These were figures to send Bletchley minds reeling. The whole of GC and CS Enigma work depended upon managing with just thirty Bombes in summer 1942, although another twenty were on the way. The Americans were proposing a take-over bid for the Atlantic work, by the brute-force expedient of building twenty-six times as many Bombes as the British had available, and using them in parallel.
But in October a second deputation from GC and CS to Washington negotiated another compromise. GC and CS ‘acceded to US desires to attack the German naval and submarine problems’ and agreed to supply the Navy Department with the intercepts and with technical assistance. In return the Navy Department … undertook to construct only 100 Bombes, accepted that GC and CS should be responsible for co-ordinating the work done by the American machines with that done by the British, and agreed to the complete and immediate exchange of the cryptanalytic results.
There was only one person who knew everything about the methods and the machines, and who was free from day to day responsibility. The responsibility for the detailed coordination thus promised now fell to the Prof. Sorting out the tensions between American bluster and British arrogance was not at all the kind of work he enjoyed, but the Anglo-American liaison had to be made concrete. There was a war on. Accredited as an official with the British Joint Staff Mission in Washington, he was issued with a visa50 on 19 October. He told Joan, ‘The first thing I shall do is to buy a Hershey bar.’
This was not to be the only purpose of his visit. Now that joint operations were being planned, the Allied authorities were in need of new technology to communicate the more subtle aspects of the Grand Alliance. Telegraph communication was not enough. They required proper means for speech signals. There being no submarine Atlantic telephone cables, all speech transmissions had to go by short-wave radio. But as a June 1942 Foreign Office memorandum had stated:51
The security device has not yet been invented which is of any protection whatever against the skilled engineers who are employed by the enemy to record every word of every conversation made.
No one could speak except on the understanding that what they were saying was being overheard in Berlin. There was a row in September 1942, when Prince Olaf of Norway had to be refused permission to talk to his five-year-old daughter, lest it set a precedent for the transmission of uncensored messages by governments-in-exile.
The essential difficulty of providing speech secrecy lay in the overwhelming redundancy of speech, as compared with writing. While the modular sum of two written messages would require painstaking work to unravel, the ear and brain could, almost without thinking, analyse and separate a sound signal into conversation, music and background noise. This was only possible because speech signals carried so much more information than was necessary for comprehension. Cryptanalysis thrived on redundancy, whether on routine ‘Probable Words’, repeated triplets in indicators, or re-enciphered messages. Any secure form of speech encipherment would have to remove it. The systems in use in 1942 did not attempt to satisfy that requirement. Systems existed which split up speech into pitch levels and then permuted them, preventing casual overhearing. But such ‘scramblers’ were easily penetrated by doing jigsaw puzzle work on a sound spectrograph of the resulting signal. They did not tackle the essential problem. Some efforts were being made at Dollis Hill to create a more sophisticated system, but American developments were much further ahead, and part of Alan’s assignment was to investigate them. It marked a shift from the cryptanalytic to the cryptographic side, reflecting the demands of the more offensive Allied war now being planned.
Speech secrecy was in another sense also a problem to the British authorities. In 1940 it had not been too difficult: a few jolly clever chaps in a country house were having a go at breaking German codes. In 1941 it changed: Churchill was getting the most important information from a source which only a select few knew about. The problem was to throw a ring of secrecy around this mushrooming department which lay outside the normal structure of the state. But by 1942 the problem had changed again. Bletchley Park was no longer outside the ordinary channels: it dominated them. Its productions were not the spice added to some other body of knowledge. It was nearly all that they had – photo-reconnaissance and POW interrogation adding points of important detail but never matching in scale what they had fresh from the horse’s mouth. There were sixty key-systems broken, producing fifty thousand decrypted messages a month – one every minute. The old days of ‘Red’ and ‘Yellow’ were long over and the soaring imagination of the analysts, exhausting the colours of the rainbow, had plundered the vegetable and animal kingdoms: Quince for the SS key, Chaffinch for Rommel’s reports to Berlin, Vulture for the Wehrmacht on the Russian front. Certain key-systems were used with the proper safeguards, and with these Bletchley was powerless. The Shark system, as they called the U-boat key, still remained intact but for those three days in February and March 1942. But except for these gaps, the German radio communication system had become an open book – to an élite.
