Increasing the size of the available entropy pool for /dev/random in Fedora?

Bruce Keats brucekeats at gmail.com
Fri Jun 13 13:38:29 UTC 2008


Hi,

I am trying to increase the size of the available pool of entropy so that
applications that use /dev/random won't block when trying to get 1K random
bytes from /dev/random.  In the 2.6.23.17 kernel, it appears that the sysctl
(proc) interface no longer allows changes to the poolsize
(/proc/sys/kernel/random/poolsize).  I had a quick look at the random driver
(kernel/drivers/char/random.c) and it looked to me that INPUT_POOL_WORDS was
the variable.

I went ahead and made the change and recompiled the kernel, but I still
don't see the available entropy larger than 4K bits (512 bytes).  When I
check poolsize, it is now reported as 16384, but entropy_avail never seems
to get larger than 4096.  Even if I leave the system running overnight, the
available entropy pool never seems to get larger than 4096.  I have been
looking at the code and the driver seems fairly convoluted, so I hope
someone might save me some digging.

Does anyone have any suggestions as to how to increase the available entropy
pool size?

Bruce
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