/dev/random

[Ben Laurie]

On Tue, Aug 21, 2012 at 8:39 AM, Steve Kargl
<sgk at troutmask.apl.washington.edu> wrote:
> On Tue, Aug 21, 2012 at 12:10:36AM -0700, Doug Barton wrote:
>> On 08/20/2012 15:55, Peter Jeremy wrote:
>> > On 2012-Aug-20 23:05:39 +0100, Ben Laurie <ben at links.org> wrote:
>> >>> Well, it's hard to comment when you failed to explain
>> >>> *why* you think it is a mistake.
>> >>
>> >> Sorry - because I do not think it is wise to trust the h/w prng so
>> >> much we discard other entropy.
>> >
>> > This depends on the relative predictability of Yarrow vs the hardware
>> > RNG.
>>
>> Throughout this thread people have been mixing up entropy sources, and
>> hardware and software PRNGs. A PRNG has (at least) 2 components, the
>> entropy source(s), and the software that turns the entropy into a stream
>> of pseudo-random output.
>>
>> You can't directly compare "yarrow" vs. Padlock without comparing both
>> elements.
>
> Well, only one person seems confused, but OP seems to
> remain adament in being terse in his questions.  Yes,
> it seems OP has conflated PRNG and entropy, but again
> he seems to not want to explain his point of view.

Entropy is a poorly defined word, and PRNGs have some (we hope).

So, as someone else already explained, there's a hardware entropy
source in the VIA Nehemiah. I don't think it really matters whether
this is "raw" entropy or a PRNG, what matters is that it seems like a
bad idea to trust it so much that we don't use other entropy sources
in conjunction with it.

As for how it should be fixed, my view is that it should be used as an
entropy source for yarrow, but I'm not against Doug's 3 options.

>> > FreeBSD random(4) currently only supports one hardware RNG - the
>> > one in the VIA Nehemiah.  VIA have published an independent evaluation
>> > of their RNG which suggests it is a good source of entropy.
>>
>> I'm not sure what paper you're referring to, but according to the
>> padlock programming guide it's a random number generator, not (directly)
>> an entropy source. That said, it certainly *could* be used as an entropy
>> source for yarrow.
>
> I suspect Jeremy has read the /dev/random code; not some paper.
>
> UTSL.
>
> --
> Steve