It meant that a cloud of mystery and obscurity was settling over the whole British war. All of its documentation had to be falsified, acting out a charade in which ‘the old procedures’, as Muggeridge saw it,52
like the setting of agents, the suborning of informants, the sending of messages written in invisible ink, the masquerading, the dressing-up, the secret transmitters, and the examining of the contents of waste paper-baskets, all turned out to be largely cover for this other source; as one might keep some old-fashioned business in rare books going in order to be able, under cover of it, to do a thriving trade in pornography and erotica.
It was the ability of the British system to absorb the necessary innovations in an ad hoc fashion, when forced to do so, that constituted its real secret weapon. Without that flexibility, all the mathematical and linguistic skill would have been of no avail. Here, perhaps, the habit of paternal Empire enjoyed its triumph. While A. V. Alexander, the trade union man who followed Churchill as First Lord of the Admiralty, was never allowed to know about naval intelligence, let alone cryptanalysis, the prefect layers of the stratified British system were characterised by a trust that allowed them to keep in control and in communication with each other. There were bitter conflicts at every level over what was the most important and exciting development ever to be thrust into the unready hands of British government. But the conflict took place within a club where the rules were agreed tacitly, not enforced by legalities or by handcuffs. Alan Turing could hardly have survived in any other system – certainly not in the German, obsessed by spying and treachery, and perhaps not in the American. He was no team man himself, preferring always to have something tidily his own, but they were able to use him as the sixth-form Maths Brain, distinguished, as the headmaster had said, within his sphere.
For those in charge, the fruits of his labours presented logical problems no less difficult than those of Bertrand Russell. Who was to know what, and who to know they knew? Liaison with the very differently organised American system was just one problem; there was the deception of Dominions, free forces and Russians. The capture of cipher material had to be avoided when it was not needed; they had to prevent the ‘indoctrinated’ from ever falling into enemy hands, and above all, they had to arrange convincing explanations for the foreknowledge that successful operations might betray. But how could this be done without vast numbers of people knowing that something strange was happening, and how could the information be used without giving itself away?
It could not. Bletchley’s continued successes depended upon the willingness of German authorities to believe that ciphers were proved secure, instead of asking whether they actually were. It was a military Gödel theorem, in which systematic inertia rendered German leadership incapable of looking at their system from the outside. Nor was the principle of ‘need to know’ one that worked like a complete and consistent logical system. At Cambridge – and at Sherborne School – people guessed the nature of work being done at Bletchley. In 1
941 the Daily Mirror had carried an article53 headed SPIES TAP NAZI CODE, which dwelt proudly upon the work of amateur radio operators who were ‘taking down the Morse messages which fill the air’. In the hands of ‘code experts’, the article explained, ‘they might produce a message of vital importance to our Intelligence Service’. ‘A letter of thanks from headquarters telling us that we have been able to supply some useful information is all the reward we ask,’ said the radio spies themselves. And more significantly, on another part of the board, the initiative of the Red Queen was allowing Soviet authorities access to Enigma decrypts. Yet the system still held together.
