[dm-crypt] (OT) Secure data wipe

Javier Juan Martínez Cabezón tazok.id0 at gmail.com
Sun Dec 9 13:26:26 CET 2012

Yes is a lot offtopic, but could be useful for dmcrypt-users

I don't know who has told you about the way of secure deleting a file
but he is too wrong.

When you delete something, you mark the physical blocks of the file as
"usable for later", that is, moves into unallocated space, that could
be allocated later. If you create a new file with the same name it
gets free blocks to suit their needs but this doesn't mean that it
will allocate the same physical blocks.

The only method I know filesystem independent to destroy data is
overwritting unallocated space several times with different patterns
(to avoid recovering with microscopy). You can do the same
overwritting allocated physical blocks of the file several times and
this is what wipe does at my knowledge.

I think the DoD published a paper about this you could check it.

On 09/12/12 12:20, jugree at lavabit.com wrote:
> Hello.
> How to securely delete data from a hard drive? Is it possible
> without physical destruction?
> How to work with sensitive data if you're using swap? Is it enough
> to run `swapoff', decrypt some data, encrypt it again, and run
> `swapon'?
> Is it possible to securely delete a single file? I've heard that
> you should create another file with the same name, write some data
> to it, and delete it.
> This is a popular topic, but it's really hard to find any proofs.
> Can you suggest any books or papers on the subject?
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