This chapter is dedicated to Anderson's Bookshops, Chicago's legendarykids' bookstore. Anderson's is an old, old family-run business, whichstarted out as an old-timey drug-store selling some books on the side.
Today, it's a booming, multi-location kids' book empire, with some in-credibly innovative bookselling practices that get books and kids togetherin really exciting ways. The best of these is the store's mobile book-fairs,in which they ship huge, rolling bookcases, already stocked with excel-lent kids' books, direct to schools on trucks — voila, instant book-fair!
Anderson's Bookshops: 123 West Jefferson, Naperville, IL 60540 USA+1 630 355 2665What would you do if you found out you had a spy in your midst?
You could denounce him, put him up against the wall and take him out.
But then you might end up with another spy in your midst, and the newspy would be more careful than the last one and maybe not get caughtquite so readily.
Here's a better idea: start intercepting the spy's communications andfeed him and his masters misinformation. Say his masters instruct him togather information on your movements. Let him follow you around andtake all the notes he wants, but steam open the envelopes that he sendsback to HQ and replace his account of your movements with a fictitiousone. If you want, you can make him seem erratic and unreliable so theyget rid of him. You can manufacture crises that might make one side orthe other reveal the identities of other spies. In short, you own them.
This is called the man-in-the-middle attack and if you think about it,it's pretty scary. Someone who man-in-the-middles your communica-tions can trick you in any of a thousand ways.
Of course, there's a great way to get around the man-in-the-middle at-tack: use crypto. With crypto, it doesn't matter if the enemy can see your129messages, because he can't decipher them, change them, and re-sendthem. That's one of the main reasons to use crypto.
But remember: for crypto to work, you need to have keys for thepeople you want to talk to. You and your partner need to share a secretor two, some keys that you can use to encrypt and decrypt your mes-sages so that men-in-the-middle get locked out.
That's where the idea of public keys comes in. This is a little hairy, butit's so unbelievably elegant too.
In public key crypto, each user gets two keys. They're long strings ofmathematical gibberish, and they have an almost magic property.
Whatever you scramble with one key, the other will unlock, and vice-versa. What's more, they're the only keys that can do this — if you canunscramble a message with one key, you know it was scrambled with theother (and vice-versa).
So you take either one of these keys (it doesn't matter which one) andyou just publish it. You make it a total non-secret. You want anyone in theworld to know what it is. For obvious reasons, they call this your "publickey."The other key, you hide in the darkest reaches of your mind. You pro-tect it with your life. You never let anyone ever know what it is. That'scalled your "private key." (Duh.)Now say you're a spy and you want to talk with your bosses. Theirpublic key is known by everyone. Your public key is known by every-one. No one knows your private key but you. No one knows theirprivate key but them.
You want to send them a message. First, you encrypt it with yourprivate key. You could just send that message along, and it would workpretty well, since they would know when the message arrived that itcame from you. How? Because if they can decrypt it with your publickey, it can only have been encrypted with your private key. This is theequivalent of putting your seal or signature on the bottom of a message.
It says, "I wrote this, and no one else. No one could have tampered withit or changed it."Unfortunately, this won't actually keep your message a secret. That'sbecause your public key is really well known (it has to be, or you'll belimited to sending messages to those few people who have your publickey). Anyone who intercepts the message can read it. They can't change130it and make it seem like it came from you, but if you don't want peopleto know what you're saying, you need a better solution.
So instead of just encrypting the message with your private key, youalso encrypt it with your boss's public key. Now it's been locked twice.
The first lock — the boss's public key — only comes off when combinedwith your boss's private key. The second lock — your private key — onlycomes off with your public key. When your bosses receive the message,they unlock it with both keys and now they know for sure that: a) youwrote it and b) that only they can read it.
It's very cool. The day I discovered it, Darryl and I immediately ex-changed keys and spent months cackling and rubbing our hands as weexchanged our military-grade secret messages about where to meet afterschool and whether Van would ever notice him.
But if you want to understand security, you need to consider the mostparanoid possibilities. Like, what if I tricked you into thinking that mypublic key was your boss's public key? You'd encrypt the message withyour private key and my public key. I'd decrypt it, read it, re-encrypt itwith your boss's real public key and send it on. As far as your bossknows, no one but you could have written the message and no one buthim could have read it.
And I get to sit in the middle, like a fat spider in a web, and all yoursecrets belong to me.
Now, the easiest way to fix this is to really widely advertise your pub-lic key. If it's really easy for anyone to know what your real key is, man-in-the-middle gets harder and harder. But you know what? Makingthings well-known is just as hard as keeping them secret. Think about it— how many billions of dollars are spent on shampoo ads and othercrap, just to make sure that as many people know about something thatsome advertiser wants them to know?
There's a cheaper way of fixing man-in-the-middle: the web of trust.
Say that before you leave HQ, you and your bosses sit down over coffeeand actually tell each other your keys. No more man-in-the-middle!
You're absolutely certain whose keys you have, because they were putinto your own hands.
