openssl-genpkey - generate a private key
openssl genpkey [
-help] [
-out filename] [
-outform DER|
PEM] [
-quiet] [
-pass
arg] [
-cipher] [
-paramfile
file] [
-algorithm alg] [
-pkeyopt
opt:
value] [
-genparam] [
-text] [
-engine
id] [
-provider name] [
-provider-path
path] [
-propquery propq] [
-config
configfile]
This command generates a 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.
-
-outform DER|PEM
- The output format, except when -genparam is given;
the default is PEM. See openssl-format-options(1) for
details.
When -genparam is given, -outform is ignored.
- -quiet
- Do not output "status dots" while generating
keys.
-
-pass arg
- The output file password source. For more information about
the format of arg see openssl-passphrase-options(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.
-
-algorithm alg
- Public key algorithm to use such as RSA, DSA, DH or DHX. If
used this option must precede any -pkeyopt options. The options
-paramfile and -algorithm are mutually exclusive. Engines
may add algorithms in addition to the standard built-in ones.
Valid built-in algorithm names for private key generation are RSA, RSA-PSS,
EC, X25519, X448, ED25519 and ED448.
Valid built-in algorithm names for parameter generation (see the
-genparam option) are DH, DSA and EC.
Note that the algorithm name X9.42 DH may be used as a synonym for DHX keys
and PKCS#3 refers to DH Keys. Some options are not shared between DH and
DHX keys.
-
-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" and "PARAMETER 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.
-
-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).
-
-config configfile
- See "Configuration Option" in
openssl(1).
The options supported by each algorithm and indeed each implementation of an
algorithm can vary. The options for the OpenSSL implementations are detailed
below. There are no key generation options defined for the X25519, X448,
ED25519 or ED448 algorithms.
- rsa_keygen_bits:numbits
- The number of bits in the generated key. If not specified
2048 is used.
- rsa_keygen_primes:numprimes
- The number of primes in the generated key. If not specified
2 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.
Note: by default an
RSA-PSS key has no parameter restrictions.
-
rsa_keygen_bits:numbits,
rsa_keygen_primes: numprimes,
rsa_keygen_pubexp:value
- These options have the same meaning as the RSA
algorithm.
-
rsa_pss_keygen_md:digest
- If set the key is restricted and can only use digest
for signing.
-
rsa_pss_keygen_mgf1_md:digest
- If set the key is restricted and can only use digest
as it's MGF1 parameter.
-
rsa_pss_keygen_saltlen:len
- If set the key is restricted and len specifies the
minimum salt length.
The EC key generation options can also be used for parameter generation.
-
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. The
default value is named_curve.
-
group:name
- The paramfile option is not required if a named
group is used here. See the "DH Parameter Generation Options"
section below.
The options supported by each algorithm and indeed each implementation of an
algorithm can vary. The options for the OpenSSL implementations are detailed
below.
-
dsa_paramgen_bits:numbits
- The number of bits in the generated prime. If not specified
2048 is used.
-
dsa_paramgen_q_bits:numbits
-
qbits:numbits
- The number of bits in the q parameter. Must be one of 160,
224 or 256. If not specified 224 is used.
-
dsa_paramgen_md:digest
-
digest:digest
- The digest to use during parameter generation. Must be one
of sha1, sha224 or sha256. If set, then the number of
bits in q will match the output size of the specified digest and
the dsa_paramgen_q_bits parameter will be ignored. If not set, then
a digest will be used that gives an output matching the number of bits in
q, i.e. sha1 if q length is 160, sha224 if it 224 or
sha256 if it is 256.
-
properties:query
- The digest property query string to use when
fetching a digest from a provider.
-
type:type
- The type of generation to use. Set this to 1 to use legacy
FIPS186-2 parameter generation. The default of 0 uses FIPS186-4 parameter
generation.
-
gindex:index
- The index to use for canonical generation and verification
of the generator g. Set this to a positive value ranging from 0..255 to
use this mode. Larger values will only use the bottom byte. This
index must then be reused during key validation to verify the value
of g. If this value is not set then g is not verifiable. The default value
is -1.
-
hexseed:seed
- The seed seed data to use instead of generating a
random seed internally. This should be used for testing purposes only.
This will either produced fixed values for the generated parameters OR it
will fail if the seed did not generate valid primes.
For most use cases it is recommended to use the
group option rather than
the
type options. Note that the
group option is not used by
default if no parameter generation options are specified.
-
group:name
-
dh_param:name
- Use a named DH group to select constant values for the DH
parameters. All other options will be ignored if this value is set.
Valid values that are associated with the algorithm of
"DH" are: "ffdhe2048", "ffdhe3072",
"ffdhe4096", "ffdhe6144", "ffdhe8192",
"modp_1536", "modp_2048", "modp_3072",
"modp_4096", "modp_6144", "modp_8192".
Valid values that are associated with the algorithm of
"DHX" are the RFC5114 names "dh_1024_160",
"dh_2048_224", "dh_2048_256".
-
dh_rfc5114:num
- If this option is set, then the appropriate RFC5114
parameters are used instead of generating new parameters. The value
num can be one of 1, 2 or 3 that are equivalent to using the option
group with one of "dh_1024_160", "dh_2048_224"
or "dh_2048_256". All other options will be ignored if this
value is set.
-
pbits:numbits
-
dh_paramgen_prime_len:numbits
- The number of bits in the prime parameter p. The
default is 2048.
-
qbits:numbits
-
dh_paramgen_subprime_len:numbits
- The number of bits in the sub prime parameter q. The
default is 224. Only relevant if used in conjunction with the
dh_paramgen_type option to generate DHX parameters.
