[dm-crypt] Encrypt all partitions with dm-crypt

Arno Wagner arno at wagner.name
Fri Aug 24 17:14:39 CEST 2012


On Fri, Aug 24, 2012 at 04:40:28PM +0200, Heinz Diehl wrote:
> On 24.08.2012, Milan Broz wrote: 
> 
> > There is currently a lot of effort to ensure that /dev/urandom
> > cannot produce weak data even in extreme situations.
> 
> I'm more than happy that Intels hardware RNG isn't used as the only
> source for randomness on systems where it is available (as proposed by 
> Linus himself).
> 
> https://patchwork.kernel.org/patch/1161881/

I agree. I think Linux does not quite understand the issue here.
If some Intel chips are compromised, nothing but a very expensive
hardware analysis or a massive intelligence blunder would reveal
that, hence it is very, very unlikely for Intel (or any other
CPU maker) to get caught red-handed.

On the other hand, mixing in a reasonable amount of other 
randomness negates any attack possibilities via the HW RNG
and at the same time allows it to be used as high-quality
"stretching" material. For example, using 512 bits of
other entropy and stretch this to a few MB with the HW RNG 
would still be fine (if done right) even if the HW RNG is 
compromised.

The solurtion by Tso makes perfect sense cryptographically
and from a risk-management perspective. Never put all your
eggs in one basket unless there really is no other choice.

Arno

-- 
Arno Wagner,    Dr. sc. techn., Dipl. Inform.,   Email: arno at wagner.name 
GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
----
One of the painful things about our time is that those who feel certainty 
are stupid, and those with any imagination and understanding are filled 
with doubt and indecision. -- Bertrand Russell 


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