Neal Stephenson - Cryptonomicon

Some people go so far as to use keys 2048 or even 3072 bits in length. These will stop the very best codebreakers on the face of the earth for astronomical periods of time, barring the invention of otherworldly technologies such as quantum computers. Most encryption software—even stuff written by extremely security-conscious cryptography experts—can't even handle keys larger than that. But Avi insists on using Ordo, generally considered the best encryption software in the world, because it can handle keys of unlimited length—as long as you don't mind waiting for it to crunch all the numbers.

Randy begins typing. He is not bothering to look at the screen; he is staring out the window at the lights on the trucks and the jeepneys. He is only using one hand, just flailing away loosely at the keyboard.

Inside Randy's computer is a precise clock. Whenever he strikes a key, Ordo uses that clock to record the current time, down to microseconds. He hits a key at 03:03:56.935788 and he hits another one at 03:05:57.290664, or about .354876 seconds later. Another .372307 seconds later, he hits another one. Ordo keeps track of all of these intervals and discards the more significant digits (in this example the .35 and the .37) because these parts will tend to be similar from one event to the next.

Ordo wants randomness. It only wants the least significant digits—say, the 76 and the 07 at the very ends of these numbers. It wants a whole lot of random numbers, and it wants them to be very, very random. It is taking somewhat random numbers and feeding them through hash functions that make them even more random. It is running statistical routines on the results to make sure that they contain no hidden patterns. It has breathtakingly high standards for randomness, and it will not stop asking Randy to whack on the keyboard until those standards are met.

The longer the key you are trying to generate, the longer this takes. Randy is trying to generate one that is ridiculously long. He has pointed out to Avi, in an encrypted e-mail message, that if every particle of matter in the universe could be used to construct one single cosmic supercomputer, and this computer was put to work trying to break a 4096-bit encryption key, it would take longer than the lifespan of the universe.

“Using today's technology,” Avi shot back. “that is true. But what about quantum computers? And what if new mathematical techniques are developed that can simplify the factoring of large numbers?”

“How long do you want these messages to remain secret?” Randy asked, in his last message before leaving San Francisco. “Five years? Ten years? Twenty-five years?”

After he got to the hotel this afternoon, Randy decrypted and read Avi's answer. It is still hanging in front of his eyes, like the afterimage of a strobe:

I want them to remain secret for as long as men are capable of evil.

The computer finally beeps. Randy rests his tired hand. Ordo politely warns him that it may be busy for a while, and then goes to work. It is searching the cosmos of pure numbers, looking for two big primes that can be multiplied by each other to produce a number 4096 bits long.

If you want your secrets to remain secret past the end of your life expectancy, then, in order to choose a key length, you have to be a futurist. You have to anticipate how much faster computers will get during this time. You must also be a student of politics. Because if the entire world were to become a police state obsessed with recovering old secrets, then vast resources might be thrown at the problem of factoring large composite numbers.

So the length of the key that you use is, in and of itself, a code of sorts. A knowledgeable government eavesdropper, noting Randy's and Avi's use of a 4096-bit key, will conclude one of the following:

—Avi doesn't know what he's talking about. This can be ruled out with a bit of research into his past accomplishments. Or,

—Avi is clinically paranoid. This can also be ruled out with some research. Or,

—Avi is extremely optimistic about the future development of computer technology, or pessimistic about the political climate, or both. Or,

—Avi has a planning horizon that extends over a period of at least a century.

Randy paces around his room while his computer soars through number space. The shipping containers on the backs of those trucks bear exactly the same logos as the ones that used to fill the streets of South Seattle when a ship was unloading. To Randy this is oddly satisfying, as if by making this crazy lunge across the Pacific, he has brought some kind of antipodal symmetry to his life. He has gone from the place where things are consumed to where they are produced, from a land where onanism has been enshrined at the highest levels of the society to one where cars have “NO to contraception!” stickers in their windows. It feels bizarrely right. He has not felt this way since Avi and he founded their first doomed business venture twelve years ago.

Randy grew up in a college town in eastern Washington State, graduated from the University of Washington in Seattle, and landed a Clerk Typist II job at the library there—specifically the Interlibrary Loan Department—where his job was to process incoming loan requests mailed in from smaller libraries all over the region and, conversely, to mail out requests to other libraries. If nine-year-old Randy Waterhouse had been able to look into the future and see himself in this career, he would have been delighted beyond measure: the primary tool of the Interlibrary Loan Department was the Staple Remover. Young Randy had seen one of these devices in the hands of his fourth-grade teacher and been enthralled by its cunning and deadly appearance, so like the jaws of some futuristic robot dragon. He had, in fact, gone out of his way to staple things incorrectly just so he could prevail on his teacher to unstaple them, giving him another glimpse of the blood-chilling mandibles in action. He had gone so far as to steal a staple remover from an untended desk at church and then incorporate it into an Erector-set robot hunter-killer device with which he terrorized much of the neighborhood; its pit-viper yawn separated many a cheap plastic toy from its parts and accessories before the theft was discovered and Randy made an example of before God and man. Now, in the Interlibrary Loan office, Randy had not just one but several staple removers in his desk drawer and was actually obligated to use them for an hour or two a day.

Since the UW library was well-endowed, its patrons didn't request books from other libraries unless they had been stolen from their own or were, in some way, peculiar. The ILL office (as Randy and his coworkers affectionately called it) had its regulars—people who had a whole lot of peculiar books on their wish lists. These people tended to be either tedious or scary or both. Randy always ended up dealing with the “both” subgroup, because Randy was the only Clerk Typist in the office who was not a lifer. It seemed clear that Randy, with his astronomy degree and his extensive knowledge of computers, would one day move on, whereas his coworkers did not harbor further ambitions. His larger sphere of interests, his somewhat broader concept of normalcy, was useful when certain patrons came into the office.

By the standards of many, Randy was himself a tedious, scary, obsessed character. He was not merely obsessed with science but also with fantasy role-playing games. The only way he could tolerate working at such a stupid job for a couple of years was that his off time was completely occupied with enacting fantasy scenarios of a depth and complexity that exercised all of the cranial circuitry that was so conspicuously going to waste in the ILL office. He was part of a group that would meet every Friday night and play until sometime on Sunday. The other stalwarts in the group were a computer science/music double major named Chester, and a history grad student named Avi.