If the key were produced truly randomly, and used on the one-time principle, then such a system would be secure, the same for binary digits as for decimal digits. If all keys were equally likely, then no weight of evidence could accrue to any particular possible plain-text. But that was not the case with these German transmissions. The key was generated by the action of a machine. There were several different kinds of teleprinter-enciphering machines in use, but they shared common features, the key being a pattern generated by the irregular motion of ten or so wheels.45 Such machines did not actually produce a paper key-tape, but from the cryptanalyst’s point of view it came to the same thing.
As with Enigma, there was always the possibility of an eventual hardware capture, and the German cryptographers should have allowed for that possibility. But the important break into this type of traffic did not, as it happened, come about in this way. In 1941 someone at Bletchley guessed that a certain message had been sent out twice, and in a very particular way. Some fault in the system for using the machine had allowed an elementary blunder. The message had been sent out each time enciphered by the same key, but with the key advanced by one character in one transmission. Once this guess had been made, the recovery of both key and plain-text was a simple step.
With a machine designed for complete security, it should have proved impossible to make any further progress. The sequence of key thus elucidated should have appeared to be random, without any discernible pattern. But it was not. The decisive observation was made by W. T. Tutte, a young Cambridge chemist turned mathematician. This was the breakthrough equivalent to what the Poles had achieved with the Enigma in 1932. Like that work, it constituted a logical rather than a physical capture of the machine, and again it was only the very first step, the sine qua non. But one difference was that this time German industry had made a more serious effort. This was not a jumped-up version of a commercial device as was the Enigma. Another difference lay in its part in the German military system. This traffic was sparse but juicy, carrying high-level reports and appreciations. It brought Bletchley much closer to Berlin, at a time when Hitler was taking over personal direction of the war.
Even with an effective capture of the machine, further cryptanalysis should have been impossible: it was the rule of good cryptography. And the ‘period’ of the enciphering mechanism was not 17576 but a truly ‘tremendously large number’. Yet these problems proved not to be entirely insuperable, and by 1942 the analysts were beginning slowly to find ways to exploit the knowledge they had. The work on this particular type* of machine-enciphered traffic became known as Fish. One of the most important and general methods was developed by Alan on the basis of Tutte’s work in the course of his months of work during 1942 on Fish. It became known as ‘Turingismus’.
A new Bletchley industry was sprouting up. It was another way in which 1942 meant starting all over again from the beginning. But this was not to become Alan Turing’s game, as naval Enigma had been. For one thing, he had not been the one to start it off. For another, it was someone else who took the step of mechanising its analysis. This person was Newman, who arrived in summer 1942.
Newman had been recruited by his friend P. M. S. Blackett, the Cambridge physicist (and King’s College Fellow), who had been Professor of Physics at Manchester since 1937, and was currently applying statistical analysis to the problem of convoy organisation. (For at last the Admiralty was allowing scientific interference with its operations as well as with its intelligence.)
Newman was assigned to the Research section to work on the Fish signals but found himself not particularly adept with the hand methods. He was thinking of going back to Cambridge, when he conceived of an approach that could be automated. The theoretical rationale was founded upon the statistical methods that Alan had developed during 1940 and 1941. These ideas, indeed, were crucial to Newman’s plans. But the implementation of them would require the construction of entirely new machines to do very fast counting operations. Newman persuaded Travis to approve this development, and the existing links with the Post Office Research Station were brought into play as early as autumn 1942. This recognition of their frustrated skills meant that the electronic engineers were able to make an impact after all. For the rest of 1942 the project was floundering on the engineering side, but this was not so much because of the electronics, as because of the mechanical difficulties associated with passing paper tape very rapidly through a reader.
Alan knew all about this project, but his active part in the Fish analysis was confined to ‘Turingismus’. This, in the autumn of 1942, was taken up by the section called the Testery,* where they tried out hand-methods on the Fish traffic – just as, years before, the Enigma decryption had painfully begun. Peter Hilton had been moved there from Hut 8, and then another arrival, in autumn 1942, was that of an even younger man, straight from Rugby School. This was Donald Michie, who had won an Oxford classics scholarship, and while waiting to do a Japanese course had entered elementary cryptological training. His talent recognised, he was thrust into the deep end at Bletchley. Both he and Peter Hilton developed Turingismus and reported their ideas back to its originator.
Although the news was so unremittingly bleak, and the prospects so uncertain, 1942 could be a wonderful, liberating year for the young, given opportunities and ideas that would never have been possible in peacetime. Alan’s own youthfulness much endeared him to the younger recruits. It was in fact his thirtieth birthday when the fall of Tobruk came as the latest in a series of disasters, but to those fresh from school it would be hard to decide whether one so ‘schoolboyish’ himself could be as much as thirty, or whether one carrying so much intellectual standing could be so young. A conversation with him was like being invited into some older boy’s study where House Colours and Chapel Parade gave way to illicit jazz and D. H. Lawrence novels, but where the housemaster had to turn a blind eye because a precious scholarship was being won.
