Go to main content

man pages section 1: User Commands

Exit Print View

Updated: Thursday, June 13, 2019
 
 

genpkey (1openssl)

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

GENPKEY(1openssl)                   OpenSSL                  GENPKEY(1openssl)



NAME
       openssl-genpkey, 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. 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).

       -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. 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 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 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.

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

       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 1024 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 160 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 1024.

       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 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


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+--------------------------+
       |ATTRIBUTE TYPE |     ATTRIBUTE VALUE      |
       +---------------+--------------------------+
       |Availability   | library/security/openssl |
       +---------------+--------------------------+
       |Stability      | Pass-through uncommitted |
       +---------------+--------------------------+
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 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.


       This software was built from source available at
       https://github.com/oracle/solaris-userland.  The original community
       source was downloaded from
       https://www.openssl.org/source/openssl-1.0.2r.tar.gz

       Further information about this software can be found on the open source
       community website at https://www.openssl.org/.



1.0.2r                            2019-02-26                 GENPKEY(1openssl)