Messages in this thread | | | Date | Thu, 24 Sep 2015 11:52:04 -0500 | From | Jeff Epler <> | Subject | Re: [PATCH 1/3] Make /dev/urandom scalable |
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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
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