On Thu, Feb 06, 2025 at 02:38:48PM +0200, Martin Storsjö wrote: > On Thu, 6 Feb 2025, Michael Niedermayer wrote: > > > > + // If the timer resolution is high, and we get the same timer > > > + // value multiple times, use variances in the number of > > > repeats > > > + // of each timer value as entropy. If the number of repeats > > > changed, > > > + // proceed to the next index. > > > > Does it still work if you check against the last 2 ? > > or does this become too slow ? > > What iam thinking of is this > > > > 7,8,7,8,8,7,8,7,8,8,7,8,7,8,8,7,8,7,8,8,... and a 9 or 6 or further distant > > would trigger it > > > > I assume both the CPU clock and the wall time are quite precisse so if we > > just compare them the entropy could be low even with 2 alternating values > > Yes, that still works for making it terminate in a reasonable amount of > time. I updated the patch to keep track of 3 numbers of repeats, and we > consider that we got valid entropy once the new number of repeats is > different from the last two. > > So in the sequence above, e.g. for 7,8,7,8,8,7, at the point of the last > one, we have old repeats 8 and 8, and the new repeat count 7, which in that > context looks unique.
I was thinking that in 7,8,8 that 7 and 8 be the 2 least recent used
values not 8,8
that is, something like:
if (old2 == new) {
FFSWAP(old,old2);
} else if (old != new) {
old2 = old;
old = new;
}
but again, iam not sure this will work or just need too much time to gather
enough entropy
thx
[...]
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Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Some people wanted to paint the bikeshed green, some blue and some pink.
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