5 openssl-genpkey - generate a private key
12 [B<-outform> B<DER>|B<PEM>]
16 [B<-paramfile> I<file>]
17 [B<-algorithm> I<alg>]
18 [B<-pkeyopt> I<opt:value>]
22 =for comment ifdef engine
26 The B<genpkey> command generates a private key.
34 Print out a usage message.
36 =item B<-out> I<filename>
38 Output the key to the specified file. If this argument is not specified then
39 standard output is used.
41 =item B<-outform> B<DER>|B<PEM>
43 This specifies the output format DER or PEM. The default format is PEM.
47 The output file password source. For more information about the format of B<arg>
48 see L<openssl(1)/Pass phrase options>.
52 This option encrypts the private key with the supplied cipher. Any algorithm
53 name accepted by EVP_get_cipherbyname() is acceptable such as B<des3>.
55 =item B<-engine> I<id>
57 Specifying an engine (by its unique B<id> string) will cause B<genpkey>
58 to attempt to obtain a functional reference to the specified engine,
59 thus initialising it if needed. The engine will then be set as the default
60 for all available algorithms. If used this option should precede all other
63 =item B<-algorithm> I<alg>
65 Public key algorithm to use such as RSA, DSA or DH. If used this option must
66 precede any B<-pkeyopt> options. The options B<-paramfile> and B<-algorithm>
67 are mutually exclusive. Engines may add algorithms in addition to the standard
70 Valid built-in algorithm names for private key generation are RSA, RSA-PSS, EC,
71 X25519, X448, ED25519 and ED448.
73 Valid built-in algorithm names for parameter generation (see the B<-genparam>
74 option) are DH, DSA and EC.
76 Note that the algorithm name X9.42 DH may be used as a synonym for the DH
77 algorithm. These are identical and do not indicate the type of parameters that
78 will be generated. Use the B<dh_paramgen_type> option to indicate whether PKCS#3
79 or X9.42 DH parameters are required. See L<DH Parameter Generation Options>
80 below for more details.
82 =item B<-pkeyopt> I<opt:value>
84 Set the public key algorithm option B<opt> to B<value>. The precise set of
85 options supported depends on the public key algorithm used and its
86 implementation. See L<KEY GENERATION OPTIONS> and
87 L<PARAMETER GENERATION OPTIONS> below for more details.
91 Generate a set of parameters instead of a private key. If used this option must
92 precede any B<-algorithm>, B<-paramfile> or B<-pkeyopt> options.
94 =item B<-paramfile> I<filename>
96 Some public key algorithms generate a private key based on a set of parameters.
97 They can be supplied using this option. If this option is used the public key
98 algorithm used is determined by the parameters. If used this option must
99 precede any B<-pkeyopt> options. The options B<-paramfile> and B<-algorithm>
100 are mutually exclusive.
104 Print an (unencrypted) text representation of private and public keys and
105 parameters along with the PEM or DER structure.
109 =head1 KEY GENERATION OPTIONS
111 The options supported by each algorithm and indeed each implementation of an
112 algorithm can vary. The options for the OpenSSL implementations are detailed
113 below. There are no key generation options defined for the X25519, X448, ED25519
116 =head2 RSA Key Generation Options
120 =item B<rsa_keygen_bits:numbits>
122 The number of bits in the generated key. If not specified 2048 is used.
124 =item B<rsa_keygen_primes:numprimes>
126 The number of primes in the generated key. If not specified 2 is used.
128 =item B<rsa_keygen_pubexp:value>
130 The RSA public exponent value. This can be a large decimal or
131 hexadecimal value if preceded by B<0x>. Default value is 65537.
135 =head2 RSA-PSS Key Generation Options
137 Note: by default an B<RSA-PSS> key has no parameter restrictions.
141 =item B<rsa_keygen_bits:numbits>, B<rsa_keygen_primes:numprimes>, B<rsa_keygen_pubexp:value>
143 These options have the same meaning as the B<RSA> algorithm.
145 =item B<rsa_pss_keygen_md:digest>
147 If set the key is restricted and can only use B<digest> for signing.
149 =item B<rsa_pss_keygen_mgf1_md:digest>
151 If set the key is restricted and can only use B<digest> as it's MGF1
154 =item B<rsa_pss_keygen_saltlen:len>
156 If set the key is restricted and B<len> specifies the minimum salt length.
160 =head2 EC Key Generation Options
162 The EC key generation options can also be used for parameter generation.
166 =item B<ec_paramgen_curve:curve>
168 The EC curve to use. OpenSSL supports NIST curve names such as "P-256".
170 =item B<ec_param_enc:encoding>
172 The encoding to use for parameters. The "encoding" parameter must be either
173 "named_curve" or "explicit". The default value is "named_curve".
177 =head1 PARAMETER GENERATION OPTIONS
179 The options supported by each algorithm and indeed each implementation of an
180 algorithm can vary. The options for the OpenSSL implementations are detailed
183 =head2 DSA Parameter Generation Options
187 =item B<dsa_paramgen_bits:numbits>
189 The number of bits in the generated prime. If not specified 2048 is used.
191 =item B<dsa_paramgen_q_bits:numbits>
193 The number of bits in the q parameter. Must be one of 160, 224 or 256. If not
194 specified 224 is used.
