testing quality of a /dev/random

David Frey david at eos.lugs.ch
Wed Mar 8 22:38:46 CET 2000

On Wed, Mar 08, 2000 at 11:37:09AM -0500, Sam Roberts wrote:
> I'm wondering at how to evaluate the quality of randomness
> it generates.
Apply John Walker's ent [1]-Test, which is a Pseudorandom Number Sequence
Test Program on it. Example run under Linux 2.0.36:

$dd if=/dev/random bs=1k count=100|./ent
0+100 records in
0+100 records out
Entropy = 7.657693 bits per byte.

Optimum compression would reduce the size
of this 631 byte file by 4 percent.

Chi square distribution for 631 samples is 279.81, and randomly
would exceed this value 25.00 percent of the times.

Arithmetic mean value of data bytes is 129.0254 (127.5 = random).
Monte Carlo value for Pi is 3.352380952 (error 6.71 percent).
Serial correlation coefficient is -0.056984 (totally uncorrelated =

Just my 0.02 CHF.

[1] Called random.zip.



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