336 lines
9.4 KiB
Plaintext
336 lines
9.4 KiB
Plaintext
=pod
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=head1 NAME
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openssl-genpkey,
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genpkey - generate a private key
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=head1 SYNOPSIS
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B<openssl> B<genpkey>
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[B<-help>]
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[B<-out filename>]
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[B<-outform PEM|DER>]
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[B<-pass arg>]
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[B<-I<cipher>>]
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[B<-engine id>]
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[B<-paramfile file>]
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[B<-algorithm alg>]
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[B<-pkeyopt opt:value>]
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[B<-genparam>]
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[B<-text>]
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=head1 DESCRIPTION
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The B<genpkey> command generates a private key.
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=head1 OPTIONS
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=over 4
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=item B<-help>
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Print out a usage message.
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=item B<-out filename>
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Output the key to the specified file. If this argument is not specified then
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standard output is used.
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=item B<-outform DER|PEM>
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This specifies the output format DER or PEM. The default format is PEM.
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=item B<-pass arg>
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The output file password source. For more information about the format of B<arg>
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see L<openssl(1)/Pass Phrase Options>.
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=item B<-I<cipher>>
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This option encrypts the private key with the supplied cipher. Any algorithm
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name accepted by EVP_get_cipherbyname() is acceptable such as B<des3>.
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=item B<-engine id>
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Specifying an engine (by its unique B<id> string) will cause B<genpkey>
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to attempt to obtain a functional reference to the specified engine,
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thus initialising it if needed. The engine will then be set as the default
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for all available algorithms. If used this option should precede all other
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options.
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=item B<-algorithm alg>
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Public key algorithm to use such as RSA, DSA or DH. If used this option must
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precede any B<-pkeyopt> options. The options B<-paramfile> and B<-algorithm>
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are mutually exclusive. Engines may add algorithms in addition to the standard
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built-in ones.
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Valid built-in algorithm names for private key generation are RSA, RSA-PSS, EC,
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X25519, X448, ED25519 and ED448.
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Valid built-in algorithm names for parameter generation (see the B<-genparam>
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option) are DH, DSA and EC.
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Note that the algorithm name X9.42 DH may be used as a synonym for the DH
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algorithm. These are identical and do not indicate the type of parameters that
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will be generated. Use the B<dh_paramgen_type> option to indicate whether PKCS#3
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or X9.42 DH parameters are required. See L<DH Parameter Generation Options>
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below for more details.
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=item B<-pkeyopt opt:value>
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Set the public key algorithm option B<opt> to B<value>. The precise set of
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options supported depends on the public key algorithm used and its
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implementation. See L<KEY GENERATION OPTIONS> and
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L<PARAMETER GENERATION OPTIONS> below for more details.
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=item B<-genparam>
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Generate a set of parameters instead of a private key. If used this option must
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precede any B<-algorithm>, B<-paramfile> or B<-pkeyopt> options.
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=item B<-paramfile filename>
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Some public key algorithms generate a private key based on a set of parameters.
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They can be supplied using this option. If this option is used the public key
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algorithm used is determined by the parameters. If used this option must
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precede any B<-pkeyopt> options. The options B<-paramfile> and B<-algorithm>
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are mutually exclusive.
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=item B<-text>
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Print an (unencrypted) text representation of private and public keys and
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parameters along with the PEM or DER structure.
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=back
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=head1 KEY GENERATION OPTIONS
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The options supported by each algorithm and indeed each implementation of an
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algorithm can vary. The options for the OpenSSL implementations are detailed
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below. There are no key generation options defined for the X25519, X448, ED25519
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or ED448 algorithms.
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=head2 RSA Key Generation Options
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=over 4
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=item B<rsa_keygen_bits:numbits>
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The number of bits in the generated key. If not specified 2048 is used.
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=item B<rsa_keygen_primes:numprimes>
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The number of primes in the generated key. If not specified 2 is used.
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=item B<rsa_keygen_pubexp:value>
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The RSA public exponent value. This can be a large decimal or
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hexadecimal value if preceded by B<0x>. Default value is 65537.
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=back
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=head2 RSA-PSS Key Generation Options
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Note: by default an B<RSA-PSS> key has no parameter restrictions.
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=over 4
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=item B<rsa_keygen_bits:numbits>, B<rsa_keygen_primes:numprimes>, B<rsa_keygen_pubexp:value>
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These options have the same meaning as the B<RSA> algorithm.
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=item B<rsa_pss_keygen_md:digest>
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If set the key is restricted and can only use B<digest> for signing.
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=item B<rsa_pss_keygen_mgf1_md:digest>
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If set the key is restricted and can only use B<digest> as it's MGF1
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parameter.
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=item B<rsa_pss_keygen_saltlen:len>
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If set the key is restricted and B<len> specifies the minimum salt length.
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=back
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=head2 EC Key Generation Options
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The EC key generation options can also be used for parameter generation.
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=over 4
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=item B<ec_paramgen_curve:curve>
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The EC curve to use. OpenSSL supports NIST curve names such as "P-256".
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=item B<ec_param_enc:encoding>
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The encoding to use for parameters. The "encoding" parameter must be either
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"named_curve" or "explicit". The default value is "named_curve".
