GENPKEY(1) OpenSSL GENPKEY(1) NNAAMMEE openssl-genpkey, genpkey - generate a private key SSYYNNOOPPSSIISS ooppeennssssll ggeennppkkeeyy [--oouutt ffiilleennaammee] [--oouuttffoorrmm PPEEMM||DDEERR] [--ppaassss aarrgg] [--_cc_ii_pp_hh_ee_rr] [--eennggiinnee iidd] [--ppaarraammffiillee ffiillee] [--aallggoorriitthhmm aallgg] [--ppkkeeyyoopptt oopptt::vvaalluuee] [--ggeennppaarraamm] [--tteexxtt] DDEESSCCRRIIPPTTIIOONN The ggeennppkkeeyy command generates a private key. OOPPTTIIOONNSS --oouutt ffiilleennaammee the output filename. If this argument is not specified then stan- dard output is used. --oouuttffoorrmm DDEERR||PPEEMM This specifies the output format DER or PEM. The default format is PEM. --ppaassss aarrgg The output file password source. For more information about the format of aarrgg see the PPAASSSS PPHHRRAASSEE AARRGGUUMMEENNTTSS section in _o_p_e_n_s_s_l(1). --_cc_ii_pp_hh_ee_rr This option encrypts the private key with the supplied cipher. Any algorithm name accepted by _E_V_P___g_e_t___c_i_p_h_e_r_b_y_n_a_m_e_(_) is acceptable such as ddeess33. --eennggiinnee iidd Specifying an engine (by its unique iidd string) will cause ggeennppkkeeyy 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. --aallggoorriitthhmm aallgg Public key algorithm to use such as RSA, DSA or DH. If used this option must precede any --ppkkeeyyoopptt options. The options --ppaarraammffiillee and --aallggoorriitthhmm 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 --ggeennppaarraamm 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 ddhh__ppaarraammggeenn__ttyyppee option to indicate whether PKCS#3 or X9.42 DH parameters are required. See "DH Parameter Generation Options" below for more details. --ppkkeeyyoopptt oopptt::vvaalluuee Set the public key algorithm option oopptt to vvaalluuee. 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. --ggeennppaarraamm Generate a set of parameters instead of a private key. If used this option must precede any --aallggoorriitthhmm, --ppaarraammffiillee or --ppkkeeyyoopptt options. --ppaarraammffiillee ffiilleennaammee 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 parame- ters. If used this option must precede and --ppkkeeyyoopptt options. The options --ppaarraammffiillee and --aallggoorriitthhmm are mutually exclusive. --tteexxtt Print an (unencrypted) text representation of private and public keys and parameters along with the PEM or DER structure. KKEEYY GGEENNEERRAATTIIOONN OOPPTTIIOONNSS The options supported by each algorith and indeed each implementation of an algorithm can vary. The options for the OpenSSL implementations are detailed below. RRSSAA KKeeyy GGeenneerraattiioonn OOppttiioonnss rrssaa__kkeeyyggeenn__bbiittss::nnuummbbiittss The number of bits in the generated key. If not specified 2048 is used. rrssaa__kkeeyyggeenn__ppuubbeexxpp::vvaalluuee The RSA public exponent value. This can be a large decimal or hexa- decimal value if preceded by 00xx. Default value is 65537. EECC KKeeyy GGeenneerraattiioonn OOppttiioonnss The EC key generation options can also be used for parameter genera- tion. eecc__ppaarraammggeenn__ccuurrvvee::ccuurrvvee The EC curve to use. OpenSSL supports NIST curve names such as "P-256". eecc__ppaarraamm__eenncc::eennccooddiinngg The encoding to use for parameters. The "encoding" parameter must be either "named_curve" or "explicit". The default value is "named_curve". PPAARRAAMMEETTEERR GGEENNEERRAATTIIOONN OOPPTTIIOONNSS The options supported by each algorithm and indeed each implementation of an algorithm can vary. The options for the OpenSSL implementations are detailed below. DDSSAA PPaarraammeetteerr GGeenneerraattiioonn OOppttiioonnss ddssaa__ppaarraammggeenn__bbiittss::nnuummbbiittss The number of bits in the generated prime. If not specified 2048 is used. ddssaa__ppaarraammggeenn__qq__bbiittss::nnuummbbiittss The number of bits in the q parameter. Must be one of 160, 224 or 256. If not specified 224 is used. ddssaa__ppaarraammggeenn__mmdd::ddiiggeesstt The digest to use during parameter generation. Must be one of sshhaa11, sshhaa222244 or sshhaa225566. If set, then the number of bits in qq will match the output size of the specified digest and the ddssaa__ppaarraammggeenn__qq__bbiittss parameter will be ignored. If not set, then a digest will be used that gives an output matching the number of bits in qq, i.e. sshhaa11 if q length is 160, sshhaa222244 if it 224 or sshhaa225566 if it is 256. DDHH PPaarraammeetteerr GGeenneerraattiioonn OOppttiioonnss ddhh__ppaarraammggeenn__pprriimmee__lleenn::nnuummbbiittss The number of bits in the prime parameter pp. The default is 2048. ddhh__ppaarraammggeenn__ssuubbpprriimmee__lleenn::nnuummbbiittss The number of bits in the sub prime parameter qq. The default is 256 if the prime is at least 2048 bits long or 160 otherwise. Only rel- evant if used in conjunction with the ddhh__ppaarraammggeenn__ttyyppee option to generate X9.42 DH parameters. ddhh__ppaarraammggeenn__ggeenneerraattoorr::vvaalluuee The value to use for the generator gg. The default is 2. ddhh__ppaarraammggeenn__ttyyppee::vvaalluuee The type of DH parameters to generate. Use 0 for PKCS#3 DH and 1 for X9.42 DH. The default is 0. ddhh__rrffcc55111144::nnuumm If this option is set, then the appropriate RFC5114 parameters are used instead of generating new parameters. The value nnuumm can take the values 1, 2 or 3 corresponding to RFC5114 DH parameters con- sisting 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. EECC PPaarraammeetteerr GGeenneerraattiioonn OOppttiioonnss The EC parameter generation options are the same as for key generation. See "EC Key Generation Options" above. GGOOSSTT22000011 KKEEYY GGEENNEERRAATTIIOONN AANNDD PPAARRAAMMEETTEERR OOPPTTIIOONNSS 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 dis- tribution 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. ppaarraammsseett::nnaammee 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 NNOOTTEESS The use of the genpkey program is encouraged over the algorithm spe- cific utilities because additional algorithm options and ENGINE pro- vided algorithms can be used. EEXXAAMMPPLLEESS 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 HHIISSTTOORRYY The ability to use NIST curve names, and to generate an EC key directly, were added in OpenSSL 1.0.2. 1.0.2u 2019-12-20 GENPKEY(1)