GENPKEY(1SSL) OpenSSL GENPKEY(1SSL)NAME
openssl-genpkey, genpkey - generate a private key
SYNOPSIS
openssl genpkey [-help] [-out filename] [-outform PEM|DER] [-pass arg]
[-cipher] [-engine id] [-paramfile file] [-algorithm alg] [-pkeyopt
opt:value] [-genparam] [-text]
DESCRIPTION
The genpkey command generates a 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.
-outform DER|PEM
This specifies the output format DER or PEM.
-pass arg
the output file password source. For more information about the
format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).
-cipher
This option encrypts the private key with the supplied cipher. Any
algorithm name accepted by EVP_get_cipherbyname() is acceptable
such as des3.
-engine id
specifying an engine (by its unique id string) will cause genpkey
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. If used this option
should precede all other options.
-algorithm alg
public key algorithm to use such as RSA, DSA or DH. If used this
option must precede any -pkeyopt options. The options -paramfile
and -algorithm are mutually exclusive.
-pkeyopt opt:value
set the public key algorithm option opt to value. The precise set
of options supported depends on the public key algorithm used and
its implementation. See KEY GENERATION OPTIONS below for more
details.
-genparam
generate a set of parameters instead of a private key. If used this
option must precede any -algorithm, -paramfile or -pkeyopt options.
-paramfile filename
Some public key algorithms generate a private key based on a set of
parameters. They can be supplied using this option. If this option
is used the public key algorithm used is determined by the
parameters. If used this option must precede any -pkeyopt options.
The options -paramfile and -algorithm are mutually exclusive.
-text
Print an (unencrypted) text representation of private and public
keys and parameters along with the PEM or DER structure.
KEY GENERATION OPTIONS
The options supported by each algorithm and indeed each implementation
of an algorithm can vary. The options for the OpenSSL implementations
are detailed below.
RSA KEY GENERATION OPTIONS
rsa_keygen_bits:numbits
The number of bits in the generated key. If not specified 1024 is
used.
rsa_keygen_pubexp:value
The RSA public exponent value. This can be a large decimal or
hexadecimal value if preceded by 0x. Default value is 65537.
DSA PARAMETER GENERATION OPTIONS
dsa_paramgen_bits:numbits
The number of bits in the generated parameters. If not specified
1024 is used.
DH PARAMETER GENERATION OPTIONS
dh_paramgen_prime_len:numbits
The number of bits in the prime parameter p.
dh_paramgen_generator:value
The value to use for the generator g.
dh_rfc5114:num
If this option is set then the appropriate RFC5114 parameters are
used instead of generating new parameters. The value num can take
the values 1, 2 or 3 corresponding to RFC5114 DH parameters
consisting of 1024 bit group with 160 bit subgroup, 2048 bit group
with 224 bit subgroup and 2048 bit group with 256 bit subgroup as
mentioned in RFC5114 sections 2.1, 2.2 and 2.3 respectively.
EC PARAMETER GENERATION OPTIONS
The EC parameter generation options below can also be supplied as EC
key generation options. This can (for example) generate a key from a
named curve without the need to use an explicit parameter file.
ec_paramgen_curve:curve
the EC curve to use. OpenSSL supports NIST curve names such as
"P-256".
ec_param_enc:encoding
the encoding to use for parameters. The "encoding" parameter must
be either "named_curve" or "explicit".
GOST2001 KEY GENERATION AND PARAMETER OPTIONS
Gost 2001 support is not enabled by default. To enable this algorithm,
one should load the ccgost engine in the OpenSSL configuration file.
See README.gost file in the engines/ccgost directory of the source
distribution for more details.
Use of a parameter file for the GOST R 34.10 algorithm is optional.
Parameters can be specified during key generation directly as well as
during generation of parameter file.
paramset:name
Specifies GOST R 34.10-2001 parameter set according to RFC 4357.
Parameter set can be specified using abbreviated name, object short
name or numeric OID. Following parameter sets are supported:
paramset OID Usage
A 1.2.643.2.2.35.1 Signature
B 1.2.643.2.2.35.2 Signature
C 1.2.643.2.2.35.3 Signature
XA 1.2.643.2.2.36.0 Key exchange
XB 1.2.643.2.2.36.1 Key exchange
test 1.2.643.2.2.35.0 Test purposes
X25519 KEY GENERATION OPTIONS
The X25519 algorithm does not currently support any key generation
options.
NOTES
The use of the genpkey program is encouraged over the algorithm
specific utilities because additional algorithm options and ENGINE
provided algorithms can be used.
EXAMPLES
Generate an RSA private key using default parameters:
openssl genpkey -algorithm RSA -out key.pem
Encrypt output private key using 128 bit AES and the passphrase
"hello":
openssl genpkey -algorithm RSA -out key.pem -aes-128-cbc -pass pass:hello
Generate a 2048 bit RSA key using 3 as the public exponent:
openssl genpkey -algorithm RSA -out key.pem -pkeyopt rsa_keygen_bits:2048 \
-pkeyopt rsa_keygen_pubexp:3
Generate 1024 bit DSA parameters:
openssl genpkey -genparam -algorithm DSA -out dsap.pem \
-pkeyopt dsa_paramgen_bits:1024
Generate DSA key from parameters:
openssl genpkey -paramfile dsap.pem -out dsakey.pem
Generate 1024 bit DH parameters:
openssl genpkey -genparam -algorithm DH -out dhp.pem \
-pkeyopt dh_paramgen_prime_len:1024
Output RFC5114 2048 bit DH parameters with 224 bit subgroup:
openssl genpkey -genparam -algorithm DH -out dhp.pem -pkeyopt dh_rfc5114:2
Generate DH key from parameters:
openssl genpkey -paramfile dhp.pem -out dhkey.pem
Generate EC parameters:
openssl genpkey -genparam -algorithm EC -out ecp.pem \
-pkeyopt ec_paramgen_curve:secp384r1 \
-pkeyopt ec_param_enc:named_curve
Generate EC key from parameters:
openssl genpkey -paramfile ecp.pem -out eckey.pem
Generate EC key directly:
openssl genpkey -algorithm EC -out eckey.pem \
-pkeyopt ec_paramgen_curve:P-384 \
-pkeyopt ec_param_enc:named_curve
Generate an X25519 private key:
openssl genpkey -algorithm X25519 -out xkey.pem
HISTORY
The ability to use NIST curve names, and to generate an EC key
directly, were added in OpenSSL 1.0.2.
COPYRIGHT
Copyright 2006-2016 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>.
1.1.0g 2017-11-04 GENPKEY(1SSL)