[dm-crypt] SSDs & flash... and secure keyslot erase

Arno Wagner arno at wagner.name
Fri Aug 24 17:54:05 CEST 2012


On Fri, Aug 24, 2012 at 05:23:05PM +0200, Thomas B?chler wrote:
> Am 24.08.2012 17:06, schrieb Milan Broz:
[...]
> > But there is no perfect solution.
> 
> Interesting write-up. If you are really paranoid, it seems you must back
> up all data, perform ATA security erase and put the data back on the
> disk (and then perform ATA security erase on the backup).

That may not be enough, see Section 3.2 of 

  http://cseweb.ucsd.edu/users/swanson/papers/Fast2011SecErase.pdf

Unfortunately, no manufacturer names given.

My current take is that the only reliable thing is to have LUKS
key-slots individually larger than the spare area and then overwrite
all free space with random data after a key-slot change. That way
the SSD would be unable to hold an old key-slot. For a 240G
SSD that may mean key-slots > 16GB each. Also, you cannot be
sure how much Flash capacity an SSD actually has without 
opening it. 

Arno
-- 
Arno Wagner,    Dr. sc. techn., Dipl. Inform.,   Email: arno at wagner.name 
GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
----
One of the painful things about our time is that those who feel certainty 
are stupid, and those with any imagination and understanding are filled 
with doubt and indecision. -- Bertrand Russell 


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