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Title "OPENSSL-GENPKEY 1ossl" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
openssl-genpkey - generate a private key Header "SYNOPSIS" \fBopenssl genpkey [-help] [-out filename] [-outform \s-1DER\s0|\s-1PEM\s0] [-quiet] [-pass arg] [-\f(BIcipher] [-paramfile file] [-algorithm alg] [-pkeyopt opt:value] [-genparam] [-text] [-engine id] [-provider name] [-provider-path path] [-propquery propq] [-config configfile] Header "DESCRIPTION" This command generates a private key. Header "OPTIONS" Item "-help" Print out a usage message. Item "-out filename" Output the key to the specified file. If this argument is not specified then standard output is used. Item "-outform DER|PEM" The output format, except when -genparam is given; the default is \s-1PEM\s0. See openssl-format-options\|(1) for details. .Sp When -genparam is given, -outform is ignored. Item "-quiet" Do not output \*(L"status dots\*(R" while generating keys. Item "-pass arg" The output file password source. For more information about the format of arg see openssl-passphrase-options\|(1). Item "-cipher" This option encrypts the private key with the supplied cipher. Any algorithm name accepted by EVP_get_cipherbyname() is acceptable such as des3. Item "-algorithm alg" Public key algorithm to use such as \s-1RSA, DSA, DH\s0 or \s-1DHX.\s0 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. .Sp Valid built-in algorithm names for private key generation are \s-1RSA,\s0 RSA-PSS, \s-1EC, X25519, X448, ED25519\s0 and \s-1ED448.\s0 .Sp Valid built-in algorithm names for parameter generation (see the -genparam option) are \s-1DH, DSA\s0 and \s-1EC.\s0 .Sp Note that the algorithm name X9.42 \s-1DH\s0 may be used as a synonym for \s-1DHX\s0 keys and PKCS#3 refers to \s-1DH\s0 Keys. Some options are not shared between \s-1DH\s0 and \s-1DHX\s0 keys. Item "-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 \*(L"\s-1KEY GENERATION OPTIONS\*(R"\s0 and \*(L"\s-1PARAMETER GENERATION OPTIONS\*(R"\s0 below for more details. Item "-genparam" Generate a set of parameters instead of a private key. If used this option must precede any -algorithm, -paramfile or -pkeyopt options. Item "-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. Item "-text" Print an (unencrypted) text representation of private and public keys and parameters along with the \s-1PEM\s0 or \s-1DER\s0 structure. Item "-engine id" See \*(L"Engine Options\*(R" in openssl\|(1). This option is deprecated. Item "-provider name"

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Item "-provider-path path" Item "-propquery propq"

See \*(L"Provider Options\*(R" in openssl\|(1), provider\|(7), and property\|(7).

Item "-config configfile" See \*(L"Configuration Option\*(R" in openssl\|(1). Header "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, \s-1ED25519\s0 or \s-1ED448\s0 algorithms. Subsection "RSA Key Generation Options" Item "rsa_keygen_bits:numbits" The number of bits in the generated key. If not specified 2048 is used. Item "rsa_keygen_primes:numprimes" The number of primes in the generated key. If not specified 2 is used. Item "rsa_keygen_pubexp:value" The \s-1RSA\s0 public exponent value. This can be a large decimal or hexadecimal value if preceded by \*(C`0x\*(C'. Default value is 65537. Subsection "RSA-PSS Key Generation Options" Note: by default an RSA-PSS key has no parameter restrictions. Item "rsa_keygen_bits:numbits, rsa_keygen_primes:numprimes, rsa_keygen_pubexp:value" These options have the same meaning as the \s-1RSA\s0 algorithm. Item "rsa_pss_keygen_md:digest" If set the key is restricted and can only use digest for signing. Item "rsa_pss_keygen_mgf1_md:digest" If set the key is restricted and can only use digest as it's \s-1MGF1\s0 parameter. Item "rsa_pss_keygen_saltlen:len" If set the key is restricted and len specifies the minimum salt length. Subsection "EC Key Generation Options" The \s-1EC\s0 key generation options can also be used for parameter generation. Item "ec_paramgen_curve:curve" The \s-1EC\s0 curve to use. OpenSSL supports \s-1NIST\s0 curve names such as \*(L"P-256\*(R". Item "ec_param_enc:encoding" The encoding to use for parameters. The encoding parameter must be either \fBnamed_curve or explicit. The default value is named_curve. Subsection "DH Key Generation Options" Item "group:name" The paramfile option is not required if a named group is used here. See the \*(L"\s-1DH\s0 Parameter Generation Options\*(R" section below. Header "PARAMETER 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. Subsection "DSA Parameter Generation Options" Item "dsa_paramgen_bits:numbits" The number of bits in the generated prime. If not specified 2048 is used. Item "dsa_paramgen_q_bits:numbits"

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Item "qbits:numbits"

The number of bits in the q parameter. Must be one of 160, 224 or 256. If not specified 224 is used.

