[dm-crypt] Authenticated Encryption for dm-crypt

Ralf Ramsauer ralf at ramses-pyramidenbau.de
Tue May 21 15:58:13 CEST 2013

Arno, your objections are legitimate.Though I think that authenticity
would be a nice feature to dm-crypt.
And i also think, that it *could* be realisable.

Head movement is a real problem, but not for SSDs. Another solution
could be to outsource additional tag
data onto other harddrives. Also, not all tags need to be stored at the
same location. Another point:
if you would tag a 512 Byte sector with a 512 Byte tag then you could
store data and tags consecutively.
Dm-verity does almost the same, but it needs two different partitions to
store data and tags.
If those partitions are on the same drive you loose performence because
of the massive head movement.
But if you store tag and data on one partition consecutively in chunks
of 512 Byte it should be no problem
any more.


On 05/21/2013 09:24 AM, octane indice wrote:
> En réponse à Arno Wagner <arno at wagner.name> :
>> The additional space is not the problem. The problem is
>> keeping  data and additonal data consistent and keeping
>> head-movements  minimal. There is quite a bit of discussion
>> and literature around about these problems as this gets
>> proposed time and again. 
>> If I remember correctly, some people even tried with custom
>> disks  that had 540 byte sectors or something like that. All
>> efforts failed, this idea always dies as soon as practical
>> filesystem aspects come  into play. 
> Maybe it's off topic, but why we don't put integrity at
> filesystem level?
> If we mess something at ciphered level, we could detect
> it at filesystem level because it's really unlikely that somebody
> could break the ciphered level *and* keep filesystem integrity.
No, that's not off topic, it's a good thought. But if integrity would
get part of an "underlying layer" then it would be filesystem independent.
As far as i know only few filesystems support integrity.
> Thanks
> Envoyé avec Inmano, ma messagerie renversante et gratuite : http://www.inmano.com
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Ralf Ramsauer

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