[dm-crypt] [Feature request] Support for "raw" key slots

[dm-crypt] [Feature request] Support for "raw" key slots

[Thomas Bächler]

The iterated hashing process used in LUKS' key slots is useful for 
(potentially weak) passphrases. However, it is useless if the key slot 
is locked with a cryptographically strong key file (like a file created 
from /dev/random).

Therefore I propose the addition of a "raw key slot" feature to LUKS, 
where a key that has the exact length of the master key is simply XOR'ed 
to the master key and saved in the key slot (after the usual striping of 
course).

I don't see any obvious security implications with this feature. If 
there are any, I'd be interested. Please consider this for a future LUKS 
specification.

Re: [dm-crypt] [Feature request] Support for "raw" key slots

[Roscoe]

It may be useless but it doesn't cause any harm.
And it may even be useful in the case of a compromised RNG.

The main advantage I see is saving on the expensive iterated hashing,
but then you could accomplish almost the same by just specifying a low
iteration count/time.

-- Roscoe

On Fri, Aug 14, 2009 at 5:36 PM, Thomas Bächler<thomas@archlinux.org> wrote:
> The iterated hashing process used in LUKS' key slots is useful for
> (potentially weak) passphrases. However, it is useless if the key slot is
> locked with a cryptographically strong key file (like a file created from
> /dev/random).
>
> Therefore I propose the addition of a "raw key slot" feature to LUKS, where
> a key that has the exact length of the master key is simply XOR'ed to the
> master key and saved in the key slot (after the usual striping of course).
>
> I don't see any obvious security implications with this feature. If there
> are any, I'd be interested. Please consider this for a future LUKS
> specification.
>
> _______________________________________________
> dm-crypt mailing list
> dm-crypt@saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt
>

Re: [dm-crypt] [Feature request] Support for "raw" key slots

[Heinz Diehl]

At Fri, 14 Aug 2009 09:36:09 +0200,
Thomas Bächler wrote:

> The iterated hashing process used in LUKS' key slots is useful for
> (potentially weak) passphrases. However, it is useless if the key slot is
> locked with a cryptographically strong key file (like a file created from
> /dev/random).

There's an option "--iter-time" where you can specify/reduce the iteration
count. It's main purpose is well to slow down bruteforce attacks.
Don't know if it's that what you're after.