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arc4random

BSD mandoc

NAME

arc4random arc4random_stir arc4random_addrandom - arc4 random number generator

LIBRARY

Lb libc

SYNOPSIS

In stdlib.h Ft u_int32_t Fn arc4random void Ft void Fn arc4random_stir void Ft void Fn arc4random_addrandom unsigned char *dat int datlen

DESCRIPTION

The Fn 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 Fn 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 Fn arc4random_stir function reads data from /dev/urandom and uses it to permute the S-Boxes via Fn arc4random_addrandom .

There is no need to call Fn arc4random_stir before using Fn arc4random , since Fn arc4random automatically initializes itself.

EXAMPLES

The following produces a drop-in replacement for the traditional Fn rand and Fn random functions using Fn 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