ARC4RANDOM(3) BSD Library Functions Manual ARC4RANDOM(3)
NAME
arc4random, arc4random_stir, arc4random_addrandom -- arc4 random number generator
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <stdlib.h>
u_int32_t
arc4random(void);
void
arc4random_stir(void);
void
arc4random_addrandom(unsigned char *dat, int datlen);
DESCRIPTION
The arc4random() function uses the key stream generator employed by the arc4 cipher, which uses 8*8 8 bit S-Boxes. The S-Boxes can be in
about (2**1700) states. The arc4random() function returns pseudo-random numbers in the range of 0 to (2**32)-1, and therefore has twice the
range of rand(3) and random(3).
The arc4random_stir() function reads data from /dev/urandom and uses it to permute the S-Boxes via arc4random_addrandom().
There is no need to call arc4random_stir() before using arc4random(), since arc4random() automatically initializes itself.
EXAMPLES
The following produces a drop-in replacement for the traditional rand() and random() functions using arc4random():
#define foo4random() (arc4random() % ((unsigned)RAND_MAX + 1))
SEE ALSO
rand(3), random(3), srandomdev(3)
HISTORY
RC4 has been designed by RSA Data Security, Inc. It was posted anonymously to the USENET and was confirmed to be equivalent by several
sources who had access to the original cipher. Since RC4 used to be a trade secret, the cipher is now referred to as ARC4.
BSD
April 15, 1997 BSD
