Sam Stelfox

Thoughts from a software engineer, systems hacker and Linux gubernāre.

RNG Tools

rng-tools allows you too supplement the /dev/random device with data from other entropy sources including /dev/urandom. Contrary to a lot of people's understanding /dev/urandom does produce fairly high quality random numbers and will continue to do so as long as SHA1 doesn't get cracked and there is a flaw allowing the escape of kernel measured data.

rng-tools also checks the quality of the random numbers before passing them into /dev/random.


yum install rng-tools -y

Testing /dev/urandom

If you don't have a hardware random number generator (which is very common especially with virtual machines), you'll need to use /dev/urandom to seed /dev/random.

You should probably and test the quality of those waters before drinking them, the following shows a test of the quality of random numbers using the rngtest utility provided by the rng-tools package.

cat /dev/urandom | rngtest -c 1000

As you can see it is FAST and it passed every one of the FIPS 140-2 tests. Compared to /dev/random: