Thanks for feedback. First of all I think it's preferable to introduce
the master-key option at the beginning. Because I see no point for a user
to use a standard slot key along with a detached header.
Decryption from key to master key takes a long time. (30 seconds for
argon2i).
Regarding keyfile-
I've read through the patch but not applied or tested it. However, it
looks like it does the job. In fact, its fairly similar in parts to a
patch, which adds LUKS2 keyfile and detached header support, I've been
waiting to send to the list until the previous LUKS1 keyfile and
detached header suppo
