random(6) [netbsd man page]

RANDOM(6)							 BSD Games Manual							 RANDOM(6)

NAME

     random -- random lines from a file or random numbers

SYNOPSIS

     random [-er] [denominator]

DESCRIPTION

     random reads lines from the standard input and copies them to the standard output with a probability of 1/denominator.  The default value for
     denominator is 2.

     The options are as follows:

     -e      If the -e option is specified, random does not read or write anything, and simply exits with a random exit value of 0 to
	     denominator-1, inclusive.

     -r      The -r option guarantees that the output is unbuffered.

SEE ALSO

     shuffle(1), fortune(6)

BSD
								  March 20, 2007							       BSD

RANDOM(4)						   BSD Kernel Interfaces Manual 						 RANDOM(4)

NAME

     random , urandom -- random data source devices.

SYNOPSIS

     pseudo-device random

DESCRIPTION

     The random device produces uniformly distributed random byte values of potentially high quality.

     To obtain random bytes, open /dev/random for reading and read from it.

     To add entropy to the random generation system, open /dev/random for writing and write data that you believe to be somehow random.

     /dev/urandom is a compatibility nod to Linux. On Linux, /dev/urandom will produce lower quality output if the entropy pool drains, while
     /dev/random will prefer to block and wait for additional entropy to be collected.	With Yarrow, this choice and distinction is not necessary,
     and the two devices behave identically. You may use either.

OPERATION

     The random device implements the Yarrow pseudo random number generator algorithm and maintains its entropy pool.  Addditional entropy is fed
     to the generator regularly by the SecurityServer daemon from random jitter measurements of the kernel.  SecurityServer is also responsible
     for periodically saving some entropy to disk and reloading it during startup to provide entropy in early system operation.

     You may feed additional entropy to the generator by writing it to the random device, though this is not required in a normal operating envi-
     ronment.

LIMITATIONS AND WARNINGS

     Yarrow is a fairly resilient algorithm, and is believed to be resistant to non-root.  The quality of its output is however dependent on regu-
     lar addition of appropriate entropy. If the SecurityServer system daemon fails for any reason, output quality will suffer over time without
     any explicit indication from the random device itself.

     Paranoid programmers can counter-act this risk somewhat by collecting entropy of their choice (e.g. from keystroke or mouse timings) and
     seeding it into random directly before obtaining important random numbers.

FILES

     /dev/random
     /dev/urandom

HISTORY

     A random device appeared in Linux operating system.

Darwin								 September 6, 2001							    Darwin