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.

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

       Generate DH key from parameters:

        openssl genpkey -paramfile dhp.pem -out dhkey.pem