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A comment on How secure is merely TRIMing all of a SSD's blocks?.

Re:How secure is merely TRIMing all of a SSD's blocks? by fdeee on Wednesday March 08, 2023 @09:51AM (#35069622)
This is why you always want to use full disk encryption (FDE). Then it doesn't really matter whether some blocks are recoverable after TRIM. It also doesn't really matter whether the Secure Delete function works. It also doesn't matter whether the very expensive security-buzzword-compliant secure deletion snakeoil software really works.

Also, TRIM is only possible with drives that are still in working order. Very often you can't TRIM or secure delete a drive that is defective and returned by RMA. In that case you either need a very expensive no-disk-return support contract. Or you just use FDE.

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Re:How secure is merely TRIMing all of a SSD's blocks? by tjoff on Wednesday March 08, 2023 @10:43AM (#35070380)
TRIM and FDE isn't perfect though as it leaks information about what parts have been written etc.

And if you turn off TRIM you get a massive performance decrease.

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Re:How secure is merely TRIMing all of a SSD's blocks? by vorticalbox on Wednesday March 08, 2023 @11:03AM (#35070661)
Why would someone turn off TRIM?
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Re:How secure is merely TRIMing all of a SSD's blocks? by danuker on Wednesday March 08, 2023 @11:06AM (#35070708)
To mask the extent to which a drive has been filled, or to figure out how many blocks have been deleted since the last TRIM. I have yet to discover any use for this minuscule "leak", even when considering nation-state adversaries. It's much easier to find other channels to leak data through.

The disadvantages are massive, such as significant slowdown when the drive gets filled. Yet the creators of dm-crypt are paranoid about enabling it by default:

https://wiki.archlinux.org/title/Dm-crypt/Specialties#Discar...

I couldn't understand ref 3: https://web.archive.org/web/20160709174950/http://www.saout....

Ref 4: "you have an information leak where filesystem-discarded blocks (by TRIM) can be identified by an attacker with low effort"

https://web.archive.org/web/20160709183108/http://www.saout....

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