[Cryptech Tech] RNG test tools wiki page

[Benedikt Stockebrand]

Hi Bernd and list,

Bernd Paysan <bernd at net2o.de> writes:

> A note for the dieharder tests: Non-deterministic inputs (that's what we are 
> interested in!) still give non-deterministic outputs.  That means, all those 
> test results do vary, and must vary.  Dieharder's tests are weighted in a way 
> that the chance of missing it with normal randomness is 1/1000.  Given that 
> dieharder has a lot of tests, and you are going to test it with a lot of data 
> (again and again), you should simply expect to have that failure rate.

correct.

> IMHO, dieharder -a should collect all the results and do a chi-square tests on 
> them, because if the data is random, and the weighting is correct, the results 
> should all be distributed with a known distribution.

No, that's not a good idea.  If any single test fails it means that it
has with high likelyhood discovered some sort of pattern or
nonrandomness in the input.  But that doesn't mean it will also be
discovered by other tests.

As a simplified example: If you had one test for bit bias (what ent
calls "entropy") and a second for correlation between bits 8 bits apart
(which might be interesting for a bytewise generator) then it takes two
different kinds of patterns overlaid in the input to make both tests
fail.


Cheers,

    Benedikt

-- 
Benedikt Stockebrand,                   Stepladder IT Training+Consulting
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