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

Jon Masters
2007-12-08T17:46:46Z

On Sat, 2007-12-08 at 12:32 -0500, Theodore Tso wrote:
> On Sat, Dec 08, 2007 at 02:37:57AM -0500, Jon Masters wrote:
> > > 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.
>
> Huh? What's the concern? All you are submitting is a list of
> hardware devices in your system. That's hardly anything sensitive....

Right, but the MAC is globally unique (well, that's normally true) so it
is an identifiable user characteristic, moreso than just a list of PCI
device IDs sitting on a particular bus. It's silly, but there it is.

Jon.