[dm-crypt] Size of LUKS header and how to overwrite

Arno Wagner arno at wagner.name
Wed Feb 10 22:50:14 CET 2016

I should probably update the FAQ with the information about the
"payload offset" field in a separate item. Maybe "How to overwrite
only the LUKS header".

Keep in mind that much of the statements in the FAQ are still 
in their first incarnation and quite a few things may lack 
a simplified description, as I like to give the full story.
Hence I am grateful if anybody points out such shortcommings.

Regards and thanks,

On Wed, Feb 10, 2016 at 21:29:07 CET, Sven Eschenberg wrote:
> Ah, I see. Well the FAQ gives alternatives and more information on
> the size of the header for different keylengths and so on. But as
> the header+keymaterial can hardly be bigger than the offset of the
> encrypted payload on the backing device a dd with
> count=payload-offset and bs=512 indeed does the trick.
> Of course you'd have to check the payload offset of that particular
> container and not mix any numbers etc. .
> Regards
> -Sven
> Am 10.02.2016 um 21:13 schrieb Michael Kjörling:
> >On 10 Feb 2016 21:07 +0100, from sven at whgl.uni-frankfurt.de (Sven Eschenberg):
> >>Yes, it will overwrite the header and potential free space after the
> >>header up to the first sector of encrypted data.
> >>
> >>Does this seem so weird?
> >
> >No, but given the somewhat roundabout way this was described in the
> >FAQ at least last I looked, this seems like a much easier way to
> >describe it...
> >
> _______________________________________________
> dm-crypt mailing list
> dm-crypt at saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt

Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
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

More information about the dm-crypt mailing list