the rest of the world 'this is how weird we are,' and distributed throughout the world on the Net. Of course Finux was fantastically powerful and flexible and enabled you, among other things, to control the machine's video circuitry to the Nth degree and choose many different scanning frequencies and pixel clocks, if you were into that kind of thing. Pekka most definitely was into it, and so like a lot of Finux maniacs he set his machine up so that it could display, if he chose, a whole lot of tiny little pixels (which displayed a lot of information but was hard on the eyes) or, alternatively, fewer and larger pixels (which he tended to use after he had been hacking for twenty-four hours straight and lost ocular muscle tone), or various settings in-between. Every time he changed from one setting to another, the monitor screen would go black for a second and there would be an audible clunk from inside of it as the resonating crystals inside locked in on a different range of frequencies.
One night at three A.M., Pekka caused this to happen, and immediately after the screen went black and made that clunking noise, it exploded in his face. The front of the picture tube was made of heavy glass (it had to be, to withstand the internal vacuum) which fragmented and sped into Pekka's face, neck, and upper body. The very same phosphors that had been glowing beneath the sweeping electron beam, moments before, conveying information into Pekka's eyes, were now physically embedded in his flesh. A hunk of glass took one of his eyes and almost went through into his brain. Another one gouged out his voicebox, another zinged past the side of his head and bit a neat triangular hunk out of his left ear.
Pekka, in other words, was the first victim of the Digibomber. He almost bled to death on the spot, and his fellow Eutropians hovered around his hospital bed for a few days with tanks of Freon, ready to jump into action in case he died. But he didn't, and he got even more press because his startup company lacked health insurance. After a lot of hand-wringing in local newspapers about how this poor innocent from the land of socialized medicine had not had the presence of mind to buy health insurance, some rich high-tech guys donated money to pay his medical bills and to equip him with a computer voicebox like Stephen Hawking's.
And now here is Pekka, sitting in Cantrell's hotel room. His cello stands in the corner, dusty around the bridge from powdered rosin. He is facing a blank wall to which he has duct-taped a bunch of wires in precise loops and whorls. These lead to some home-brewed circuit boards which are in turn hooked up to his laptop.
'Hello Randy congratulations on your success,' says a computer-generated voice as soon as the door is shut behind Randy and Cantrell. This is a little greeting that Pekka has obviously typed in ahead of time, anticipating his arrival. None of the foregoing seems particularly odd to Randy except for the fact that Pekka seems to think that Epiphyte has already achieved some kind of success.
'How are we doing?' Cantrell asks.
Pekka types in a response. Then he cups one hand to his mutilated ear while using his other hand to cue the voice generator: 'He showers.' Indeed, it's possible now to hear the pipes hissing in the wall. 'His laptop radiates.'
'Oh,' Randy says, 'Tom Howard's room is right next door?'
'Just on the other side of that wall,' Cantrell says. 'I specifically requested it, so that I could win this bet. See, his room is a mirror image of this one, so his computer is only a few inches away, just on the other side of this wall. Perfect conditions for Van Eck phreaking.'
'Pekka, are you receiving signals from his computer right now?' Randy asks.
Pekka nods, types, and fires back, 'I tune. I calibrate.' The input device for his voice generator is a one- handed chord-board strapped to his thigh. He puts his right hand on it and makes flopping and groping motions. Moments later speech emerges, 'I require Cantrell.'
'Excuse me,' Cantrell says, and goes to Pekka's side. Randy watches over their shoulders for a bit, understanding vaguely what they're doing.
