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

Alan Cox
2007-12-04T20:46:21Z

> Alan, are you sure you're not talking about Helge Deller's attempt to
> push a Time-based UUID generator into the kernel because you can get
> duplicates from the current userspace library?

Yes

> I've not heard of *any* claim where the kernel uuid random generator
> has been returning duplicates.

Then the original reports got lost somewhere.

The Fedora tools use a kernel random uuid for system identifiers (to
preserve anonymity while allowing system profiles etc to be generated and
to know which are duplicates).

We seen a huge number of duplicates for certain values:

>From Mike McGrath (added to Cc)

> Here's the top 5:
>
> 266 28caf2c3-9766-4fe1-9e4c-d6b0ba8a0132
> 336 810e7126-1c69-4aff-b8b1-9db0fa8aa15a
> 402 c8dbb9d3-a9bd-4ba6-b92e-4a294ba5a95f
> 884 06e84493-e024-44b1-9b32-32d78af04039
> 931 e2b67e1d-e325-4740-b938-795addb45280
>
> The left number is times this month someone has submitted a profile with
> that UUID. If we take the last one as an example has come from over 800
> IP's in the last 20 days. It seems very unlikely that one person would
> find his way to 800 different IP's this month. Let me know if you'd
> like more.