RANDOM(7)RANDOM(7)NAME
random, urandom - sources of random numbers
DESCRIPTION
The special files /dev/random and /dev/urandom provide an access to the
kernel implementation of a Pseudo Random Number Generator (PRNG).
They are accessed like any ordinary file.
Read calls return a buffer filled up with random bits.
Write calls are reserved to the superuser. They perturb the state of the
kernel PRNG. A subsequent close call forces a reseed of the PRNG.
The kernel PRNG implements the Yarrow algorithm.
As opposed to some implementations of the random devices, where the
characteristics of /dev/random and /dev/urandom differ, the Yarrow
algorithm allows a similar behaviour of both special files.
On IRIX, /dev/random and /dev/urandom do behave identically.
/dev/urandom is shipped for compatibility purposes.
FILES
/dev/random
/dev/urandom
NOTES
The design of the Yarrow algorithm was published in this document:
"Yarrow-160: Notes on the design and analysis of the
yarrow cryptographic pseudo random number generator"
KESLEY, J. SCHNEIDER, B., and FERGUSON, N.
6th Annual Workshop on Selected Areas in Cryptography,
Springer-Verlag, 1999
At the date this man page is written, the original information about the
Yarrow algorithm can be retrieved at this URL:
http://www.counterpane.com/yarrow.html
HISTORY
The devices /dev/random and /dev/urandom were added in 6.5.19.
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