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ARC4RANDOM(3)          FreeBSD 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.

FreeBSD 11.0-PRERELEASE         April 15, 1997         FreeBSD 11.0-PRERELEASE
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | HISTORY

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