On Tue, 2017-06-20 at 16:59 +0200, Torsten Duwe wrote: > On Tue, Jun 20, 2017 at 10:21:17PM +0800, Sean Wang wrote: > > Hi Herbert, > > > > thanks for effort reviewing on those patches. > > > > By the way, also loop in Torsten > > > > Could you kindly guide me how to determine appropriate > > rng->ops.quality value used by the driver? > > > > I have tested with rngtest on mtk-cir and the result is got as > > the below log shown. If the rngtest always gives the result for > > success rate over 99.8%, can I set the rng->ops.quality 998? > > > > rngtest: starting FIPS tests... > > rngtest: bits received from input: 20000032 > > rngtest: FIPS 140-2 successes: 998 > > rngtest: FIPS 140-2 failures: 2 > > No! You'd have to determine the failure threshold of the test and > apply some math to find a lower boundary of your RNG's entropy. > > What the quality is for: your RNG produces bits, but not all of them > are completely independent of each other i.e. not completely random. > So you simply lower the quality rating to express the net entropy > contained in the data stream. > > Torsten > Hi Torsten, Understood, appreciate your quick and clear explanation. For the math, is there existing any well-known or recommended open source software assisting identify the lower boundary of RNG entropy? I think the logic should be common for all RNGs. thanks again Sean Sean -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
