[ale] destroy old drives

[Jim Kinney]

Really? The only groups that want the data _that_bad_ have subpeonas.
The other groups that can read around the holes already have your data.
All you're really trying to do is make sure the drive is not usable for
the basic computer bad guy.
As areal densities have increased exponentially from 10M drives to 10TB
drives in the same space, the size, and thus strength, of the magnetic
domains has decreased exponentially. So the bleed over has also
decreased. The transition to vertical magnetic domains  has made the
crosstalk to the platter substrate nearly zero. Add in the platters are
simply not magnetizable at all and there's basically no data bits
anywhere possible except on the platter surface.
bad ascii art:
N-S   bit domain on surface___    platter surface
S-N   induced bit domain subsurface
  N  S   |    |        2 adjacent vertical domains 1
0  S   N____       platter surface
  N - S     Induced data bits are just wrong! Now mix in the 2D spacial
arrangement and which subsurface pole pairs with which other? No
monopoles in magnetic media (yet :-)


On Thu, 2019-04-11 at 13:31 -0700, Alex Carver via Ale wrote:
> If someone really wants your data, holes don't matter.  The rest of
> theplatter is still intact in that case and can have the data
> extracted.
> There's also no guarantee that Dban can write enough to be sure that
> themagnetic domains are fully randomized deep in the platter.  The
> longerdata sits statically on the disk  the more opportunity for the
> surfacedomain to imprint on deeper domains (this is actually a
> problem withmagnetic tape, magnetic data can print through from one
> layer of tape tothe next layer when it's wound on the spindle).
> A serious entity can perform a deep level scan of the platter
> andretrieve the low level signal under the surface domains and see
> previousdata.  The drive head typically isn't powerful enough to
> write thatdeeply because it has to keep the tracks narrow.
> On 2019-04-11 12:13, Steve Litt via Ale wrote:
> > On Wed, 10 Apr 2019 22:11:42 -0400Jim Kinney <jim.kinney at gmail.com>
> > wrote:
> > > Dban advantage: it can be done across hundreds or thousands of
> > > drivesbefore larcenous third party "shredders" physically touch
> > > the drives.
> > 
> > That's a good point.
> > Doesn't dban take an hour or more? How many drives can I do with
> > onecomputer? How long would it take to test whether each is really
> > blank?
> > What might be nice with 1000 drives to do is dban followed by
> > drilling3 holes in each drive. I'd say each drive would take 1
> > minute for 3holes, so it's about 2 days for one employee to drill
> > the holes. Or,perhaps, one employee could both dban and drill the
> > holes, drilling theholes while the next batch is dbanning.
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-- 
James P. Kinney III

Every time you stop a school, you will have to build a jail. What you
gain at one end you lose at the other. It's like feeding a dog on his
own tail. It won't fatten the dog.
- Speech 11/23/1900 Mark Twain

http://heretothereideas.blogspot.com/

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