Andreas Dilger wrote:
On Oct 31, 2006 15:14 -0500, Nikolai Joukov wrote:
1. One of the patches performs N overwrites with configurable patterns
(can comply with NIST and NISPOM standards). Because of the transaction
compaction we had to separately add overwriting as separate transactions.
Fortunately, the whole procedure is still atomic due to the orphan list.
The problem that we have right now is per-file syncing of dirty data
buffers between overwrites. We sync the whole device at the moment.
Did anyone discuss doing this with crypto instead of actually overwriting
the whole file? It would be pretty easy to store a per-file crypto key
in each inode as an EA, then to "delete" the file all that would be
needed would be to erase the key in a secure matter (which is a great
deal easier because inodes don't move around on disk).
This is an interesting idea with some annoying implementation details.
For example, we would still need to "shred" that data block used to
store the EA in order to prevent key recovery.
Also interesting to note that various people are putting encryption into
various offload parts which could be useful in this context.
The drawback is there is a runtime overhead to encrypt/decrypt the file
data, but honestly, if people care about secure deletion don't they also
care about security of the undeleted data also? By having an (unknown
to the user) per-file crypto key then if the file is deleted the user
can also plausibly deny the ability to recover the file data even if
they are forced to surrender their key.
Cheers, Andreas
--
I think that having the data encrypted on disk is a generically useful
feature, but in this case it might not count for much since the key is
stored right next to the data in that EA...
ric
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