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In a scenario where a person wants to give away their device (magnetic disk included), leaving the disk usable for the receiver, how might that person go about destroying ALL data (except firmware) on the disk only via a digital medium? Encryption is not an answer, because the disk needs to be used by the receiver. Assume no encryption was used before.

  • Is one zero pass enough?
  • Is one random pass enough?
  • If not, then what method should be used?
  • Can the same method be effective for an electronic disk?

under the assumption that the adversary is theoretically able to exercise any technique to recover the data

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    There are various options shown in How can I reliably erase all information on a hard drive? which do not destroy the drive itself.
    – Steffen Ullrich
    Commented Oct 18, 2023 at 5:29
  • @SteffenUllrich DBAN says no gaurantee of full data removal (dban.org) and does not erase all data (security.stackexchange.com/a/5843/288820). ATA secure erase may not be supported, or may not even securely erase any data for that matter since its not documented without any guarantee of actually being implemented. The rest of the solutions are thermite and encryption.
    – Anm
    Commented Oct 18, 2023 at 18:23
  • Realistically, one zero pass is enough. AFAIK nobody has ever demonstrated the ability to recover data from a drive - it's only theoretical. To defeat theoretical attacks as well, do a few random passes.
    – user20574
    Commented Jul 14 at 18:35

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To an extent, you have to choose which option is best for you given your individual situation such as how important it is that the information does not fall into someone else's hands and whether you are anticipating that any skilled person will be trying to get at it.

The most secure option would be not to give away the hard drive at all and, perhaps, supply a new one with the device instead. You can retain or destroy the existing drive.

Barring that, the current guidelines from NIST are to use the drive's own secure erase method, which in modern drives should be accessible as a command that the host can run over the SATA or SCSI connection. Previous assumptions underpinning erase methods that relied on writing zeroes or random data did not take into account newer surface mapping technologies which may be in use in newer drives in which at some times in their life not all of the surface may be mapped to a logical sector accessible from the host computer.

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If you want to be 100% sure that nothing can be read, remove the hard drive and replace it with a brand new one. If you take into account the risk, and payment for your time, this is likely also the cheapest solution, and you get a new drive with better life expectancy, and likely higher capacity and faster speed.

In the future, start full disk encryption on the drive at the earliest possible time. Anything encrypted can be destroyed by just throwing away the encryption keys, and if an attacker finds fragments of a fresh install of Linux, Windows of MacOS on your drive, that is public knowledge and nobody cares.

Bits of data could survive anything you do, so if there is any unencrypted data on the drive, sn attacker might be able to read it. There are often commands that should erase everything, but with enough paranoia you wouldn’t rely on that.

So destroy the drive, or throw away encryption keys.

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