Martin J. Bligh wrote:
> > Some success is rumored to be able to be achieved by sampling the
> > normal signal, and then subtracting the "expected signal assuming the
> > current sequence of bits that was read". That way you might be able to
> > recover the information that peeks out from below.
>
> It's more than rumour - I've seen this done. Dr Solomon's (whatever
> they called their data recovery branch), early 1990's, England.
> Maybe it was easier on older hardware like the MFM / RLL disks,
> and certainly easier to piece together fragmented data with earlier
> file formats.
Maybe the difference is in "what's the goal". For datarecovery we
don't really care about just a couple of bits here and there: We want
to piece together the whole thing.
If you don't want a piece of your data getting into wrong hands
however, you'd better be safe than sorry.
So I (and the Ibas guy) are talking about practical recovery of a
useful amount of data, while even a couple of bits is in theory
dangerous if you really want it "gone".
> I believe the point of overwriting 3 times (or whatever) is to reduce
> the "subtracted difference" to noise levels where it's no longer useful.
Right.
Roger.
-- ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 ** *-- BitWizard writes Linux device drivers for any device you may have! --* * There are old pilots, and there are bold pilots. * There are also old, bald pilots. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sat Feb 23 2002 - 21:00:21 EST