‘Oh, dear. Sorry, old thing. Sorry.’
He shuffled off down the corridor, patting his pockets to make sure he had his pipe and tobacco pouch. They heard him mutter again, something about ‘bloody admirals’, and he was gone.
Hut 8 was thirty-five yards long by ten wide and Jericho could have toured it in his sleep, probably had toured it in his sleep, for all he knew. The outside walls were thin and the damp from the lake seemed to rise through the floorboards so that at night the rooms were chilly, cast in a sepia glow by bare, low-wattage bulbs. The furniture was mostly trestle tables and folding wooden chairs. It reminded Jericho of a church hall on a winter’s night. All that was missing was a badly tuned piano and somebody thumping out ‘Land of Hope and Glory’.
It was laid out like an assembly line, the main stage in a process that originated somewhere far out in the darkness, maybe two thousand miles away, when the grey hull of a U-boat rose close to the surface and squirted off a radio message to its controllers. The signals were intercepted at various listening-posts and teleprintered to Bletchley and within ten minutes of transmission, even as the U-boats were preparing to dive, they were emerging via a tunnel into Hut 8’s Registration Room. Jericho helped himself to the contents of a wire basket labelled ‘Shark’ and carried them to the nearest light. The hours immediately after midnight were usually the busiest time. Sure enough, six messages had been intercepted in the last eighteen minutes. Three consisted of just eight letters: he guessed they were weather reports. Even the longest of the other cryptograms was no more than a couple of dozen four-letter groups:
JRLO GOPL DNRZ LOBT –
Puck made a weary face at him, as if to say: What can you do?
Jericho said: ‘What’s the volume?’
‘It varies. One hundred and fifty, perhaps two hundred messages a day. And rising.’
The Registration Room didn’t just handle Shark. There was Porpoise and Dolphin and all the other different Enigma keys to log and then pass across the corridor to the Crib Room. Here, the cribsters sifted them for clues – radio station call signs they recognised (Kiel was JDU, for example, Wilhelmshaven KYU), messages whose contents they could guess at, or cryptograms that had already been enciphered in one key and then retransmitted in another (they marked these ‘XX’ and called them ‘kisses’). Atwood was the champion cribster and the Wrens said cattily behind his back that these were the only kisses he had ever had.
It was in the big room next door – which they called, with their solemn humour, the Big Room – that the cryptanalysts used the cribs to construct possible solutions that could be tested on the bombes. Jericho took in the rickety tables, the hard chairs, the weak lighting, the fug of tobacco, the college-library atmosphere, the night chill (most of the cryptanalysts were wearing coats and mittens) and he wondered why – why? – he had been so ready to come back. Kingcome and Proudfoot were there, and Upjohn and Pinker and de Brooke, and maybe half a dozen newcomers whose faces he didn’t recognise, including one young man sitting bold as you please in the seat which had once been reserved for Jericho. The tables were stacked with cryptograms, like ballot papers at an election count.
Puck was muttering something about back-breaks but Jericho, fascinated by the sight of someone else in his place, lost track and had to interrupt him. ‘I’m sorry, Puck. What was that?’
‘I was saying that from twenty minutes ago we are up to date. Shark is now fully read to the point of the code change. So that there is nothing left to us. Except history.’ He gave a weak smile and patted Jericho’s shoulder. ‘Come. I’ll show you.’
When a cryptanalyst believed he’d glimpsed a possible break into a message, his guess was sent out of the hut to be tested on a bombe. And if he’d been skilful enough, or lucky enough, then in an hour, or a day, the bombe would churn through a million permutations and reveal how the Enigma machine had been set up. That information was relayed back from the bombe bays to the Decoding Room.
Because of its noise, the Decoding Room was tucked away at the far end of the hut. Personally, Jericho liked the clatter. It was the sound of success. His worst memories were of the nights when the building was silent. A dozen British Type-X enciphering machines had been modified to mimic the actions of the German Enigma. They were big, cumbersome devices – typewriters with rotors, a plugboard and a cylinder – at which sat young and well-groomed debutantes.
