Читать книгу Mercy - David Kessler - Страница 30

David Sedaka had to pull strings to leapfrog the queue for the scanning tunneling microscope at the Berkeley lab. But he was an old hand at university politics and he knew which strings to pull. There had been a bit of grumbling about this. One aggrieved PhD student pointed out that Sedaka was a theoretical physicist not an experimental one. Theoretical and experimental physicists regarded each other with mutual disdain: the thinkers and the stinkers was the way the former group liked to describe it.

David was a member of the Joint Particle Theory Group at Berkeley, where he was developing exotic theories on anti-matter and gravity. He had recently published a paper called ‘Unilateral anti-matter decay in an accelerated expansion universe,’ in which he had advanced the revolutionary prediction that anti-matter possessed neither gravity nor anti-gravity but was subject to the gravity of matter and could decay into photons on its own without needing to collide with matter.

In appearance, he was the epitome of a nerd: slightly short, wearing glasses—even though he could afford laser surgery—and with dark hair so curly that it was rumored that he used hot rollers and foil to keep it that way.

He had removed the hard disk from the computer and had carefully separated the platters, removing them from the spindle. Then he had placed the first platter in the chamber under the head of the scanning tunneling microscope.

There was an old and ongoing debate in the computer industry as to whether it was possible to recover overwritten data from a computer hard disk with a scanning tunneling microscope. One of the more common scaremongering rumors was that the data was never deleted completely because the magnetization that overwrote it ‘was not in exactly the same place on the disk as the original bit’ or because the ‘magnetization levels varied.’

There were even rumors that the National Security Agency was routinely recovering erased data in this way. In fact, a number of computer companies had made an awful lot of money, at the expense of gullible and paranoid computer users, by selling them products that promised to overwrite their deleted data with ‘multiple passes’ and offering them ‘military level’ security.

The reality was that it was practically impossible to recover overwritten data from the newer computers, or data that had been overwritten with more than one pass. With older computers, where each ‘bit’ was spread out more than on modern computers, you might be able to recover data that was overwritten with a single pass. But that was about it.

The good news for David Sedaka was that this computer was about ten years old and the hard disk was only five gigabytes and so the bits were spread out over a larger area. The other piece of good news was that the data had been wiped with only one pass, as far as David could determine. That meant that he could recover it—in theory.

The trouble was, there was so much of it. Where to begin? The reality was that data recovery was as much an art as a science. You could start off by looking at the directory and the tables that allocate file space, but they too may have been changed or overwritten. And also, a file that was created and then changed a few times, might be ‘fragmented.’ In other words, different parts of it might be stored on different parts of the disk.

In practice, what this meant was that even if part of the task of recovering data could be automated, a lot of it was a hunt-and-find exercise. And that had to be done painstakingly, using subjective judgement.

David knew that it was going to be a long day.

But as he looked at some of the data he had recovered, he felt as if he might have found something interesting already. He decided to tell his father. The trouble was, he’d had to leave his cell phone outside the lab in case it interfered with the sensitive electronic apparatus. Now he went to get it—and he was walking briskly.