Item "dsa_paramgen_md:digest"

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Item "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.

Item "properties:query" The digest property query string to use when fetching a digest from a provider. Item "type:type" The type of generation to use. Set this to 1 to use legacy \s-1FIPS186-2\s0 parameter generation. The default of 0 uses \s-1FIPS186-4\s0 parameter generation. Item "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. Item "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 \s-1OR\s0 it will fail if the seed did not generate valid primes. Subsection "DH Parameter Generation Options" 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. Item "group:name"

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Item "dh_param:name"

Use a named \s-1DH\s0 group to select constant values for the \s-1DH\s0 parameters. All other options will be ignored if this value is set. .Sp Valid values that are associated with the algorithm of \*(L"\s-1DH\*(R"\s0 are: \*(L"ffdhe2048\*(R", \*(L"ffdhe3072\*(R", \*(L"ffdhe4096\*(R", \*(L"ffdhe6144\*(R", \*(L"ffdhe8192\*(R", \*(L"modp_1536\*(R", \*(L"modp_2048\*(R", \*(L"modp_3072\*(R", \*(L"modp_4096\*(R", \*(L"modp_6144\*(R", \*(L"modp_8192\*(R". .Sp Valid values that are associated with the algorithm of \*(L"\s-1DHX\*(R"\s0 are the \s-1RFC5114\s0 names \*(L"dh_1024_160\*(R", \*(L"dh_2048_224\*(R", \*(L"dh_2048_256\*(R".

Item "dh_rfc5114:num" If this option is set, then the appropriate \s-1RFC5114\s0 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 \*(L"dh_1024_160\*(R", \*(L"dh_2048_224\*(R" or \*(L"dh_2048_256\*(R". All other options will be ignored if this value is set. Item "pbits:numbits"

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Item "dh_paramgen_prime_len:numbits"

The number of bits in the prime parameter p. The default is 2048.

Item "qbits:numbits"

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Item "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 \s-1DHX\s0 parameters.

Item "safeprime-generator:value"

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Item "dh_paramgen_generator:value"

The value to use for the generator g. The default is 2. The algorithm option must be \*(L"\s-1DH\*(R"\s0 for this parameter to be used.

Item "type:string" The type name of \s-1DH\s0 parameters to generate. Valid values are: Item "dh_paramgen_type:value" The type of \s-1DH\s0 parameters to generate. Valid values are 0, 1, 2 or 3 which correspond to setting the option type to \*(L"generator\*(R", \*(L"fips186_2\*(R", \*(L"fips186_4\*(R" or \*(L"group\*(R". Item "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 \*(L"fips186_4\*(R" and \*(L"fips186_2\*(R" key generation. Item "properties:query" The digest property query string to use when fetching a digest from a provider. This is only used by \*(L"fips186_4\*(R" and \*(L"fips186_2\*(R" key generation. Item "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 \*(L"fips186_4\*(R" and \*(L"fips186_2\*(R" key generation. Item "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 \s-1OR\s0 it will fail if the seed did not generate valid primes. This is only used by \*(L"fips186_4\*(R" and \*(L"fips186_2\*(R" key generation. Subsection "EC Parameter Generation Options" The \s-1EC\s0 parameter generation options are the same as for key generation. See \*(L"\s-1EC\s0 Key Generation Options\*(R" above. Header "NOTES" The use of the genpkey program is encouraged over the algorithm specific utilities because additional algorithm options and \s-1ENGINE\s0 provided algorithms can be used. Header "EXAMPLES" Generate an \s-1RSA\s0 private key using default parameters:

.Vb 1 openssl genpkey -algorithm RSA -out key.pem .Ve

Encrypt output private key using 128 bit \s-1AES\s0 and the passphrase \*(L"hello\*(R":

.Vb 1 openssl genpkey -algorithm RSA -out key.pem -aes-128-cbc -pass pass:hello .Ve

Generate a 2048 bit \s-1RSA\s0 key using 3 as the public exponent:

.Vb 2 openssl genpkey -algorithm RSA -out key.pem \e -pkeyopt rsa_keygen_bits:2048 -pkeyopt rsa_keygen_pubexp:3 .Ve

Generate 2048 bit \s-1DSA\s0 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).

