83a03b388f
srandomdev(), but can be used inside libraries. random() can't be used inside libraries because it breaks its possible predictable sequence. arc4random() is true random as designed, so its usage is library-safe. Obtained from: OpenBSD
84 lines
2.9 KiB
Groff
84 lines
2.9 KiB
Groff
.\" $OpenBSD: arc4random.3,v 1.2 1997/04/27 22:40:25 angelos Exp $
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.\" Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Niels Provos.
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" Manual page, using -mandoc macros
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.\"
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.Dd April 15, 1997
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.Dt ARC4RANDOM 3
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.Os
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.Sh NAME
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.Nm arc4random,
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.Nm arc4random_stir,
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.Nm arc4random_addrandom
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.Nd arc4 random number generator.
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.Sh SYNOPSIS
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.Fd #include <stdlib.h>
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.Ft u_int32_t
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.Fn arc4random "void"
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.Ft void
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.Fn arc4random_stir "void"
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.Ft void
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.Fn arc4random_addrandom "u_char *dat" "int datlen"
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.Sh DESCRIPTION
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The
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.Fn arc4random
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function uses the key stream generator employed by the
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arc4 cipher, which uses 8*8 8 bit S-Boxes. The S-Boxes
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can be in about
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.if t 2\u\s71700\s10\d
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.if n (2**1700)
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states.
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.Pp
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The
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.Fn arc4random_stir
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function reads data from
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.Pa /dev/urandom
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and uses it to permutate the S-Boxes via
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.Fn arc4random_addrandom .
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.Pp
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There is no need to call
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.Fn arc4random_stir
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before using
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.Fn arc4random ,
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since
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.Fn arc4random
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automatically initalizes itself.
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.Sh SEE ALSO
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.Xr rand 3 ,
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.Xr random 3 ,
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.Xr srandomdev 3
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.Sh HISTORY
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.Pa RC4
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has been designed by RSA Data Security, Inc. It was posted anonymously
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to the USENET and was confirmed to be equivalent by several sources who
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had access to the original cipher. Since
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.Pa RC4
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used to be a trade secret, the cipher is now refered to as
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.Pa ARC4 .
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