Baxter, who was the hut’s resident Marxist, had a theory that Bletchley’s workforce (which was mainly female) was arranged in what he called ‘a paradigm of the English class system’. The wireless interceptors, shivering in their coastal radio stations, were generally working-class and laboured in ignorance of the Enigma secret. The bombe operators, who worked in the grounds of some nearby country houses and in a big new installation just outside London, were petit-bourgeois and had a vague idea. And the Decoding Room girls, in the heart of the Park, were mostly upper-middle-class, even aristocratic, and they saw it all – the secrets literally passed through their fingers. They typed out the letters of the original cryptogram, and from the cylinder on the right of the Type-X a strip of sticky-backed paper, the sort you saw gummed down on telegram forms, slowly emerged, bearing the decrypted plaintext.
‘Those three are doing Dolphin,’ said Puck, pointing across the room, ‘and the two by the door are just starting on Porpoise. And this charming young lady here, I believe’ – he bowed to her – ‘has Shark. May we?’
She was young, about eighteen, with curly red hair and wide hazel eyes. She looked up and smiled at him, a dazzling Tatler smile, and he leaned across her and began uncoiling the strip of tape from the cylinder. Jericho noticed as he did so that he left one hand resting casually on her shoulder, just as simply as that, and he thought how much he envied Puck the ease of that gesture. It would have taken him a week to pluck up the nerve. Puck beckoned him down to read the decrypt.
VONSCHULZEQU88521DAMPFER1TANKERWAHRSCHEINLICHAM63TANKERFACKEL …
Jericho ran his finger along it, separating the words and translating it in his mind: U-boat commander von Schulze was in grid square 8852 and had sunk one steamship (for certain) and one tanker (probably) and had set one other tanker on fire …
‘What date is this?’
‘You can see it there,’ said Puck. ‘Sechs drei. The sixth of March. We’ve broken everything from this week up to the code change on Wednesday night, so now we go back and pick up the intercepts we missed earlier in the month. This is – what? – six days old. Herr Kapitän von Schulze may be five hundred miles away by now. It is of academic interest only, I fear.’
‘Poor devils,’ said Jericho, passing his finger along the tape for a second time. IDAMPFERITANKER … What freezing and drowning and burning were concentrated in that one line! What were the ships called, he wondered, and had the families of the crews been told?
‘We have approximately a further eighty messages from the sixth still to run through the Type-Xs. I shall put two more operators on to it. A couple of hours and we should be finished.’
‘And then what?’
‘Then, my dear Tom? Then I suppose we shall make a start on back-breaks from February. But that barely qualifies even as history. February? February in the Atlantic? Archaeology!’
‘Any progress on the four-wheel bombe?’
Puck shook his head. ‘First, it is impossible. It is out of the question. Then there is a design, but the design is theoretical nonsense. Then there is a design that should work, but doesn’t. Then there is a shortage of materials. Then there is a shortage of engineers …’ He made a weary gesture with his hand, as if he were pushing it all out of the way.
‘Has anything else changed?’
‘Nothing that affects us. According to the direction finders, U-boat HQ has moved from Paris to Berlin. They have some wonderful new transmitter at Magdeburg they say will reach a U-boat forty-five feet under water at a range of two thousand miles.’
Jericho murmured: ‘How very ingenio
us of them.’
The red-headed girl had finished deciphering the message. She tore off the tape, stuck it on the back of the cryptogram and handed it to another girl, who rushed out of the room. Now it would be turned into recognisable English and teleprintered to the Admiralty.
Puck touched Jericho’s arm. ‘You must be tired. Why don’t you go now and rest?’
But Jericho didn’t feel like sleeping. ‘I’d like to see all the Shark traffic we haven’t been able to break. Everything since midnight on Wednesday.’
Puck gave a puzzled smile. ‘Why? There’s nothing you can do with it.’
‘Maybe so. But I’d like to see it.’
‘Why?’
‘I don’t know.’ Jericho shrugged. ‘Just to handle it. To get a feel of it. I’ve been out of the game for a month.’
‘You think we may have missed something, perhaps?’
‘Not at all. But Logie has asked me.’
‘Ah yes. The celebrated Jericho “inspiration” and “intuition”.’ Puck couldn’t conceal his irritation. ‘And so from science and logic we descend to superstition and “feelings”.’
