1. Purpose[edit | edit source]
Hardware random framework offers the interface to control RNG devices from userspace.
This article shows three ways to control a RNG in userspace:
- using /dev/random command to generate a random number
- using /dev/hwrng command to generate a random number
- using rng-tools to validate the RNG
2. RNG control through /dev/random[edit | edit source]
/dev/random is a special file that can be used to generate random numbers based on a pseudo-random generator that runs on the Linux Kernel entropy pool. When a hardware random number generator device is available, the pool is periodically supplied with data generated by this device. Else, it is entirely software generated.
od (octal dump) command is used to extract the number of bytes and display the decimal number.
E.g:
- Random number (0 - 255):
od -An -N1 -i /dev/random
172
- Random number (0 - 65535):
od -An -N2 -i /dev/random
20041
3. RNG control through /dev/hwrng[edit | edit source]
/dev/hwrng is a special file that can be used to generate random numbers based on a hardware random number generator.
E.g - Random number (0 - 65535):
od -An -N2 -i /dev/hwrng
5719
4. RNG control through rng-tools[edit | edit source]
rng-tools[1] is a set of tools related to random number generation.
rng-tools will connect to the hardware random number generator through /dev/hwrng.
rngtest is a basic test that checks data using FIPS 140-2 tests[2] which is a security requirement test for cryptographic module compliance.
rngtest -c 100 </dev/hwrng rngtest 5 Copyright (c) 2004 by Henrique de Moraes Holschuh This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. rngtest: starting FIPS tests... rngtest: bits received from input: 2000032 rngtest: FIPS 140-2 successes: 100 rngtest: FIPS 140-2 failures: 0 rngtest: FIPS 140-2(2001-10-10) Monobit: 0 rngtest: FIPS 140-2(2001-10-10) Poker: 0 rngtest: FIPS 140-2(2001-10-10) Runs: 0 rngtest: FIPS 140-2(2001-10-10) Long run: 0 rngtest: FIPS 140-2(2001-10-10) Continuous run: 0 rngtest: input channel speed: (min=33.154; avg=33.656; max=34.217) Kibits/s rngtest: FIPS tests speed: (min=21.193; avg=23.180; max=23.403) Mibits/s rngtest: Program run time: 58114432 microseconds
It is normal for any random generator to fail in small number of tests, but failures must not exceed a reasonable proportion on a large sample (<= 0.5%).
5. References[edit | edit source]