OPENSSL-GENRSA(1SSL) OpenSSL OPENSSL-GENRSA(1SSL)
NAME
openssl-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] [-f4] [-3]
[-primes num] [-verbose] [-quiet] [-traditional] [-rand files]
[-writerand file] [-engine id] [-provider name] [-provider-path path]
[-provparam [name:]key=value] [-propquery propq] [numbits]
DESCRIPTION
This 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 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.
-quiet
Print fewer details about the operations being performed, which may
be handy during batch scripts and pipelines.
-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
-provparam [name:]key=value
-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.
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
openssl(1), openssl-genpkey(1), openssl-gendsa(1)
COPYRIGHT
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>.
3.5.4 2025-09-30 OPENSSL-GENRSA(1SSL)
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