R Parent topic: R

random

Source of secure random data

Note: You must be root to start this service.

Syntax:

random [-hpt] [-i #] [-l library[:init_string]] [-m mode] [-s path] [-U string]

Runs on:

QNX Neutrino

Options:

-h
Show the usage message.
-i#
Use interrupt number # as a source for collecting random data. You may specify more than one interrupt, to a maximum of 32.
-l library[:init_string]
Load the given library to get more entropy. The value of init_string depends on the library.
-m mode
Specify the permissions, in octal, for the entry under /dev. The default is 0644.
-p
Poll system information from /proc for random data.
-s path
Save the state of the service in the given file, so that it can be reloaded when random is next started.
-t
Use the high-performance clock as a random data source.
-U string
(QNX Neutrino 6.6 or later) Once running, run as the specified user, so that the program doesn't need to run as root. The string can be in one of these forms:
  • uid[:gid[,sup_gid]*]
  • user_name[,sup_gid]*

In the second form, the primary group is the one specified for user_name in /etc/passwd.

Description:

The random service runs in the background providing a source of secure, pseudo-random data suitable for encryption and security. The service builds its internal pool of pseudo-random data from sources specified when it is started. These sources may include timers, interrupts, and detailed system runtime information. The service makes this random data available by providing device entries that any application can read:

These device entries provide the same functionality.

The user controls all of the sources to be used to collect random data by specifying source options on the command line.

Note: Using interrupts as sources imposes an overhead on system performance. When using the -i option, you might want to minimize the impact of this overhead by specifying only one or two interrupts from low interrupt rate devices such as disk drivers and input/serial devices.

Examples:

Start the random service using three PC interrupts as sources: 

random -i12 -i14 -i15

From an application, read 4 bytes of random data like this: 

int data;
int fd;

fd = open( "/dev/random", O_RDWR );
if( fd == -1 )
{
    exit( 1 );
}

read( fd, &data, sizeof( data ) );

close( fd );

Exit status:

0
The random data is available from /dev/random and /dev/urandom.
Any other value
An error occurred; /dev/random and /dev/urandom aren't created.

Errors:

If an error occurs, random sends a description of the error to slogger and doesn't create /dev/random or /dev/urandom.

Contributing author:

The random service uses the core algorithm from the copyright-free Yarrow pseudo-random number generator (PRNG) from Counterpane Security (http://www.counterpane.com/yarrow.html). Bruce Schneier and John Kelsey designed the Yarrow PRNG.

Caveats:

The random service doesn't work unless you specify at least one source of random data (options -p, -t, or -i).

Parent topic: R