| 1 | =pod
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| 2 | {- OpenSSL::safe::output_do_not_edit_headers(); -}
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| 3 |
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| 4 | =head1 NAME
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| 5 |
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| 6 | openssl-dhparam - DH parameter manipulation and generation
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| 7 |
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| 8 | =head1 SYNOPSIS
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| 9 |
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| 10 | B<openssl dhparam>
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| 11 | [B<-help>]
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| 12 | [B<-inform> B<DER>|B<PEM>]
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| 13 | [B<-outform> B<DER>|B<PEM>]
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| 14 | [B<-in> I<filename>]
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| 15 | [B<-out> I<filename>]
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| 16 | [B<-dsaparam>]
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| 17 | [B<-check>]
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| 18 | [B<-noout>]
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| 19 | [B<-text>]
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| 20 | [B<-2>]
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| 21 | [B<-3>]
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| 22 | [B<-5>]
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| 23 | {- $OpenSSL::safe::opt_engine_synopsis -}{- $OpenSSL::safe::opt_r_synopsis -}
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| 24 | {- $OpenSSL::safe::opt_provider_synopsis -}
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| 25 | [I<numbits>]
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| 26 |
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| 27 | =head1 DESCRIPTION
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| 28 |
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| 29 | This command is used to manipulate DH parameter files.
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| 30 |
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| 31 | See L<openssl-genpkey(1)/EXAMPLES> for examples on how to generate
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| 32 | a key using a named safe prime group without generating intermediate
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| 33 | parameters.
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| 34 |
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| 35 | =head1 OPTIONS
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| 36 |
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| 37 | =over 4
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| 38 |
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| 39 | =item B<-help>
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| 40 |
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| 41 | Print out a usage message.
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| 42 |
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| 43 | =item B<-inform> B<DER>|B<PEM>, B<-outform> B<DER>|B<PEM>
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| 44 |
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| 45 | The input format and output format; the default is B<PEM>.
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| 46 | The object is compatible with the PKCS#3 B<DHparameter> structure.
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| 47 | See L<openssl-format-options(1)> for details.
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| 48 |
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| 49 | =item B<-in> I<filename>
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| 50 |
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| 51 | This specifies the input filename to read parameters from or standard input if
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| 52 | this option is not specified.
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| 53 |
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| 54 | =item B<-out> I<filename>
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| 55 |
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| 56 | This specifies the output filename parameters to. Standard output is used
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| 57 | if this option is not present. The output filename should B<not> be the same
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| 58 | as the input filename.
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| 59 |
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| 60 | =item B<-dsaparam>
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| 61 |
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| 62 | If this option is used, DSA rather than DH parameters are read or created;
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| 63 | they are converted to DH format. Otherwise, safe primes (such
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| 64 | that (p-1)/2 is also prime) will be used for DH parameter generation.
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| 65 |
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| 66 | DH parameter generation with the B<-dsaparam> option is much faster.
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| 67 | Beware that with such DSA-style DH parameters, a fresh DH key should be
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| 68 | created for each use to avoid small-subgroup attacks that may be possible
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| 69 | otherwise.
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| 70 |
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| 71 | =item B<-check>
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| 72 |
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| 73 | Performs numerous checks to see if the supplied parameters are valid and
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| 74 | displays a warning if not.
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| 75 |
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| 76 | =item B<-2>, B<-3>, B<-5>
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| 77 |
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| 78 | The generator to use, either 2, 3 or 5. If present then the
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| 79 | input file is ignored and parameters are generated instead. If not
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| 80 | present but I<numbits> is present, parameters are generated with the
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| 81 | default generator 2.
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| 82 |
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| 83 | =item I<numbits>
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| 84 |
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| 85 | This option specifies that a parameter set should be generated of size
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| 86 | I<numbits>. It must be the last option. If this option is present then
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| 87 | the input file is ignored and parameters are generated instead. If
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| 88 | this option is not present but a generator (B<-2>, B<-3> or B<-5>) is
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| 89 | present, parameters are generated with a default length of 2048 bits.
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| 90 | The minimum length is 512 bits. The maximum length is 10000 bits.
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| 91 |
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| 92 | =item B<-noout>
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| 93 |
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| 94 | This option inhibits the output of the encoded version of the parameters.
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| 95 |
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| 96 | =item B<-text>
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| 97 |
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| 98 | This option prints out the DH parameters in human readable form.
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| 99 |
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| 100 | {- $OpenSSL::safe::opt_engine_item -}
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| 101 |
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| 102 | {- $OpenSSL::safe::opt_r_item -}
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| 103 |
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| 104 | {- $OpenSSL::safe::opt_provider_item -}
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| 105 |
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| 106 | =back
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| 107 |
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| 108 | =head1 NOTES
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| 109 |
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| 110 | This command replaces the B<dh> and B<gendh> commands of previous
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| 111 | releases.
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| 112 |
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| 113 | =head1 SEE ALSO
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| 114 |
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| 115 | L<openssl(1)>,
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| 116 | L<openssl-pkeyparam(1)>,
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| 117 | L<openssl-dsaparam(1)>,
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| 118 | L<openssl-genpkey(1)>.
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| 119 |
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| 120 | =head1 HISTORY
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| 121 |
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| 122 | The B<-engine> option was deprecated in OpenSSL 3.0.
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| 123 |
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| 124 | The B<-C> option was removed in OpenSSL 3.0.
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| 125 |
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| 126 | =head1 COPYRIGHT
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| 127 |
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| 128 | Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.
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| 129 |
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| 130 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 131 | this file except in compliance with the License. You can obtain a copy
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| 132 | in the file LICENSE in the source distribution or at
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| 133 | L<https://www.openssl.org/source/license.html>.
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| 134 |
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| 135 | =cut
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