1.\" $OpenBSD: arc4random.3,v 1.2 1997/04/27 22:40:25 angelos Exp $ 2.\" Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. All advertising materials mentioning features or use of this software 14.\" must display the following acknowledgement: 15.\" This product includes software developed by Niels Provos. 16.\" 4. The name of the author may not be used to endorse or promote products 17.\" derived from this software without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 20.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 23.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29.\" 30.\" Manual page, using -mandoc macros 31.\" $FreeBSD$ 32.\" 33.Dd April 15, 1997 34.Dt ARC4RANDOM 3 35.Os 36.Sh NAME 37.Nm arc4random , 38.Nm arc4random_stir , 39.Nm arc4random_addrandom 40.Nd arc4 random number generator. 41.Sh SYNOPSIS 42.Fd #include <stdlib.h> 43.Ft u_int32_t 44.Fn arc4random "void" 45.Ft void 46.Fn arc4random_stir "void" 47.Ft void 48.Fn arc4random_addrandom "unsigned char *dat" "int datlen" 49.Sh DESCRIPTION 50The 51.Fn arc4random 52function uses the key stream generator employed by the 53arc4 cipher, which uses 8*8 8 bit S-Boxes. The S-Boxes 54can be in about 55.if t 2\u\s71700\s10\d 56.if n (2**1700) 57states. 58.Pp 59The 60.Fn arc4random_stir 61function reads data from 62.Pa /dev/urandom 63and uses it to permute the S-Boxes via 64.Fn arc4random_addrandom . 65.Pp 66There is no need to call 67.Fn arc4random_stir 68before using 69.Fn arc4random , 70since 71.Fn arc4random 72automatically initializes itself. 73.Sh SEE ALSO 74.Xr rand 3 , 75.Xr random 3 , 76.Xr srandomdev 3 77.Sh HISTORY 78.Pa RC4 79has been designed by RSA Data Security, Inc. It was posted anonymously 80to the USENET and was confirmed to be equivalent by several sources who 81had access to the original cipher. Since 82.Pa RC4 83used to be a trade secret, the cipher is now referred to as 84.Pa ARC4 . 85