Re: [PATCH 2/2] lguest: virtio-rng support

From: Jeremy Fitzhardinge
Date: Mon May 19 2008 - 05:46:10 EST

Rusty Russell wrote:
Unfortunately not. Hardware randomness devices export /dev/hwrng, and it's up to userspace to feed that into /dev/random (or not). That's usually done by rngd, which at least on my system, assumes 1 bit of entropy per bit of data from /dev/hwrng by default.

I was a little surprised that this decision was exported to userspace, but if you're not prepared to unconditionally trust hw rngs, it makes sense to palm it off.

Yeah, that's a bit of a pity. Hardware rngs can often generate really crappy randomness, which needs tons of processing to remove noise like 50/60hz hum, etc.

We could write a boutique device for virtualization which *did* feed directly, but that would be a little gauche.

Well, yes, we can certainly do any amount of processing we like to the stuff provided to guests, so that the 1:1 bits/entropy ratio is as true as we can make it.

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