6 genpkey - generate a private key
18 [B<-pkeyopt opt:value>]
24 The B<genpkey> command generates a private key.
30 =item B<-out filename>
32 the output filename. If this argument is not specified then standard output is
35 =item B<-outform DER|PEM>
37 This specifies the output format DER or PEM. The default format is PEM.
41 The output file password source. For more information about the format of B<arg>
42 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
46 This option encrypts the private key with the supplied cipher. Any algorithm
47 name accepted by EVP_get_cipherbyname() is acceptable such as B<des3>.
51 Specifying an engine (by its unique B<id> string) will cause B<genpkey>
52 to attempt to obtain a functional reference to the specified engine,
53 thus initialising it if needed. The engine will then be set as the default
54 for all available algorithms. If used this option should precede all other
57 =item B<-algorithm alg>
59 Public key algorithm to use such as RSA, DSA or DH. If used this option must
60 precede any B<-pkeyopt> options. The options B<-paramfile> and B<-algorithm>
61 are mutually exclusive. Engines may add algorithms in addition to the standard
64 Valid built-in algorithm names for private key generation are RSA and EC.
66 Valid built-in algorithm names for parameter generation (see the B<-genparam>
67 option) are DH, DSA and EC.
69 Note that the algorithm name X9.42 DH may be used as a synonym for the DH
70 algorithm. These are identical and do not indicate the type of parameters that
71 will be generated. Use the B<dh_paramgen_type> option to indicate whether PKCS#3
72 or X9.42 DH parameters are required. See L<DH Parameter Generation Options>
73 below for more details.
75 =item B<-pkeyopt opt:value>
77 Set the public key algorithm option B<opt> to B<value>. The precise set of
78 options supported depends on the public key algorithm used and its
79 implementation. See L<KEY GENERATION OPTIONS> and
80 L<PARAMETER GENERATION OPTIONS> below for more details.
84 Generate a set of parameters instead of a private key. If used this option must
85 precede any B<-algorithm>, B<-paramfile> or B<-pkeyopt> options.
87 =item B<-paramfile filename>
89 Some public key algorithms generate a private key based on a set of parameters.
90 They can be supplied using this option. If this option is used the public key
91 algorithm used is determined by the parameters. If used this option must
92 precede and B<-pkeyopt> options. The options B<-paramfile> and B<-algorithm>
93 are mutually exclusive.
97 Print an (unencrypted) text representation of private and public keys and
98 parameters along with the PEM or DER structure.
102 =head1 KEY GENERATION OPTIONS
104 The options supported by each algorith and indeed each implementation of an
105 algorithm can vary. The options for the OpenSSL implementations are detailed
108 =head2 RSA Key Generation Options
112 =item B<rsa_keygen_bits:numbits>
114 The number of bits in the generated key. If not specified 2048 is used.
116 =item B<rsa_keygen_pubexp:value>
118 The RSA public exponent value. This can be a large decimal or
119 hexadecimal value if preceded by B<0x>. Default value is 65537.
123 =head2 EC Key Generation Options
125 The EC key generation options can also be used for parameter generation.
129 =item B<ec_paramgen_curve:curve>
131 The EC curve to use. OpenSSL supports NIST curve names such as "P-256".
133 =item B<ec_param_enc:encoding>
135 The encoding to use for parameters. The "encoding" parameter must be either
136 "named_curve" or "explicit". The default value is "named_curve".
140 =head1 PARAMETER GENERATION OPTIONS
142 The options supported by each algorithm and indeed each implementation of an
143 algorithm can vary. The options for the OpenSSL implementations are detailed
146 =head2 DSA Parameter Generation Options
150 =item B<dsa_paramgen_bits:numbits>
152 The number of bits in the generated prime. If not specified 2048 is used.
154 =item B<dsa_paramgen_q_bits:numbits>
156 The number of bits in the q parameter. Must be one of 160, 224 or 256. If not
157 specified 224 is used.
159 =item B<dsa_paramgen_md:digest>
161 The digest to use during parameter generation. Must be one of B<sha1>, B<sha224>
162 or B<sha256>. If set, then the number of bits in B<q> will match the output size
163 of the specified digest and the B<dsa_paramgen_q_bits> parameter will be
164 ignored. If not set, then a digest will be used that gives an output matching
165 the number of bits in B<q>, i.e. B<sha1> if q length is 160, B<sha224> if it 224
166 or B<sha256> if it is 256.
