credit for building the world's first electronic computer in 1945. Their machine comprised 18,000 electronic valves capable of performing 5,000 calculations per second, and was called ENIAC (Electronic Numerical Integrator and Calculator). It was originally commissioned by the US Army to speed up ballistic computations, needed to compile firing and bombing tables. Finished too late to play a part in the war, up until its demise in 1955 it was used for an assortment of tasks, including running millions of discrete calculations associated with top-secret studies of thermonuclear chain reactions—i.e. the hydrogen bomb. For decades it was ENIAC and not Colossus that was considered the mother of all computers. Nowdays it is generally accepted that Turing, Newman and Flowers were the fathers of the modern computer.

The mansion today

The famous Hut 6

Hut 8

Bombe mock-up

Close-up of rotors

Rotors for bombe rebuild

Colossus rebuild project
Bletchley Park Today

AT THE END OF THE WAR, 12,000 cryptanalysis staff were demobilised from Bletchley Park. Before the site could be reused for another purpose, all classified material had to be removed and/or destroyed. The bombes and Colossus machines were dismantled, and literally tons of paper, mostly duplicate decrypts, were shredded. Some Wrens who had not yet been demobbed formed a small clear-up party. One of them recalls:

    "We were near completion of site clearance, when I noticed a crumpled piece of paper wedged in a crack in a wall. Pulling it out I noticed it was, inevitably, another incriminating signal. All the huts and blocks had been hurriedly built and the holes bored to take heating and plumbing pipes were pretty rough. There had been some bitterly cold winters and people had stuffed the cracks with whatever paper came to hand. Wearily we went back through all the hundreds of rooms we thought we had cleared and on our hands and knees, or perched on ladders, armed with skewers, we gouged out an incredible amount of crumpled documents."

The Government Code and Cypher School at Bletchley was closed, and Britain's codebreaking activities transferred to the newly formed Government Communications Headquarters (GCHQ) in London, which was moved to Cheltenham in 1952. Some of the cryptanalysts went to GCHQ, but most of them returned to private life, sworn to secrecy about their wartime exploits. Britain wanted to continue its intelligence activities, and was reluctant to have its capabilities known. Thousands of Enigma machines had been captured during the war, and these were distributed among its former colonies, who believed the cipher was as secure as it had seemed to the Germans. The British did nothing to disabuse them of this belief, and routinely deciphered their secret communications in the years that followed.

Bletchley became in turn a teacher training college, some buildings a training centre for GCHQ, a General Post Office (GPO) training school, and later a CAA Air Traffic Control training school. In 1991 the site was to be cleared of all buildings to make way for a housing development. A get-together was organised of as many former codebreakers as could be traced for a farewell "thank you". Over 400 people attended, and as a result of the stories they told, it was decided to attempt the restoration of the site for posterity, and the Bletchley Park Trust was formed. It is thanks to the hard work of the people of the Trust, and their employees and many volunteers, that we today can see Bletchley as it was during those bleak wartime years.