If you lay a sheet of white paper on an old gravestone, and sweep the tip of a pencil across it, you get one horizontal line, dark in some places and faint in others, and not very meaningful. If you move downwards on the page by a small distance, a single pencil-line-width, and repeat, an image begins to emerge. The process of working your way down the page in a series of horizontal sweeps is what a nerd would call raster-scanning, or just rastering. With a conventional video monitor-a cathode-ray tube-the electron beam physically rasters down the glass something like sixty to eighty times a second. In the case of a laptop screen like Randy's, there is no physical scanning; the individual pixels are turned on or off directly. But still a scanning process is taking place; what's being scanned and made manifest on the screen is a region of the computer's memory called the screen buffer. The contents of the screen buffer have to be slapped up onto the screen sixty to eighty times every second or else (1) the screen flickers and (2) the images move jerkily.
The way that the computer talks to you is not by controlling the screen directly but rather by manipulating the bits contained in that buffer, secure in the knowledge that other subsystems inside the machine handle the drudge work of pipelining that information onto the actual, physical screen. Sixty to eighty times a second, the video system says shit! time to refresh the screen again, and goes to the beginning of the screen buffer-which is just a particular hunk of memory, remember-and it reads the first few bytes, which dictate what color the pixel in the upper left-hand corner of the screen is supposed to be. This information is sent on down the line to whatever is actually refreshing the screen, whether it's a scanning electron beam or some laptop-style system for directly controlling the pixels. Then the next few bytes are read, typically for the pixel just to the right of that first one, and so on all the way to the right edge of the screen. That draws the first line of the grave-rubbing.
Since the right edge of the screen has now been reached, there are no more pixels off in that direction. It is implicit that the next bytes read from memory will be for the leftmost pixel in the second raster-line down from the top. If this is a cathode-ray tube type of screen, we have a little timing problem here in that the electron beam is currently at the right edge of the screen and now it's being asked to draw a pixel at the left edge. It has to move back. This takes a little while-not long, but much longer than the interval of time between drawing two pixels that are cheek-by-jowl. This pause is called the
These issues all stem from inherent physical limitations of sweeping electron beams through space in a cathode-ray tube, and basically disappear in the case of a laptop screen like the one Tom Howard has set up a few inches in front of Pekka, on the other side of that wall. But the video timing of a laptop screen is still patterned after that of a cathode-ray tube screen anyway. (This is simply because the old technology is universally understood by those who need to understand it, and it works well, and all kinds of electronic and software technology has been built and tested to work within that framework, and why mess with success, especially when your profit margins are so small that they can only be detected by using techniques from quantum mechanics, and any glitches vis-a-vis compatibility with old stuff will send your company straight into the toilet.)
On Tom's laptop, each second of time is divided into seventy-five perfectly regular slices, during which a full grave-rubbing is performed followed by a vertical retrace interval. Randy can follow Pekka and Cantrell's conversation well enough to gather that they have already figured out, from analyzing the signals coming through the wall, that Tom Howard has his screen set up to give him 768 lines, and 1,024 pixels on each line. For every pixel, four bytes will be read from the video buffer and sent on down the line to the screen. (Tom is using the highest possible level of color definition on his screen, which means that one byte apiece is needed to represent the intensity of blue, green, and red and another is basically left over, but kept in there anyway because computers like powers of two, and computers are so ridiculously fast and powerful now that, even though all of this is happening on a timetable that would strike a human being as rather aggressive, the extra bytes just don't make any difference.) Each byte is eight binary digits or bits and so, 1,024 times a line, 4 x 8 = 32 bits are being read from the screen buffer.
Unbeknownst to Tom, his computer happens to be sitting right next to an antenna. The wires Pekka taped to the wall can read the electromagnetic waves that are radiating out of the computer's circuitry at all times.
Tom's laptop is sold as a computer, not as a radio station, and so it might seem odd that it should be radiating anything at all. It is all a byproduct of the fact that computers are binary critters, which means that all chip-to-chip, subsystem-to-subsystem communication taking place inside the machine-everything moving down those flat ribbons of wire, and the little metallic traces on the circuit boards-consists of transitions from zero to one and back again. The way that you represent bits in a computer is by switching the wire's voltage back and forth between zero and five volts. In computer textbooks these transitions are always graphed as if they were perfect
