.\" $OpenBSD: arc4random.3,v 1.10 1999/07/04 18:59:42 aaron Exp $
.\" Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de>
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.\" Manual page, using -mandoc macros
.\"
.Dd April 15, 1997
.Dt ARC4RANDOM 3
.Os
.Sh NAME
.Nm arc4random,
.Nm arc4random_stir,
.Nm arc4random_addrandom
.Nd arc4 random number generator
.Sh SYNOPSIS
.Fd #include <stdlib.h>
.Ft u_int32_t
.Fn arc4random "void"
.Ft void
.Fn arc4random_stir "void"
.Ft void
.Fn arc4random_addrandom "u_char *dat" "int datlen"
.Sh 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.
.Pp
The
.Fn arc4random_stir
function reads data from 
.Pa /dev/arandom
and uses it to permute the S-Boxes via
.Fn arc4random_addrandom .
.Pp
There is no need to call 
.Fn arc4random_stir
before using
.Fn arc4random ,
since
.Fn arc4random
automatically initializes itself.
.Sh SEE ALSO
.Xr rand 3 ,
.Xr rand48 3 ,
.Xr random 3
.Sh HISTORY
An algorithm call
.Pa RC4 
was designed by RSA Data Security, Inc.  It was considered a trade secret,
but not trademarked.
A clone of this was posted anonymously to the USENET and was confirmed to
be equivalent by several sources who had access to the original cipher.
Because of the trade secret situation, RSA Data Security, Inc. can do
nothing about the situation.
Since
.Pa RC4
used to be a trade secret, the cipher is now referred to as 
.Pa ARC4 .