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=back
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=head1 PARAMETER GENERATION OPTIONS
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The options supported by each algorithm and indeed each implementation of an
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algorithm can vary. The options for the OpenSSL implementations are detailed
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below.
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=head2 DSA Parameter Generation Options
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=over 4
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=item B<dsa_paramgen_bits:numbits>
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The number of bits in the generated prime. If not specified 2048 is used.
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=item B<dsa_paramgen_q_bits:numbits>
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The number of bits in the q parameter. Must be one of 160, 224 or 256. If not
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specified 224 is used.
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=item B<dsa_paramgen_md:digest>
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The digest to use during parameter generation. Must be one of B<sha1>, B<sha224>
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or B<sha256>. If set, then the number of bits in B<q> will match the output size
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of the specified digest and the B<dsa_paramgen_q_bits> parameter will be
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ignored. If not set, then a digest will be used that gives an output matching
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the number of bits in B<q>, i.e. B<sha1> if q length is 160, B<sha224> if it 224
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or B<sha256> if it is 256.
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=back
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=head2 DH Parameter Generation Options
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=over 4
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=item B<dh_paramgen_prime_len:numbits>
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The number of bits in the prime parameter B<p>. The default is 2048.
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=item B<dh_paramgen_subprime_len:numbits>
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The number of bits in the sub prime parameter B<q>. The default is 256 if the
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prime is at least 2048 bits long or 160 otherwise. Only relevant if used in
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conjunction with the B<dh_paramgen_type> option to generate X9.42 DH parameters.
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=item B<dh_paramgen_generator:value>
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The value to use for the generator B<g>. The default is 2.
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=item B<dh_paramgen_type:value>
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The type of DH parameters to generate. Use 0 for PKCS#3 DH and 1 for X9.42 DH.
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The default is 0.
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=item B<dh_rfc5114:num>
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If this option is set, then the appropriate RFC5114 parameters are used
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instead of generating new parameters. The value B<num> can take the
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values 1, 2 or 3 corresponding to RFC5114 DH parameters consisting of
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1024 bit group with 160 bit subgroup, 2048 bit group with 224 bit subgroup
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and 2048 bit group with 256 bit subgroup as mentioned in RFC5114 sections
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2.1, 2.2 and 2.3 respectively. If present this overrides all other DH parameter
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options.
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=back
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=head2 EC Parameter Generation Options
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The EC parameter generation options are the same as for key generation. See
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L<EC Key Generation Options> above.
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=head1 NOTES
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The use of the genpkey program is encouraged over the algorithm specific
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utilities because additional algorithm options and ENGINE provided algorithms
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can be used.
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=head1 EXAMPLES
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Generate an RSA private key using default parameters:
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openssl genpkey -algorithm RSA -out key.pem
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Encrypt output private key using 128 bit AES and the passphrase "hello":
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openssl genpkey -algorithm RSA -out key.pem -aes-128-cbc -pass pass:hello
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Generate a 2048 bit RSA key using 3 as the public exponent:
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openssl genpkey -algorithm RSA -out key.pem \
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-pkeyopt rsa_keygen_bits:2048 -pkeyopt rsa_keygen_pubexp:3
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Generate 2048 bit DSA parameters:
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openssl genpkey -genparam -algorithm DSA -out dsap.pem \
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-pkeyopt dsa_paramgen_bits:2048
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Generate DSA key from parameters:
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openssl genpkey -paramfile dsap.pem -out dsakey.pem
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Generate 2048 bit DH parameters:
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openssl genpkey -genparam -algorithm DH -out dhp.pem \
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-pkeyopt dh_paramgen_prime_len:2048
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Generate 2048 bit X9.42 DH parameters:
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openssl genpkey -genparam -algorithm DH -out dhpx.pem \
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-pkeyopt dh_paramgen_prime_len:2048 \
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-pkeyopt dh_paramgen_type:1
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Output RFC5114 2048 bit DH parameters with 224 bit subgroup:
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openssl genpkey -genparam -algorithm DH -out dhp.pem -pkeyopt dh_rfc5114:2
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Generate DH key from parameters:
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openssl genpkey -paramfile dhp.pem -out dhkey.pem
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Generate EC parameters:
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openssl genpkey -genparam -algorithm EC -out ecp.pem \
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-pkeyopt ec_paramgen_curve:secp384r1 \
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-pkeyopt ec_param_enc:named_curve
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Generate EC key from parameters:
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openssl genpkey -paramfile ecp.pem -out eckey.pem
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Generate EC key directly:
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openssl genpkey -algorithm EC -out eckey.pem \
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-pkeyopt ec_paramgen_curve:P-384 \
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-pkeyopt ec_param_enc:named_curve
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Generate an X25519 private key:
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openssl genpkey -algorithm X25519 -out xkey.pem
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Generate an ED448 private key:
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openssl genpkey -algorithm ED448 -out xkey.pem
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=head1 HISTORY
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The ability to use NIST curve names, and to generate an EC key directly,
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were added in OpenSSL 1.0.2.
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The ability to generate X25519 keys was added in OpenSSL 1.1.0.
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The ability to generate X448, ED25519 and ED448 keys was added in OpenSSL 1.1.1.
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=head1 COPYRIGHT
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Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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