The traffic in signals was indeed like ‘a thriving trade in pornography and erotica’, inasmuch as what mattered was not so much the guarding of any particular fact, or thing, as the maintenance of the whole subject as something improper for discussion, like ‘dirty talk’. A deeply ingrained fear and embarrassment about the unmentionable was the keynote of all that depended upon the Bletchley work, rather than this or that rule. This was how it worked so well, but it left Alan Turing in an extreme position. It was difficult enough being a mathematician, this being the frightening subject of which even educated people knew nothing, not even what it was, and of which they might proudly boast ignorance. His sexuality might at best elicit a similar condescension, but more likely the associations of evil, tragedy and disease. Above all, it was a matter on which society still demanded silence. Such silence was for him tantamount to an uneasy game of deceit, and he loathed pretence. But as chief consultant to GC and CS, he was living at the heart of yet another imitation game, doing work that did not officially exist. Now there was almost nothing in his life that he could talk about but chess-playing and fir cones.
Fragments of ordinary life continued. Occasionally he saw his friend David Champernowne, himself now working in the Ministry of Aircraft Production, but of course they never spoke of their work. He had continued to concern himself with Bob’s future, being concerned that he should try for a Cambridge scholarship. This he did, cramming for Latin, but reaching only the standard for an ordinary place. In the circumstances this was quite an achievement, but Bob felt that he had disappointed Alan, in not possessing a feel for abstract ideas. Alan could not possibly afford to send him to Cambridge, so Bob went in autumn 1942 to take the telescoped chemistry course at Manchester University, earning his own keep by stoking the boilers in the Friends Meeting House.
Bob had a sharp eye, and guessed that Alan, ‘Champ’ and Fred Clayton formed a team working together in Intelligence. He was mistaken in that respect, but right about Alan, though all he knew was that Alan worked at a place called Bletchley. Other people likewise were able to put two and two together. John Turing, while serving in Egypt, found that his superior officer had a brother working at the same town, and they guessed it had to do with ciphers. Mrs Turing guessed correctly too, remembering Alan’s letter about ‘the most general code or cipher’ in 1936, and knowing he worked for ‘the Foreign Office’. She liked the idea of him being assigned duties once more, although perhaps it was a disappointment that these did not oblige a military haircut. Her long letters sometimes found their way unread into the Hut 8 waste-paper basket, Alan telling Peter Hilton ‘Oh, she’s all right.’ She also visited him in autumn 1941. He tried to hint that he was doing an important job, with ‘about a hundred girls’ working for him, but neither she nor indeed anyone else had the faintest idea of how important it was. How could they? The concept of an information processing system, one matching the organisation of an advanced industrial power, had only just been invented.
Which was now the ordinary and which the extraordinary? Which the reality and which the illusion? The pure mathematician of 1938 had wandered into an amazing position on the board, so that his brain concentrated ideas upon which the struggle for Europe depended. Miranda was playing chess when she saw the brave new world – and here it was in this organisation, a progressive scientist’s dream in which the experts had confounded the Blimps, and forced them to play the modern tune. Far above the heads of its slaves, far above the heads of the British people, the secret technocracy was working like an intelligent machine. There at the centre was the brain of the Alpha Plus who had breathed life into it and nurtured its growth – the unhappy Alpha, cursed with the ability to think for himself, and beginning to be edged out by his own creation.
The broken Enigma and Fish systems were only just decipherable, and were stretching the fastest minds and the resources of modern science to the limit. They also depended upon luck and sudden, brilliant observations. On 30 October another stroke of fortune, the capture of U-559 off Port Said, at last gave Bletchley the key to the blank Atlantic, just as Alan was preparing to cross it. Thus elements of pure chance, amplified by a youthful will that had thrown off the ‘old fogies’ of the 1930s, had implanted into the British state a fantastic new element. In his central control of the war, Churchill now relied totally upon an unmentionable department, in which no one knew what anyone else was doing, and which made deceit into second nature. Starting with those early discoveries in the outhouses of Bletchley Park, a great explosion of implications had, in silence, proliferated through level after level of military and political organisation. It was a logical chain reaction, whose after-effects no one had time or inclination to consider.