‘For heaven’s sake, Puck!’ Jericho was starting to become annoyed himself. ‘Just humour me, if that’s how you prefer to look at it.’
Puck glared at him for a moment, and then, as quickly as they had arisen, the clouds seemed to pass. ‘Of course.’ He held up his hands in a gesture of surrender. ‘You must see it all. Forgive me. I’m tired. We’re all tired.’
Five minutes later, when Jericho walked into the Big Room carrying the folder of Shark cryptograms, he found his old seat had been vacated. Someone had also laid out in his place a new pile of jotting paper and three freshly sharpened pencils. He looked around, but nobody seemed to be paying him any attention.
He laid the intercepts out on the table. He loosened his scarf. He felt the radiator – as ever, it was lukewarm. He blew some warmth on to his hands and sat down.
He was back.
3
Whenever anyone asked Jericho why he was a mathematician – some friend of his mother, perhaps, or an inquisitive colleague with no interest in science – he would shake his head and smile and claim he had no idea. If they persisted, he might, with some diffidence, direct them to the definition offered by G. H. Hardy in his famous Apology: ‘a mathematician, like a painter or a poet, is a maker of patterns’. If that didn’t satisfy them, he would try to explain by quoting the most basic illustration he could think of: pi – 3.14 – the ratio of a circle’s circumference to its diameter. Calculate pi to a thousand decimal places, he would say, or a million or more, and you will discover no pattern to its unending sequence of digits. It appears random, chaotic, ugly. Yet Leibnitz and Gregory can take the same number and tease from it a pattern of crystalline elegance:
and so on to infinity. Such a pattern had no practical usefulness, it was merely beautiful – as sublime, to Jericho, as a line in a fugue by Bach – and if his questioner still couldn’t see what he was driving at, then, sadly, he would give up on them as a waste of time.
On the same principle, Jericho thought the Enigma machine was beautiful – a masterpiece of human ingenuity that created both chaos and a tiny ribbon of meaning. In the early days at Bletchley he used to fantasise that some day, when the war was over, he would track down its German inventor, Herr Arthur Scherbius, and buy him a glass of beer. But then he’d heard that Scherbius had died in 1929, killed – of all ludicrously illogical things – by a runaway horse, and hadn’t lived to see the success of his patent.
If he had, he would have been a rich man. By the end of 1942 Bletchley estimated that the German had manufactured at least a hundred thousand Enigmas. Every Army headquarters had one, every Luftwaffe base, every warship, every submarine, every port, every big railway station, every SS brigade and Gestapo HQ. Never before had a nation entrusted so much of its secret communications to a single device.
In the mansion at Bletchley the cryptanalysts had a roomful of captured Enigmas and Jericho had played with them for hours. They were small (little more than a foot square by six inches deep), portable (they weighed just twenty-six pounds) and simple to operate. You set up your machine, typed in your message, and the ciphertext was spelled out, letter by letter, on a panel of small electric bulbs. Whoever received the enciphered message merely had to set up his machine in exactly the same way, type in the cryptogram, and there, spelled out on the bulbs, would be the original plaintext.
The genius lay in the vast number of different permutations the Enigma could generate. Electric current on a standard Enigma flowed from keyboard to lamps via a set of three wired rotors (at least one of which turned a notch every time a key was struck) and a plugboard with twenty-six jacks. The circuits changed constantly; their potential number was astronomical, but calculable. There were five different rotors to choose from (two were kept spare) which meant they could be arranged in any one of sixty possible orders. Each rotor was slotted on to a spindle and had twenty-six possible starting positions. Twenty-six to the power of three was 17,576. Multiply that by the sixty potential rotor-orders and you got 1,054,560. Multiply that by the possible number of plugboard connections – about 150 million million – and you were looking at a machine that had around 150 million million million different starting positions. It didn’t matter how many Enigma machines you captured or how long you played with them. They were useless unless you knew the rotor order, the rotor starting positions and the plugboard connections. And the Germans changed these daily, sometimes twice a day.
The machine had only one tiny – but, as it turned out, crucial – flaw. It could never encipher a letter as itself: an A would never emerge from it as an A, or a B as a B, or a C as a C … Nothing is ever itself: that was the great guiding principle in the breaking of Enigma, the infinitesimal weakness that the bombes exploited.
