[ivank]

Good point. I've toned down my comment because that root password would be getting typed in less often.

An attacker might still bring an evil-su in addition to an evil-sudo, though. And even if you're logging into that root user only in an another tty, it seems like an unnecessary risk to share the password with LUKS.

[mricon]

You actually tend to never use the root password on a modern workstation -- just sudo. The situations where you have to use a root password are usually if something has gone wrong and you have to log in via tty.