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arc4random, arc4random_stir, arc4random_addrandom - arc4 random number

 

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))
      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.
 

Sections

Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.