Date: Sat, 10 Apr 2004 23:08:17 +0100 From: Mark Murray <mark@grondar.org> To: Sam Leffler <sam@errno.com> Cc: cvs-src@FreeBSD.org Subject: Re: cvs commit: src/sys/modules/random Makefile src/sys/dev/random harvest.c hash.c hash.h nehemiah.c nehemiah.h probe.c randomdev.c randomdev.h randomdev_soft.c randomdev_soft.h yar Message-ID: <200404102208.i3AM8HIn071704@grimreaper.grondar.org> In-Reply-To: Your message of "Sat, 10 Apr 2004 13:58:36 PDT." <D5A255CF-8B31-11D8-872E-000A95AD0668@errno.com>
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Sam Leffler writes: > On Apr 10, 2004, at 1:54 AM, Mark Murray wrote: > > If it is felt that further whitening of the VIA C3 RNG is needed, > > then I believe that Yarrow would be overkill, and that a much > > smaller hash function will be sufficient. > > Unless I misread the paper it seemed very clear in stating that you > need to post-process the h/w RNG. I run all my h/w entropy sources > through the rndtest module (FIPS-140 testing) and frequently see that > h/w entropy sources are not to be trusted (note that rndtest samples > the entropy and that the FIPS test suite is far less stringent than > the testing done in the papers). I'll look at putting a low-overhead entropy-pool-stirrer after the C3 RNG. > I have not had time to review Marks changes but I agree with Nate > that h/w entropy sources should not be trusted and some form of > post-processing must be done. Whether this is Yarrow or something > else is unclear but the papers cited did a thorough analysis while all > I've seen from Mark are statements that he believes these sources are > good. When it comes to stuff like this I believe strongly in taking a > conservative approach. Actually, the paper that Nate pointed at said that each bit of entropy that the C3 RNG supplied delivered between 2/3 and nearly 1 bit of "good" randomness. If the on-chip whitener was on, then "0.99 bits per bit supplied" (my paraphrase) was given. Still, opinion seems to be in favour of further postprocessing, so I'll do it. M -- Mark Murray iumop ap!sdn w,I idlaH
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