> Data Recovery Systems and other companies make a good living recovering
> data from computers that have been in fires, floods, and accidental
> erasures, and they are frequently hired by law enforcement agencies to
> recover from intentional erasures--even sophisticated ones. A single
> "bit" on a hard drive comprises thousands of flux changes, and each time
> it is written, the boundaries are a little different, and the intensities
> are a little different. The techniques are all very well known and well
> reported for decades. All you need is a reader that can produce a map
> of the flux intensities about 100 times finer than the read head itself,
> and good software will tell you what the last dozen or so written bits
> were at each location, and analyzing the positional offsets can tell
> you which bits were written at similar times.
>
I'm already thinking about countermeasures, and am wondering if this
isn't just a little bit hyped here. This idea works provided the disk is
spinning at a constant speed, but aren't most HD motor servo controlled,
so the velocity is always wandering back and forth??
Not that it matters very much. I realized long ago that the only secure
storage is in my head, and I don't have much that needs that kind of
security. Moderately sensitive stuff goes on floppies or gets
encrypted....
O---------------------------------O
| Hara Ra <harara@shamanics.com> |
| Box 8334 Santa Cruz, CA 95061 |
O---------------------------------O