1.\" $OpenBSD: random.4,v 1.29 2011/01/11 15:26:05 deraadt Exp $ 2.\" 3.\" Copyright (c) 1996, 1997 Michael Shalayeff 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.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.Dd $Mdocdate: January 11 2011 $ 27.Dt RANDOM 4 28.Os 29.Sh NAME 30.Nm random , 31.Nm arandom 32.Nd random data source devices 33.Sh SYNOPSIS 34.Fd #include <sys/types.h> 35.Fd #include <dev/rndvar.h> 36.Sh DESCRIPTION 37The various 38.Nm 39devices produce high quality random output data. 40Entropy data is collected from system activity (like disk, network, 41and clock device interrupts and such), and then run through various 42hash or message digest functions to generate the output. 43All the random devices are expected to provide high quality 44pseudo-random output data. 45.Pp 46The 47.Xr arc4random 3 48function in userland libraries seeds itself from this device (or with 49the 50.Xr sysctl 3 51interface), 52providing a second level of ARC4 hashed data without the need to access 53these devices every time. 54.Sh FILES 55.Bl -tag -width /dev/arandom -compact 56.It Pa /dev/random 57.It Pa /dev/arandom 58.El 59.Sh SEE ALSO 60.Xr arc4random 3 , 61.Xr md5 3 , 62.Xr random 3 , 63.Xr amdpm 4 , 64.Xr glxsb 4 , 65.Xr pchb 4 , 66.Xr arc4random 9 , 67.Xr md5 9 68.Sh HISTORY 69A 70.Nm 71device first appeared in the Linux operating system. 72This is a cloned interface. 73.Pp 74ARC4 routines added by David Mazieres. 75.Sh BUGS 76No randomness testing suite provided. 77