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2010-07-09
, 16:15
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Posts: 663 |
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Joined on Nov 2009
@ London, UK
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#2
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2010-07-09
, 17:57
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Posts: 2,802 |
Thanked: 4,491 times |
Joined on Nov 2007
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#3
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The Following User Says Thank You to lma For This Useful Post: | ||
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2010-07-09
, 18:05
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Posts: 3,159 |
Thanked: 2,023 times |
Joined on Feb 2008
@ Finland
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#4
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2010-07-09
, 19:20
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Posts: 15 |
Thanked: 6 times |
Joined on Jun 2010
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#5
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2010-07-09
, 19:25
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Posts: 15 |
Thanked: 6 times |
Joined on Jun 2010
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#6
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2010-07-09
, 22:31
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Posts: 336 |
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Joined on Apr 2008
@ France
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#7
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2010-07-10
, 00:22
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Posts: 2,802 |
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Joined on Nov 2007
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#8
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$ 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 ${x}6; done
...
Doesn't look like a very even distribution to me. Not a single 86 or 96 appeared in the sample.
I also noticed this bug report on it:
https://dev.laptop.org/ticket/8089
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2010-07-10
, 00:52
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Posts: 186 |
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Joined on Jan 2010
@ Finland
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#9
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Except that CCD noise isn't random at all, and very much retraceable.
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2010-07-10
, 08:06
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Posts: 15 |
Thanked: 6 times |
Joined on Jun 2010
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#10
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A quick test with ent on a 1MiB sample suggests it is:
Code:$ ent hwrngdump Entropy = 7.999823 bits per byte. Optimum compression would reduce the size of this 1048576 byte file by 0 percent.
Well, as its name suggests, od outputs octal values by default so that's to be expected ;-)
The solution is to use noise from the CCD as a random number generator. The n800 CCD is quite noisey (when the camera is not ejected, the black screen shows copious random noise).
It's also more convenient than asking the user to doodle and press random buttons.