My wife and I visited Bletchley Park whilst holidaying in England in September 2002. (The first five pictures to the left (under 'Bletchley Park Today') are straight off the camcorder tape, so I apologise for the quality not being up to the usual standard.) It was a place I had long wanted to visit, as I had been interested in WWII cryptology (and the Enigma story in particular) for a long time. After paying the reasonable entrance fee we were ushered into a small hall, where our knowledgeable guide sketched out the pre-war history of the Park and some ground rules for our tour. We then sallied forth to visit the various buildings, mews, huts and blocks, many of which had exhibits for us to linger over. Just to see and feel those old huts with their boarded up windows and peeling paint brought a rush of emotions to me. It was easy to close one's eyes and imagine the constant activity that must have gone on inside, the elation of a sucessful breakthrough, the misery of the Shark blackout, the thousands of wireless transcripts brought around the clock by motorcycle couriers from listening stations around the country. And of course, the life, loves, gossips and intrigues that people anywhere get up to, no matter how serious the situation.
    Hut 4 (Naval Enigma) next to the mansion is now a café; one can quietly sip a cup of tea and imagine what it must have been like (the taste of the tea hasn't changed, anyway). Hut 11 was the original home for the Turing bombes, and today houses a bombe mock-up—which incidentally was created for and used in the recent movie 'Enigma'. Hidden away from prying eyes (and fingers) at the back of Hut 11 is the nearly-completed bombe reconstruction project. This project involves Computer Conservation Society volunteers actually re-creating a working Turing bombe. As can be imagined, it's been a long and difficult project with many problems, but great progress has been made. Round the corner one encounters a ¾ scale U-boat—also used in the movie—and in a nearby building one can actually try one's hand on a real Enigma machine. I did, and to someone used to a computer keyboard, the 60-year-old keys are quite stiff to push down. But the lamps lit up!
    The large buildings which housed most of the Colossus machines have been demolished, but in another building there is a surprise—Colossus has been rebuilt! Largely thanks to Tony Sale (who did the actual construction work) and Dr Tommy Flowers' ability to recall much of the construction and wiring details from his memory, Colossus is computing once more—and can still give modern machines a run for their money!
    The tour takes 2-2½ hours but you can spend much more time than that if the subject really interests you. I found the whole experience fascinating and could easily go back again for another visit. I'd have to bribe Teresa with some retail therapy, though.

Arthur Scherbius

Rajewski and wife Irena - 1930s

Turing going to athletics meeting

Alan Turing
Whatever Happened To...

Arthur Scherbius, inventor of the Enigma machine, did not live long enough to see the successes and failures of his cipher system. In 1929, while driving a team of horses, he lost control of his carriage and crashed into a wall. He died on May 13 of internal injuries.

'Rex', aka Rodolphe Lemoine, the French spymaster who 'ran' Hans-Thilo Schmidt, was put under house arrest in Paris in March 1943. At first he said nothing about Enigma, but then he confessed everything about how he had met Schmidt in 1931, and how Schmidt had handed over information about the Enigma machine. Lemoine refused to act as a double agent against France. Later, as the Allies invaded France he was taken to Berlin, where he was captured and interrogated by the French. He died in October 1946.

Marian Rejewski eventually made his way to England in 1943, after escaping from first Poland and then France. Once in England he and Zygalski broke the code used by the SS. However, because of some rule about 'foreigners' not being allowed to work at Bletchley Park, instead of becoming part of the British Enigma effort he was relegated to tackling menial ciphers at a minor intelligence unit near Hemel Hempstead. He went back to Poland in 1946, only to find the local Communists where he lived—who knew nothing of his codebreaking work—regarded him as 'decadent' because he had lived abroad. It wasn't until the publication of Winterbotham's book in 1974, that he realised how fundamental his ideas had been for the routine decipherment of Enigma messages throughout the war. He received the Polonia Restituta, the equivalent of the French Légion d'Honneur, in 1978, two years before he died.
    The Polish Post Office issued a special stamp in 1983 to commemorate the part that Rejewski, Zygalski and Rozycki had played in breaking Enigma. Unfortunately, by then all three men had died.

