Messages in this thread | | | Date | Fri, 5 Sep 2003 12:05:29 -0500 | From | Matt Mackall <> | Subject | Re: [PATCH] add_mouse_randomness |
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On Fri, Sep 05, 2003 at 11:16:05AM +0200, Andries.Brouwer@cwi.nl wrote: > From oxymoron@waste.org Fri Sep 5 07:01:30 2003 > From: Matt Mackall <mpm@selenic.com> > > > Today: > > Every keypress and every key release causes two calls of > > add_mouse_randomness and one call of add_keyboard_randomness. > > Key repeat causes lots of calls of add_mouse_randomness. > > > > The random driver contains a mechanism (delta, delta2, delta3) > > for estimating the amount of entropy in a stream of moments in > > time. But the fact that every event causes two calls, very > > quickly after each other, poisons this mechanism, and makes us > > overestimate. > > The real problem is that the deltas are calculated from gigahertz > cycle counters, but yes, we're calling too frequently and blowing away > useful history. I've experimented with making the deltas per-source as > well. > > I wouldnt know what is wrong with using gigahertz cycle counters. > The deltas are already per-source.
Actually, they're only per-class. So if you have multiple mice, keyboards, drives, etc., they interfere with each other's deltas and increase the entropy estimates overall.
-- Matt Mackall : http://www.selenic.com : of or relating to the moon - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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