Russell Leidich (at Saturday, May 7, 2016, 8:47:33 PM): > Whatever its absolute value might be, the amount of entropy in the > DMA timing skew has to be higher in practice than that in interrupt > timing. The reason is that, for every interrupt, thousands or even > billions of DMA transactions occur.
how do you plan to get notice of them? the very point of DMA is that it goes on in the background, and then you get a notification. > But can userspace see any of this via the timestamp counter? this is not the question at all. i don't doubt that userspace can see some entropy. my point was that the kernel sees everything, while userspace sees less. it is not refuted by showing examples of entropy userspace can collect. please note that i also pointed out a danger: all the entropy visible to userspace might be easier to steal, because there is a chance that other programs can gather the exact same entropy (hence my example of the sound card noise). to some extent, havege might alleviate this, because there is no direct way to observe the parameters it collects. but this is highly speculative, as the true source of havege random is not the CPU, but the same irqs and other hw events. the CPU just acts as a hard to observe prng. so actually i'm not a fan. without looking into it deeper, i believe this is also true for enranda. _______________________________________________ cryptography mailing list [email protected] http://lists.randombit.net/mailman/listinfo/cryptography
