"You forgot Darryl," Dad said. He didn't like Darryl much -- once he'd figured out that a couple inches were missing out of one of the bottles in his liquor cabinet, and to my enduring shame I'd blamed it on Darryl. In truth, of course, it had been both of us, just fooling around, trying out vodka-and-Cokes during an all-night gaming session.

"He wasn't with us," I said. The lie tasted bitter in my mouth.

"Oh my God," my mom said. She squeezed her hands together. "We just assumed when you came home that you'd all been together."

"No," I said, the lie growing. "No, he was supposed to meet us but we never met up. He's probably just stuck over in Berkeley. He was going to take the BART over."

Mom made a whimpering sound. Dad shook his head and closed his eyes. "Don't you know about the BART?" he said.

I shook my head. I could see where this was going. I felt like the ground was rushing up to me.

"They blew it up," Dad said. "The bastards blew it up at the same time as the bridge."

That hadn't been on the front page of the Chronicle, but then, a BART blowout under the water wouldn't be nearly as picturesque as the images of the bridge hanging in tatters and pieces over the Bay. The BART tunnel from the Embarcadero in San Francisco to the West Oakland station was submerged.

#

I went back to Dad's computer and surfed the headlines. No one was sure, but the body count was in the thousands. Between the cars that plummeted 191 feet to the sea and the people drowned in the trains, the deaths were mounting. One reporter claimed to have interviewed an "identity counterfeiter" who'd helped "dozens" of people walk away from their old lives by simply vanishing after the attacks, getting new ID made up, and slipping away from bad marriages, bad debts and bad lives.

Dad actually got tears in his eyes, and Mom was openly crying. They each hugged me again, patting me with their hands as if to assure themselves that I was really there. They kept telling me they loved me. I told them I loved them too.

We had a weepy dinner and Mom and Dad had each had a couple glasses of wine, which was a lot for them. I told them that I was getting sleepy, which was true, and mooched up to my room. I wasn't going to bed, though. I needed to get online and find out what was going on. I needed to talk to Jolu and Vanessa. I needed to get working on finding Darryl.

I crept up to my room and opened the door. I hadn't seen my old bed in what felt like a thousand years. I lay down on it and reached over to my bedstand to grab my laptop. I must have not plugged it in all the way -- the electrical adapter needed to be jiggled just right -- so it had slowly discharged while I was away. I plugged it back in and gave it a minute or two to charge up before trying to power it up again. I used the time to get undressed and throw my clothes in the trash -- I never wanted to see them again -- and put on a clean pair of boxers and a fresh t-shirt. The fresh-laundered clothes, straight out of my drawers, felt so familiar and comfortable, like getting hugged by my parents.

I powered up my laptop and punched a bunch of pillows into place behind me at the top of the bed. I scooched back and opened my computer's lid and settled it onto my thighs. It was still booting, and man, those icons creeping across the screen looked good. It came all the way up and then it started giving me more low-power warnings. I checked the power-cable again and wiggled it and they went away. The power-jack was really flaking out.

In fact, it was so bad that I couldn't actually get anything done. Every time I took my hand off the power-cable it lost contact and the computer started to complain about its battery. I took a closer look at it.

The whole case of my computer was slightly misaligned, the seam split in an angular gape that started narrow and widened toward the back.

Sometimes you look at a piece of equipment and discover something like this and you wonder, "Was it always like that?" Maybe you just never noticed.

But with my laptop, that wasn't possible. You see, I built it. After the Board of Ed issued us all with SchoolBooks, there was no way my parents were going to buy me a computer of my own, even though technically the SchoolBook didn't belong to me, and I wasn't supposed to install software on it or mod it.

I had some money saved -- odd jobs, Christmases and birthdays, a little bit of judicious ebaying. Put it all together and I had enough money to buy a totally crappy, five-year-old machine.

So Darryl and I built one instead. You can buy laptop cases just like you can buy cases for desktop PCs, though they're a little more specialized than plain old PCs. I'd built a couple PCs with Darryl over the years, scavenging parts from Craigslist and garage sales and ordering stuff from cheap cheap Taiwanese vendors we found on the net. I figured that building a laptop would be the best way to get the power I wanted at the price I could afford.