Alan Turing had stopped working on the Enigma problem by mid-1943. He assisted with the attack on the Lorenz ciphers, and began working on a machine to encipher speech (codenamed 'Delilah', and which eventually he got to work). At the end of the war he took a post as Senior Principal Scientific Officer at the National Physical Laboratory in Teddington, Surrey, working on a project to build a digital computer (the Automatic Computing Engine or 'ACE') rivalling John von Neumann's planned EDVAC machine in the United States. He had always liked long-distance running and could often be seen after work in his running gear, grunting noisily whilst pounding the pavements around the NPL. The fact that he ran so fast prompted members of Walton AC (his local athletic club) to ask him to join them, which he did. His best marathon time was 2 hours, 46 minutes and 3 seconds, which was only 11 minutes slower than the winner in the 1948 Olympic Games. Had it not been for an injury he would probably have been selected for the British team for those Games. He was once asked why he punished himself so much in training. He replied that he had such a stressful job, that the only way he could get it out of his mind was by running hard. Naturally he didn't let on what his job was, or the pivotal role he had played during the war. Nor did he tell them he was awarded the OBE for his services during wartime.
    Unlike the wartime environment where Turing could progress in his projects from theoretical design to hands-on construction, the NPL administration frowned upon their theoreticians getting their hands dirty (which Turing loved to do). They got contractors in to actually build things. Eventually he became disillusioned with the lack of cooperation he was receiving, the lack of progress and the internal politicking. So when in 1948 wartime associate Max Newman, who was now Chair of Pure Mathematics at Manchester University, offered Turing the position of Deputy Director of the computing laboratory at the University, he accepted with alacrity. Manchester was in the forefront of computer design. But it proved to be a confused time for Turing, who had no real control over developments and was left to write the operating manual for the University's digital computer and some software programs.
    Whilst living in Manchester in 1952, Turing had an affair with a young man he met in a pub. The young man would stay at Turing's house from time to time. A 'friend' of the man took some items from the house whilst Turing was out. When reporting the burglary to the police, Turing naively let it slip that he was in a sexual relationship with the young man, who turned out to be 19 years old. The police, more interested in the relationship than the theft, charged Turing with 'gross indecency' (which according to Turing, was no more than mutual masturbation). His trial and conviction was reported in the papers, publicly humiliating him.
    Unknown to most people, Turing had continued his connection with GCHQ, the successor to Bletchley Park. But since 1948 the coming of the Cold War, and the alliance with the United States, meant that homosexuals were now regarded as a security risk. As a result of his conviction the authorities revoked Turing's security clearance, and he was forbidden to work on research projects relating to the development of the computer. The codebreaking genius who had played such an important part in Britain's wartime intelligence success now felt bitter and excluded.
    Turing escaped going to jail for his crime by agreeing see a psychiatrist and undergoing 'organo-therapy'—injections of the female hormone oestrogen for a year. The treatment was supposed to "kill male sexual interest." It made him impotent, and he also put on weight and grew breasts. According to some sources who knew him personally, Turing endured all this with amused fortitude. Others thought he became depressed. Whatever his state of mind, and despite (or maybe to spite) close attention by the police, he holidayed in Norway and Corfu where he had mild 'dalliances'.
    At about 5pm on the afternoon of 8 June 1954 his cleaner entered his house to make his dinner and tidy up as usual. She was surprised to find all the lights on even though it wasn't dark. Upstairs, she found Turing dead in his bed. Beside him was an apple with several bites out of it, and a jar of cyanide solution. There was an inquest, and the coroner returned a verdict of suicide. His mother could not accept he had killed himself, and maintained he must have been conducting an experiment which went wrong. There were even fanciful suggestions from some quarters who knew of Turing's wartime work that perhaps the security services had become nervous about his overseas trips and his being compromised, and had arranged his demise. Only Turing knows what really happened. Perhaps in a fit of depression he recalled the lines from the film he had seen sixteen years earlier:
"Dip the apple in the brew, Let the sleeping death seep through."
    One plausible explanation for Turing taking his own life was offered by a long-time work associate:
    "Mathematics is a young man's game. Remember, Turing produced his most seminal work, 'On Computable Numbers', when he was twenty-five."
    Maybe after six years of war and a less than stellar post-war career, not to mention the revocation of his security clearance, he realised his best years were behind him. Whatever the reason, Alan Turing FRS OBE, Britain's most brilliant cryptanalyst and computer visionary, former marathon runner, unsung hero and convicted 'sexual deviant', died a lonely, painful death in his own bed. He had helped save the State during the war, and the State repaid him by crucifying him. He was just forty-two years old.
Hans-Thilo Schmidt had just finished moving into his new flat in Berlin when the Gestapo burst in and dragged him off to Gestapo HQ. The date was 1 April 1943. He languished in a prison cell for some time before his daughter Gisela was allowed to see him. His family was never told the reason for his arrest. He managed to secretly pass a message to Gisela, asking her to bring him some potassium cyanide pills. He wanted to kill himself. Somehow she got hold of some pills and got them to her father. She later found out her brother had done the same thing.
    Around the middle of September 1943 Gisela was called in to identify her father's body. He had become terribly thin during his six months in captivity but his body was unmarked, leading her to believe he hadn't been tortured. His brother General Rudolf Schmidt, who had been sacked from the Army as a result of Hans-Thilo's treachery, paid for Hans-Thilo's body to be buried beside his mother and father in an unmarked grave in a cemetery outside Berlin. No-one apart from his interrogators and Hitler's inner circle was told what he had done; only they and Hans-Thilo's family knew where he had been laid to rest. As far as the Nazis were concerned, all traces that the Enigma spy had ever existed were wiped from the face of the earth. They probably thought that so many changes had been made to Enigma since Schmidt had been able to pass on documents to the French, that the Enigma secret was safe. But by then it was too late. Hans-Thilo's greed for money to support his desired lifestyle (which included having a flat in Berlin where he could have discreet affairs), and his general disillusionment with the way the country was being governed, had set off a train of events that was to hasten the eventual defeat of the Nazi regime by several years.

