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

Marc Haber
2007-12-05T12:29:21Z

On Tue, Dec 04, 2007 at 05:18:11PM +0100, Adrian Bunk wrote:
> On Tue, Dec 04, 2007 at 12:41:25PM +0100, Marc Haber wrote:
> > While debugging Exim4's GnuTLS interface, I recently found out that
> > reading from /dev/urandom depletes entropy as much as reading from
> > /dev/random would. This has somehow surprised me since I have always
> > believed that /dev/urandom has lower quality entropy than /dev/random,
> > but lots of it.
>
> man 4 random

Thanks for this pointer, I was not aware of the documentation. After
reading this thread and the docs, I am now convinced that GnuTLS
should seed a PRNG from /dev/(u)random instead of using the entropy
directly. I will go filing a bug against GnuTLS.

Greetings
Marc

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