To build your own laptop, you start by ordering a "barebook" -- a machine with just a little hardware in it and all the right slots. The good news was, once I was done, I had a machine that was a whole pound lighter than the Dell I'd had my eye on, ran faster, and cost a third of what I would have paid Dell. The bad news was that assembling a laptop is like building one of those ships in a bottle. It's all finicky work with tweezers and magnifying glasses, trying to get everything to fit in that little case. Unlike a full-sized PC -- which is mostly air -- every cubic millimeter of space in a laptop is spoken for. Every time I thought I had it, I'd go to screw the thing back together and find that something was keeping the case from closing all the way, and it'd be back to the drawing board.

So I knew exactly how the seam on my laptop was supposed to look when the thing was closed, and it was not supposed to look like this.

I kept jiggling the power-adapter, but it was hopeless. There was no way I was going to get the thing to boot without taking it apart. I groaned and put it beside the bed. I'd deal with it in the morning.

#

That was the theory, anyway. Two hours later, I was still staring at the ceiling, playing back movies in my head of what they'd done to me, what I should have done, all regrets and esprit d'escalier.

I rolled out of bed. It had gone midnight and I'd heard my parents hit the sack at eleven. I grabbed the laptop and cleared some space on my desk and clipped the little LED lamps to the temples of my magnifying glasses and pulled out a set of little precision screwdrivers. A minute later, I had the case open and the keyboard removed and I was staring at the guts of my laptop. I got a can of compressed air and blew out the dust that the fan had sucked in and looked things over.

Something wasn't right. I couldn't put my finger on it, but then it had been months since I'd had the lid off this thing. Luckily, the third time I'd had to open it up and struggle to close it again, I'd gotten smart: I'd taken a photo of the guts with everything in place. I hadn't been totally smart: at first, I'd just left that pic on my hard drive, and naturally I couldn't get to it when I had the laptop in parts. But then I'd printed it out and stuck it in my messy drawer of papers, the dead-tree graveyard where I kept all the warranty cards and pin-out diagrams. I shuffled them -- they seemed messier than I remembered -- and brought out my photo. I set it down next to the computer and kind of unfocused my eyes, trying to find things that looked out of place.

Then I spotted it. The ribbon cable that connected the keyboard to the logic-board wasn't connected right. That was a weird one. There was no torque on that part, nothing to dislodge it in the course of normal operations. I tried to press it back down again and discovered that the plug wasn't just badly mounted -- there was something between it and the board. I tweezed it out and shone my light on it.

There was something new in my keyboard. It was a little chunk of hardware, only a sixteenth of an inch thick, with no markings. The keyboard was plugged into it, and it was plugged into the board. It other words, it was perfectly situated to capture all the keystrokes I made while I typed on my machine.

It was a bug.

My heart thudded in my ears. It was dark and quiet in the house, but it wasn't a comforting dark. There were eyes out there, eyes and ears, and they were watching me. Surveilling me. The surveillance I faced at school had followed me home, but this time, it wasn't just the Board of Education looking over my shoulder: the Department of Homeland Security had joined them.

I almost took the bug out. Then I figured that who ever put it there would know that it was gone. I left it in. It made me sick to do it.

I looked around for more tampering. I couldn't find any, but did that mean there hadn't been any? Someone had broken into my room and planted this device -- had disassembled my laptop and reassembled it. There were lots of other ways to wiretap a computer. I could never find them all.

I put the machine together with numb fingers. This time, the case wouldn't snap shut just right, but the power-cable stayed in. I booted it up and set my fingers on the keyboard, thinking that I would run some diagnostics and see what was what.

But I couldn't do it.

Hell, maybe my room was wiretapped. Maybe there was a camera spying on me now.

I'd been feeling paranoid when I got home. Now I was nearly out of my skin. It felt like I was back in jail, back in the interrogation room, stalked by entities who had me utterly in their power. It made me want to cry.

Only one thing for it.

