.\" Copyright IBM Corp. 2007, 2017
.\" s390-tools is free software; you can redistribute it and/or modify
.\" it under the terms of the MIT license. See LICENSE for details.
.\"
.TH PRANDOM 4 "Jan 2007" "s390-tools"

.SH NAME
prandom \- kernel pseudo random number generator device for s390
.SH DESCRIPTION
The character special file \fI/dev/prandom\fP provides an interface to the 
pseudo random number generator. The s390 pseudo random number generator uses
the hardware accelerated cryptographic assist functions which are integrated
in the CPU. \fI/dev/prandom\fP is available starting with the z9 processor.
.LP
Reading from \fI/dev/prandom\fP is non-blocking. Any amount of data could
be read from the device.
.LP
The s390 pseudo random number generator provides cryptographically secure 
pseudo random numbers following the algorithm in ANSI X9.17. Entropy is added 
periodically to the generator to protect against a compromised key.

.LP
.SH CONFIGURATION
The \fI/dev/prandom\fP device node is generated by udev while loading the corresponding kernel
module or while booting a kernel with the generator built-in. By default
\fI/dev/prandom\fP is readable only by root. If it should be readable by every user
add the following to /etc/rules.d/50-udev.rules:

.nf
	KERNEL=="prandom",              MODE="0444", OPTIONS="last_rule"
.fi

.SH FILES
/dev/prandom

.SH SEE ALSO
Linux on zSeries: Device Drivers, Features and Commands