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Your tests do not agree w/ mine.

Your tests do not agree w/ mine.

Posted Nov 15, 2006 7:30 UTC (Wed) by simoncion (guest, #41674)
In reply to: Holes in the Linux random number generator? by unruh
Parent article: Holes in the Linux random number generator?

> Also the claim that /dev/urandom will use up the entropy pool for /dev/random on Linux does not seem to be born out tests.

My tests do not agree with yours:

dd if=/dev/urandom of=/tmp/rand1 &

Wait for a few hundred MB (This takes a couple of minutes)

dd if=/dev/random of=/tmp/rand2 &

Wait a couple of minutes, check the size of /tmp/rand2... It's 512 bytes in size.

cat /proc/sys/kernel/random/entropy_avail

And I get a number in the low double digits. When I terminate the first instance of dd, /tmp/rand2 (the file fed by /dev/random) begins increasing in size much more quickly. catting /proc/.../entropy_avail still returns a number in the single digits, as is expected. When I terminate the remaining instance of dd, catting /proc/.../entropy_avail reveals a number that increases to ~3500; also as expected.
Tested on 2.6.18-ck1-r1, Gentoo Linux.

Cheers,
Simon C. Ion


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