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

Herbert Xu
2005-03-29T10:48:15Z

On Tue, Mar 29, 2005 at 12:38:01PM +0200, Pavel Machek wrote:
>
> It seems to me that people wanting this level of assurance should do
> their own FIPS (or whatever) tests.

That's exactly what the current scheme of driver + rngd allows you
to do. For those that require high assurance, they can let rngd
do the checks. Otherwise they can disable the checks and just let
rngd feed data from /dev/hw_random into /dev/random.

It's not just about the quality checks. It's also about deciding the
rate at which data should be fed into /dev/random.

Feeding too much means that you might be wasting system resources
(CPU/PCI bus/etc.). Feeding too little means that /dev/random users
may block unnecessarily.

Doing the feeding in a process means that you can feed exactly the
right amount. You feed only when the /dev/random's pool is depleted
and you feed exactly the amount of data that is needed to replenish
the pool.

> Interrupts are not totally unpredictable, either, yet noone runs FIPS

I haven't looked at this but if that's the case we might want to
look at lowering the entropy count for that.

> > Someone else raised the example of Casinos using hardware RNGs. Some
> > of them are doing this to comply with government regulation. In that
> > case, using data from the software RNG when the hardware has failed
> > would be violating the law.
>
> Well, you are still using hardware RNG, but failed one. I do not see
> how you can break law with that... given that hardware RNG had proper
> certification in the first place.

Actually in the scheme proposed in this thread the hardware RNG could
be feeding a stream of zeros into /dev/random which means that the
/dev/random user will be using a software RNG.

Cheers,
--
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