On Mon, Sep 19, 2011 at 12:21:19PM -0400, Lee Winter wrote:
> On Mon, Sep 19, 2011 at 10:27 AM, Aaron Toponce <firstname.lastname@example.org
> > Have anything to back that up? If you're using drives that used the old MFMShow me otherwise.
> > or RLL encoding schemes, and had massive space for bits per linear inch,
> > then sure, but on today's drives, with perpindicular encoding, and the
> > extremely dense bit capacity, going more than once is silly.
> That conclusion is not valid.
FUD. Prove it. Show something that backs up your claim, because logic is
> All such analysis is sensitive to the value of the data. If you are
> going up against a serious adversary, colloquially known as "National
> Technical Means", then no amount of overwriting is secure.
Nope. On older drives, there was a "jitter" that caused the bit to not be
> If you are going up against an ordinary thief of the machine or drive,
> then a single overwrite is sufficient. In fact there is no need to
> overwrite the entire drive when the meta-data of directories, inodes,
> journals, etc. is a small fraction of the entire drive.
> I perform this service for commercial recyclers. In addition to
> scrubbing techniques, some need to damage the drive by rendering it
> non-functional (with a hammer or a drill). Some need to destroy the
> drive, usually by shredding. Some need to destroy the recording
> medium, for which incineration tends to be the least expensive.
> For high security situations a combination of scrubbing and physical
> measures are recommended. For example, unscrubbed media that has been
> finely shredded can still offer recoverable data because the high
> density of the recording means that a very small shred may contain
> many intact sectors of data.
written in exactly the same spot. So, overwritting by only a single pass,
left some of that jitter behind. Using a magnetic microscope, you could
"view" the jitter, as will as the current data, and determine what the
overwritten data was. Thus, the Gutmann Method.
> >> 'shred' does delete data several times. We hardly are able to recover
> >> data that one time really was deleted at home, but CSI is able to do
> >> this
> > 
> >> and I'm not talking about the trash that is produced by Jerry
> >> Bruckheimer. There e.g. are real methods with lasers that make it
> >> possible to recover magnetic data from sledgehammer deformed HDDs and
> >> even a private person legally just need to pay some k of Euros to a
> >> company and can benefit from those methods. OTOH nobody is able to
> >> factorise primes, it would take 20 or 30 years to crack openPGP with a
> >> super computer, but if there should be delicate data on your HDDs, that
> >> isn't encrypted, note, it just takes some seconds to open the door of
> >> your flat and to get your HDD that's still in use.
> > You may want to read this, as well as the references the article links to:
> > http://goo.gl/5QG4U
> > Claiming that you can recover data after a single pass of zeros on today's
> > spinning platters is urban legend.
> Consider that those organizations able to recover after a single pass
> with known mask pattern have a negative incentive to advertise their
Because I only have so many drive bays, and they get used for much more
> One pass scrubbing, even with a variable mask pattern driven by a TRNG
> rather than a PRNG, is ineffective because the write activity hands
> the adversary a complete copy of the mask pattern. A second pass to
> obscure the mask pattern is strongly recommended.
> > I guess if you like wasting your time,
> > go for it. I've got better things to do than do several passes on a 2TB
> > SATA disk, running at 30MBps, and I can sleep at night knowing that no one
> > will get access to the data.
> Why do you care how long it takes? Stick the drive in in a spare,
> low-end machine and let it hum for as long as it takes.
important things than wasting time erasing magic pixie dust.
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