I went into the bathroom and took off the toilet-paper roll and replaced it with a fresh one. Luckily, it was almost empty already. I unrolled the rest of the paper and dug through my parts box until I found a little plastic envelope full of ultra-bright white LEDs I'd scavenged out of a dead bike-lamp. I punched their leads through the cardboard tube carefully, using a pin to make the holes, then got out some wire and connected them all in series with little metal clips. I twisted the wires into the leads for a nine-volt battery and connected the battery. Now I had a tube ringed with ultra-bright, directional LEDs, and I could hold it up to my eye and look through it.

I'd built one of these last year as a science fair project and had been thrown out of the fair once I showed that there were hidden cameras in half the classrooms at Chavez High. Pinhead video-cameras cost less than a good restaurant dinner these days, so they're showing up everywhere. Sneaky store clerks put them in changing rooms or tanning salons and get pervy with the hidden footage they get from their customers -- sometimes they just put it on the net. Knowing how to turn a toilet-paper roll and three bucks' worth of parts into a camera-detector is just good sense.

This is the simplest way to catch a spy-cam. They have tiny lenses, but they reflect light like the dickens. It works best in a dim room: stare through the tube and slowly scan all the walls and other places someone might have put a camera until you see the glint of a reflection. If the reflection stays still as you move around, that's a lens.

There wasn't a camera in my room -- not one I could detect, anyway. There might have been audio bugs, of course. Or better cameras. Or nothing at all. Can you blame me for feeling paranoid?

I loved that laptop. I called it the Salmagundi, which means anything made out of spare parts.

Once you get to naming your laptop, you know that you're really having a deep relationship with it. Now, though, I felt like I didn't want to ever touch it again. I wanted to throw it out the window. Who knew what they'd done to it? Who knew how it had been tapped?

I put it in a drawer with the lid shut and looked at the ceiling. It was late and I should be in bed. There was no way I was going to sleep now, though. I was tapped. Everyone might be tapped. The world had changed forever.

"I'll find a way to get them," I said. It was a vow, I knew it when I heard it, though I'd never made a vow before.

I couldn't sleep after that. And besides, I had an idea.

Somewhere in my closet was a shrink-wrapped box containing one still-sealed, mint-in-package Xbox Universal. Every Xbox has been sold way below cost -- Microsoft makes most of its money charging games companies money for the right to put out Xbox games -- but the Universal was the first Xbox that Microsoft decided to give away entirely for free.

Last Christmas season, there'd been poor losers on every corner dressed as warriors from the Halo series, handing out bags of these game-machines as fast as they could. I guess it worked -- everyone says they sold a whole butt-load of games. Naturally, there were countermeasures to make sure you only played games from companies that had bought licenses from Microsoft to make them.

Hackers blow through those countermeasures. The Xbox was cracked by a kid from MIT who wrote a best-selling book about it, and then the 360 went down, and then the short-lived Xbox Portable (which we all called the "luggable" -- it weighed three pounds!) succumbed. The Universal was supposed to be totally bulletproof. The high school kids who broke it were Brazilian Linux hackers who lived in a favela -- a kind of squatter's slum.

Never underestimate the determination of a kid who is time-rich and cash-poor.

Once the Brazilians published their crack, we all went nuts on it. Soon there were dozens of alternate operating systems for the Xbox Universal. My favorite was ParanoidXbox, a flavor of Paranoid Linux. Paranoid Linux is an operating system that assumes that its operator is under assault from the government (it was intended for use by Chinese and Syrian dissidents), and it does everything it can to keep your communications and documents a secret. It even throws up a bunch of "chaff" communications that are supposed to disguise the fact that you're doing anything covert. So while you're receiving a political message one character at a time, ParanoidLinux is pretending to surf the Web and fill in questionnaires and flirt in chat-rooms. Meanwhile, one in every five hundred characters you receive is your real message, a needle buried in a huge haystack.

I'd burned a ParanoidXbox DVD when they first appeared, but I'd never gotten around to unpacking the Xbox in my closet, finding a TV to hook it up to and so on. My room is crowded enough as it is without letting Microsoft crashware eat up valuable workspace.

Tonight, I'd make the sacrifice. It took about twenty minutes to get up and running. Not having a TV was the hardest part, but eventually I remembered that I had a little overhead LCD projector that had standard TV RCA connectors on the back. I connected it to the Xbox and shone it on the back of my door and got ParanoidLinux installed.

