data shredder

[Kent Borg]

Ray Leventhal wrote:
> 'Clear' calls for the systematic overwriting of every addressable sector 
> of a drive and is sufficient for eradication, bypassing most labs' 
> ability to recover data, even data recovery companies (I work for one).
>   

The word "clear" might suggest to some that writing all zeros is as good
as writing fancy random data. And it might well be--*if* you can
actually write all zeros. The problem is that disks (and OSs) are
constantly trying to find ways to squeeze in more capacity and speed.
The whole topic of shredding data is complicated by ways disks have
already gotten clever and don't do what you might expect.

Think about it: Writing 100 GB of zeros is *easy*, one might just make a
note of the intention of writing all those zeros and not really write
them, at least not right away. (All those zeros upon zeros, so much
work, I'll do it later...) Random data is better because the operating
system and disk have no choice but to actually write it. It can't be
described, so it has to be written. I don't know of any disk that cheats
in writing zeros, the OS well might. I do know that with quality random
data there is no way to cheat this way, it has to be recorded.


-kb