So far, so good. But there's a natural limit to this: how many peoplecan you physically meet with and swap keys? How many hours in theday do you want to devote to the equivalent of writing your own phonebook? How many of those people are willing to devote that kind of timeto you?
131Thinking about this like a phonebook helps. The world was once aplace with a lot of phonebooks, and when you needed a number, youcould look it up in the book. But for many of the numbers that youwanted to refer to on a given day, you would either know it by heart, oryou'd be able to ask someone else. Even today, when I'm out with mycell-phone, I'll ask Jolu or Darryl if they have a number I'm looking for.
It's faster and easier than looking it up online and they're more reliable,too. If Jolu has a number, I trust him, so I trust the number, too. That'scalled "transitive trust" — trust that moves across the web of ourrelationships.
A web of trust is a bigger version of this. Say I meet Jolu and get hiskey. I can put it on my "keyring" — a list of keys that I've signed with myprivate key. That means you can unlock it with my public key and knowfor sure that me — or someone with my key, anyway — says that "thiskey belongs to this guy."So I hand you my keyring and provided that you trust me to have ac-tually met and verified all the keys on it, you can take it and add it toyour keyring. Now, you meet someone else and you hand the whole ringto him. Bigger and bigger the ring grows, and provided that you trustthe next guy in the chain, and he trusts the next guy in his chain and soon, you're pretty secure.
Which brings me to keysigning parties. These are exactly what theysound like: a party where everyone gets together and signs everyoneelse's keys. Darryl and I, when we traded keys, that was kind of a mini-keysigning party, one with only two sad and geeky attendees. But withmore people, you create the seed of the web of trust, and the web can ex-pand from there. As everyone on your keyring goes out into the worldand meets more people, they can add more and more names to the ring.
You don't have to meet the new people, just trust that the signed key youget from the people in your web is valid.
So that's why web of trust and parties go together like peanut butterand chocolate.
"Just tell them it's a super-private party, invitational only," I said. "Tellthem not to bring anyone along or they won't be admitted."Jolu looked at me over his coffee. "You're joking, right? You tell peoplethat, and they'll bring extra friends."132"Argh," I said. I spent a night a week at Jolu's these days, keeping thecode up to date on indienet. Pigspleen actually paid me a non-zero sumof money to do this, which was really weird. I never thought I'd be paidto write code.
"So what do we do? We only want people we really trust there, and wedon't want to mention why until we've got everyone's keys and can sendthem messages in secret."Jolu debugged and I watched over his shoulder. This used to be called"extreme programming," which was a little embarrassing. Now we justcall it "programming." Two people are much better at spotting bugs thanone. As the cliche goes, "With enough eyeballs, all bugs are shallow."We were working our way through the bug reports and getting readyto push out the new rev. It all auto-updated in the background, so ourusers didn't really need to do anything, they just woke up once a week orso with a better program. It was pretty freaky to know that the code Iwrote would be used by hundreds of thousands of people, tomorrow!
"What do we do? Man, I don't know. I think we just have to live withit."I thought back to our Harajuku Fun Madness days. There were lots ofsocial challenges involving large groups of people as part of that game.
"OK, you're right. But let's at least try to keep this secret. Tell them thatthey can bring a maximum of one person, and it has to be someonethey've known personally for a minimum of five years."Jolu looked up from the screen. "Hey," he said. "Hey, that wouldtotally work. I can really see it. I mean, if you told me not to bring any-one, I'd be all, 'Who the hell does he think he is?' But when you put itthat way, it sounds like some awesome 007 stuff."I found a bug. We drank some coffee. I went home and played a littleClockwork Plunder, trying not to think about key-winders with nosyquestions, and slept like a baby.
Sutro baths are San Francisco's authentic fake Roman ruins. When itopened in 1896, it was the largest indoor bathing house in the world, ahuge Victorian glass solarium filled with pools and tubs and even anearly water slide. It went downhill by the fifties, and the owners torchedit for the insurance in 1966. All that's left is a labyrinth of weatheredstone set into the sere cliff-face at Ocean Beach. It looks for all the worldlike a Roman ruin, crumbled and mysterious, and just beyond them is a133set of caves that let out into the sea. In rough tides, the waves rushthrough the caves and over the ruins — they've even been known to suckin and drown the occasional tourist.
Ocean Beach is way out past Golden Gate park, a stark cliff lined withexpensive, doomed houses, plunging down to a narrow beach studdedwith jellyfish and brave (insane) surfers. There's a giant white rock thatjuts out of the shallows off the shore. That's called Seal Rock, and it usedto be the place where the sea lions congregated until they were relocatedto the more tourist-friendly environs of Fisherman's Wharf.
After dark, there's hardly anyone out there. It gets very cold, with asalt spray that'll soak you to your bones if you let it. The rocks are sharpand there's broken glass and the occasional junkie needle.
It is an awesome place for a party.
Bringing along the tarpaulins and chemical glove-warmers was myidea. Jolu figured out where to get the beer — his older brother, Javier,had a buddy who actually operated a whole underage drinking service:
pay him enough and he'd back up to your secluded party spot with ice-chests and as many brews as............