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Do we need to wipe data from SSDs too?

When I sell/give/trash my used (mechanical) HDDs I securely wipe them with sdelete:

sdelete -p 4 -c e:

where "e" is the drive letter. Do I need to do the same thing with SSDs or just zeroing the free space is enough?


What do you use to permanently wipe your data on your HDDs/SSDs?

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You only need to zero the drive once for hdds, no point it wasting time doing multiple passes.


Most ssds support a secure earse command, so it will wipe the drive in a few seconds. Or do a zero wipe if it doesn't support it.

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  • 2 weeks later...

This is partially wrong.


To clean data from a conventional HDD you have the following solutions:

  • Wipe the index (e.g. diskpart clean). This is really easy to recover from. This is what undelete apps take advantage of.
  • Overwrite the whole disk. This is OK for most normal users. If you have access to a very sensitive hardware, the kind only governments have access to, then you may be able to recover some of the data. Think of it as erasing pencil written notes and writing new text. A shadow still remains.
  • Overwrite the disk several times with varying patterns, defeating even the most capable attackers. This is what the department of defence requires and this is what I usually do.

So yes zeroing a HDD is OK for most users but I'm more careful (and maybe more paranoid) than most.


So I did some research on wiping SSDs and "conventional" wiping (like sdelete) are useless and this is what I found:


SSDs work differently. They have a number of blocks which are grouped. Writes can only happen to a group. Think of it as a book where you can only write to a page. If you want to add a sentence then the SSD's controller will read the whole page and write a new page (with the extra sentence) to a different location. It will then mark the old page as empty and assign the old page number to the new page.


This means that there is no direct mapping between what the OS sees are sectors (pages) and what is on disk.


You could fill the whole disk with a new file (say one containing only zero's) and the reserve space would not be touched. So there is still recoverable data. You could do this 7 times and still have the same data recoverable.


The good news is that SSDs often ship with on disk encryption. Throw away the encryption key and the data is worthless.


Even better news is that this data encryption can always be used. Even when you did not explicitly enable encryption. In that case the disk still writes encrypted data with a key stored somewhere on the SSD. Tell it to throw away this key and replace it with a new one and you are done. It is fast and secure.


There is even a command to do this (ATA secure erase).


So (real) secure wiping of SSD is possible but is trickier (and like you said you could take advantage of the firmware secure erase of your SSD but that depend on manufacturer).


Source #1 Source #2

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