I was just catching up on best practices for securely erasing data from a Mac. At one point I remember reading:
For SSD drives it is no longer recommended to fully write ones/zeroes/random bits on the disk. Use encryption instead.
Now, I am thinking of two starting points:
- Your disk was not encrypted
- Your disk was encrypted, but you are not sure if the new owner had the key
In both cases giving the laptop to the new owner would not be secure, deleting everything beforehand is a good step (and in practice strong enough for me personally) but I am not sure if that is sufficient.
Now my question:
Suppose you have one of these two starting points, THEN you erase the drive normally and format it to be encrypted, are you then secure?
The 'threat' I was worried about, is that the new owner would be able to format it back to the old way (e.g. without encryption, or with a specific encryption key) and it might be possible to use classical data retrieval techniques.
Perhaps it does not work like this (or it depends on the hardware), but I am hoping to understand if encryption of a disk means its previous contents can also not be retrieved anymore.