Re: detached LUKS header size

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If you do that, you kill the security model of LUKS.
The anti-forensic stripes are not some gadget, they
are central. Also, the key-slots are the stripes. There
are no 4kB you can take out and reconstruct the key
from them. 

That said, I think if you have an issue with 10MB extra 
today and are willing to sacrifice security to get rid
of them, then you are doing it massively wrong. Maybe
just do without encryption and security, it clearly is 
not your first priority....

Regards,
Arno




On Sat, Nov 23, 2019 at 06:43:56 CET, Fourhundred Thecat wrote:
> Hello,
> 
> I am using full-disk encryption with detached LUKS header.
> 
> The LUKS header file itself is stored on an initrd image which I boot
> from USB, and then I decrypt the cryptsetup partition on my disk and
> chroot into it.
> 
> The initrd system that I boot is very minimal, around 8MB in size.
> 
> The LUKS image, being 2MB, is making the initrd image needlessly bigger.
> 
> And the new LUKS2 format seems to use even larger header (10MB ?)
> 
> >From what I understand, the keyslots themselves only use up 4KB of
> space, and the rest is used for "antiforensic stripes".
> 
> This is probably a good idea when LUKS header is stored on disk together
> with the cryptsetup partition.
> 
> But when using detached header, which is never stored on disk, this
> makes less sense
> 
> Thus my question:
> 
> is it possible, somehow, to reduce the size of the LUKS header to
> absolute minimum (4KB ?), when I don't need the antiforensic stripes ?
> 
> thank you,
> _______________________________________________
> dm-crypt mailing list
> dm-crypt@xxxxxxxx
> https://www.saout.de/mailman/listinfo/dm-crypt

-- 
Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno@xxxxxxxxxxx
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
----
A good decision is based on knowledge and not on numbers. -- Plato

If it's in the news, don't worry about it.  The very definition of 
"news" is "something that hardly ever happens." -- Bruce Schneier
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