General Montgomery always put his troops ‘in the picture’. Indeed he was prone to give too much of the ultra-modern picture away, and had to be reprimanded by Churchill. But with that picture integrated effectively into Montgomery’s plans, his troops inflicted defeat at last upon the Afrika Korps. It was the first decisive British victory over German arms in three years of war. On 6 November 1942, General Alexander signalled ‘Ring out the bells!’. The British occupation of Egypt was preserved, its puppet regime saved, the southern German pincer on the Middle East destroyed. Then on 8 November, the Allied forces landed in Morocco and Algeria, achieving complete surprise. It was a first victory for planning and the coordination of Intelligence. The Americans were now back in the Old World – and to British consternation, would treat with the Vichyiste Darlan. But the British could not complain, for they had handed over the torch.
Alan Turing had boarded the Queen Elizabeth on 7 November.54 As the refitted Monster zigzagged alone towards America, the fighter escort left behind, the King’s First Minister was explaining that he did not intend to preside over the liquidation of the British Empire. Churchill also said that it was only the end of the beginning. But for the goose that laid the greatest golden egg, it was already the beginning of the end.
* * *
* J. R. F. Jeffries, Research Fellow in mathematics at Downing College, Cambridge, contracted tuberculosis in early 1941 and died.
* For consistency the word ‘radio’ is used henceforth, although at the time this was the American term, English people calling it ‘wireless’, or more formally ‘wireless telegraph’. At the time of Roosevelt’s re-election in 1936, Alan wrote from Princeton ‘all the results are coming out over the wireless (“radio” they say in the native language). My method of getting the results is to go to bed and read them in the paper next morning.’
* There were complications, but not affecting the account that follows.
* The rather tiresome complication introduced by the ring-setting is, unfortunately, required to make sense of what the Poles achieved. It will play no part thereafter.
* i.e.
* i.e., Actually 11 pairs gives slightly more ways – not that it makes any difference; 12 or 13 pairs rather less
† i.e., 26! This is also the number of possible wirings for each rotor of an Enigma.
* Questions about the chance of obtaining loops could be posed and answered in the language of probability theory and combinatorial mathematics – very much what Alan, or indeed any Cambridge mathematician, would be well-placed to tackle. One would be lucky to get a loop within one word, as shown in the artificial example; in practice the analyst would have to p
ick letters out of a longer ‘crib’ sequence. Furthermore one loop would not be enough – far too many rotor positions would satisfy the consistency condition by chance. Three loops would be required – a taller order.
† The Bombe, nevertheless, had nothing whatever to do with the Universal Turing Machine. It was more general than the Polish Bombe, which worked on a specific indicator system; but otherwise it could hardly have been less universal, being specific to the Enigma wirings and requiring an absolutely accurate ‘crib’.
* Welchman, whose first work had been on the identification of the different key-systems, had devised a way of naming them by colours. ‘Red’ was the general purpose Luftwaffe system; ‘Green’ the Home Administration of the Wehrmacht. Despite these early breaks, ‘Green’ turned out to be an example of where an Enigma system was almost totally unbreakable because it was used properly.
* Knox’s work had a very direct pay-off in the battle of Matapan, in March 1941.
* Literally, in future parlance, software.
* The Yellow was the temporary inter-service system used in Norway.
* They might well have worried that the German occupiers would now learn of the successful start to Enigma decryption from a French source. But no such disclosure or discovery was ever made.
* She was not a country vicar’s daughter, but that was what they thought.
* Though any but a very naive player would be able to do better than this and play so as to exploit the particular weaknesses of the opponent.
* More strictly, any ‘zero-sum’ game, one in which the loss of one player would always be the gain of the other.
† Less complicated than poker (which in fact is much too complex for a full mathematical analysis), the game of ‘stone, paper, scissors’ illustrates the idea. In this game the optimal strategy, for both players, is a ‘mixed’ strategy, that of choosing the three options randomly and with equal probability. For clearly, if one player departs from randomness, the other can exploit the departure to gain an advantage.
Alan Turing: The Enigma: The Book That Inspired the Film The Imitation Game Page 39