On Thu, Sep 24, 2015 at 12:00:44PM -0400, Austin S Hemmelgarn wrote:
> I've had cases where I've done thousands of dieharder runs, and it
> failed almost 10% of the time, while stuff like mt19937 fails in
> otherwise identical tests only about 1-2% of the time
That is a startling result. Please say what architecture, kernel
version, dieharder version and commandline arguments you are using to
get 10% WEAK or FAILED assessments from dieharder on /dev/urandom.
Since the structure of linux urandom involves taking a cryptographic
hash the basic expectation is that it would fail statistical randomness
tests at similar rates to e.g., dieharder's AES_OFB (-g 205) even in the
absence of any entropy in the kernel pools.
So if 10% failures at correct statistical tests can be replicated it is
important and needs attention.
I did take a few moments to look into this today and got starling
failures (p-value 0.00000000) with e.g.,
dieharder -g 501 -d 10
(and a few other tests) using dieharder 3.31.1 on both debian
linux-4.1-rt-amd64 and debian kfreebsd-10-amd64, but this seems to be an
upstream bug known at least to debian and redhat, possibly fixed in
current Fedora but apparently not in Debian.
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=745742
https://bugzilla.redhat.com/show_bug.cgi?format=multiple&id=803292
if you have an affected version, these failures are seen only with -g
501, not with -g 200 < /dev/urandom. They are probably also not seen
with 32-bit dieharder.
diehard_parking_lot| 0| 12000| 100|0.00000000| FAILED
diehard_2dsphere| 2| 8000| 100|0.00000000| FAILED
diehard_3dsphere| 3| 4000| 100|0.00000000| FAILED
diehard_squeeze| 0| 100000| 100|0.00000000| FAILED
diehard_sums| 0| 100| 100|0.00000000| FAILED
Jeff
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
