[NCLUG] My attempts using /dev/random...

[Jeremy Hinegardner]

On Sun, Apr 13, 2008 at 03:15:59PM -0600, Sean Reifschneider wrote:
> I went ahead and generated a bunch of randomness from /dev/random on
> several different hosts.  My laptop, over the last 4 days or so, didn't
> even get enough randomness for 100,000 rolls of 2 dies (using the mechanism
> suggested by Stephen's research).  The other systems I tried were able to
> get enough randomness for 4 iterations of 100,000 rolls.
> 
> See the README for more details, but I ran this against an OpenSolaris
> (backup1) system, 2 Linux systems with plenty of activity on them (routera
> and mirrors), /dev/urandom on my laptop, and then also a pass running the
> Python random number generator.
> 
> The results are:
> 
> ======================== randomness-backup1 ========================
> chi squared: 13.56146 iters: 100000
> chi squared: 10.712816 iters: 100000
> chi squared: 9.986612 iters: 100000
> chi squared: 15.16541 iters: 100000
> 
> ======================== randomness-mirrors ========================
> chi squared: 9.383732 iters: 100000
> chi squared: 5.289914 iters: 100000
> chi squared: 7.222466 iters: 100000
> chi squared: 10.234694 iters: 100000
> 
> ======================== randomness-routera ========================
> chi squared: 6.807866 iters: 100000
> chi squared: 10.522898 iters: 100000
> chi squared: 9.53456 iters: 100000
> chi squared: 3.227186 iters: 100000
> 
> ======================== urandomness-guin ========================
> chi squared: 8.0114 iters: 100000
> chi squared: 7.466174 iters: 100000
> chi squared: 9.163472 iters: 100000
> chi squared: 7.094624 iters: 100000
> 
> ======================== pyrandomness-guin ========================
> chi squared: 12.198728 iters: 100000
> chi squared: 16.710518 iters: 100000
> chi squared: 14.67455 iters: 100000
> chi squared: 14.655584 iters: 100000
> 
> My findings:
> 
>    1,008 and 10,000 iterations were really showing huge discrepancies
>    between iterations.  Which isn't surprising for random data sets.
>    Things seemed to settle down at 100,000, but there are still fairly
>    large swings (3-10 in one set).
> 
>    The Python random number generator isn't great.  I'll probably continue
>    to use it though, as I don't think I have anything that really cares
>    about things being THAT random.
> 
>    Linux /dev/random seems to be pretty good, if we say that random.org is
>    scoring a chi^2 of 7-ish.
> 
>    OpenSolaris' /dev/random is not as good as Linux's, /dev/random *OR*
>    /dev/urandom.
> 
>    Linux's /dev/urandom is probably good enough.  I'd definitely use it for
>    populating randomness on a hard drive before putting a crypto
>    file-system on it, for example.
> 

I ran the code against /dev/arandom on my OpenBSD 4.2 machine with these
results:

  % dd if=/dev/arandom of=randomness-obsd-arandom.out bs=1 count=2000000

  % ./dorolls randomness-obsd-arandom.out 4 1000 
  chi squared: 9.2672 iters: 1000
  chi squared: 12.26 iters: 1000
  chi squared: 17.0228 iters: 1000
  chi squared: 7.7282 iters: 1000

  % ./dorolls randomness-obsd-arandom.out 4 10000
  chi squared: 12.48554 iters: 10000
  chi squared: 18.97622 iters: 10000
  chi squared: 6.26474 iters: 10000
  chi squared: 7.95584 iters: 10000

  % ./dorolls randomness-obsd-arandom.out 4 100000
  chi squared: 9.010736 iters: 100000
  chi squared: 8.099072 iters: 100000
  chi squared: 4.86659 iters: 100000
  chi squared: 6.07481 iters: 100000

/dev/arandom on OpenBSD is what is returned for the arc4rand() system call.
/dev/srandom (Strong Random) hasn't returned enough entropy to run anything yet.

enjoy,

-jeremy

-- 
========================================================================
 Jeremy Hinegardner                              jeremy at hinegardner.org