[Cryptography] LUKS on ATA versus on SSD

[John Levine]

It appears that Jon Callas <jon at callas.org> said:
>
>> On Dec 31, 2025, at 22:57, Douglas Lucas <dal at riseup.net> wrote:
>> -- because of how Turing machines / Godel numbering work, basically?
>
>Think of it slightly differently -- you're right but over-complexifying it. ...

To loop back around, modern disks present themselves to the computer as a list
of fixed sized blocks numbered from 0 to N. It's not Gödel numbering, it's just
a one-dimensional array. The block size used to be 512 bytes, now usually 4K
bytes. There's all sorts of other stuff going on underneath but it's generally
hidden from the computer unless it uses maintenance features.

When you read block N, you get back whatever was previously written to block N.
When you write block N, from your point of view the new contents replace the
old, but underneath, who knows. It might physically overwrite the old contents,
it might put it somewhere else for load levelling or error recovery.

I think a better security model is as a long stream of write-once blocks where
the blocks that are no longer logicially accessible might still be accessible to
an attacker through a back door.

R's,
John

Useless detail: Gödel lived down the street from my high school piano teacher.