[dm-crypt] Prepare SSD for encrypted linux install
arno at wagner.name
Thu Nov 9 11:55:26 CET 2017
On Thu, Nov 09, 2017 at 01:34:38 CET, Robert Nichols wrote:
> On 11/08/2017 11:36 AM, Merlin Büge wrote:
> >Hello all,
> >I thought of TRIMing the SSD via 'blkdiscard' instead of using
> >'ATA secure erase' after putting random data on it (twice, see ),
> >but that should make no difference, since the SSD will most probably
> >report all zeros for TRIMed sectors. Either way, the flash chips will
> >contain all random data ...
> No, they won't. They will all be cleared. The whole point of TRIM or
> blkdiscard is to allow the controller to clear the blocks of flash cells
> so that they will be immediately available for writing when needed.
> Writing random data to the flash cells and then immediately clearing them
> is fairly pointless. All it does is mask any residue a cleared cell might
> have of the last data it contained. People who need that level of
> security don't ask about it here.
And that is just it: To get any security benefit, the random
data must be still there on a read-back.
Hence the procedure is exactly the same as for a HDD:
Write random data to disk and leave it there, no "secure" erase,
Arno Wagner, Dr. sc. techn., Dipl. Inform., Email: arno at wagner.name
GnuPG: ID: CB5D9718 FP: 12D6 C03B 1B30 33BB 13CF B774 E35C 5FA1 CB5D 9718
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