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


On Sat, 2007-12-08 at 12:49 -0500, Theodore Tso wrote:
On Sat, Dec 08, 2007 at 11:33:57AM -0600, Mike McGrath wrote:
Huh? What's the concern? All you are submitting is a list of
hardware devices in your system. That's hardly anything sensitive....

We actually had a very vocal minority about all of that which ended up
putting us in the unfortunate position of generating a random UUID instead
of using a hardware UUID from hal :-/

Tinfoil hat responses indeed! Ok, if those folks are really that
crazy, my suggestion then would be to do a "ifconfig -a > /dev/random"
before generating the UUID, and/or waiting until you just about to
send the first profile, and/or if you don't yet have a UUID,
generating it at that very moment. The first will mix in the MAC
address into the random pool, which will help guarantee uniqueness,
and waiting until just before you send the result will mean it is much
more likely that the random pool will have collected some entropy from
user I/O, thus making the random UUID not only unique, but also
unpredictable.

I do like that idea, and it could be combined with the DMI data for the
system containing things like asset tracking numbers, etc. Could use HAL
to generate a UUID based on hardware IDs and feed that in as entropy ;-)

Jon.


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