OPENSSL-GENPKEY(1ossl)

✨ NAME ✨

openssl-genpkey — generate a private key or key pair. Welcome to the OPENSSL-GENPKEY(1ossl) page, bestie — this is the OpenSSL manual energy you asked for. Key-making main character behavior.

🦋 SYNOPSIS 🦋

openssl genpkey [-help] [-out filename] [-outpubkey filename] [-outform
DER|PEM] [-verbose] [-quiet] [-pass arg] [-cipher] [-paramfile file]
[-algorithm alg] [-pkeyopt opt:value] [-genparam] [-text] [-rand files]
[-writerand file] [-engine id]

[-provider name] [-provider-path path] [-provparam [name:]key=value]
[-propquery propq] [-config configfile]

💖 DESCRIPTION 💖

This command generates a private key or key pair. That's it. That's the whole job. No cap.

🌸 OPTIONS 🌸

okay bestie, here's the flag menu. Every single one, no skipping.

-help — Print out a usage message. the "help me" button, iconic.
-out filename — Output the private key to the specified file. If this argument is not specified then standard output is used. so if you don't name a file, it sends the key to stdout.
-outpubkey filename — Output the public key to the specified file. If this argument is not specified then the public key is not output.
-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. the way that -outform gets ignored with -genparam? it's giving "not invited to the party."
-verbose — Output "status dots" while generating keys. little progress dots, we love a visual.
-quiet — Do not output "status dots" while generating keys. silent mode, lowkey mysterious.
-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 or providers 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, ED448, ML-DSA and ML-KEM. 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. this is the big one, bestie — read it twice.
-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. To list the possible opt values for an algorithm use: openssl genpkey -algorithm XXX -help. iykyk, the help flag is your bestie here.
-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. unencrypted text representation, so maybe don't paste it in the group chat.
-rand files — See "Random State Options" in openssl(1) for details.
-writerand file — See "Random State Options" in openssl(1) for details.
-engine id — See "Engine Options" in openssl(1). This option is deprecated. ⚠️ deprecated, fr fr.
-provider name — See "Provider Options" in openssl(1), provider(7), and property(7).
-provider-path path — See "Provider Options" in openssl(1), provider(7), and property(7).
-provparam [name:]key=value — See "Provider Options" in openssl(1), provider(7), and property(7).
-propquery propq — See "Provider Options" in openssl(1), provider(7), and property(7).
-config configfile — See "Configuration Option" in openssl(1).

🔥 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. There are no key generation options defined for the X25519, X448, ED25519 or ED448 algorithms. so if you're using one of those four, the options section is giving empty plate energy.

🎀 RSA Key Generation Options 🎀

rsa_keygen_bits:numbits — The number of bits in the generated key. If not specified 2048 is used. default bop.
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. iconic default.

🌈 RSA-PSS Key Generation Options 🌈

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 its MGF1 parameter.
rsa_pss_keygen_saltlen:len — If set the key is restricted and len specifies the minimum salt length.

🦋 EC Key Generation Options 🦋

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.

💜 ML-DSA Key Generation Options 💜

hexseed:seed — This specifies the optional ML-DSA seed in hexadecimal form. The seed is 32 bytes, giving 64 hexadecimal digits. When generated from an explicit seed the key is completely determined by the seed value. If other users can see the command-line arguments of the running process, this option may compromise the secret key, it is best avoided, tests-aside. See EVP_PKEY-ML-DSA(7) for more detail. ⚠️ secret-key safety warning, fr fr.

🧚 ML-KEM Key Generation Options 🧚

hexseed:seed — This specifies the optional ML-KEM seed in hexadecimal form. The seed is 64 bytes, giving 128 hexadecimal digits. When generated from an explicit seed the key is completely determined by the seed value. If other users can see the command-line arguments of the running process, this option may compromise the secret key, it is best avoided, tests-aside. See EVP_PKEY-ML-KEM(7) for more detail. same secret-key warning, no cap.

🍓 DH Key Generation Options 🍓

group:name — The paramfile option is not required if a named group is used here. See the "DH Parameter Generation Options" section below.

