5 genpkey - generate a private key
18 [B<-pkeyopt opt:value>]
24 The B<genpkey> command generates a private key.
32 Print out a usage message.
34 =item B<-out filename>
36 Output the key to the specified file. If this argument is not specified then
37 standard output is used.
39 =item B<-outform DER|PEM>
41 This specifies the output format DER or PEM.
45 the output file password source. For more information about the format of B<arg>
46 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
50 This option encrypts the private key with the supplied cipher. Any algorithm
51 name accepted by EVP_get_cipherbyname() is acceptable such as B<des3>.
55 specifying an engine (by its unique B<id> string) will cause B<genpkey>
56 to attempt to obtain a functional reference to the specified engine,
57 thus initialising it if needed. The engine will then be set as the default
58 for all available algorithms. If used this option should precede all other
61 =item B<-algorithm alg>
63 public key algorithm to use such as RSA, DSA or DH. If used this option must
64 precede any B<-pkeyopt> options. The options B<-paramfile> and B<-algorithm>
65 are mutually exclusive.
67 =item B<-pkeyopt opt:value>
69 set the public key algorithm option B<opt> to B<value>. The precise set of
70 options supported depends on the public key algorithm used and its
71 implementation. See B<KEY GENERATION OPTIONS> below for more details.
75 generate a set of parameters instead of a private key. If used this option must
76 precede any B<-algorithm>, B<-paramfile> or B<-pkeyopt> options.
78 =item B<-paramfile filename>
80 Some public key algorithms generate a private key based on a set of parameters.
81 They can be supplied using this option. If this option is used the public key
82 algorithm used is determined by the parameters. If used this option must
83 precede any B<-pkeyopt> options. The options B<-paramfile> and B<-algorithm>
84 are mutually exclusive.
88 Print an (unencrypted) text representation of private and public keys and
89 parameters along with the PEM or DER structure.
93 =head1 KEY GENERATION OPTIONS
95 The options supported by each algorithm and indeed each implementation of an
96 algorithm can vary. The options for the OpenSSL implementations are detailed
99 =head1 RSA KEY GENERATION OPTIONS
103 =item B<rsa_keygen_bits:numbits>
105 The number of bits in the generated key. If not specified 1024 is used.
107 =item B<rsa_keygen_pubexp:value>
109 The RSA public exponent value. This can be a large decimal or
110 hexadecimal value if preceded by B<0x>. Default value is 65537.
114 =head1 RSA-PSS KEY GENERATION OPTIONS
116 Note: by default an B<RSA-PSS> key has no parameter restrictions.
120 =item B<rsa_keygen_bits:numbits>, B<rsa_keygen_pubexp:value>
122 These options have the same meaning as the B<RSA> algorithm.
124 =item B<rsa_pss_keygen_md:digest>
126 If set the key is restricted and can only use B<digest> for signing.
128 =item B<rsa_pss_keygen_mgf1_md:digest>
130 If set the key is restricted and can only use B<digest> as it's MGF1
133 =item B<rsa_pss_keygen_saltlen:len>
135 If set the key is restricted and B<len> specifies the minimum salt length.
139 =head1 DSA PARAMETER GENERATION OPTIONS
143 =item B<dsa_paramgen_bits:numbits>
145 The number of bits in the generated parameters. If not specified 1024 is used.
149 =head1 DH PARAMETER GENERATION OPTIONS
153 =item B<dh_paramgen_prime_len:numbits>
155 The number of bits in the prime parameter B<p>.
157 =item B<dh_paramgen_generator:value>
159 The value to use for the generator B<g>.
161 =item B<dh_rfc5114:num>
163 If this option is set then the appropriate RFC5114 parameters are used
164 instead of generating new parameters. The value B<num> can take the
165 values 1, 2 or 3 corresponding to RFC5114 DH parameters consisting of
166 1024 bit group with 160 bit subgroup, 2048 bit group with 224 bit subgroup
167 and 2048 bit group with 256 bit subgroup as mentioned in RFC5114 sections
168 2.1, 2.2 and 2.3 respectively.
