Many years ago (well, 1998, to be exact) when the science of computer forensics was basically in it’s infancy, there already were rumors of various TLAs being able to read data that was overwritten on the hard drive. Some folks were telling of tunneling microscopes, and other high tech gizmos that could recover data up to 7 overwritions ago. I don’t know how true it is, however am inclined to believe that it is true. Now a days, products such as Encase can do wonders, and Linux based and occasionally open source tools are close behind commercial vendors. Forensics field turned into science, with an entire industry to support it – hardware write blockers, special court proceedings, expert witnesses, data recovery software, etc. One of these days…
This time I’ll just address a simple question: What media should one store the data on, if one expects that one would need to destroy the data on the media some time in the future, and adversary with great financial and technical resources would be interested in reconstructing the data?
For something like this, I’d recommend rewritable CDs and DVDs. Primary reason is ease of data disposal – if one has 30 seconds to get rid of incriminating evidence, all one really has to do is to drop a styrofoam cup half-full of water with a CD on it into microwave, and tell it to reheat.
While I don’t know about recent models of microwaves, older systems would generate a satisfying arcing and media destruction in about 10 seconds. Media will not melt to slug, however the data layer would be covered by a spider web of cracks, that would pretty much be rendered unusable. Here is an example. A google search for “microwave CD” should provide plenty more links to images.
Now, to a physicist in me this looks like a rather complete way of getting rid of unwanted data irrecoverably.
However, this is a reason why I suggested CD-RW and DVD-RW in the first place:
So my advice to dissidents world-wide – first erase the DVD-RW and CD-RWs, and then microwave them. After that, toss them out and don’t toss and turn while in bed 😛
Edit1: Note! When I talk about erasing CD-R or DVD-R, I mean about full erase, that takes ~15 minutes, NOT quick erase. Quick erase generally just zeros out first megabyte of data on disk, including TOC, so it seems like it’s a clean disk, yet all of the previously recorded data is still there!
Edit2: I wonder if the crystalline properties of the layer change from being melted and re-cooled during the erasure process. In other words, is it still possible to detect where data was based on the different structure of the “re-flowed” layer after erasure? Any material scientists around? 😛
That’s why I recommend microwaving of the disk, just to make reconstruction of the data just that much harder.