On Mon, Mar 26, 2012 at 6:55 PM, Chris Murphy <lists(a)colorremedies.com> wrote:
So then the question is, if urandom is what's recommended, are
faster substitutes just as good? If they are just as good, then why aren't they the
first recommendation? And if this step is superfluous, then I'd suggest documentation
be changed to eliminate the suggestion altogether.
Personally, I setup dmcrypt (w/o luks) first using /dev/urandom as the
key and one of the secure block modes (e.g. aes-lrw or aes-essiv).
Then I fill the dmcrypt device with /dev/zero. This goes fairly fast,
filling the device with securely encrypted zeros.
Then I drop the volume and set up luks normally.
From a security perspective an attack which allowed the attacker to
distinguish the randomly encrypted /dev/zero from your other data
would be a fairly bad vulnerability generally against the encrypted
volume... much worse than the information leak wrt used blocks.