The Hut 6 Registry Afterthoughts

ALTHOUGH FOR THE SAKE OF BREVITY (!) I have concentrated on a few individuals and codebreaking techniques, there were many brilliant codebreaking contributors on both sides of the Atlantic. I haven't even touched on the British TYPEX coding machine, which had its design roots in the original commercial Enigma but ended up much more complicated, or the American SIGABA machine which apparently was never broken by the Axis powers.
    Bletchley Park also had enormous numbers of people engaged in translating, collating and extracting the most information out of the thousands of messages received, thus producing the 'real' intelligence. Everything was catalogued, cross-referenced and indexed in a vast punched-card installation. Thus by following a trail through the index, an innocuous-sounding message relating to, say, requisitioning of new shoulder flashes for an Army unit could reveal where to, when, how, and why that particular unit was to be relocated, who was going to command it, what equipment they would be taking with them, etc. At the height of the war Bletchley was using two million punched cards a week!
It is also interesting to reflect upon the two men at the heart of this story—Schmidt and Turing. Schmidt was vain, greedy, and an urbane womaniser who was a slave to his sexual urges. (But let's not forget that Berlin night club society in the '20s and early '30s was the most sexually-liberated in the whole of Europe—just think 'Cabaret'. It must have been difficult sometimes separating night club fantasy from everyday reality.) Did he think he was 'doing his bit' to stop the Nazis when he turned over those manuals to 'Rex'? It's unlikely. To him it was probably just a market transaction. And yet if he hadn't done what he did, the Allies might never have realised Enigma could be broken, and the British and Americans could easily have lost the battle of the Atlantic to Dönitz and his U-boat wolf packs. And if that had happened ...
    By way of contrast Turing was awkward, brilliant, somewhat naive, dedicated, and also a slave to his sexual urges. (Regarding his dedication, there is a lovely story that during the darkest days of the war, he became so despondent about Britain's chances of winning that he exchanged most of his life's savings for silver ingots which he promptly buried in a field. Needless to say, when he went to dig them up at the end of the war he couldn't find them again.)
    In many ways they were like chalk and cheese, but in two ways they were the same: their actions considerably shortened the war, and they both died, by their own hand, of potassium cyanide poisoning. In the one case it might be thought that a traitor had met his just deserts, but the other was a tragedy of a man ahead of his time.

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