It's got lots of applications -- you can ask a computer to count the lines in a picture and see if it's more like a "dog" line-frequency histogram or a "cat" line-frequency histogram. It can find porn, bank fraud, and flamewars. Useful stuff.

And it was bad news for the Xnet. Say you had the whole Internet wiretapped -- which, of course, the DHS has. You can't tell who's passing Xnet packets by looking at the contents of those packets, thanks to crypto.

What you can do is find out who is sending way, way more encrypted traffic out than everyone else. For a normal Internet surfer, a session online is probably about 95 percent cleartext, five percent ciphertext. If someone is sending out 95 percent ciphertext, maybe you could dispatch the computer-savvy equivalents of Booger and Zit to ask them if they're terrorist drug-dealer Xnet users.

This happens all the time in China. Some smart dissident will get the idea of getting around the Great Firewall of China, which is used to censor the whole country's Internet connection, by using an encrypted connection to a computer in some other country. Now, the Party there can't tell what the dissident is surfing: maybe it's porn, or bomb-making instructions, or dirty letters from his girlfriend in the Philippines, or political material, or good news about Scientology. They don't have to know. All they have to know is that this guy gets way more encrypted traffic than his neighbors. At that point, they send him to a forced labor camp just to set an example so that everyone can see what happens to smart-asses.

So far, I was willing to bet that the Xnet was under the DHS's radar, but it wouldn't be the case forever. And after tonight, I wasn't sure that I was in any better shape than a Chinese dissident. I was putting all the people who signed onto the Xnet in jeopardy. The law didn't care if you were actually doing anything bad; they were willing to put you under the microscope just for being statistically abnormal. And I couldn't even stop it -- now that the Xnet was running, it had a life of its own.

I was going to have to fix it some other way.

I wished I could talk to Jolu about this. He worked at an Internet Service Provider called Pigspleen Net that had hired him when he was twelve, and he knew way more about the net than I did. If anyone knew how to keep our butts out of jail, it would be him.

Luckily, Van and Jolu and I were planning to meet for coffee the next night at our favorite place in the Mission after school. Officially, it was our weekly Harajuku Fun Madness team meeting, but with the game canceled and Darryl gone, it was pretty much just a weekly weep-fest, supplemented by about six phone-calls and IMs a day that went, "Are you OK? Did it really happen?" It would be good to have something else to talk about.