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

Pavel Machek
2007-12-11T13:58:36Z

On Wed 2007-12-05 09:49:34, 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 thought that /dev/random blocks when 0 entropy is available...? I'd
expect uuid generation to block, not to issue duplicates.

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