Now I was up and running, and ParanoidLinux was looking for other Xbox Universals to talk to. Every Xbox Universal comes with built-in wireless for multiplayer gaming. You can connect to your neighbors on the wireless link and to the Internet, if you have a wireless Internet connection. I found three different sets of neighbors in range. Two of them had their Xbox Universals also connected to the Internet. ParanoidXbox loved that configuration: it could siphon off some of my neighbors' Internet connections and use them to get online through the gaming network. The neighbors would never miss the packets: they were paying for flat-rate Internet connections, and they weren't exactly doing a lot of surfing at 2AM.

The best part of all this is how it made me feel: in control. My technology was working for me, serving me, protecting me. It wasn't spying on me. This is why I loved technology: if you used it right, it could give you power and privacy.

My brain was really going now, running like 60. There were lots of reasons to run ParanoidXbox -- the best one was that anyone could write games for it. Already there was a port of MAME, the Multiple Arcade Machine Emulator, so you could play practically any game that had ever been written, all the way back to Pong -- games for the Apple ][+ and games for the Colecovision, games for the NES and the Dreamcast, and so on.

Even better were all the cool multiplayer games being built specifically for ParanoidXbox -- totally free hobbyist games that anyone could run. When you combined it all, you had a free console full of free games that could get you free Internet access.

And the best part -- as far as I was concerned -- was that ParanoidXbox was paranoid. Every bit that went over the air was scrambled to within an inch of its life. You could wiretap it all you wanted, but you'd never figure out who was talking, what they were talking about, or who they were talking to. Anonymous web, email and IM. Just what I needed.

All I had to do now was convince everyone I knew to use it too.

Chapter 6

This chapter is dedicated to Powell's Books, the legendary "City of Books" in Portland, Oregon. Powell's is the largest bookstore in the world, an endless, multi-storey universe of papery smells and towering shelves. They stock new and used books on the same shelves -- something I've always loved -- and every time I've stopped in, they've had a veritable mountain of my books, and they've been incredibly gracious about asking me to sign the store-stock. The clerks are friendly, the stock is fabulous, and there's even a Powell's at the Portland airport, making it just about the best airport bookstore in the world for my money!

Powell's Books: 1005 W Burnside, Portland, OR 97209 USA +1 800 878 7323

Believe it or not, my parents made me go to school the next day. I'd only fallen into feverish sleep at three in the morning, but at seven the next day, my Dad was standing at the foot of my bed, threatening to drag me out by the ankles. I managed to get up -- something had died in my mouth after painting my eyelids shut -- and into the shower.

I let my mom force a piece of toast and a banana into me, wishing fervently that my parents would let me drink coffee at home. I could sneak one on the way to school, but watching them sip down their black gold while I was drag-assing around the house, getting dressed and putting my books in my bag -- it was awful.

I've walked to school a thousand times, but today it was different. I went up and over the hills to get down into the Mission, and everywhere there were trucks. I saw new sensors and traffic cameras installed at many of the stop-signs. Someone had a lot of surveillance gear lying around, waiting to be installed at the first opportunity. The attack on the Bay Bridge had been just what they needed.

It all made the city seem more subdued, like being inside an elevator, embarrassed by the close scrutiny of your neighbors and the ubiquitous cameras.

The Turkish coffee shop on 24th Street fixed me up good with a go-cup of Turkish coffee. Basically, Turkish coffee is mud, pretending to be coffee. It's thick enough to stand a spoon up in, and it has way more caffeine than the kiddee-pops like Red Bull. Take it from someone who's read the Wikipedia entry: this is how the Ottoman Empire was won: maddened horsemen fueled by lethal jet-black coffee-mud.

I pulled out my debit card to pay and he made a face. "No more debit," he said.

"Huh? Why not?" I'd paid for my coffee habit on my card for years at the Turk's. He used to hassle me all the time, telling me I was too young to drink the stuff, and he still refused to serve me at all during school hours, convinced that I was skipping class. But over the years, the Turk and me have developed a kind of gruff understanding.

He shook his head sadly. "You wouldn't understand. Go to school, kid."

