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GENPKEY(1)                   OpenSSL                   GENPKEY(1)


NAME

     openssl-genpkey, genpkey - generate a private key


SYNOPSIS

     openssl genpkey [-out filename] [-outform PEM|DER] [-pass
     arg] [-cciipphheerr] [-engine id] [-paramfile file] [-algorithm
     alg] [-pkeyopt opt:value] [-genparam] [-text]


DESCRIPTION

     The genpkey command generates a private key.


OPTIONS

     -out filename
         the output filename. If this argument is not specified
         then standard output is used.

     -outform DER|PEM
         This specifies the output format DER or PEM. The default
         format is 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).

     -cciipphheerr
         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. Engines may add algorithms in addition to the
         standard built-in ones.

         Valid built-in algorithm names for private key
         generation are RSA and EC.

         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

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GENPKEY(1)                   OpenSSL                   GENPKEY(1)

         synonym for the DH algorithm. These are identical and do
         not indicate the type of parameters that will be
         generated. Use the dh_paramgen_type option to indicate
         whether PKCS#3 or X9.42 DH parameters are required. See
         "DH Parameter Generation Options" below for more
         details.

     -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 and -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 algorith 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 2048 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.

     EC Key Generation Options

     The EC key generation options can also be used for parameter
     generation.

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GENPKEY(1)                   OpenSSL                   GENPKEY(1)

     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".


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.

     DSA Parameter Generation Options

     dsa_paramgen_bits:numbits
         The number of bits in the generated prime. If not
         specified 2048 is used.

     dsa_paramgen_q_bits: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
         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.

     DH Parameter Generation Options

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

     dh_paramgen_subprime_len:numbits
         The number of bits in the sub prime parameter q. The
         default is 256 if the prime is at least 2048 bits long
         or 160 otherwise. Only relevant if used in conjunction
         with the dh_paramgen_type option to generate X9.42 DH
         parameters.

     dh_paramgen_generator:value
         The value to use for the generator g. The default is 2.

     dh_paramgen_type:value
         The type of DH parameters to generate. Use 0 for PKCS#3

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GENPKEY(1)                   OpenSSL                   GENPKEY(1)

         DH and 1 for X9.42 DH.  The default is 0.

     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. If present this overrides all other DH
         parameter options.

     EC Parameter Generation Options

     The EC parameter generation options are the same as for key
     generation. See "EC Key Generation Options" above.


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 directiry 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


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:

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GENPKEY(1)                   OpenSSL                   GENPKEY(1)

      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:

      openssl genpkey -genparam -algorithm DSA -out dsap.pem \
                                                     -pkeyopt dsa_paramgen_bits:2048

     Generate DSA key from parameters:

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

     Generate 2048 bit DH parameters:

      openssl genpkey -genparam -algorithm DH -out dhp.pem \
                                             -pkeyopt dh_paramgen_prime_len:2048

     Generate 2048 bit X9.42 DH parameters:

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

     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 key directly:

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


HISTORY

     The ability to use NIST curve names, and to generate an EC
     key directly, were added in OpenSSL 1.0.2.

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See also openssl-genpkey(1)

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