arc4random, arc4random_stir, arc4random_addrandom -- arc4 random number
Standard C Library (libc, -lc)
arc4random_addrandom(unsigned char *dat, int datlen);
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.
The following produces a drop-in replacement for the traditional rand()
and random() functions using arc4random():
#define foo4random() (arc4random() % ((unsigned)RAND_MAX + 1))
rand(3), random(3), srandomdev(3)
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.
FreeBSD 5.2.1 April 15, 1997 FreeBSD 5.2.1 [ Back ]