Riptide

of the cryptographic art up to Macallan's time.'

'They sound worse than my second-year med school textbooks.'

'They're fascinating, actually,' St. John said, a flush of enthusiasm briefly coloring his tone.

'Was code writing common in those days?' Hatch asked curiously.

St. John laughed, a kind of seal bark that gave his ruddy cheeks a brief jiggle. 'Common? It was practically universal, one of the essential arts of diplomacy and war. Both the British and Spanish governments had departments that specialized in making and breaking ciphers. Even some pirates had crewmen who could crack codes. After all, ships papers included all kinds of interesting coded documents.'

'But coded how?'

'They were usually nomenclators—long lists of word substitutions. For example, in a message, the word 'eagle' might be substituted for 'King George' and 'daffodils' for 'doubloons'—that sort of thing. Sometimes they included simple substitution alphabets, where a letter, number, or symbol replaced a letter of the alphabet, one for one.'

'And Macallan's code?'

'The first part of the journal was written with a rather clever monophonic substitution code. The second—we're still working on that.'

'That's my department,' said Wopner, pride and a trace of jealousy mixing in his voice. 'It's all on the computer.' He struck a key and a long string of gibberish appeared on the screen:

AB3 RQB7 E50LA W IEW D8P OL QS9MN WX 4JR 2K WN 18N7 WPDO EKS N2T YX ER9 W DF3 DEI FK IE DF9F DFS K DK F6RE DF3 V3E IE4DI 2F 9GE DF W FEIB5 MLER BLK BV6 Fl PET BOP IBSDF K2LJ BVF EIO PUOER WB13 OPDJK LBL JKF

'Here's the ciphertext of the first code,' he said. 'How did you break it?'

'Oh, please. The letters of the English alphabet occur in fixed ratios, E being the commonest letter, X being the rarest. You create what we call a contact chart of the code symbols and letter pairs. Bang! The computer does the rest.'

St. John waved his hand dismissively. 'Kerry is programming the computer attacks against the code, but I am supplying the historical data. Without the old cipher tables, the computer is hopeless. It only knows what's been programmed into it.'

Wopner turned around in his seat and stared at St. John. 'Hopeless? Fact is, big mama here would have cracked that code without your precious cipher tables. It just would have taken a little longer, is all.'

'No longer than twenty monkeys typing at random might take to write King Lear,' said St. John, with another brief bark of laughter.

'Haw haw. No longer than one St. John typing with two fingers on that Royal shitwriter back there. Jeez, get a laptop. And a life.' Wopner turned back to Hatch. 'Well, to make a long story short, here's how it decoded.'

There was a flurry of keystrokes and the screen split, showing the code on one side and the plaintext on the other. Hatch looked at it eagerly.

The 2nd of June, Anno D. 1696. The pirate Ockham hath taken our fleet, scuttled the ships, and butcherd every soull. Our man-of-war scandalously struck her colours without a fight and the captain went to his ende blubbering like a babe. I alone was spared, clapped in chaines and straightaway taken down to Ockham's cabin, where the blackguard drewe a saber against my person and said, Lete God build his owen damned church, I have ye a newe commission. And then he placed in front of me the articalls. Lete this journal bear witnesse before God that I refused to sign...

'Amazing,' breathed Hatch as he came to the end of the screen. 'Can I read more?'

'I'll print out a copy for you,' said Wopner, hitting a key. A printer began humming somewhere in the darkened room.

'Basically,' said St. John, 'the decrypted section of the journal covers Macallan's being taken prisoner, agreeing on pain of death to design the Water Pit, and finding the right island. Unfortunately, Macallan switches to a new code just when they began actual construction. We believe the rest of the journal consists of a description of the design and construction of the Pit itself. And, of course, the secret for getting to the treasure chamber.'

'Neidelman said the journal mentions St. Michael's Sword.'

'You bet it does,' Wopner interrupted, hitting the keys. More text popped up:

Ockham hath unburthened three of his ships in hopes of taking a prize along the coast. Today a long leaden coffin trimmed in golde came ashore with a dozen casks of Jewells. The corsairs say the coffin holds St. Michael's Sword, a costly treasure seized from a Spanish galleon and highly esteemd by the Captain, who swaggerd most shamefully, boasting that it was the greatest prize of the Indies. The Captain hath forbidden the opening of the casket, and it is guarded by day and night. The men are suspicious of each other, and constantly make stryfe. Were it not for the cruell discipline of the Captain, I feare every one would come to a bad end, and shortly.

'And now here's what the second code looks like.' Wopner tapped on the keys and the screen filled again:

348345902345823944389234923409234098569023467890234905623490839342908639981234901284912340 04949034120895098689073476057835684963240987350783904570923404589539045623482602569834587576708 76450734059340389090890805645045560345689034598734689072345890739087590872508723459035696590873 02

'The old boy got smart,' Wopner said. 'No more spaces, so we can't go by word shapes. All numbers, too, not a character to be seen. Just look at that fucker.'

St. John winced. 'Kerry, must you use such language?'

'Oh, I must, old thing, I must.'

St. John looked apologetically at Hatch.

'So far,' Wopner continued, 'this puppy's resisted all of Chris's pretty little cipher tables. So I took the matter into my own hands and wrote a brute-force attack. It's running as we speak.'

'Brute-force attack?' Hatch asked.

'You know. An algorithm that runs through a ciphertext, trying all patterns in the order of likelihood. It's just a matter of time.'

'A matter of a waste of time,' St. John said. 'I'm working up a new set of cipher tables from a Dutch book on cryptography. What's needed here is more historical research, not more CPU time. Macallan was a man of his age.