Suppose one had a cryptogram that began:
IGWH BSTU XNTX EYLK PEAZ ZNSK UFJR CADV _
And suppose one knew that this message originated from the Kriegsmarine’s weather station in the Bay of Biscay, a particular friend of the Hut 8 cribsters, which always began its reports in the same way:
WEUBYYNULLSEQSNULLNULL
(‘Weather survey 0600’, WEUB being an abbreviation for WETTERÜBERSICHT and SEQS for SECHS; YY and NULL being inserted to baffle eavesdroppers).
The cryptanalyst would lay out the ciphertext and slide the crib beneath it and on the principle that nothing is ever itself he would keep sliding it until he found a position in which there were no matching letters between the top and bottom lines. The result in this case would be:
BSTUXNTXEYLKPEAZZNSKUF
WEUBYYNULLSEQSNULLNULL
And at this point it became theoretically possible to calculate the original Enigma settings that alone could have produced this precise sequence of letter pairings. It was still an immense calculation, one which would have taken a team of human beings several weeks. The Germans assumed, rightly, that whatever intelligence might be gained would be too old to be of use. But Bletchley – and this was what the Germans had never reckoned on – Bletchley didn’t use human beings. It used bombes. For the first time in history, a cipher mass-manufactured by machine was being broken by machine.
Who needed spies now? What need now of secret inks and dead-letter drops and midnight assignations in curtained wagons-lits? Now you needed mathematicians and engineers with oilcans and fifteen hundred filing clerks to process five thousand secret messages a day. They had taken espionage into the machine age.
But none of this was of much help to Jericho in breaking Shark.
Shark defied every tool he could bring to bear on it. For a start, there were almost no cribs. In the case of a surface Enigma key, if Hut 8 ran out of cribs, they had tricks to get round it – ‘gardening’, for example. ‘Gardening’ was arranging for the RAF to lay mines in a particular naval grid square outside a German harbour. An hour later, you could guarantee, the harbour master, with T
eutonic efficiency, would send a message using that day’s Enigma settings, warning ships to beware of mines in naval grid square such-and-such. The signal would be intercepted, flashed to Hut 8, and give them their missing crib.
But you couldn’t do that with Shark and Jericho could make only the vaguest guesses at the contents of the cryptograms. There were eight long messages originating from Berlin. They would be orders, he supposed, probably directing the U-boats into ‘wolf packs’ and stationing them in front of the oncoming convoys. The shorter signals – there were a hundred and twenty-two, which Jericho sorted into a separate pile – had been sent by the submarines themselves. These could contain anything: reports of ships sunk and of engine trouble; details of survivors floating in the water and of crewmen washed overboard; requests for spare parts and fresh orders. Shortest of all were the U-boats’ weather messages or, very occasionally, contact reports: ‘Convoy in naval grid square BE9533 course 70 degrees speed 9 knots …’ But these were encoded, like the weather bulletins, with one letter of the alphabet substituting for each piece of information. And then they were enciphered in Shark.
He tapped his pencil against the desk. Puck was quite right. There was not enough material to work with.
And even if there had been, there was still the wretched fourth rotor on the Shark Enigma, the innovation that made U-boat messages twenty-six times more difficult to break than those of surface ships. One hundred and fifty million million million multiplied by twenty-six. A phenomenal number. The engineers had been struggling for a year to develop a four-rotor bombe – but still, apparently, without success. It seemed to be just that one step beyond their technical ability.
No cribs, no bombes. Hopeless.
Hours passed during which Jericho tried every trick he could think of to prompt some fresh inspiration. He arranged the cryptograms chronologically. Then he arranged them by length. Then he sorted them by frequency. He doodled on the pile of paper. He prowled around the hut, oblivious now to who was looking at him and who wasn’t. This was what it had been like for ten interminable months last year. No wonder he had gone mad. The chorus-lines of meaningless letters danced before his eyes. But they were not meaningless. They were loaded with the most vital meaning imaginable, if only he could find it. But where was the pattern? Where was the pattern? Where was the pattern?
Enigma Page 6