Peter Hilton was a racy raconteur, and his favourite Turing story concerned the Home Guard. The authorities quaintly insisted upon the Bletchley analysts doing soldierly work in their spare time. The heads of sections were exempt, but Alan conceived a passion for becoming proficient with a rifle, which amazed Harry Golombek, who after two years in the army had no such enthusiasm. Alan enrolled in the infantry section of the Home Guard, and to do so46
had to complete a form, and one of the questions on this form was: ‘Do you understand that by enrolling in the Home Guard you place yourself liable to military law?’ Well, Turing, absolutely characteristically, said: ‘There can be no conceivable advantage in answering this question “Yes”’ and therefore he answered it ‘No’. And of course he was duly enrolled, because people only look to see that these things are signed at the bottom. And so … he went through the training, and became a first-class shot. Having become a first-class shot he had no further use for the Home Guard. So he ceased to attend parades. And then in particular we were approaching a time when the danger of a German invasion was receding and so Turing wanted to get on to other and better things. But of course the reports that he was missing on parade were constantly being relayed back to Headquarters and the officer commanding the Home Guard eventually summoned Turing to explain his repeated absence. It was a Colonel Fillingham, I remember him very well, because he became absolutely apopletic in situations of this kind.
This was perhaps the worst that he had had to deal with, because Turing went along and when asked why he had not been attending parades he explained it was because he was now an excellent shot and that was why he had joined. And Fillingham said, ‘But it is not up to you whether you attend parades or not. When you are called on parade, it is your duty as a soldier to attend.’ And Turing said, ‘But I am not a soldier.’ Fillingham: ‘What do you mean, you are not a soldier! You are under military law!’ And Turing: ‘You know, I rather thought this sort of situation could arise,’ and to Fillingham he said: ‘I don’t know I am under military law.’ And anyway, to cut a lo
ng story short, Turing said, ‘If you look at my form you will see that I protected myself against this situation.’ And so, of course, they got the form; they could not touch him; he had been improperly enrolled. So all they could do was to declare that he was not a member of the Home Guard. Of course that suited him perfectly. It was quite characteristic of him. And it was not being clever. It was just taking this form, taking it at its face value and deciding what was the optimal strategy if you had to complete a form of this kind. So much like the man all the way through.
This Looking Glass ploy of taking instructions literally was one that created a similar fuss when his identity card was found unsigned, on the grounds that he had been told not to write anything on it. It came to light when he was stopped and interrogated by two policemen as he took a country walk. His awkward appearance and habit of examining wild flowers in the hedgerows had excited the imagination of a spy-conscious citizen.47
But besides sharing in such victories over blimps and bureaucrats, there was the experience of free association with people who were among the best in British mathematics, in a sort of secret university, one in which tradition and form, together with rank, age, degrees and all such superficialities were ignored. All that mattered was the ability to think. And they had a mathematical Flash Gordon, a logical Superboy, to encourage them – someone who refused to admit defeat, or any limitations on their capacities to succeed. To Peter Hilton, Alan was
… a very easily approachable man – though you always felt there was lots more you did not know anything about. There was always a sense of this immense power and of his ability to tackle every problem, and always from first principles. I mean, he not only … did a lot of theoretical work, but he actually designed machines to help in the solution of problems – and with all the electrical circuitry that would be involved, as well.
He did, for instance, design a special machine to help Harry Golombek with the analysis of the particular Enigma system employed by the German motor torpedo boats. There was another designed for use on the main naval Enigma problem; there was far more to it than the Bombe. The technology was not always new; thus the Banburismus process involved the use of paper sheets on which cipher-text messages were represented as punched holes. These had to be moved against each other and coincident holes laboriously counted before the sophisticated statistical methods could be used. There was a hint of irony in the way that Alan chose to call the process romsing – a reference to that progressive slogan, the Resources of Modern Science. But it also represented the essential truth about the Bletchley work, and Alan Turing was at the heart of it, never too proud to get his hands dirty with the ‘dull and elementary’:
In all these ways he always tackled the whole problem and never ran away from a calculation. If it was a question of wanting to know how something would in fact behave in practice, he would do all the numerical calculations as well.
We were all very much inspired by him, his interest in the work but the simultaneous interest in almost everything else … And he was a delightful person to work with. He had great patience with those who were not as gifted as himself. I remember he always gave me enormous encouragement when I did anything that was at all noteworthy. And we were very very fond of him.
Alan’s ‘great patience’ was not usually his most conspicuous characteristic, nor his approachability. But Peter Hilton was in fact the fastest thinker of the new Fish group, and drew out the most rewarding aspects of the ‘creative anarchy’ that was Alan Turing. It was pure joy to achieve something new, and show him, and have him grunt, gasp, brush back his hair, and exclaim, stabbing with his strange fingers, ‘I see! I see!’ But then it was down to earth again with the rules and regulations:
But there again, he began to be beset by the bureaucrats who wanted him to be in at a certain time and work till five o’clock and leave. His procedure – and that of many others of us, let me say, not only he, who were really fascinated by the work – would be maybe to come in at midday and work until midnight the next day. And then, the problem being essentially solved, go off and rest up and not come back for 24 hours perhaps … they were getting much more work out of Alan Turing that way. But, as I say, the bureaucrats came along and wanted forms to be filled in and wanted us to clock in, and so on.