There's no surer way to make me want to understand than to tell me I won't. I wheedled him, demanding that he tell me. He looked like he was going to throw me out, but when I asked him if he thought I wasn't good enough to shop there, he opened up.

"The security," he said, looking around his little shop with its tubs of dried beans and seeds, its shelves of Turkish groceries. "The government. They monitor it all now, it was in the papers. PATRIOT Act II, the Congress passed it yesterday. Now they can monitor every time you use your card. I say no. I say my shop will not help them spy on my customers."

My jaw dropped.

"You think it's no big deal maybe? What is the problem with government knowing when you buy coffee? Because it's one way they know where you are, where you been. Why you think I left Turkey? Where you have government always spying on the people, is no good. I move here twenty years ago for freedom -- I no help them take freedom away."

"You're going to lose so many sales," I blurted. I wanted to tell him he was a hero and shake his hand, but that was what came out. "Everyone uses debit cards."

"Maybe not so much anymore. Maybe my customers come here because they know I love freedom too. I am making sign for window. Maybe other stores do the same. I hear the ACLU will sue them for this."

"You've got all my business from now on," I said. I meant it. I reached into my pocket. "Um, I don't have any cash, though."

He pursed his lips and nodded. "Many peoples say the same thing. Is OK. You give today's money to the ACLU."

In two minutes, the Turk and I had exchanged more words than we had in all the time I'd been coming to his shop. I had no idea he had all these passions. I just thought of him as my friendly neighborhood caffeine dealer. Now I shook his hand and when I left his store, I felt like he and I had joined a team. A secret team.

#

I'd missed two days of school but it seemed like I hadn't missed much class. They'd shut the school on one of those days while the city scrambled to recover. The next day had been devoted, it seemed, to mourning those missing and presumed dead. The newspapers published biographies of the lost, personal memorials. The Web was filled with these capsule obituaries, thousands of them.

Embarrassingly, I was one of those people. I stepped into the schoolyard, not knowing this, and then there was a shout and a moment later there were a hundred people around me, pounding me on the back, shaking my hand. A couple girls I didn't even know kissed me, and they were more than friendly kisses. I felt like a rock star.

My teachers were only a little more subdued. Ms Galvez cried as much as my mother had and hugged me three times before she let me go to my desk and sit down. There was something new at the front of the classroom. A camera. Ms Galvez caught me staring at it and handed me a permission slip on smeary Xeroxed school letterhead.

The Board of the San Francisco Unified School District had held an emergency session over the weekend and unanimously voted to ask the parents of every kid in the city for permission to put closed circuit television cameras in every classroom and corridor. The law said they couldn't force us to go to school with cameras all over the place, but it didn't say anything about us volunteering to give up our Constitutional rights. The letter said that the Board were sure that they would get complete compliance from the City's parents, but that they would make arrangements to teach those kids' whose parents objected in a separate set of "unprotected" classrooms.

Why did we have cameras in our classrooms now? Terrorists. Of course. Because by blowing up a bridge, terrorists had indicated that schools were next. Somehow that was the conclusion that the Board had reached anyway.

I read this note three times and then I stuck my hand up.

"Yes, Marcus?"

"Ms Galvez, about this note?"

"Yes, Marcus."

"Isn't the point of terrorism to make us afraid? That's why it's called terrorism, right?"

"I suppose so." The class was staring at me. I wasn't the best student in school, but I did like a good in-class debate. They were waiting to hear what I'd say next.

"So aren't we doing what the terrorists want from us? Don't they win if we act all afraid and put cameras in the classrooms and all of that?"

There was some nervous tittering. One of the others put his hand up. It was Charles. Ms Galvez called on him.

"Putting cameras in makes us safe, which makes us less afraid."

"Safe from what?" I said, without waiting to be called on.

"Terrorism," Charles said. The others were nodding their heads.

"How do they do that? If a suicide bomber rushed in here and blew us all up --"

"Ms Galvez, Marcus is violating school policy. We're not supposed to make jokes about terrorist attacks --"

"Who's making jokes?"

"Thank you, both of you," Ms Galvez said. She looked really unhappy. I felt kind of bad for hijacking her class. "I think that this is a really interesting discussion, but I'd like to hold it over for a future class. I think that these issues may be too emotional for us to have a discussion about them today. Now, let's get back to the suffragists, shall we?"

