1GENPKEY(1)                          OpenSSL                         GENPKEY(1)
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NAME

6       openssl-genpkey, genpkey - generate a private key
7

SYNOPSIS

9       openssl genpkey [-help] [-out filename] [-outform PEM|DER] [-pass arg]
10       [-cipher] [-engine id] [-paramfile file] [-algorithm alg] [-pkeyopt
11       opt:value] [-genparam] [-text]
12

DESCRIPTION

14       The genpkey command generates a private key.
15

OPTIONS

17       -help
18           Print out a usage message.
19
20       -out filename
21           Output the key to the specified file. If this argument is not
22           specified then standard output is used.
23
24       -outform DER|PEM
25           This specifies the output format DER or PEM. The default format is
26           PEM.
27
28       -pass arg
29           The output file password source. For more information about the
30           format of arg see "Pass Phrase Options" in openssl(1).
31
32       -cipher
33           This option encrypts the private key with the supplied cipher. Any
34           algorithm name accepted by EVP_get_cipherbyname() is acceptable
35           such as des3.
36
37       -engine id
38           Specifying an engine (by its unique id string) will cause genpkey
39           to attempt to obtain a functional reference to the specified
40           engine, thus initialising it if needed. The engine will then be set
41           as the default for all available algorithms. If used this option
42           should precede all other options.
43
44       -algorithm alg
45           Public key algorithm to use such as RSA, DSA or DH. If used this
46           option must precede any -pkeyopt options. The options -paramfile
47           and -algorithm are mutually exclusive. Engines may add algorithms
48           in addition to the standard built-in ones.
49
50           Valid built-in algorithm names for private key generation are RSA,
51           RSA-PSS, EC, X25519, X448, ED25519 and ED448.
52
53           Valid built-in algorithm names for parameter generation (see the
54           -genparam option) are DH, DSA and EC.
55
56           Note that the algorithm name X9.42 DH may be used as a synonym for
57           the DH algorithm. These are identical and do not indicate the type
58           of parameters that will be generated. Use the dh_paramgen_type
59           option to indicate whether PKCS#3 or X9.42 DH parameters are
60           required. See "DH Parameter Generation Options" below for more
61           details.
62
63       -pkeyopt opt:value
64           Set the public key algorithm option opt to value. The precise set
65           of options supported depends on the public key algorithm used and
66           its implementation. See "KEY GENERATION OPTIONS" and "PARAMETER
67           GENERATION OPTIONS" below for more details.
68
69       -genparam
70           Generate a set of parameters instead of a private key. If used this
71           option must precede any -algorithm, -paramfile or -pkeyopt options.
72
73       -paramfile filename
74           Some public key algorithms generate a private key based on a set of
75           parameters.  They can be supplied using this option. If this option
76           is used the public key algorithm used is determined by the
77           parameters. If used this option must precede any -pkeyopt options.
78           The options -paramfile and -algorithm are mutually exclusive.
79
80       -text
81           Print an (unencrypted) text representation of private and public
82           keys and parameters along with the PEM or DER structure.
83

KEY GENERATION OPTIONS

85       The options supported by each algorithm and indeed each implementation
86       of an algorithm can vary. The options for the OpenSSL implementations
87       are detailed below. There are no key generation options defined for the
88       X25519, X448, ED25519 or ED448 algorithms.
89
90   RSA Key Generation Options
91       rsa_keygen_bits:numbits
92           The number of bits in the generated key. If not specified 2048 is
93           used.
94
95       rsa_keygen_primes:numprimes
96           The number of primes in the generated key. If not specified 2 is
97           used.
98
99       rsa_keygen_pubexp:value
100           The RSA public exponent value. This can be a large decimal or
101           hexadecimal value if preceded by 0x. Default value is 65537.
102
103   RSA-PSS Key Generation Options
104       Note: by default an RSA-PSS key has no parameter restrictions.
105
106       rsa_keygen_bits:numbits, rsa_keygen_primes:numprimes,
107       rsa_keygen_pubexp:value
108           These options have the same meaning as the RSA algorithm.
109
110       rsa_pss_keygen_md:digest
111           If set the key is restricted and can only use digest for signing.
112
113       rsa_pss_keygen_mgf1_md:digest
114           If set the key is restricted and can only use digest as it's MGF1
115           parameter.
116
117       rsa_pss_keygen_saltlen:len
118           If set the key is restricted and len specifies the minimum salt
119           length.
120
121   EC Key Generation Options
122       The EC key generation options can also be used for parameter
123       generation.
124
125       ec_paramgen_curve:curve
126           The EC curve to use. OpenSSL supports NIST curve names such as
127           "P-256".
128
129       ec_param_enc:encoding
130           The encoding to use for parameters. The "encoding" parameter must
131           be either "named_curve" or "explicit". The default value is
132           "named_curve".
133

