.\"	$OpenBSD: idgen32.9,v 1.2 2011/01/09 00:06:50 deraadt Exp $
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.\" Copyright (c) 2008 Damien Miller <djm@mindrot.org>
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.Dd $Mdocdate: January 9 2011 $
.Dt IDGEN32 9
.Os
.Sh NAME
.Nm idgen32
.Nd non-repeating ID generation
.Sh SYNOPSIS
.Fd #include <crypto/idgen.h>
.Ft void
.Fn idgen32_init "struct idgen32_ctx *ctx"
.Ft uint32_t
.Fn idgen32 "struct idgen32_ctx *ctx"
.Sh DESCRIPTION
The
.Fn idgen32
functions provide a facility to generate a stream of 32-bit numbers
that are strongly unpredictable and have a repetition cycle close to
2^32.
Such numbers are useful as protocol identifiers where there are negative
consequences to reusing an ID within a short time period, as may happen
if they are simply assigned at random.
.Pp
The
.Fn idgen32_init
function prepares a context structure for use.
.Pp
The
.Fn idgen32
function returns a new ID in host byte order.
Note that this function will never return 0 as it often has a special
meaning in network protocols.
.Sh SEE ALSO
.Xr arc4random 9
.Sh HISTORY
The
.Nm
functions were added in
.Ox 4.4 .