So we spent the rest of the hour talking about suffragists and the new lobbying strategies they'd devised for getting four women into every congresscritter's office to lean on him and let him know what it would mean for his political future if he kept on denying women the vote. It was normally the kind of thing I really liked -- little guys making the big and powerful be honest. But today I couldn't concentrate. It must have been Darryl's absence. We both liked Social Studies and we would have had our SchoolBooks out and an IM session up seconds after sitting down, a back-channel for talking about the lesson.

I'd burned twenty ParanoidXbox discs the night before and I had them all in my bag. I handed them out to people I knew were really, really into gaming. They'd all gotten an Xbox Universal or two the year before, but most of them had stopped using them. The games were really expensive and not a lot of fun. I took them aside between periods, at lunch and study hall, and sang the praises of the ParanoidXbox games to the sky. Free and fun -- addictive social games with lots of cool people playing them from all over the world.

Giving away one thing to sell another is what they call a "razor blade business" -- companies like Gillette give you free razor-blade handles and then stiff you by charging you a small fortune for the blades. Printer cartridges are the worst for that -- the most expensive Champagne in the world is cheap when compared with inkjet ink, which costs all of a penny a gallon to make wholesale.

Razor-blade businesses depend on you not being able to get the "blades" from someone else. After all, if Gillette can make nine bucks on a ten-dollar replacement blade, why not start a competitor that makes only four bucks selling an identical blade: an 80 percent profit margin is the kind of thing that makes your average business-guy go all drooly and round-eyed.

So razor-blade companies like Microsoft pour a lot of effort into making it hard and/or illegal to compete with them on the blades. In Microsoft's case, every Xbox has had countermeasures to keep you from running software that was released by people who didn't pay the Microsoft blood-money for the right to sell Xbox programs.

The people I met didn't think much about this stuff. They perked up when I told them that the games were unmonitored. These days, any online game you play is filled with all kinds of unsavory sorts. First there are the pervs who try to get you to come out to some remote location so they can go all weird and Silence of the Lambs on you. Then there are the cops, who are pretending to be gullible kids so they can bust the pervs. Worst of all, though, are the monitors who spend all their time spying on our discussions and snitching on us for violating their Terms of Service, which say, no flirting, no cussing, and no "clear or masked language which insultingly refers to any aspect of sexual orientation or sexuality."

I'm no 24/7 horn-dog, but I'm a seventeen year old boy. Sex does come up in conversation every now and again. But God help you if it came up in chat while you were gaming. It was a real buzz-kill. No one monitored the ParanoidXbox games, because they weren't run by a company: they were just games that hackers had written for the hell of it.

So these game-kids loved the story. They took the discs greedily, and promised to burn copies for all of their friends -- after all, games are most fun when you're playing them with your buddies.

When I got home, I read that a group of parents were suing the school board over the surveillance cameras in the classrooms, but that they'd already lost their bid to get a preliminary injunction against them.

#

I don't know who came up with the name Xnet, but it stuck. You'd hear people talking about it on the Muni. Van called me up to ask me if I'd heard of it and I nearly choked once I figured out what she was talking about: the discs I'd started distributing last week had been sneakernetted and copied all the way to Oakland in the space of two weeks. It made me look over my shoulder -- like I'd broken a rule and now the DHS would come and take me away forever.

They'd been hard weeks. The BART had completely abandoned cash fares now, switching them for arphid "contactless" cards that you waved at the turnstiles to go through. They were cool and convenient, but every time I used one, I thought about how I was being tracked. Someone on Xnet posted a link to an Electronic Frontier Foundation white paper on the ways that these things could be used to track people, and the paper had tiny stories about little groups of people that had protested at the BART stations.

I used the Xnet for almost everything now. I'd set up a fake email address through the Pirate Party, a Swedish political party that hated Internet surveillance and promised to keep their mail accounts a secret from everyone, even the cops. I accessed it strictly via Xnet, hopping from one neighbor's Internet connection to the next, staying anonymous -- I hoped -- all the way to Sweden. I wasn't using w1n5ton anymore. If Benson could figure it out, anyone could. My new handle, come up with on the spur of the moment, was M1k3y, and I got a lot of email from people who heard in chat rooms and message boards that I could help them troubleshoot their Xnet configurations and connections.