172 =head1 EC PARAMETER GENERATION OPTIONS
174 The EC parameter generation options below can also
175 be supplied as EC key generation options. This can (for example) generate a
176 key from a named curve without the need to use an explicit parameter file.
180 =item B<ec_paramgen_curve:curve>
182 the EC curve to use. OpenSSL supports NIST curve names such as "P-256".
184 =item B<ec_param_enc:encoding>
186 the encoding to use for parameters. The "encoding" parameter must be either
187 "named_curve" or "explicit".
191 =head1 GOST2001 KEY GENERATION AND PARAMETER OPTIONS
193 Gost 2001 support is not enabled by default. To enable this algorithm,
194 one should load the ccgost engine in the OpenSSL configuration file.
195 See README.gost file in the engines/ccgost directory of the source
196 distribution for more details.
198 Use of a parameter file for the GOST R 34.10 algorithm is optional.
199 Parameters can be specified during key generation directly as well as
200 during generation of parameter file.
204 =item B<paramset:name>
206 Specifies GOST R 34.10-2001 parameter set according to RFC 4357.
207 Parameter set can be specified using abbreviated name, object short name or
208 numeric OID. Following parameter sets are supported:
211 A 1.2.643.2.2.35.1 Signature
212 B 1.2.643.2.2.35.2 Signature
213 C 1.2.643.2.2.35.3 Signature
214 XA 1.2.643.2.2.36.0 Key exchange
215 XB 1.2.643.2.2.36.1 Key exchange
216 test 1.2.643.2.2.35.0 Test purposes
220 =head1 X25519 KEY GENERATION OPTIONS
222 The X25519 algorithm does not currently support any key generation options.
227 The use of the genpkey program is encouraged over the algorithm specific
228 utilities because additional algorithm options and ENGINE provided algorithms
233 Generate an RSA private key using default parameters:
235 openssl genpkey -algorithm RSA -out key.pem
237 Encrypt output private key using 128 bit AES and the passphrase "hello":
239 openssl genpkey -algorithm RSA -out key.pem -aes-128-cbc -pass pass:hello
241 Generate a 2048 bit RSA key using 3 as the public exponent:
243 openssl genpkey -algorithm RSA -out key.pem -pkeyopt rsa_keygen_bits:2048 \
244 -pkeyopt rsa_keygen_pubexp:3
246 Generate 1024 bit DSA parameters:
248 openssl genpkey -genparam -algorithm DSA -out dsap.pem \
249 -pkeyopt dsa_paramgen_bits:1024
251 Generate DSA key from parameters:
253 openssl genpkey -paramfile dsap.pem -out dsakey.pem
255 Generate 1024 bit DH parameters:
257 openssl genpkey -genparam -algorithm DH -out dhp.pem \
258 -pkeyopt dh_paramgen_prime_len:1024
260 Output RFC5114 2048 bit DH parameters with 224 bit subgroup:
262 openssl genpkey -genparam -algorithm DH -out dhp.pem -pkeyopt dh_rfc5114:2
264 Generate DH key from parameters:
266 openssl genpkey -paramfile dhp.pem -out dhkey.pem
268 Generate EC parameters:
270 openssl genpkey -genparam -algorithm EC -out ecp.pem \
271 -pkeyopt ec_paramgen_curve:secp384r1 \
272 -pkeyopt ec_param_enc:named_curve
274 Generate EC key from parameters:
276 openssl genpkey -paramfile ecp.pem -out eckey.pem
278 Generate EC key directly:
280 openssl genpkey -algorithm EC -out eckey.pem \
281 -pkeyopt ec_paramgen_curve:P-384 \
282 -pkeyopt ec_param_enc:named_curve
284 Generate an X25519 private key:
286 openssl genpkey -algorithm X25519 -out xkey.pem
290 The ability to use NIST curve names, and to generate an EC key directly,
291 were added in OpenSSL 1.0.2.
295 Copyright 2006-2016 The OpenSSL Project Authors. All Rights Reserved.
297 Licensed under the OpenSSL license (the "License"). You may not use
298 this file except in compliance with the License. You can obtain a copy
299 in the file LICENSE in the source distribution or at
300 L<https://www.openssl.org/source/license.html>.