PARAMETER GENERATION OPTIONS

135       The options supported by each algorithm and indeed each implementation
136       of an algorithm can vary. The options for the OpenSSL implementations
137       are detailed below.
138
139   DSA Parameter Generation Options
140       dsa_paramgen_bits:numbits
141           The number of bits in the generated prime. If not specified 2048 is
142           used.
143
144       dsa_paramgen_q_bits:numbits
145           The number of bits in the q parameter. Must be one of 160, 224 or
146           256. If not specified 224 is used.
147
148       dsa_paramgen_md:digest
149           The digest to use during parameter generation. Must be one of sha1,
150           sha224 or sha256. If set, then the number of bits in q will match
151           the output size of the specified digest and the dsa_paramgen_q_bits
152           parameter will be ignored. If not set, then a digest will be used
153           that gives an output matching the number of bits in q, i.e. sha1 if
154           q length is 160, sha224 if it 224 or sha256 if it is 256.
155
156   DH Parameter Generation Options
157       dh_paramgen_prime_len:numbits
158           The number of bits in the prime parameter p. The default is 2048.
159
160       dh_paramgen_subprime_len:numbits
161           The number of bits in the sub prime parameter q. The default is 256
162           if the prime is at least 2048 bits long or 160 otherwise. Only
163           relevant if used in conjunction with the dh_paramgen_type option to
164           generate X9.42 DH parameters.
165
166       dh_paramgen_generator:value
167           The value to use for the generator g. The default is 2.
168
169       dh_paramgen_type:value
170           The type of DH parameters to generate. Use 0 for PKCS#3 DH and 1
171           for X9.42 DH.  The default is 0.
172
173       dh_rfc5114:num
174           If this option is set, then the appropriate RFC5114 parameters are
175           used instead of generating new parameters. The value num can take
176           the values 1, 2 or 3 corresponding to RFC5114 DH parameters
177           consisting of 1024 bit group with 160 bit subgroup, 2048 bit group
178           with 224 bit subgroup and 2048 bit group with 256 bit subgroup as
179           mentioned in RFC5114 sections 2.1, 2.2 and 2.3 respectively. If
180           present this overrides all other DH parameter options.
181
182   EC Parameter Generation Options
183       The EC parameter generation options are the same as for key generation.
184       See "EC Key Generation Options" above.
185

NOTES

187       The use of the genpkey program is encouraged over the algorithm
188       specific utilities because additional algorithm options and ENGINE
189       provided algorithms can be used.
190

EXAMPLES

192       Generate an RSA private key using default parameters:
193
194        openssl genpkey -algorithm RSA -out key.pem
195
196       Encrypt output private key using 128 bit AES and the passphrase
197       "hello":
198
199        openssl genpkey -algorithm RSA -out key.pem -aes-128-cbc -pass pass:hello
200
201       Generate a 2048 bit RSA key using 3 as the public exponent:
202
203        openssl genpkey -algorithm RSA -out key.pem \
204            -pkeyopt rsa_keygen_bits:2048 -pkeyopt rsa_keygen_pubexp:3
205
206       Generate 2048 bit DSA parameters:
207
208        openssl genpkey -genparam -algorithm DSA -out dsap.pem \
209            -pkeyopt dsa_paramgen_bits:2048
210
211       Generate DSA key from parameters:
212
213        openssl genpkey -paramfile dsap.pem -out dsakey.pem
214
215       Generate 2048 bit DH parameters:
216
217        openssl genpkey -genparam -algorithm DH -out dhp.pem \
218            -pkeyopt dh_paramgen_prime_len:2048
219
220       Generate 2048 bit X9.42 DH parameters:
221
222        openssl genpkey -genparam -algorithm DH -out dhpx.pem \
223            -pkeyopt dh_paramgen_prime_len:2048 \
224            -pkeyopt dh_paramgen_type:1
225
226       Output RFC5114 2048 bit DH parameters with 224 bit subgroup:
227
228        openssl genpkey -genparam -algorithm DH -out dhp.pem -pkeyopt dh_rfc5114:2
229
230       Generate DH key from parameters:
231
232        openssl genpkey -paramfile dhp.pem -out dhkey.pem
233
234       Generate EC parameters:
235
236        openssl genpkey -genparam -algorithm EC -out ecp.pem \
237               -pkeyopt ec_paramgen_curve:secp384r1 \
238               -pkeyopt ec_param_enc:named_curve
239
240       Generate EC key from parameters:
241
242        openssl genpkey -paramfile ecp.pem -out eckey.pem
243
244       Generate EC key directly:
245
246        openssl genpkey -algorithm EC -out eckey.pem \
247               -pkeyopt ec_paramgen_curve:P-384 \
248               -pkeyopt ec_param_enc:named_curve
249
250       Generate an X25519 private key:
251
252        openssl genpkey -algorithm X25519 -out xkey.pem
253
254       Generate an ED448 private key:
255
256        openssl genpkey -algorithm ED448 -out xkey.pem
257

HISTORY

259       The ability to use NIST curve names, and to generate an EC key
260       directly, were added in OpenSSL 1.0.2.  The ability to generate X25519
261       keys was added in OpenSSL 1.1.0.  The ability to generate X448, ED25519
262       and ED448 keys was added in OpenSSL 1.1.1.
263
265       Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved.
266
267       Licensed under the OpenSSL license (the "License").  You may not use
268       this file except in compliance with the License.  You can obtain a copy
269       in the file LICENSE in the source distribution or at
270       <https://www.openssl.org/source/license.html>.
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2741.1.1l                            2021-09-15                        GENPKEY(1)
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