-
safeprime-generator:value
-
dh_paramgen_generator:value
- The value to use for the generator g. The default is
2. The algorithm option must be "DH" for this
parameter to be used.
-
type:string
- The type name of DH parameters to generate. Valid values
are:
- "generator"
- Use a safe prime generator with the option
safeprime_generator The algorithm option must be
"DH".
- "fips186_4"
- FIPS186-4 parameter generation. The algorithm option
must be "DHX".
- "fips186_2"
- FIPS186-4 parameter generation. The algorithm option
must be "DHX".
- "group"
- Can be used with the option pbits to select one of
"ffdhe2048", "ffdhe3072", "ffdhe4096",
"ffdhe6144" or "ffdhe8192". The algorithm
option must be "DH".
- "default"
- Selects a default type based on the algorithm. This
is used by the OpenSSL default provider to set the type for backwards
compatibility. If algorithm is "DH" then
"generator" is used. If algorithm is
"DHX" then "fips186_2" is used.
-
dh_paramgen_type:value
- The type of DH parameters to generate. Valid values are 0,
1, 2 or 3 which correspond to setting the option type to
"generator", "fips186_2", "fips186_4" or
"group".
-
digest:digest
- The digest to use during parameter generation. Must be one
of sha1, sha224 or sha256. If set, then the number of
bits in qbits will match the output size of the specified digest
and the qbits parameter will be ignored. If not set, then a digest
will be used that gives an output matching the number of bits in q,
i.e. sha1 if q length is 160, sha224 if it is 224 or
sha256 if it is 256. This is only used by "fips186_4" and
"fips186_2" key generation.
-
properties:query
- The digest property query string to use when
fetching a digest from a provider. This is only used by
"fips186_4" and "fips186_2" key generation.
-
gindex:index
- The index to use for canonical generation and verification
of the generator g. Set this to a positive value ranging from 0..255 to
use this mode. Larger values will only use the bottom byte. This
index must then be reused during key validation to verify the value
of g. If this value is not set then g is not verifiable. The default value
is -1. This is only used by "fips186_4" and
"fips186_2" key generation.
-
hexseed:seed
- The seed seed data to use instead of generating a
random seed internally. This should be used for testing purposes only.
This will either produced fixed values for the generated parameters OR it
will fail if the seed did not generate valid primes. This is only used by
"fips186_4" and "fips186_2" key generation.
The EC parameter generation options are the same as for key generation. See
"EC Key Generation Options" above.
The use of the genpkey program is encouraged over the algorithm specific
utilities because additional algorithm options and ENGINE provided algorithms
can be used.
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 2048 bit DSA parameters that can be validated: The output values for
gindex and seed are required for key validation purposes and are not saved to
the output pem file).
openssl genpkey -genparam -algorithm DSA -out dsap.pem -pkeyopt pbits:2048 \
-pkeyopt qbits:224 -pkeyopt digest:SHA256 -pkeyopt gindex:1 -text
Generate DSA key from parameters:
openssl genpkey -paramfile dsap.pem -out dsakey.pem
Generate 4096 bit DH Key using safe prime group ffdhe4096:
openssl genpkey -algorithm DH -out dhkey.pem -pkeyopt group:ffdhe4096
Generate 2048 bit X9.42 DH key with 256 bit subgroup using RFC5114 group3:
openssl genpkey -algorithm DHX -out dhkey.pem -pkeyopt dh_rfc5114:3
Generate a DH key using a DH parameters file:
openssl genpkey -paramfile dhp.pem -out dhkey.pem
Output DH parameters for safe prime group ffdhe2048:
openssl genpkey -genparam -algorithm DH -out dhp.pem -pkeyopt group:ffdhe2048
Output 2048 bit X9.42 DH parameters with 224 bit subgroup using RFC5114 group2:
openssl genpkey -genparam -algorithm DHX -out dhp.pem -pkeyopt dh_rfc5114:2
Output 2048 bit X9.42 DH parameters with 224 bit subgroup using FIP186-4 keygen:
openssl genpkey -genparam -algorithm DHX -out dhp.pem -text \
-pkeyopt pbits:2048 -pkeyopt qbits:224 -pkeyopt digest:SHA256 \
-pkeyopt gindex:1 -pkeyopt dh_paramgen_type:2
Output 1024 bit X9.42 DH parameters with 160 bit subgroup using FIP186-2 keygen:
openssl genpkey -genparam -algorithm DHX -out dhp.pem -text \
-pkeyopt pbits:1024 -pkeyopt qbits:160 -pkeyopt digest:SHA1 \
-pkeyopt gindex:1 -pkeyopt dh_paramgen_type:1
Output 2048 bit DH parameters:
openssl genpkey -genparam -algorithm DH -out dhp.pem \
-pkeyopt dh_paramgen_prime_len:2048
Output 2048 bit DH parameters using a generator:
openssl genpkey -genparam -algorithm DH -out dhpx.pem \
-pkeyopt dh_paramgen_prime_len:2048 \
-pkeyopt dh_paramgen_type:1
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
Generate an ED448 private key:
openssl genpkey -algorithm ED448 -out xkey.pem
The ability to use NIST curve names, and to generate an EC key directly, were
added in OpenSSL 1.0.2. The ability to generate X25519 keys was added in
OpenSSL 1.1.0. The ability to generate X448, ED25519 and ED448 keys was added
in OpenSSL 1.1.1.
The
-engine option was deprecated in OpenSSL 3.0.
Copyright 2006-2023 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>.