✨ PARAMETER GENERATION OPTIONS ✨

okay so every algorithm — and honestly every implementation of every algorithm — can support a different lil menu of options, and you can't just assume they're all the same. The ones for the OpenSSL implementations are all laid out below, bestie 🫶

🔢 DSA Parameter Generation Options

dsa_paramgen_bits:numbits — how many bits go into the generated prime, periodt. If you don't say anything, it's 2048.
dsa_paramgen_q_bits:numbits, qbits:numbits — the number of bits in the q parameter. Gotta be one of 160, 224 or 256 — those are the only vibes allowed 💅 If you don't specify, it's 224.
dsa_paramgen_md:digest, digest:digest — the digest used during parameter generation. Must be one of sha1, sha224 or sha256. If you set this, the number of bits in q will match the output size of that digest and dsa_paramgen_q_bits just gets ignored (sorry bestie, it's not the main character anymore). If you don't set it, a digest gets picked that gives an output matching the number of bits in q — so sha1 if q length is 160, sha224 if it's 224, or sha256 if it's 256.
properties:query — the digest property query string used when fetching a digest from a provider.
type:type — the type of generation to use. Set it to 1 for legacy FIPS186-2 parameter generation. The default of 0 uses FIPS186-4 parameter generation.
gindex:index — the index used for canonical generation and verification of the generator g. Set it to a positive value ranging from 0..255 to use this mode — larger values only use the bottom byte, so like, don't overthink it. This index then has to be reused during key validation to verify the value of g. If you don't set it, g is not verifiable 😭 The default value is -1.
hexseed:seed — the seed seed data to use instead of generating a random seed internally. Testing purposes only, fr fr 🙈 This will either produce fixed values for the generated parameters OR it'll fail if the seed didn't generate valid primes.

🌀 DH Parameter Generation Options

For most use cases it's recommended to use the group option rather than the type options. And note that the group option is not used by default if you specify no parameter generation options at all — it's not gonna just slide in uninvited.

group:name, dh_param:name — use a named DH group to select constant values for the DH parameters. All other options get ignored if this value is set (they're being sent home 💀).

Valid values 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 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, the appropriate RFC5114 parameters get used instead of generating new ones. The value num can be one of 1, 2 or 3, equivalent to using the group option 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, the number of bits in qbits will match the output size of the specified digest and the qbits parameter gets ignored. If not set, 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 used for canonical generation and verification of the generator g. Set it to a positive value ranging from 0..255 to use this mode; larger values only use the bottom byte. This index must then be reused during key validation to verify the value of g. If not set, 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. Testing purposes only 🧪 This will either produce fixed values for the generated parameters OR it'll fail if the seed didn't generate valid primes. This is only used by "fips186_4" and "fips186_2" key generation.

🌸 EC Parameter Generation Options

The EC parameter generation options are literally the same as for key generation. Go peek at "EC Key Generation Options" above — it's giving déjà vu, but make it valid 💜

📝 NOTES

Using the genpkey program is highly encouraged over the algorithm-specific utilities, because you get extra algorithm options and ENGINE-provided algorithms. It's the upgrade, bestie 👑 periodt.

💖 EXAMPLES

okay this is the fun part — copy-paste these and slay ✨

Generate an RSA private key using default parameters:

openssl genpkey -algorithm RSA -out key.pem

Encrypt the 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 😭 (rude, honestly):

openssl genpkey -genparam -algorithm DSA -out dsap.pem -pkeyopt pbits:2048 \
    -pkeyopt qbits:224 -pkeyopt digest:SHA256 -pkeyopt gindex:1 -text

Generate a DSA key from parameters:

openssl genpkey -paramfile dsap.pem -out dsakey.pem

Generate a 4096 bit DH Key using safe prime group ffdhe4096:

openssl genpkey -algorithm DH -out dhkey.pem -pkeyopt group:ffdhe4096

Generate a 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 an EC key from parameters:

openssl genpkey -paramfile ecp.pem -out eckey.pem

Generate an 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

Generate an ML-DSA-65 private key:

openssl genpkey -algorithm ML-DSA-65 -out ml-dsa-key.pem

Generate an ML-KEM-768 private key:

openssl genpkey -algorithm ML-KEM-768 -out ml-kem-key.pem

🦋 HISTORY

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. And the ability to generate X448, ED25519 and ED448 keys was added in OpenSSL 1.1.1. Look at the glow-up timeline 🌈

The -engine option was deprecated in OpenSSL 3.0. she's retired, let her rest 💀

Support for ML-DSA and ML-KEM was added in OpenSSL 3.5 🔥

👑 COPYRIGHT

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>.

and that's the whole page, bestie, you ATE that 🎀 this one's from OpenSSL 3.5.0, dated 2026-09-25, and it lives at OPENSSL-GENPKEY(1ossl) — go forth and generate keys, ily 💖✨🫶

📦 where this page comes from

opensuse-leap 16.0: openssl-3 3.5.0-160000.11.1 · Apache-2.0
opensuse-leap 16.0: openssl-3 3.5.0-160000.11.1 · Apache-2.0
opensuse-leap 16.0: openssl-3 3.5.0-160000.11.1 · Apache-2.0
opensuse-leap 16.0: openssl-3 3.5.0-160000.11.1 · Apache-2.0
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms