openssl-genrsa - generate an RSA private key
openssl genrsa [-help] [-out filename]
[-passout arg] [-aes128] [-aes192]
[-aes256] [-aria128] [-aria192] [-aria256]
[-camellia128] [-camellia192] [-camellia256]
[-des] [-des3] [-idea] [-F4] [-f4]
[-3] [-primes num] [-verbose]
[-traditional] [-rand files] [-writerand
file] [-engine id] [-provider name]
[-provider-path path] [-propquery propq]
[numbits]
This command generates an RSA private key.
- -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 see
openssl-passphrase-options(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, -f4, -3
- The public exponent to use, either 65537 or 3. The default is 65537. The
-3 option has been deprecated.
- -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.
- -verbose
- Print extra details about the operations being performed.
- -traditional
- Write the key using the traditional PKCS#1 format instead of the PKCS#8
format.
- -rand files, -writerand file
- See "Random State Options" in openssl(1) for
details.
- -engine id
- See "Engine Options" in openssl(1). This option is
deprecated.
- -provider name
- -provider-path path
- -propquery propq
- See "Provider Options" in openssl(1), provider(7),
and property(7).
- 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.
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.
openssl(1), openssl-genpkey(1), openssl-gendsa(1)
Copyright 2000-2023 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>.