Re: [PATCH] API for true Random Number Generators to add entropy (2.6.11)

Evgeniy Polyakov
2005-03-29T11:37:05Z

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On Tue, 2005-03-29 at 20:46 +1000, Herbert Xu wrote:
> On Tue, Mar 29, 2005 at 02:50:28PM +0400, Evgeniy Polyakov wrote:
> >
> > Without ability speed this up in kernel, we completely [ok, almost]
> > loose all RNG advantages.
>
> Well if you can demonstrate that you're getting a higher rate of
> throughput from your RNG by doing this in kernel space vs. doing
> it in user space please let me know.

Quote from VIA RNG crypto analysis:

"Bitrate. The RNG generates output at significantly
higher rates than most PC-based randomness resources.
Raw bits are produced at rates of 30 to 50 Mbits/sec,
and whitened bits were observed at rates of 4 to 9
Mbits/sec. Variations in output rates depend on the
RNG configuration and the oscillator rates. PRNGs
seeded with the Nehemiah RNG should be able to
easily sustain output in excess of 2 Mbits of entropy per
second, which should eliminate blocked PRNG reads in
virtually all applications."

While raw bits reading from hw_random on the fastest
VIA boards can exceed 55mbits per second
[above quite was taken from VIA C3 Nehemiah analysis],
it is not evaluated in rngd and is not written
back to the /dev/random.

David provided his patch exactly because of
"Adding this can dramatically improve the performance of
/dev/random on small embedded systems which do not
generate much entropy."
and it works.

--
Evgeniy Polyakov

Crash is better than data corruption -- Arthur Grabowski

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