[dm-crypt] Variable data offset for a LUKS volume that uses a detached header.

Arno Wagner arno at wagner.name
Tue Dec 22 14:01:57 CET 2015

On Tue, Dec 22, 2015 at 13:00:08 CET, .. ink .. wrote:
> Happy holidays everybody,
> I am trying to create a LUKS volume with a detached header that has
> data offset at sector 256 and things fail with
>  an error that reads:
> "Data offset for detached LUKS header must be either 0 or higher than
> header size (4036 sectors)."
> Is there a technical reason why this is so and is it possible to allow
> other data offsets?

No idea. What about doing an offset with LVM first and then zero
offset for LUKS?
> Reason for doing this is an attempt at having a detached LUKS header
> capable of unlocking a VeraCrypt volume since
> unlocking a VeraCrypt volume takes too long and its annoying.

Oh, yes. I did complain to them, never got an answer. I plan 
to move my Windows machine back to the last Truecrypt, since
the one known vulnerability seems not to affect single-user
machines anyways.

Currently I am attaching 8 zeros to the pasphrase, so I can unlock 
my high-entropy passhrase with iteration 10 and not wait 70 seconds 
in VeraCrypt. Somebody there really has no clue why usability is 
important and that users should be able to ovverride most things.
They may just know more than the developers about their application

Does anybody know what the status of CipherShed and TCnext is and 
whether they have more of a clue?


> Everything seems to be working except for the data offset since i cant
> set it to 256 sectors through the library API.
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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
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