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

First question:

[fluch]

Why wasn't the content of the harddrive encrypted?

Re:First question:

[gweihir]

It probably was. Encryption can be broken. Always. Doesn't matter how strong.

Heard often, that is an urban myth and nonsense. There is proven secure encryption that is impossible to break, unless the assumption that you can generate secure (i.e. random) keys and some other very simple ones are wrong. ElGamal has this property. Even for less secure ciphers, the statement is untrue. Sure, a single cipher may have weaknesses that may allow a break with high (and often prohibitive) effort. Just use two different ciphers with independen keys and the problem becomes exponentially more difficult since you now need to find a joint vulnerability.

Of course there is a lot of bad encryption on the market, like home-brewed, not peer-reviewed ciphers. Ciphers are also often used in an insecure way, see, e.g., the very good ECB example here: Wikipedia

But the basic problem can be solved. There is just a lot of ignorance.

Re:First question:

[dhasenan]

At the present level of computing technology, the expression "billions of years" pales in comparison to the length of time required to brute force a 4096-bit key.

Given Moore's law, and assuming it holds beyond physical limits, the expression "billions of years" accurately describes the length of time required to brute force a 4096-bit key.

Given the possibility of quantum computing, the only thing you can do is use one-time pads for all your needs, provided you need these things to stay secret for more than the 50-100 years required to develop quantum codebreaking systems.

Now, that solution is quite feasible, but time-consuming. Here's how you'd do it:
1. Have a secure [D]RNG fill a hard drive to capacity. Copy that to the plane's hard drive.
2. Have a filesystem that writes raw data to the disk--you only want one file containing all data that's collected, and that should be append-only.
3. Instead of simply writing data, XOR the block you're writing with the one that's currently on disk.
4. Once you're back on base, another XOR gets your information back.

Why not use flash memory?

[Richard_J_N]

Wouldn't it be easier to use a flash memory chip? It's unlikely that more than a few GB would be needed. And destroying a flash chip is much easier.
Or, just encrypt the data with the key in RAM. (Linux can already do this with swap - it's completely transparent to the user, and the key only lasts as long as the system remains running).

Re:Joe does it

[Anonymous Coward]

That is mostly urban legend. There is a theoretical possibility that overwritten data could be reconstructed, even several layers "deep", but in practice there is no commercially available service capable of that stunt. If you know of one, name it (with references that they can do it). If they could do it, they would have to have technology available which could instantly multiply the space on these platters. It's not just a matter of having a reader with twice as good a SNR as a standard RW head. The writing harddisk doesn't just add signal, it also adds noise. The SNR on the platter will be barely good enough to read the signal of the last write. Otherwise the harddisk manufacturer could have made a bigger harddisk at the same price. The economics of the situation make recovering a previous write unlikely. The real problem with deletion by overwriting data is that it is really slow. It takes hours per disk.

Instead of worrying about residual magnetism which can at best be detected by government agencies with extreme funding, people should simply never write unencrypted confidential information anywhere. This also protects you in cases where you didn't schedule the removal of a harddisk, i.e. theft.

Sounds fishy to me

[gweihir]

Degaussers are nothing new. But there is no need to use them. Encryption does the trick as well. Just erase the key securely and you are done. If the device that the disk is installed in does not support encryption, then develop a module that sits between disk and device and encrypt on that. Attach a switch that triggers key erasure.

There is a second problem with degaussers: You have to physically remove the disks from their housing. That may take more than minutes.

And there is a third problem with degaussers: You have to very carefully check they work with each device they are to be used on. For example, older degaussers do fine for older disks, but are completely useless for modern ones.

And a 4th problem: Degaussers do not work at all for solid-state disks. Since they are not that uncommon in military application and actually may look the same, that seems to be a serious problem. One that encryption does not have.

I see one advantage for the permanent-magnet solution in military application: It works without power. But if you use the encryption-in-the-cable approach I described above, you can keep the key in a battery-buffered memory chip and erase that securely using the power of the battery (not quite as simple as it sounds, but it is possible to do). All in all, this mainly seems to be a scheme to sell the military something expensive.

China??

[nephridium]

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)

What's with all this hate mongering against China? Why was this totally OT snippet even up there anyway? To keep us reminded that there are "bad guys" out there and when we think about harddisks we also should be completely aware that we should be afraid, very afraid of an "undeclared" enemy?

China may have different attitudes and morals standards than the US, but they are doing many things right as well; more than western media tends to portray (e.g. according to the CIA world factbook China has a lower percentage of citizens suffering from poverty than the richest country in the world (namely the US)). I don't want to whitewash anything, but reading things like "undeclared enemy" in a tech article on an international website just pisses me off.