170 =head2 DH Parameter Generation Options
174 =item B<dh_paramgen_prime_len:numbits>
176 The number of bits in the prime parameter B<p>. The default is 2048.
178 =item B<dh_paramgen_subprime_len:numbits>
180 The number of bits in the sub prime parameter B<q>. The default is 256 if the
181 prime is at least 2048 bits long or 160 otherwise. Only relevant if used in
182 conjunction with the B<dh_paramgen_type> option to generate X9.42 DH parameters.
184 =item B<dh_paramgen_generator:value>
186 The value to use for the generator B<g>. The default is 2.
188 =item B<dh_paramgen_type:value>
190 The type of DH parameters to generate. Use 0 for PKCS#3 DH and 1 for X9.42 DH.
193 =item B<dh_rfc5114:num>
195 If this option is set, then the appropriate RFC5114 parameters are used
196 instead of generating new parameters. The value B<num> can take the
197 values 1, 2 or 3 corresponding to RFC5114 DH parameters consisting of
198 1024 bit group with 160 bit subgroup, 2048 bit group with 224 bit subgroup
199 and 2048 bit group with 256 bit subgroup as mentioned in RFC5114 sections
200 2.1, 2.2 and 2.3 respectively. If present this overrides all other DH parameter
205 =head2 EC Parameter Generation Options
207 The EC parameter generation options are the same as for key generation. See
208 L<EC Key Generation Options> above.
210 =head1 GOST2001 KEY GENERATION AND PARAMETER OPTIONS
212 Gost 2001 support is not enabled by default. To enable this algorithm,
213 one should load the ccgost engine in the OpenSSL configuration file.
214 See README.gost file in the engines/ccgost directiry of the source
215 distribution for more details.
217 Use of a parameter file for the GOST R 34.10 algorithm is optional.
218 Parameters can be specified during key generation directly as well as
219 during generation of parameter file.
223 =item B<paramset:name>
225 Specifies GOST R 34.10-2001 parameter set according to RFC 4357.
226 Parameter set can be specified using abbreviated name, object short name or
227 numeric OID. Following parameter sets are supported:
230 A 1.2.643.2.2.35.1 Signature
231 B 1.2.643.2.2.35.2 Signature
232 C 1.2.643.2.2.35.3 Signature
233 XA 1.2.643.2.2.36.0 Key exchange
234 XB 1.2.643.2.2.36.1 Key exchange
235 test 1.2.643.2.2.35.0 Test purposes
241 The use of the genpkey program is encouraged over the algorithm specific
242 utilities because additional algorithm options and ENGINE provided algorithms
247 Generate an RSA private key using default parameters:
249 openssl genpkey -algorithm RSA -out key.pem
251 Encrypt output private key using 128 bit AES and the passphrase "hello":
253 openssl genpkey -algorithm RSA -out key.pem -aes-128-cbc -pass pass:hello
255 Generate a 2048 bit RSA key using 3 as the public exponent:
257 openssl genpkey -algorithm RSA -out key.pem -pkeyopt rsa_keygen_bits:2048 \
258 -pkeyopt rsa_keygen_pubexp:3
260 Generate 2048 bit DSA parameters:
262 openssl genpkey -genparam -algorithm DSA -out dsap.pem \
263 -pkeyopt dsa_paramgen_bits:2048
265 Generate DSA key from parameters:
267 openssl genpkey -paramfile dsap.pem -out dsakey.pem
269 Generate 2048 bit DH parameters:
271 openssl genpkey -genparam -algorithm DH -out dhp.pem \
272 -pkeyopt dh_paramgen_prime_len:2048
274 Generate 2048 bit X9.42 DH parameters:
276 openssl genpkey -genparam -algorithm DH -out dhpx.pem \
277 -pkeyopt dh_paramgen_prime_len:2048 \
278 -pkeyopt dh_paramgen_type:1
280 Output RFC5114 2048 bit DH parameters with 224 bit subgroup:
282 openssl genpkey -genparam -algorithm DH -out dhp.pem -pkeyopt dh_rfc5114:2
284 Generate DH key from parameters:
286 openssl genpkey -paramfile dhp.pem -out dhkey.pem
288 Generate EC key directly:
290 openssl genpkey -algorithm EC -out eckey.pem \
291 -pkeyopt ec_paramgen_curve:P-384 \
292 -pkeyopt ec_param_enc:named_curve
296 The ability to use NIST curve names, and to generate an EC key directly,
297 were added in OpenSSL 1.0.2.