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GENPKEY(1)                          OpenSSL                         GENPKEY(1)

NAME
       genpkey - generate a private key
SYNOPSIS
       openssl genpkey [-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
       -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.
       -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 and -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 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
       ec_paramgen_curve:curve
           the EC curve to use.
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:
        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

1.0.2k                            2017-01-26                        GENPKEY(1)