Once he ordered a barrel of beer for the office, but it was ‘disallowed’. Such questions were trivial, but behind them lay more serious confrontations with the old mentality, which little by little and nearly too late had been obliged to give way to intelligence. Alan’s role in this process, however annoying to authority, was not entirely unrewarded. One day in 1942 he, Gordon Welchman and Hugh Alexander were suddenly summoned to the Foreign Office and awarded £200 each. Alan told Joan that they could not be given decorations, so had been given money instead. He probably found it more useful.
In September 1942 the British position was a little less hopeless, but only inasmuch as there had been no serious loss since that of Tobruk. Rommel’s eastward advance on Egypt had been checked by Auchinleck in July and by Montgomery in August, the latter being particularly helped by deciphered signals. The desert war was more like a naval war than a conventional front, and was particularly dependent upon information. It desperately required the effective integration of the three services, who had been obliged to swallow a bitter pill indeed by allowing Bletchley information and interpretation to be transmitted over the heads of the London chiefs directly to an intelligence centre in Cairo. But a more centralised system was forced upon them by the cornucopia of north Buckinghamshire. By May 1942 they were breaking every Enigma key system of the African theatre. In August this was joined by a new Hut 8 success, the breaking of the system used by Mediterranean surface ships. Rommel was now losing one quarter of his supplies through British attacks which were almost totally dependent on detailed Enigma information – sometimes enabling them to pick out the more important cargoes for destruction. News of this triumph was passed back to the analysts in Hut 8 to encourage them in their work.
But the Mediterranean was, ultimately, an Anglo-German diversion. In the world struggle there had been a major setback for Japan at the battle of Midway, where the US Navy proved it could put its own Intelligence to devastating effect. But in Europe there was no such hint of a reverse. The Axis attack on Russia had reached Stalingrad, and the Dieppe raid had ended lingering fantasies of an easy victory in the west. More frightening than either of these developments, however, for Churchill and for everyone else, was the state of the fragile Atlantic bridge. Without it Britain was nothing.
Although the first American troops had arrived in Britain early in 1942, it was the stream of war materials, tanks and aircraft in particular, that alone could make the reconquest of western Europe conceivable. That stream had to face the Atlantic U-boat fleet, which by October amounted to 196 in number. Since 1940 the numbers had trebled, and the sinkings had trebled too. Until mid-1942, American reluctance to provide coastal convoys had diverted U-boats to easy pickings off the eastern seaboard, but in August counter-measures had remedied this gap in defence. Accordingly, the U-boats had turned back to the Atlantic convoys, exploiting the area in mid-ocean where air cover was not supplied, and were now accounting for over half the merchant fleet required to supply Britain within a year. The revived American shipyards were turning out new vessels at top speed, only to have each sunk after three or so ocean voyages. But now the United States had its own pressing demands in the Pacific. The total Allied stock of shipping was actually declining, while the number of U-boats was increasing: there would be 212 at the end of 1942, with another 181 on trial.
Fast approaching was the crisis of the western war. 1943 might see either Britain stocked up as the forward base of an impregnable American industry, or might see it slowly sink. Though more diffuse a crisis than that of the air war of September 1940, it likewise stood to see a make-or-break resolution. Ten years earlier, Alan had conceived a model of action: ‘We have a will which is able to determin
e the actions of the atoms probably in a small portion of the brain … The rest of the body acts so as to amplify this.’ Now he was one of the clustered nerve-cells, and around him a colossal system which had translated his ideas into concrete form: a British brain, an electric brain of relays clicking through the contradictions, perhaps the most complex logical system ever devised. Meanwhile the two years of the reprieve had rendered the rest of the body more prepared and coordinated to use its intelligence. In the Middle East it was amplifying the dim Morse signals into the sinking of Rommel’s army. But the Atlantic was different; here Eisenhower and Marshall might be cut off on a far greater scale than Rommel unless the brain could awaken into life again.
But those two years had seen another momentous change. The ten-fold increase in rotor positions had forced Poland to turn to the technically superior West. And now the twenty-six-fold increase had brought the United States into the electromagnetic relay race. Its Admiral King, who had been more obstinate than the British Admiralty, resisted the setting up of a tracking room until mid-1942. But the US Navy’s cryptanalysts had been quick off the mark to see what was needed. Their department had been using modern machinery since 1935, and when the black-out came in February 1942 they were not content to stand and wait until the British caught up: they could do it themselves. This did not accord at all with the British view, which held that the Americans should concentrate on the Japanese ciphers, and not duplicate the work done at Bletchley. But the US Navy was particularly insistent. Already in June, its relations with GC and CS were ‘strained’ by complaints at the delay they experienced in obtaining a promised Bombe, and then49
in September the Navy Department announced that it had developed a more advanced machine of its own, would have built 360 copies of it by the end of the year, and intended to attack the U-boat Enigma settings forthwith.
Alan Turing: The Enigma: The Book That Inspired the Film The Imitation Game Page 38