It was <2020-05-14 czw 22:20>, when Stephan Mueller wrote: > Am Donnerstag, 14. Mai 2020, 21:07:33 CEST schrieb Łukasz Stelmach: > > Hi Łukasz, > >> The value has been estimaded by obtainig 1024 chunks of data 128 bytes >> (1024 bits) each from the generator and finding chunk with minimal >> entropy using the ent(1) tool. The value was 6.327820 bits of entropy >> in each 8 bits of data. > > I am not sure we should use the ent tool to define the entropy > level. Ent seems to use a very coarse entropy estimation. > > I would feel more comfortable when using other measures like SP800-90B > which even provides a tool for the analysis. > > I understand that entropy estimates, well, are estimates. But the ent > data is commonly not very conservative. > > [1] https://github.com/usnistgov/SP800-90B_EntropyAssessment Thank you for pointing this out. I am running tests using SP800-90B tools and the first issue I can see is the warning that samples contain less than 1e6 bytes of data. I know little about maths behind random number generators, but I have noticed that the bigger chunk of data from an RNG I feed into either ent or ea_iid the higher entropy they report. That is why I divided the data into 1024 bit chunks in the first place. To get worse results. With ea_iid they get even worse (128 bytes of random data) Calculating baseline statistics... H_original: 4.107376 H_bitstring: 0.795122 min(H_original, 8 X H_bitstring): 4.107376 but I don't know how much I can trust it, when I get such warning *** Warning: data contains less than 1000000 samples *** ea_non_iid refuses to run tests with less than 4096 bytes of input. I may suspect that lack of any warnings from ent doesn't make its results any more reliable. Anyway. I collected 1024 files 1024 bits each once again and ran the following tests for f in exynos-trng/random*; do ./ea_iid "$f" | grep ^min; done | sort | head -1 for f in rng200/random*; do ./ea_iid "$f" | grep ^min; done | sort | head -1 For both RNGs I got the same min(H_original, 8 X H_bitstring): 3.393082 which, if I understand correctly, means I should set quality to no more than 434. Do you think 400 is OK? Kind regards, -- Łukasz Stelmach Samsung R&D Institute Poland Samsung Electronics
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