maemo.org - Talk - View Single Post - Use CCD noise to make the random number generator uncrackable

lma	2010-07-10 , 00:22
Posts: 2,802 \| Thanked: 4,491 times \| Joined on Nov 2007	#8

Originally Posted by samualwalters

It's apparently not very random.

A quick test with ent on a 1MiB sample suggests it is:

Code:

$ ent hwrngdump
Entropy = 7.999823 bits per byte.

Optimum compression would reduce the size
of this 1048576 byte file by 0 percent.

Chi square distribution for 1048576 samples is 256.82, and randomly
would exceed this value 50.00 percent of the times.

Arithmetic mean value of data bytes is 127.4373 (127.5 = random).
Monte Carlo value for Pi is 3.143978668 (error 0.08 percent).
Serial correlation coefficient is 0.000647 (totally uncorrelated = 0.0).

for x in {0..9}; do od ./dump | grep -c ${x}6; done
...
Doesn't look like a very even distribution to me. Not a single 86 or 96 appeared in the sample.

Well, as its name suggests, od outputs octal values by default so that's to be expected ;-)

I also noticed this bug report on it:

https://dev.laptop.org/ticket/8089

Note that that report talks about a completely different hardware random number generator.

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