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>.

1.1.1f                                             2025-02-05                                         RAND(1SSL)