196 =item B<dsa_paramgen_md:digest>
198 The digest to use during parameter generation. Must be one of B<sha1>, B<sha224>
199 or B<sha256>. If set, then the number of bits in B<q> will match the output size
200 of the specified digest and the B<dsa_paramgen_q_bits> parameter will be
201 ignored. If not set, then a digest will be used that gives an output matching
202 the number of bits in B<q>, i.e. B<sha1> if q length is 160, B<sha224> if it 224
203 or B<sha256> if it is 256.
207 =head2 DH Parameter Generation Options
211 =item B<dh_paramgen_prime_len:numbits>
213 The number of bits in the prime parameter B<p>. The default is 2048.
215 =item B<dh_paramgen_subprime_len:numbits>
217 The number of bits in the sub prime parameter B<q>. The default is 256 if the
218 prime is at least 2048 bits long or 160 otherwise. Only relevant if used in
219 conjunction with the B<dh_paramgen_type> option to generate X9.42 DH parameters.
221 =item B<dh_paramgen_generator:value>
223 The value to use for the generator B<g>. The default is 2.
225 =item B<dh_paramgen_type:value>
227 The type of DH parameters to generate. Use 0 for PKCS#3 DH and 1 for X9.42 DH.
230 =item B<dh_rfc5114:num>
232 If this option is set, then the appropriate RFC5114 parameters are used
233 instead of generating new parameters. The value B<num> can take the
234 values 1, 2 or 3 corresponding to RFC5114 DH parameters consisting of
235 1024 bit group with 160 bit subgroup, 2048 bit group with 224 bit subgroup
236 and 2048 bit group with 256 bit subgroup as mentioned in RFC5114 sections
237 2.1, 2.2 and 2.3 respectively. If present this overrides all other DH parameter
242 =head2 EC Parameter Generation Options
244 The EC parameter generation options are the same as for key generation. See
245 L<EC Key Generation Options> above.
249 The use of the genpkey program is encouraged over the algorithm specific
250 utilities because additional algorithm options and ENGINE provided algorithms
255 Generate an RSA private key using default parameters:
257 openssl genpkey -algorithm RSA -out key.pem
259 Encrypt output private key using 128 bit AES and the passphrase "hello":
261 openssl genpkey -algorithm RSA -out key.pem -aes-128-cbc -pass pass:hello
263 Generate a 2048 bit RSA key using 3 as the public exponent:
265 openssl genpkey -algorithm RSA -out key.pem \
266 -pkeyopt rsa_keygen_bits:2048 -pkeyopt rsa_keygen_pubexp:3
268 Generate 2048 bit DSA parameters:
270 openssl genpkey -genparam -algorithm DSA -out dsap.pem \
271 -pkeyopt dsa_paramgen_bits:2048
273 Generate DSA key from parameters:
275 openssl genpkey -paramfile dsap.pem -out dsakey.pem
277 Generate 2048 bit DH parameters:
279 openssl genpkey -genparam -algorithm DH -out dhp.pem \
280 -pkeyopt dh_paramgen_prime_len:2048
282 Generate 2048 bit X9.42 DH parameters:
284 openssl genpkey -genparam -algorithm DH -out dhpx.pem \
285 -pkeyopt dh_paramgen_prime_len:2048 \
286 -pkeyopt dh_paramgen_type:1
288 Output RFC5114 2048 bit DH parameters with 224 bit subgroup:
290 openssl genpkey -genparam -algorithm DH -out dhp.pem -pkeyopt dh_rfc5114:2
292 Generate DH key from parameters:
294 openssl genpkey -paramfile dhp.pem -out dhkey.pem
296 Generate EC parameters:
298 openssl genpkey -genparam -algorithm EC -out ecp.pem \
299 -pkeyopt ec_paramgen_curve:secp384r1 \
300 -pkeyopt ec_param_enc:named_curve
302 Generate EC key from parameters:
304 openssl genpkey -paramfile ecp.pem -out eckey.pem
306 Generate EC key directly:
308 openssl genpkey -algorithm EC -out eckey.pem \
309 -pkeyopt ec_paramgen_curve:P-384 \
310 -pkeyopt ec_param_enc:named_curve
312 Generate an X25519 private key:
314 openssl genpkey -algorithm X25519 -out xkey.pem
316 Generate an ED448 private key:
318 openssl genpkey -algorithm ED448 -out xkey.pem
322 The ability to use NIST curve names, and to generate an EC key directly,
323 were added in OpenSSL 1.0.2.
324 The ability to generate X25519 keys was added in OpenSSL 1.1.0.
325 The ability to generate X448, ED25519 and ED448 keys was added in OpenSSL 1.1.1.
329 Copyright 2006-2019 The OpenSSL Project Authors. All Rights Reserved.
331 Licensed under the Apache License 2.0 (the "License"). You may not use
332 this file except in compliance with the License. You can obtain a copy
333 in the file LICENSE in the source distribution or at
334 L<https://www.openssl.org/source/license.html>.