I missed Harajuku Fun Madness. The company had suspended the game indefinitely. They said that for "security reasons" they didn't think it would be a good idea to hide things and then send people off to find them. What if someone thought it was a bomb? What if someone put a bomb in the same spot?

What if I got hit by lightning while walking with an umbrella? Ban umbrellas! Fight the menace of lightning!

I kept on using my laptop, though I got a skin-crawly feeling when I used it. Whoever had wiretapped it would wonder why I didn't use it. I figured I'd just do some random surfing with it every day, a little less each day, so that anyone watching would see me slowly changing my habits, not doing a sudden reversal. Mostly I read those creepy obits -- all those thousands of my friends and neighbors dead at the bottom of the Bay.

Truth be told, I was doing less and less homework every day. I had business elsewhere. I burned new stacks of ParanoidXbox every day, fifty or sixty, and took them around the city to people I'd heard were willing to burn sixty of their own and hand them out to their friends.

I wasn't too worried about getting caught doing this, because I had good crypto on my side. Crypto is cryptography, or "secret writing," and it's been around since Roman times (literally: Augustus Caesar was a big fan and liked to invent his own codes, some of which we use today for scrambling joke punchlines in email).

Crypto is math. Hard math. I'm not going to try to explain it in detail because I don't have the math to really get my head around it, either -- look it up on Wikipedia if you really want.

But here's the Cliff's Notes version: Some kinds of mathematical functions are really easy to do in one direction and really hard to do in the other direction. It's easy to multiply two big prime numbers together and make a giant number. It's really, really hard to take any given giant number and figure out which primes multiply together to give you that number.

That means that if you can come up with a way of scrambling something based on multiplying large primes, unscrambling it without knowing those primes will be hard. Wicked hard. Like, a trillion years of all the computers ever invented working 24/7 won't be able to do it.

There are four parts to any crypto message: the original message, called the "cleartext." The scrambled message, called the "ciphertext." The scrambling system, called the "cipher." And finally there's the key: secret stuff you feed into the cipher along with the cleartext to make ciphertext.

It used to be that crypto people tried to keep all of this a secret. Every agency and government had its own ciphers and its own keys. The Nazis and the Allies didn't want the other guys to know how they scrambled their messages, let alone the keys that they could use to descramble them. That sounds like a good idea, right?

Wrong.

The first time anyone told me about all this prime factoring stuff, I immediately said, "No way, that's BS. I mean, sure it's hard to do this prime factorization stuff, whatever you say it is. But it used to be impossible to fly or go to the moon or get a hard-drive with more than a few kilobytes of storage. Someone must have invented a way of descrambling the messages." I had visions of a hollow mountain full of National Security Agency mathematicians reading every email in the world and snickering.

In fact, that's pretty much what happened during World War II. That's the reason that life isn't more like Castle Wolfenstein, where I've spent many days hunting Nazis.

The thing is, ciphers are hard to keep secret. There's a lot of math that goes into one, and if they're widely used, then everyone who uses them has to keep them a secret too, and if someone changes sides, you have to find a new cipher.

The Nazi cipher was called Enigma, and they used a little mechanical computer called an Enigma Machine to scramble and unscramble the messages they got. Every sub and boat and station needed one of these, so it was inevitable that eventually the Allies would get their hands on one.

When they did, they cracked it. That work was led by my personal all-time hero, a guy named Alan Turing, who pretty much invented computers as we know them today. Unfortunately for him, he was gay, so after the war ended, the stupid British government forced him to get shot up with hormones to "cure" his homosexuality and he killed himself. Darryl gave me a biography of Turing for my 14th birthday -- wrapped in twenty layers of paper and in a recycled Batmobile toy, he was like that with presents -- and I've been a Turing junkie ever since.

Now the Allies had the Enigma Machine, and they could intercept lots of Nazi radio-messages, which shouldn't have been that big a deal, since every captain had his own secret key. Since the Allies didn't have the keys, having the machine shouldn't have helped.

