A New Technique to Quickly Erase Hard Drives

RockDoctor writes "Stories about 'wiped' hard drives appearing on eBay (and other channels) and being stuffed with personably-identifiable data are legion; rarer are spy planes having to land on enemy territory, but it happened in 2001 to a US spy plane over an un-declared enemy (China, and that's a topic in itself). Dark Reading reports the development of a technique to securely wipe a hard drive in seconds, and which is safe for flying. (The safe for flying criterion rules out things like fun with packing the drives in thermite. Also thermiting the drives may not erase the platters to the standard required, which is moderately interesting itself."

Comments

Re:New technique?

[Anonymous Coward]

Aluminum can act oddly in the presens of magnetic feels. see this link for information on how it might be able to bens platters.

Degaussing Technique

[Kadin2048]

It depends on the type of magnetic field used and how it's applied. If you just put a drive platter (or magnetic tape, or floppy disk) into a static magnetic field, you might bend the platters or disturb the media, without actually destroying the data itself.

I'm most familiar with procedures for erasing magnetic tape than hard drives. The conventional method that I was always taught was to put the tape very close to source of a strong alternating electromagnetic field (so easy way is to just have a small coil hooked up to the wall socket). Then -- and this is the important part -- you move the media away from the coil, while the coil is still operating. So it goes from the near field out to where the field is basically no longer having any effect, but without the field going off. The result is that different layers of the media end up with different magnetic fields: as the media moves further and further away from the coil, the field is no longer able to saturate the center of it, so it's left with a certain state. The material just next to that gets left with a different state, because by then the coil's field has changed directions. So you end up with different magnetic states (polarizations) being written to the media both in the depth direction, and lengthwise (as you pull the tape along past the coil). I guess the thickness of the "stripes" would depend on characteristics of the media, plus the frequency of the coil's field and the speed with which the media was moving past it. I just always moved it slowly away at a few inches per second, personally.

Just holding the media next to a magnet, even an AC electromagnet, and turning the magnet on and off, doesn't erase the data as effectively as moving the media from close to the coil to far away. Or at least that's what I was always told. I suppose if you had a circuit that powered down the coil slowly, it would have much the same effect.

Re:New technique?

[tomhudson]

Poster wrote:

Powerful magnets do rather little to wipe hard drives

If you had read the article , you would have found that they ARE using magnets to wipe the hard drives. FTFA:

The researchers concluded that permanent magnets are the best solution.

Wrong

[bwd]

The paper you are quoting from is horribly out of date and very little of that applies to modern drives. This post does a good job of explaining Gutmann's more recent comments.

Plus, some people have called into question a lot of the sources used in that paper. It seems that some of the sources don't even exist.

Re:Joe does it

[gweihir]

Now if it's just some random joe with an undelete program he got for $19.99 at the local shop then a single pass is often enough, more sophisticated software only tools might get past a few,

Let me correct that: There is no way in this universe software can recover anything from a disk overwritten once with zeros. It is fundamentally impossible.

Also to Peter Gutman's paper: It is still relevant, but the technology has changed. Gutman is very relevant for things like floppy disks (that can hold 100MB, but are used only for 2MB). But todays HDDs go so close to the limits of the amount of data that can be physically present on a disk (as dictated by S/N ratio and surface area), that even a single overwrite with random data may be completely unrecoverable with any technology. Nobody really knows.

Re:First question:

[Jackmn]

Encryption can be broken. Always.

One time pads cannot be broken.

Strong encryption algorithms with suitably long key lengths will take longer than the lifetime of the sun to crack (barring the possibility of quantum computing taking off).

Re:New technique?

[Cromac]

According to the article, yes it is more effective than a hammer. It said that techniques such as crushing the drive still allowed the data to be recovered, given enough time.

Other methods, including burning disks with heat-generating thermite, crushing drives in presses, chemically destroying the media or frying them with microwaves all proved susceptible to sensitive, patient, recovery efforts.

Re:the product is stupid

[Anonymous Coward]

You might be glossing over the flight critical requirement though. "Keep the key in RAM" is likely not something that would be allowed.. or incredibly hard to get certified. Would have to prove (which is harder than just showing) that while in flight, there was no way the key could get lost, or changed, or ... such that the software could get locked down in flight. I don't think that it would be impossible, just that the hoops you might have to go through may make other options more attractive.

I work on UAV's, so we have to care about this a lot.

Check out some of the standards:
DO-178B
Or STANAG 4044, but I don't have a good link.

Not a spy plane!

[Bowling Moses]

The US aircraft alluded to was a US Navy EP-3E Aries II, a slow four-engined turboprop plane based on a passenger airliner. It's a surveillance aircraft, not a spy plane. It's out in the open, in international airspace (usually), and a modern military will immediately pick up on where it is and what it's doing. It's completely dependent on international treaties to not get shot down by whoever it's checking out. A SR-71 or U-2 on a secrete high-altitude flight over a hostile nation it isn't.

Interesting stuff

[TheSpoom]

I have commonly heard it said that overwritten data can be recovered, so I went Googling for a rebuttal to this argument. Turns out, you appear to be right! Recovering of overwritten data is largely a myth. /me continues to use good ole' shred.