Randomness testing Was: On the "randomness" of DNS

Alexander Klimov alserkli at inbox.ru
Sun Aug 3 07:54:54 EDT 2008

On Thu, 31 Jul 2008, Pierre-Evariste Dagand wrote:
> Just by curiosity, I ran the Diehard tests[...]
> Sum-up for /dev/random:
> "Abnormally" high value: 0.993189 [1]
> "Abnormally" low value: 0.010507 [1]
> Total: 2
> Sum up for Sha1(n):
> "Abnormally" high values: 0.938376, 0.927501 [2]
> "Abnormally" low values: 0.087107, 0.091750, 0.060212, 0.050921 [4]
> Total: 6
> So, I would say that Sha1(n) does not pass DieHard (while
> /dev/random does). But this would require further examination, in
> particular to understand why some tests failed. And, in fact, I have
> no clue why they failed...

See <http://en.wikipedia.org/wiki/P-value>.

Since p-value is supposed to be uniform on the interval [0,1]
for a truly random source, it is no wonder that with so many
p-values some of them are close to 0 and some are close to 1.

If your p-value is smaller than the significance level (say, 1%)
you should repeat the test with different data and see if the
test persistently fails or it was just a fluke.


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