Enigma Read Online Free PDF Page B

take account of the fourth rotor. But that was proving a
nightmarishly slow process. If only they could somehow complete the
mission Fasson and Grazier had begun so heroically and steal a
Shark Enigma. That would make the redesign easier. But Shark
Enigmas were the crown jewels of the German Navy. Only the U-boats
had them. Only the U-boats and, of course, U-boat communication
headquarters in Sainte-Assise, southeast of Paris.
    A commando raid on Sainte-Assise, perhaps? A parachute drop? He
played with the image for a moment and then dismissed it.
Impossible. And, in any case, useless. Even if, by some miracle,
they got away with a machine, the Germans would know about it, and
switch to a different system of communications. Bletchley’s future
rested on the Germans continuing to believe that Enigma was
impregnable. Nothing could ever be done which might jeopardise that
confidence. Wait a minute. Jericho sat upright. Wait a bloody
minute.
    If only the U-boats and their controllers in Saint-Assise were
allowed to have four-rotor Enigmas—and Bletchley knew for a fact
that that was the case—how the hell were the coastal weather
stations deciphering the U-boat’s transmissions?
    It was a question no one had bothered to stop and ask, yet it
was fundamental.
    To read a message enciphered on a four-rotor machine you had to
have a four-rotor machine.
    Or did you?
    If it is true, as someone once said, that genius is “a zigzag of
lightning across the brain”, then, in that instant, Jericho knew
what genius was. He saw the solution lit up like a landscape before
him.
    He seized his dressing gown and pulled it over his pyjamas. He
grabbed his overcoat, his scarf, his socks and his boots and in
less than a minute he was on his bike, wobbling down the moonlit
country lane towards the Park. The stars were bright, the ground
was iron-hard with frost. He felt absurdly euphoric, laughing like
a madman, steering directly into the frozen puddles along the edge
of the road, the ice crusts rupturing under his tyres like drum
skins. Down the hill he freewheeled into Bletchley. The countryside
fell away and the town spread out beneath him in the moonlight,
familiarly drab and ugly but on this night beautiful, as beautiful
as Prague or Paris, perched on either bank of a gleaming river of
railway tracks. In the still air he could hear a train half a mile
away being shunted in the sidings—the sudden, frantic chugging of a
locomotive followed by a series of clanks, then a long exhalation
of steam. A dog barked and set off another. He passed the church
and the war memorial, braked to avoid skidding on the ice, and
turned left into Wilton Avenue.
    He was panting with exertion by the time he reached the Hut,
fifteen minutes later, so much so he could barely blurt out his
discovery and catch his breath and stop himself from laughing at
the same time:
“—They’re—using—it—as—a—three-rotor—machine—they’re—leaving—the—fourth—rotor—in—neutral—when—they—do—the—weather—stuff—the—silly—bloody—buggers—”
    His arrival caused a commotion. The night shift all stopped
working and gathered in a concerned half-circle round him—he
remembered Logie, Kingcome, Puck and Proudfoot—and it was clear
from their expressions they thought he really had gone mad. They
sat him down and gave him a mug of tea and told him to take it
again, slowly, from the beginning.
    He went through it once more, step by step, suddenly anxious
there might be a flaw in his logic. Four-rotor Enigmas were
restricted to U-boats and Sainte-Assise: correct? Correct.
Therefore, coastal stations could only decipher three-rotor Enigma
messages: correct? Pause. Correct. Therefore, when the U-boats sent
their weather reports, the wireless operators must logically
disengage the fourth rotor, probably by setting it at zero.
    After that, everything happened quickly. Puck ran along the
corridor to the Big Room and laid out the best of the weather