OPENSSL-RAND(1SSL) OpenSSL OPENSSL-RAND(1SSL)
NAME
openssl-rand - generate pseudo-random bytes
SYNOPSIS
openssl rand [-help] [-out file] [-base64] [-hex] [-engine id] [-rand
files] [-writerand file] [-provider name] [-provider-path path]
[-provparam [name:]key=value] [-propquery propq] num[K|M|G|T]
DESCRIPTION
This command generates num random bytes using a cryptographically secure
pseudo random number generator (CSPRNG). A suffix [K|M|G|T] may be
appended to the num value to indicate the requested value be scaled as a
multiple of KiB/MiB/GiB/TiB respectively. Note that suffixes are case
sensitive, and that the suffixes represent binary multiples (K = 1024
bytes, M = 1024*1024 bytes, etc).
The string 'max' may be substituted for a numerical value in num, to
request the maximum number of bytes the CSPRNG can produce per
instantiation. Currently, this is restricted to 2^61 bytes as per NIST
SP 800-90C.
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 EVP_RAND(7).
OPTIONS
-help
Print out a usage message.
-out file
Write to file instead of standard output.
-base64
Perform base64 encoding on the output.
-hex
Show the output as a hex string.
-engine id
See "Engine Options" in openssl(1). This option is deprecated.
-rand files, -writerand file
See "Random State Options" in openssl(1) for details.
-provider name
-provider-path path
-provparam [name:]key=value
-propquery propq
See "Provider Options" in openssl(1), provider(7), and property(7).
SEE ALSO
openssl(1), RAND_bytes(3), RAND(7), EVP_RAND(7)
HISTORY
The -engine option was deprecated in OpenSSL 3.0.
COPYRIGHT
Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (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>.
3.5.4 2025-09-30 OPENSSL-RAND(1SSL)
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