Authors: Robert Harris
“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
Kapitan 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 ingenious 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.
§
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:
♦
Pi⁄4=1-1⁄3+1⁄5-1⁄7+1⁄9—
♦
—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
WETTERUBERSICHT 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 Teutonic 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?
♦
It was the practice on the night shift at about four o’clock in
the morning for everyone to take a meal-break. The cryptanalysts
went off when they liked, depending on the stage they’d reached in
their work. The Decoding Room girls and the clerks in the
Registration and Catalogue rooms had to leave according to a rota
so that the hut was never caught short-staffed.