Re: [dm-crypt] LUKS and LVM

[Arno Wagner <arno@wagner.name>]

On Sat, Feb 19, 2011 at 03:39:07AM +1100, Eric Bauman wrote:
> Hi,
>
> When using LVM with LUKS, is it more secure to:
> 1 - have a single container containing LVM, or
> 2 - LVM containing multiple containers?

Technologically, security is the same. Reliability is
lower on (2) as you have more headers you can damage and
lose. 

As with RAID, encryption should sit on top, not somewhere 
in between.

With regard to interface and usability (allways _very_ important
in security!), (1) is a lot better, since (2) requires you
to unlock multiple containers and keep multiple passowrds or
enter the same password multiple times.

That makes option (1) the thing to do and option (2) 
a curiosity that violates a number of principles, among them
simplicity, crypto as last/highest layer below the filesystem,
leas amount of credentials, least exposure of the credentials. 

> I typically randomise my block device before creating a LUKS container  
> on it.  Option 2 would seem to reduce the effectiveness of this because  
> LVM will give clues to where real data might be.

I don't follow. That encrypted data is present is obvious from
the LUKS header. What is in the container(s) is as opaque in
(1) as it is in (2), given that cryptographically strong
randomness is used for the overwrite (I use plain dm-crypt
with a random password and overwrite with conventional,
mt19997-generated randomness).

Arno

-- 
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno@wagner.name 
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