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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 num-
     bers 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 anony-
     mously 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 5.4			April 15, 1997			   FreeBSD 5.4

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