Re: Why does reading from /dev/urandom deplete entropy so much?

Jon Masters
2007-12-08T07:39:01Z

On Wed, 2007-12-05 at 09:49 -0500, Theodore Tso wrote:
> On Wed, Dec 05, 2007 at 08:26:19AM -0600, Mike McGrath wrote:
> >
> > Ok, whats going on here is an issue with how the smolt RPM installs the
> > UUID and how Fedora's Live CD does an install. It's a complete false alarm
> > on the kernel side, sorry for the confusion.
>
> BTW, You may be better off using "uuidgen -t" to generate the UUID in
> the smolt RPM, since that will use 12 bits of randomness from
> /dev/random, plus the MAC, address and timestamp. So even if there is
> zero randomness in /dev/random, and the time is January 1, 1970, at
> least the MAC will contribute some uniqueness to the UUID.

I haven't checked how uuidgen uses the MAC, but I would suggest that
that is not something Fedora should jump at doing - although it would
help ensure unique UUIDs, it also contributes to the tinfoil hat
responses that usually come up with things like smolt.

Jon.