.Vb 2 openssl genpkey -genparam -algorithm DSA -out dsap.pem -pkeyopt pbits:2048 \e -pkeyopt qbits:224 -pkeyopt digest:SHA256 -pkeyopt gindex:1 -text .Ve

Generate \s-1DSA\s0 key from parameters:

.Vb 1 openssl genpkey -paramfile dsap.pem -out dsakey.pem .Ve

Generate 4096 bit \s-1DH\s0 Key using safe prime group ffdhe4096:

.Vb 1 openssl genpkey -algorithm DH -out dhkey.pem -pkeyopt group:ffdhe4096 .Ve

Generate 2048 bit X9.42 \s-1DH\s0 key with 256 bit subgroup using \s-1RFC5114\s0 group3:

.Vb 1 openssl genpkey -algorithm DHX -out dhkey.pem -pkeyopt dh_rfc5114:3 .Ve

Generate a \s-1DH\s0 key using a \s-1DH\s0 parameters file:

.Vb 1 openssl genpkey -paramfile dhp.pem -out dhkey.pem .Ve

Output \s-1DH\s0 parameters for safe prime group ffdhe2048:

.Vb 1 openssl genpkey -genparam -algorithm DH -out dhp.pem -pkeyopt group:ffdhe2048 .Ve

Output 2048 bit X9.42 \s-1DH\s0 parameters with 224 bit subgroup using \s-1RFC5114\s0 group2:

.Vb 1 openssl genpkey -genparam -algorithm DHX -out dhp.pem -pkeyopt dh_rfc5114:2 .Ve

Output 2048 bit X9.42 \s-1DH\s0 parameters with 224 bit subgroup using \s-1FIP186-4\s0 keygen:

.Vb 3 openssl genpkey -genparam -algorithm DHX -out dhp.pem -text \e -pkeyopt pbits:2048 -pkeyopt qbits:224 -pkeyopt digest:SHA256 \e -pkeyopt gindex:1 -pkeyopt dh_paramgen_type:2 .Ve

Output 1024 bit X9.42 \s-1DH\s0 parameters with 160 bit subgroup using \s-1FIP186-2\s0 keygen:

.Vb 3 openssl genpkey -genparam -algorithm DHX -out dhp.pem -text \e -pkeyopt pbits:1024 -pkeyopt qbits:160 -pkeyopt digest:SHA1 \e -pkeyopt gindex:1 -pkeyopt dh_paramgen_type:1 .Ve

Output 2048 bit \s-1DH\s0 parameters:

.Vb 2 openssl genpkey -genparam -algorithm DH -out dhp.pem \e -pkeyopt dh_paramgen_prime_len:2048 .Ve

Output 2048 bit \s-1DH\s0 parameters using a generator:

.Vb 3 openssl genpkey -genparam -algorithm DH -out dhpx.pem \e -pkeyopt dh_paramgen_prime_len:2048 \e -pkeyopt dh_paramgen_type:1 .Ve

Generate \s-1EC\s0 parameters:

.Vb 3 openssl genpkey -genparam -algorithm EC -out ecp.pem \e -pkeyopt ec_paramgen_curve:secp384r1 \e -pkeyopt ec_param_enc:named_curve .Ve

Generate \s-1EC\s0 key from parameters:

.Vb 1 openssl genpkey -paramfile ecp.pem -out eckey.pem .Ve

Generate \s-1EC\s0 key directly:

.Vb 3 openssl genpkey -algorithm EC -out eckey.pem \e -pkeyopt ec_paramgen_curve:P-384 \e -pkeyopt ec_param_enc:named_curve .Ve

Generate an X25519 private key:

.Vb 1 openssl genpkey -algorithm X25519 -out xkey.pem .Ve

Generate an \s-1ED448\s0 private key:

.Vb 1 openssl genpkey -algorithm ED448 -out xkey.pem .Ve

Header "HISTORY" The ability to use \s-1NIST\s0 curve names, and to generate an \s-1EC\s0 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, \s-1ED25519\s0 and \s-1ED448\s0 keys was added in OpenSSL 1.1.1.

The -engine option was deprecated in OpenSSL 3.0.

Header "COPYRIGHT" Copyright 2006-2023 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.