genpkey - generate a private key


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


   The genpkey command generates a private key.


   -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).

       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

       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.

       Print an (unencrypted) text representation of private and public
       keys and parameters along with the PEM or DER structure.


   The options supported by each algorith and indeed each implementation
   of an algorithm can vary. The options for the OpenSSL implementations
   are detailed below.


       The number of bits in the generated key. If not specified 1024 is

       The RSA public exponent value. This can be a large decimal or
       hexadecimal value if preceded by 0x. Default value is 65537.


       The number of bits in the generated parameters. If not specified
       1024 is used.


       The number of bits in the prime parameter p.

       The value to use for the generator g.

       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.


       the EC curve to use.


   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.

       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.  Signature
         B          1.2.643.  Signature
         C          1.2.643.  Signature
         XA         1.2.643.  Key exchange
         XB         1.2.643.  Key exchange
         test       1.2.643.  Test purposes


   The use of the genpkey program is encouraged over the algorithm
   specific utilities because additional algorithm options and ENGINE
   provided algorithms can be used.


   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

    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


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