Re: Why does reading from /dev/urandom deplete entropy so much?
- From: Adrian Bunk <bunk@xxxxxxxxxx>
- Date: Tue, 4 Dec 2007 17:18:11 +0100
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
This also means that I can "sabotage" applications reading from
/dev/random just by continuously reading from /dev/urandom, even not
meaning to do any harm.
Before I file a bug on bugzilla,
...
The bug would be closed as invalid.
No matter what you consider as being better, changing a 12 years old and
widely used userspace interface like /dev/urandom is simply not an
option.
Greetings
Marc
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
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