[dm-crypt] Best practice for storing header backup and protecting against mistakes/misuse.

Arno Wagner arno at wagner.name
Wed Mar 29 20:32:43 CEST 2017

On Wed, Mar 29, 2017 at 15:42:03 CEST, Waqar Khan wrote:
> Hi,
> I have read through the FAQ and its got a lot of useful information
> from the backup section.

> Lastly, a few people have access to this machine (through the same
> passphrase), some work colleagues, how can I protect against one
> disgruntled member leaving the company and changing the passphrase
> (then unmounting the volume for good measure) and not telling anyone?

Simple: Have a header backup with a known passphrase and make sure 
that potentially disgruntled employee cannot kill that backup. 
Then you can just restore that header backup and use the known 
good passphrase in there. I would recommend using a passphrase
for this that is used nowhere else and is the only passphrase
in that header.

Alternatively, you could write down or print the master key on
paper and put that in a sealed envelope and that in a safe
or bank lockbox. You should probably encrypt the master-key with 
PGP/GnuPG before and will still get something that still easily 
fits on paper and can be typed in with reasonable effort, but 
is less exposed than an unprotected master key and can be stored
in a place where it is just not easily destroyed,

Of course, you can also put a header-backup on paper, but that 
takes something like 50 pages or so if you just store the first 

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

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