[dm-crypt] [RFC] dm-thin: Random block placement strategy?
eternaleye+usenet at gmail.com
Thu Jul 19 23:49:51 CEST 2012
This may be insufficiently useful to justify implementing, but I thought it
was an interesting concept.
One of the current issues with dm-crypt and discard is that enabling it can
leak information about the filesystem and usage patterns of the disk.
If a dm-thin device with a random block placement strategy is layered on top
of dm-crypt however, this could solve some of the issues involved and
partially mitigate others.
Such a random block placement strategy would heavily disguise any layout
patterns that could be used to identify the filesystem, most likely to the
point of being completely unrecognizable.
Issues arising from discarded blocks being nonzero are avoided by default
due to dm-thin pre-zeroing allocations (unless skip_block_zeroing is
However, some issues would still be present:
While the *distribution* of unused sectors would be concealed, their
existence and how many there are would still be detectable.
In addition, the issues with trim and a hidden device are still present.
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