[dm-crypt] nuke password to delete luks header

Arno Wagner arno at wagner.name
Thu Jan 16 12:50:41 CET 2014


On Wed, Jan 15, 2014 at 20:36:53 CET, Milan Broz wrote:
> On 01/14/2014 08:22 PM, .. ink .. wrote:
> >  
> > 
> >     While I have not looked at it for some time, the last time I looked,
> >     FAT did a create-at-end Strategy. This way the data "wanders" over
> >     the partition towrds the end. ext2/3/4 will create files all over
> >     the disk in the first place.
> > 
> > 
> > My own tests have shown that with fat fs,files are not added randomly
> > all over the disk and are added sequentially.Meaning,if the volume is
> > used normally without exceeding a certain amount of disk space,the
> > rest of the disk will remain untouched.
> 
> The whole hidden disk idea in TrueCrypt is based on this assumption,
> and it works.
> 
> >From "Filesystem Forensic Analysis" by Brian Carrier
> (ISBN 978-0-321-26817-4), page 224, FAT allocation algorithms:
> 
> "The OS gets to choose which allocation algorithm it uses when it allocates
> the clusters. I tested Windows98 and XP, and it appeared that a next available
> algorithm was being used in both. The next available algorithm searches for
> the first available cluster starting from the previously allocated cluster."
> 
> I think this will be very similar for other FAT implementations.
> 
> Milan

Indeed. However if you delete files and add files over a time,
the allocated area has a tendency to wander towards the 
end. If you just create and extend, all will be at the
start in FAT, but that does not represent normal operation.

Because of this. TrueCrypt does protect the hidden container
when it is open or "protected". (It cannot protect it when it 
is not.) The effects of this protection can be visible.
See here:

http://www.truecrypt.org/docs/hidden-volume-protection

Arno
-- 
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
----
There are two ways of constructing a software design: One way is to make it
so simple that there are obviously no deficiencies, and the other way is to
make it so complicated that there are no obvious deficiencies. The first
method is far more difficult.  --Tony Hoare


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