secure data erasing

["Wolfgang S. Rupprecht" at wsrcc.com]

Hi Alvin!

alvin at Mail.Linux-Consulting.com (Alvin Oga) writes:
> On Tue, 6 Dec 2005 Wolfgang S. Rupprecht at wsrcc.com wrote:
>> If you find a degausser strong enough to erase the disk data then you
>> will also be erasing the tracking track's information, the spares /
>> bad-block data,
> that'd be okay ...  one would hopefully lowlevel format a used disk
> before they use it
>> and perhaps the drive's second-stage firmware.
>
> that stuff should be in eeprom ?? magnetics should not erase it
> but uv will ..
> 	- if they used solid state flash instead .. that'd
> 	be another problem too as you say, strong magnetics might 
> 	screw up the disk controller firmware

There is vital data in tracks that are inaccessible to users and can't
be rebuilt by users.  Modern disks have "system tracks" on the outside
of the disk, slightly further out than track-0 where they keep the
defect lists and sometimes the second-stage firmware.  Erasing the
this second-stage firmware with a degausser will turn your disk into a
brick, just using more cumbersome methods than hitting it with a
hammer.

Tracking data will also be erased by any degausser that is strong
enough to erase the data.  Tracking info is either on a dedicated
surface that the user can never write to, or located between the disk
blocks as another sort of sector header.  Erasing either kind of
tracking data will also turn the disk into a brick and require a trip
to the factory for recreating it.

The only reference I could quickly find is this one.  (Search for
"4.1.2 Replace the Firmware".)

        http://www.actionfront.com/ts_whitepaper.asp

-wolfgang