Rainfall

snapped the car into gear and hauled the steering wheel to the right, doing a burning-rubber U-turn on Meiji-dori and cutting off oncoming traffic in the process. I saw the Japanese hurrying back to their car.

    “Isoide! Isoide! Byoin ni tanomu!”
Hurry! We need a hospital!

    At the intersection of Meiji-dori and Waseda-dori, the driver ripped through a light that had just turned red, braking into a sliding lefthand turn in the direction of the National Medical Center. The G-force ripped Holtzer away from me. The flow of traffic on Waseda-dori closed in behind us a second later, and I knew the sedan would be stuck for a minute, maybe more.

    Tozai Waseda Station was just ahead. Time for me to bail. I told the driver to pull over. Holtzer was slumped against the driver-side door, unconscious but breathing. I wanted to put the strangle back in — one less adversary to worry about. But there was no time.

    The driver started to protest, saying that we had to get my friend to a hospital, that we needed to call the police, but I insisted again that he pull over. He stopped and I took out the half of the ten-thousand-yen note I owed him, then threw in one more.

    I grabbed the package I had bought for Midori, jumped out of the cab, and bolted down the steps to the subway. If I had to wait for a train I was going to use an alternate exit and stay on foot, but my timing was good — the Tozai was just pulling in. I took it to Nihonbashi Station, switched to the Ginza line, and then changed at Shinbashi to the Yamanote. I did a careful SDR on the way, and by the time I surged through the station turnstiles at Shibuya, I knew I was safe for the moment. But they’d flushed me into the open, and the moment wouldn’t last.

16

    AN HOUR LATER I got Harry’s page, and we met at the Doutor coffee shop per our previous arrangement. He was waiting for me when I got there.

    “Tell me what you’ve got,” I said.

    “Well, it’s strange.”

    “Explain ‘strange.’ ”

    “Well, the first thing is, this disk has some pretty advanced copy management protection built into it.”

    “Can you break it?”

    “That’s not what I’m talking about. Copy management is different than encryption. The disk can’t be copied, can’t be distributed electronically, can’t be sent over the Internet.”

    “You mean you can make only one copy from the source?”

    “One copy or many copies, I’m not sure, but the point is you can’t make copies of copies. No grandchildren in this family.”

    “And there’s no way to send the contents of the disk over the Internet, upload to a bulletin board, anything like that?”

    “No. If you try, the data will get corrupted. You won’t be able to read it.”

    “Well, that explains a few things,” I said.

    “Like what?”

    “Like why they were messing with disks in the first place. Like why they’re so eager to get this one back. They know it hasn’t been copied or uploaded, so they know their potential damage is still limited to this one disk.”

    “That’s right.”

    “Now tell me this. Why would whoever controls the data that got copied onto that disk permit even a single copy to be made? Why not no copies? Wouldn’t that be more secure?”

    “Probably more secure, but risky, too. If something happened to the master, all your records would be gone. You’d want some kind of backup.”

    I considered. “What else is there?”

    “Well, as you know, it’s encrypted.”

    “Yes.”

    “The encryption is strange.”

    “You keep saying that.”

    “Ever hear of a lattice reduction?”

    “I don’t think so.”

    “It’s a kind of code. The cryptographer encodes a message in a pattern, a pattern like the flowers in a symmetrical wallpaper design. But wallpaper patterns are simple — only one image in two dimensions. A more complex code uses a pattern that repeats itself at various levels of detail, in multiple mathematical dimensions. To break the code, you have to find the most basic way the lattice repeats itself — the origin of the pattern, in a way.”

    “I get the picture. Can you break it?”

    “I’m not sure. I did some work with lattice reductions at Fort Meade, but this one is strange.”

    “Harry, if you say that one more time . . .”

    “Sorry, sorry. It’s strange because the lattice seems to be a musical pattern, not a physical one.”

    “Now I’m not following you.”

    “There’s an overlay of what look like musical notes —