diff options
| -rw-r--r-- | share/man/man4/random.4 | 64 |
1 files changed, 39 insertions, 25 deletions
diff --git a/share/man/man4/random.4 b/share/man/man4/random.4 index 1633c4d5fbd..160b72b9aae 100644 --- a/share/man/man4/random.4 +++ b/share/man/man4/random.4 @@ -1,4 +1,4 @@ -.\" $OpenBSD: random.4,v 1.31 2015/09/10 17:55:21 schwarze Exp $ +.\" $OpenBSD: random.4,v 1.32 2017/10/17 22:25:41 schwarze Exp $ .\" .\" Copyright (c) 1996, 1997 Michael Shalayeff .\" @@ -23,52 +23,66 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.Dd $Mdocdate: September 10 2015 $ +.Dd $Mdocdate: October 17 2017 $ .Dt RANDOM 4 .Os .Sh NAME .Nm random , -.Nm arandom -.Nd random data source devices +.Nm urandom +.Nd random data source device .Sh SYNOPSIS .In sys/types.h .In dev/rndvar.h .Sh DESCRIPTION -The various -.Nm -devices produce high quality random output data. +The +.Nm urandom +device produces high quality pseudo-random output data without ever +blocking, even immediately after booting. Entropy data is collected from system activity (such as disk, network, -and clock device interrupts), and then used to key the -ChaCha stream cipher to generate the output. -All the random devices are expected to provide high quality -pseudo-random output data. +and clock device interrupts), and then used to key a stream cipher +to generate the output. .Pp The +.Nm urandom +device is intended to be used in scripts. +In C programs, use the .Xr arc4random 3 -function in userland libraries should be used instead, as it works -without the need to access these devices every time. +family of functions instead, which can be called in almost all +coding environments, including +.Xr pthreads 3 , +.Xr chroot 2 , +and +.Xr pledge 2 , +and which avoids accessing a device every time. +.Pp +Never use +.Pa /dev/random . +On +.Ox , +it does the same as +.Pa /dev/urandom , +but on many other systems, it misbehaves. +For example, it may block, directly return entropy instead of using +a stream cipher, or only return data from hardware random generators. .Sh FILES .Bl -tag -width /dev/arandom -compact -.It Pa /dev/random -.It Pa /dev/arandom +.It Pa /dev/urandom .El .Sh SEE ALSO .Xr arc4random 3 , -.Xr md5 3 , -.Xr random 3 , .Xr amdpm 4 , .Xr glxsb 4 , .Xr pchb 4 , -.Xr arc4random 9 , -.Xr md5 9 +.Xr arc4random 9 .Sh HISTORY A .Nm -device first appeared in the Linux operating system. -This is a cloned interface. -.Pp -ARC4 routines added by David Mazieres. -Changed to use the ChaCha cipher in -.Ox 5.5 . +device first appeared in Linux in 1994. +The +.Nm random +and +.Nm urandom +devices have been available since +.Ox 2.0 . .Sh BUGS No randomness testing suite provided. |