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+.\" $OpenBSD: arc4random.3,v 1.2 1997/04/27 22:40:25 angelos Exp $
+.\" Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de>
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"      This product includes software developed by Niels Provos.
+.\" 4. The name of the author may not be used to endorse or promote products
+.\"    derived from this software without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.\"
+.\" Manual page, using -mandoc macros
+.\" $FreeBSD$
+.\"
+.Dd April 15, 1997
+.Dt ARC4RANDOM 3
+.Os
+.Sh NAME
+.Nm arc4random ,
+.Nm arc4random_stir ,
+.Nm arc4random_addrandom
+.Nd arc4 random number generator
+.Sh LIBRARY
+.Lb libc
+.Sh 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"
+.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
+.if t 2\u\s71700\s10\d
+.if n (2**1700)
+states.
+The
+.Fn arc4random
+function returns pseudo-random numbers in the range of 0 to
+.if t 2\u\s731\s10\d\(mi1,
+.if n (2**32)\(mi1,
+and therefore has twice the range of
+.Xr rand 3
+and
+.Xr random 3 .
+.Pp
+The
+.Fn arc4random_stir
+function reads data from
+.Pa /dev/urandom
+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 EXAMPLES
+The following produces a drop-in replacement for the traditional
+.Fn rand
+and
+.Fn random
+functions using
+.Fn arc4random :
+.Pp
+.Dl "#define foo4random() (arc4random() % ((unsigned)RAND_MAX + 1))"
+.Sh SEE ALSO
+.Xr rand 3 ,
+.Xr random 3 ,
+.Xr srandomdev 3
+.Sh HISTORY
+.Pa 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
+.Pa RC4
+used to be a trade secret, the cipher is now referred to as
+.Pa ARC4 .