.\"	$OpenBSD: random.9,v 1.12 2002/05/27 01:59:58 deraadt Exp $
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.\" Copyright (c) 1996,2000 Michael Shalayeff
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.Dd March 26, 1996
.Dt RND 9
.Os
.Sh NAME
.Nm random
.Nd device kernel interface
.Sh SYNOPSIS
.Fd #include <dev/rndvar.h>
.Ft void
.Fn add_true_randomness "int"
.Ft void
.Fn add_timer_randomness "int"
.Ft void
.Fn add_mouse_randomness "int"
.Ft void
.Fn add_tty_randomness "int"
.Ft void
.Fn add_net_randomness "int"
.Ft void
.Fn add_disk_randomness "int"
.Ft void
.Fn add_audio_randomness "int"
.Ft void
.Fn get_random_bytes "void *buf" "size_t nbytes"
.Ft u_int32_t
.Fn arc4random "void"
.br
.Sh DESCRIPTION
.Nm add_mouse_randomness ,
.Nm add_tty_randomness ,
.Nm add_net_randomness ,
.Nm add_disk_randomness ,
.Nm add_audio_randomness
routines are used to
supply data for the random data source device for further processing.
The processing involves calculating inter-event time delta and measuring
entropy contained in the resulting delta-T, supplied in argument data
is just mixed into the pool and does not increase entropy counter.
.br
.Nm add_true_randomness
does not involve usual timing calculations
and causes supplied data argument added to the entropy pool
increasing the entropy counter by 32 bits.
.br
.Nm add_timer_randomness
will not cause entropy counter to rise, it
is used to change the state of the pool periodically mostly
by meaning of timing random driver's operations.
.Pp
.Nm get_random_bytes
may be used to retrieve strong random data, just
as it would by
.Xr srandom 4
device.
.br
.Nm arc4random
will give random 32 bit numbers hashed with
the ARC4 algorithm, which appears to be faster and less abusive
to the entropy pool.
.Sh SEE ALSO
.Xr arc4random 3 ,
.Xr pchb 4 ,
.Xr random 4