Linux-style kernel PRNGs and the FIPS140-2 test

[Greg Rose]

There was an error in the bounds for the runs test specified by NIST; last 
october they updated FIPS 140-2 to specify new bounds. An updated version 
of my code can be found at http://people.qualcomm.com/ggr/QC/ (our old web 
pages are stale, and I'm still trying to have them taken down by our ex-ISP).

Here's an excerpt from the comment in the new code:
  * Version 1.3 -- Bill Chauncey and his colleages pointed out to NIST that
  * the bounds in the runs test were incorrect.
  * They issued an update 2001-oct-10.

If the new one still shows an anomalous number of runs test failures, there 
is a real problem.

regards,
Greg.

At 03:23 PM 1/15/2002 -0500, Thor Lancelot Simon wrote:
>Many operating systems use "Linux-style" (environmental noise
>stirred with a hash function) generators to provide "random"
>and pseudorandom data on /dev/random and /dev/urandom
>respectively.  A few modify the general Linux design by adding an
>output buffer which is not stirred so that bits which have already
>been output are not stirred into the pool of "new" "random" data
>(IMO, not doing this is insane, but that's a different subject).
>
>The enclosed implementation of the FIPS140-1/2 statistical test
>appears to show that such generators fail the "runs" test quite
>regularly.  Interestingly, the Linux generator seems to do better
>the longer you let it run (which, perhaps, suggests that quite a
>bit of data should be run through it at boot time and discarded)
>but other, related generators do not.
>
>The usual failure mode is "too many runs of 1 1s".  Using MD5
>instead of SHA1 as the mixing function, the Linux generator
>also displays "too many runs of 1 0s".  I have not yet seen
>other failure modes from these generators.
>
>To reproduce my results, just compile the enclosed and do
>"a.out < /dev/urandom" on your platform of choice.
>
>Thor


Greg Rose                                       INTERNET: ggr at qualcomm.com
Qualcomm Australia          VOICE:  +61-2-9817 4188   FAX: +61-2-9817 5199
Level 3, 230 Victoria Road,                http://people.qualcomm.com/ggr/
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