|File: [cvs.NetBSD.org] / src / lib / libc / gen / arc4random.3 (download)
Revision 1.9, Sat Feb 5 00:24:08 2011 UTC (2 years, 4 months ago) by wiz
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Remove trailing whitespace.
.\" $NetBSD: arc4random.3,v 1.9 2011/02/05 00:24:08 wiz Exp $
.\" $OpenBSD: arc4random.3,v 1.17 2000/12/21 14:07:41 aaron Exp $
.\" Copyright 1997 Niels Provos <email@example.com>
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.\" Manual page, using -mandoc macros
.Dd February 4, 2011
.Dt ARC4RANDOM 3
.Nm arc4random ,
.Nm arc4random_buf ,
.Nm arc4random_uniform ,
.Nm arc4random_stir ,
.Nd arc4 random number generator
.Fn arc4random "void"
.Fn arc4random_buf "void *buffer" "size_t length"
.Fn arc4random_uniform "uint32_t upper_bound"
.Fn arc4random_stir "void"
.Fn arc4random_addrandom "u_char *dat" "int datlen"
function provides a high quality 32-bit pseudo-random
number very quickly.
seeds itself on a regular basis from the kernel strong random number
subsystem described in
.Xr rnd 4 .
On each call, an ARC4 generator is used to generate a new result.
function uses the ARC4 cipher key stream generator,
which uses 8*8 8 bit S-Boxes.
The S-Boxes can be in about (2**1700) states.
fits into a middle ground not covered by other subsystems such as
the strong, slow, and resource expensive random
devices described in
.Xr rnd 4
versus the fast but poor quality interfaces described in
.Xr rand 3 ,
.Xr random 3 ,
.Xr drand48 3 .
function fills the
bytes of ARC4-derived random data.
function returns a uniformly distributed random number less than
avoiding modulo bias when the upper bound is not a power of two.
function reads data from
and uses it to permute the S-Boxes via
.Fn arc4random_addrandom .
There is no need to call
.Fn arc4random ,
automatically initializes itself.
.Sh SEE ALSO
.Xr rand 3 ,
.Xr rand48 3 ,
.Xr random 3
An algorithm called
was designed by RSA Data Security, Inc.
It was considered a trade secret, but not trademarked.
Because it was a trade secret, it obviously could not be patented.
A clone of this was posted anonymously to USENET and 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 release of the ARC4 algorithm.
used to be a trade secret, the cipher is now referred to as
.Pa ARC4 .
These functions first appeared in
.Ox 2.1 .