The Hydra Protocol by David Wellington

stay very long. I have an appointment in Brooklyn to keep.”
    Hollingshead’s face broke into a beaming smile that would have lit up any fallout shelter. He knew all about Julia, of course, and what Chapel hadn’t told him personally he would have heard from Angel. “You are a very lucky man, Captain Chapel. You couldn’t have picked a better helpmeet.”
    “I am blessed, sir, it’s true. I know it’s premature, but I hope you’ll come to the wedding.”
    “Wouldn’t miss it, son, not for rubies or pearls.”
    Chapel grinned. “Just talking about it out loud like that, like it’s something that I need to put on my schedule . . . it still feels weird. But it should be official by tonight.” He shook his head in disbelief. “I admit, I’m a little nervous. What if she says no?”
    “Then my intelligence estimates will have been proven wrong.”
    Chapel started in surprise. “You didn’t—I mean, you haven’t—”
    “Just a small joke, son. No, I haven’t had DIA analysts working out the likelihood of Julia Taggart becoming Mrs. Julia Chapel. Call it an intuition. Or rather, let’s say that I couldn’t think of two people I hold in higher regard, and better suited to a life of shared bliss. Maybe we should have that drink after all, to celebrate.”
    “Thank you, sir,” Chapel said, his grin returning, “but I’d just as soon get this debriefing over with and get on the train to New York.” He reached in his pocket and took out the little black book. He riffled through it, seeing once more the grids of numbers and Cyrillic characters that filled each page. Then he handed it over. “I hope it’s worth the trouble it took to secure it.”
    Hollingshead took the book and tucked it into a pocket of his jacket. “It’s worth more than its weight in diamonds, believe me. You know what it is, of course.”
    That was a question, and maybe some kind of test. Chapel nodded. “It’s a one-time pad.” A codebook, in other words, containing the key to a cipher that theoretically couldn’t be cracked. The captain of the Kurchatov would have consulted those grids when sending secret messages back to his superiors in Russia. Each character in his plaintext message was transposed with a character from one of those grids, using basic modular addition. On the other end of the transmission, in a Kremlin basement perhaps, someone else would have an identical pad and be able to decrypt the message. If the characters in the grids were truly random, and if nobody else had access to the pad, the message could never be decrypted since the cipher was unique to that particular message.
    One-time pads had been used by both sides throughout the Cold War. They had only been replaced by the advent of computer cryptography. The Kremlin and the Pentagon had relied on them for decades, but unfortunately they weren’t very practical. One problem was that the receiver of the message needed to know which page of his own pad to use when deciphering the message, or even which pad to use if more than one existed. In real-world use, the KGB had ended up using what were essentially one-day pads—the same cipher matrix being used for every coded transmission sent in a twenty-four-hour window. There was also the difficulty of making sure every submarine commander, say, received a new pad every month—a tricky bit of logistics when some submarines went on six-month-long cruises and rarely called in at friendly ports.
    Because of these issues, one-time pads had fallen out of use—as far as Chapel knew, no major intelligence operation had used them in years.
    Which raised the question of why Hollingshead wanted this pad.
    “Completely useless, of course,” Chapel said.
    “Of course,” Hollingshead said, though a mischievous grin threatened to crack his face in half.
    “Even if codebooks like that were still in use—even if the Russian Federation used the same sort of codes as the Soviet Union used to, which they don’t—this