Here's where secrecy hurts crypto. The Enigma cipher was flawed. Once Turing looked hard at it, he figured out that the Nazi cryptographers had made a mathematical mistake. By getting his hands on an Enigma Machine, Turing could figure out how to crack any Nazi message, no matter what key it used.

That cost the Nazis the war. I mean, don't get me wrong. That's good news. Take it from a Castle Wolfenstein veteran. You wouldn't want the Nazis running the country.

After the war, cryptographers spent a lot of time thinking about this. The problem had been that Turing was smarter than the guy who thought up Enigma. Any time you had a cipher, you were vulnerable to someone smarter than you coming up with a way of breaking it.

And the more they thought about it, the more they realized that anyone can come up with a security system that he can't figure out how to break. But no one can figure out what a smarter person might do.

You have to publish a cipher to know that it works. You have to tell as many people as possible how it works, so that they can thwack on it with everything they have, testing its security. The longer you go without anyone finding a flaw, the more secure you are.

Which is how it stands today. If you want to be safe, you don't use crypto that some genius thought of last week. You use the stuff that people have been using for as long as possible without anyone figuring out how to break them. Whether you're a bank, a terrorist, a government or a teenager, you use the same ciphers.

If you tried to use your own cipher, there'd be the chance that someone out there had found a flaw you missed and was doing a Turing on your butt, deciphering all your "secret" messages and chuckling at your dumb gossip, financial transactions and military secrets.

So I knew that crypto would keep me safe from eavesdroppers, but I wasn't ready to deal with histograms.

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I got off the BART and waved my card over the turnstile as I headed up to the 24th Street station. As usual, there were lots of weirdos hanging out in the station, drunks and Jesus freaks and intense Mexican men staring at the ground and a few gang kids. I looked straight past them as I hit the stairs and jogged up to the surface. My bag was empty now, no longer bulging with the ParanoidXbox discs I'd been distributing, and it made my shoulders feel light and put a spring in my step as I came up the street. The preachers were at work still, exhorting in Spanish and English about Jesus and so on.

The counterfeit sunglass sellers were gone, but they'd been replaced by guys selling robot dogs that barked the national anthem and would lift their legs if you showed them a picture of Osama bin Laden. There was probably some cool stuff going on in their little brains and I made a mental note to pick a couple of them up and take them apart later. Face-recognition was pretty new in toys, having only recently made the leap from the military to casinos trying to find cheats, to law enforcement.

I started down 24th Street toward Potrero Hill and home, rolling my shoulders and smelling the burrito smells wafting out of the restaurants and thinking about dinner.

I don't know why I happened to glance back over my shoulder, but I did. Maybe it was a little bit of subconscious sixth-sense stuff. I knew I was being followed.

They were two beefy white guys with little mustaches that made me think of either cops or the gay bikers who rode up and down the Castro, but gay guys usually had better haircuts. They had on windbreakers the color of old cement and blue-jeans, with their waistbands concealed. I thought of all the things a cop might wear on his waistband, of the utility-belt that DHS guy in the truck had worn. Both guys were wearing Bluetooth headsets.

I kept walking, my heart thumping in my chest. I'd been expecting this since I started. I'd been expecting the DHS to figure out what I was doing. I took every precaution, but Severe-Haircut woman had told me that she'd be watching me. She'd told me I was a marked man. I realized that I'd been waiting to get picked up and taken back to jail. Why not? Why should Darryl be in jail and not me? What did I have going for me? I hadn't even had the guts to tell my parents -- or his -- what had really happened to us.

I quickened my steps and took a mental inventory. I didn't have anything incriminating in my bag. Not too incriminating, anyway. My SchoolBook was running the crack that let me IM and stuff, but half the people in school had that. I'd changed the way I encrypted the stuff on my phone -- now I did have a fake partition that I could turn back into cleartext with one password, but all the good stuff was hidden, and needed another password to open up. That hidden section looked just like random junk -- when you encrypt data, it becomes indistinguishable from random noise -- and they'd never even know it was there.

There were no discs in my bag. My laptop was free of incriminating evidence. Of course, if they thought to look hard at my Xbox, it was game over. So to speak.