Cryptonomicon

'Why not?'

'I forgot. It just wouldn't work out.'

Alan raises his eyebrows, clearly not convinced.

'Something to do with cranks,' Waterhouse ventures, feeling a little defensive.

'I don't know that I agree,' Alan says.

'Just stipulate it-think of it as a boundary condition,' Waterhouse says. But Alan is already hard at work, he suspects, mentally designing a rotary aircraft engine with an even number of cylinders.

'Anyway, if you look at them, they all have an odd number of cylinders,' Lawrence continues. 'So the exhaust noise combines with the propeller noise to produce that two-tone sound.'

Alan climbs back onto his bicycle and they ride into the woods for some distance without any more talking. Actually, they have not been talking so much as mentioning certain ideas and then leaving the other to work through the implications. This is a highly efficient way to communicate; it eliminates much of the redundancy that Alan was complaining about in the case of FDR and Churchill.

Waterhouse is thinking about cycles within cycles. He's already made up his mind that human society is one of these cycles-within-cycles things[8] and now he's trying to figure out whether it is like Turing's bicycle (works fine for a while, then suddenly the chain falls off, hence the occasional world war) or like an Enigma machine (grinds away incomprehensibly for a long time, then suddenly the wheels line up like a slot machine and everything is made plain in some sort of global epiphany or, if you prefer, apocalypse) or just like a rotary airplane engine (runs and runs and runs; nothing special happens; it just makes a lot of noise).

'It's somewhere around . . . here!' Alan says, and violently brakes to a stop, just to chaff Lawrence, who has to turn his bicycle around, a chancy trick on such a narrow lane, and loop back.

They lean their bicycles against trees and remove pieces of equipment from the baskets: dry cells, electronic breadboards, poles, a trenching tool, loops of wire. Alan looks about somewhat uncertainly and then strikes off into the woods.

'I'm off to America soon, to work on this voice encryption problem at Bell Labs,' Alan says.

Lawrence laughs ruefully. 'We're ships passing in the night, you and I.'

'We are passengerson ships passing in the night,' Alan corrects him. 'It is no accident. They need you precisely because I am leaving. I've been doing all of the 2701 work to this point.'

'It's Detachment 2702 now,' Lawrence says.

'Oh,' Alan says, crestfallen. 'You noticed.'

'It was reckless of you, Alan.'

'On the contrary!' Alan says. 'What will Rudy think if he notices that, of all the units and divisions and detachments in the Allied order of battle, there is not a single one whose number happens to be the product of two primes?'

'Well, that depends upon how common such numbers are compared to all of the other numbers, and on how many other numbers in the range are going unused . . .' Lawrence says, and begins to work out the first half of the problem. 'Riemann Zeta function again. That thing pops up everywhere.'

'That's the spirit!' Alan says. 'Simply take a rational and common-sense approach. Theyare really quite pathetic.'

'Who?'

'Here,' Alan says, slowing to a stop and looking around at the trees, which to Lawrence look like all the other trees. 'This looks familiar.' He sits down on the bole of a windfall and begins to unpack electrical gear from his bag. Lawrence squats nearby and does the same. Lawrence does not know how the device works-it is Alan's invention-and so he acts in the role of surgical assistant, handing tools and supplies to the doctor as he puts the device together. The doctor is talking the entire time, and so he requests tools by staring at them fixedly and furrowing his brow.

'Theyare-well, who do you suppose? The fools who use all of the information that comes from Bletchley Park!'

'Alan!'

'Well, it is foolish! Like this Midway thing. That's a perfect example, isn't it?'

'Well, I was happy that we won the battle,' Lawrence says guardedly.

'Don't you think it's a bit odd,a bit striking,a bit noticeable,that after all of Yamamoto's brilliant feints and deceptions and ruses, this Nimitz fellow knew exactlywhere to go looking for him? Out of the entirePacific Ocean?'

'All right,' Lawrence says, 'I was appalled. I wrote a paper about it. Probably the paper that got me into this mess with you.'

'Well, it's no better with us Brits,' Alan says.

'Really?'

'You would be horrified at what we've been up to in the Mediterranean. It is a scandal. A crime.

'What have we been up to?' Lawrence asks. 'I say 'we' rather than 'you' because we are allies now.'

'Yes, yes,' Alan says impatiently. 'So they claim.' He paused for a moment, tracing an electrical circuit with his finger, calculating inductances in his head. Finally, he continues: 'Well, we've been sinking convoys, that's what. German convoys. We've been sinking them right and left.'

'Rommel's?'

'Yes, exactly. The Germans put fuel and tanks and ammunition on ships in Naples and send them south. We go out and sink them. We sink nearly all of them, because we have broken the Italian C38m cipher and we know when they are leaving Naples. And lately we've been sinking justthe very onesthat are most crucial to Rommel's efforts, because we have alsobroken his Chaffinch cipher and we know which ones he is complaining loudest about not having.'

Turing snaps a toggle switch on his invention and a weird, looping squeal comes from a dusty black paper cone lashed onto the breadboard with twine. The cone is a speaker, apparently scavenged from a radio. There is a broomstick with a loop of stiff wire dangling from the end, and a wire running from that loop up the stick to the breadboard. He swings the broomstick around until the loop is dangling, like a lasso, in front of Lawrence's midsection. The speaker yelps.

'Good. It's picking up your belt buckle,' Alan says.

He sets the contraption down in the leaves, gropes in several pockets, and finally pulls out a scrap of paper on which several lines of text have been written in block letters. Lawrence would recognize it anywhere: it is a decrypt worksheet. 'What's that, Alan?'

'I wrote out complete instructions and enciphered them, then hid them under a bridge in a benzedrine container,' Alan says. 'Last week I went and recovered the container and decyphered the instructions.' He waves the paper in the air.

'What encryption scheme did you use?'

'One of my own devising. You are welcome to take a crack at it, if you like.'

'What made you decide it was time to dig this stuff up?'

'It was nothing more than a hedge against invasion,' Alan says. 'Clearly, we're not going to be invaded now, not with you chaps in the war.'

'How much did you bury?'

'Two silver bars, Lawrence, each with a value of some hundred and twenty-five pounds. One of them should be very close to us.' Alan stands up, pulls a compass out of his pocket, turns to face magnetic north, and squares his shoulders. Then he rotates a few degrees. 'Can't remember whether I allowed for declination,' he mumbles. 'Right! In any case. One hundred paces north.' And he strides off into the woods, followed by Lawrence, who has been given the job of carrying the metal detector.

Just as Dr. Alan Turing can ride a bicycle and carry on a conversation while mentally counting the revolutions of the pedals, he can count paces and talk at the same time too. Unless he has lost count entirely, which seems just as possible.

'If what you are saying is true,' Lawrence says, 'the jig must be up already. Rudy must have figured out