genrsa

GENRSA(1SSL)                        OpenSSL                       GENRSA(1SSL)

NAME
       openssl-genrsa, genrsa - generate an RSA private key

SYNOPSIS
       openssl genrsa [-help] [-out filename] [-passout arg] [-aes128]
       [-aes192] [-aes256] [-aria128] [-aria192] [-aria256] [-camellia128]
       [-camellia192] [-camellia256] [-des] [-des3] [-idea] [-f4] [-3] [-rand
       file...]  [-writerand file] [-engine id] [-primes num] [numbits]

DESCRIPTION
       The genrsa command generates an RSA private key.

OPTIONS
       -help
           Print out a usage message.

       -out filename
           Output the key to the specified file. If this argument is not
           specified then standard output is used.

       -passout arg
           The output file password source. For more information about the
           format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).

       -aes128, -aes192, -aes256, -aria128, -aria192, -aria256, -camellia128,
       -camellia192, -camellia256, -des, -des3, -idea
           These options encrypt the private key with specified cipher before
           outputting it. If none of these options is specified no encryption
           is used. If encryption is used a pass phrase is prompted for if it
           is not supplied via the -passout argument.

       -F4|-3
           The public exponent to use, either 65537 or 3. The default is
           65537.

       -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.

       [-writerand file]
           Writes random data to the specified file upon exit.  This can be
           used with a subsequent -rand flag.

       -engine id
           Specifying an engine (by its unique id string) will cause genrsa to
           attempt to obtain a functional reference to the specified engine,
           thus initialising it if needed. The engine will then be set as the
           default for all available algorithms.

       -primes num
           Specify the number of primes to use while generating the RSA key.
           The num parameter must be a positive integer that is greater than 1
           and less than 16.  If num is greater than 2, then the generated key
           is called a 'multi-prime' RSA key, which is defined in RFC 8017.

       numbits
           The size of the private key to generate in bits. This must be the
           last option specified. The default is 2048 and values less than 512
           are not allowed.

NOTES
       RSA private key generation essentially involves the generation of two
       or more prime numbers. When generating a private key various symbols
       will be output to indicate the progress of the generation. A .
       represents each number which has passed an initial sieve test, + means
       a number has passed a single round of the Miller-Rabin primality test,
       * means the current prime starts a regenerating progress due to some
       failed tests. A newline means that the number has passed all the prime
       tests (the actual number depends on the key size).

       Because key generation is a random process the time taken to generate a
       key may vary somewhat. But in general, more primes lead to less
       generation time of a key.

SEE ALSO
       gendsa(1)

COPYRIGHT
       Copyright 2000-2018 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                            2023-10-10                      GENRSA(1SSL)