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>.
1.1.1g 2020-04-21 GENRSA(1SSL)