RAND(1SSL) OpenSSL RAND(1SSL)
NAME
openssl-rand, rand - generate pseudo-random bytes
SYNOPSIS
openssl rand [-help] [-out file] [-rand file...] [-writerand file]
[-base64] [-hex] num
DESCRIPTION
This command generates num random bytes using a cryptographically
secure pseudo random number generator (CSPRNG).
The random bytes are generated using the RAND_bytes(3) function, which
provides a security level of 256 bits, provided it managed to seed
itself successfully from a trusted operating system entropy source.
Otherwise, the command will fail with a nonzero error code. For more
details, see RAND_bytes(3), RAND(7), and RAND_DRBG(7).
OPTIONS
-help
Print out a usage message.
-out file
Write to file instead of standard output.
-rand file...
A file or files containing random data used to seed the random
number generator. Multiple files can be specified separated by an
OS-dependent character. The separator is ; for MS-Windows, , for
OpenVMS, and : for all others. Explicitly specifying a seed file
is in general not necessary, see the "NOTES" section for more
information.
[-writerand file]
Writes random data to the specified file upon exit. This can be
used with a subsequent -rand flag.
-base64
Perform base64 encoding on the output.
-hex
Show the output as a hex string.
NOTES
Prior to OpenSSL 1.1.1, it was common for applications to store
information about the state of the random-number generator in a file
that was loaded at startup and rewritten upon exit. On modern operating
systems, this is generally no longer necessary as OpenSSL will seed
itself from a trusted entropy source provided by the operating system.
The -rand and -writerand flags are still supported for special
platforms or circumstances that might require them.
It is generally an error to use the same seed file more than once and
every use of -rand should be paired with -writerand.
SEE ALSO
RAND_bytes(3), RAND(7), RAND_DRBG(7)
COPYRIGHT
Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
1.1.1g 2020-04-21 RAND(1SSL)