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      1 =pod
      2 {- OpenSSL::safe::output_do_not_edit_headers(); -}
      3 
      4 =head1 NAME
      5 
      6 openssl-dhparam - DH parameter manipulation and generation
      7 
      8 =head1 SYNOPSIS
      9 
     10 B<openssl dhparam>
     11 [B<-help>]
     12 [B<-inform> B<DER>|B<PEM>]
     13 [B<-outform> B<DER>|B<PEM>]
     14 [B<-in> I<filename>]
     15 [B<-out> I<filename>]
     16 [B<-dsaparam>]
     17 [B<-check>]
     18 [B<-noout>]
     19 [B<-text>]
     20 [B<-verbose>]
     21 [B<-quiet>]
     22 [B<-2>]
     23 [B<-3>]
     24 [B<-5>]
     25 {- $OpenSSL::safe::opt_engine_synopsis -}{- $OpenSSL::safe::opt_r_synopsis -}
     26 {- $OpenSSL::safe::opt_provider_synopsis -}
     27 [I<numbits>]
     28 
     29 =head1 DESCRIPTION
     30 
     31 This command is used to manipulate DH parameter files.
     32 
     33 See L<openssl-genpkey(1)/EXAMPLES> for examples on how to generate
     34 a key using a named safe prime group without generating intermediate
     35 parameters.
     36 
     37 =head1 OPTIONS
     38 
     39 =over 4
     40 
     41 =item B<-help>
     42 
     43 Print out a usage message.
     44 
     45 =item B<-inform> B<DER>|B<PEM>, B<-outform> B<DER>|B<PEM>
     46 
     47 The input format and output format; the default is B<PEM>.
     48 The object is compatible with the PKCS#3 B<DHparameter> structure.
     49 See L<openssl-format-options(1)> for details.
     50 
     51 =item B<-in> I<filename>
     52 
     53 This specifies the input file to read parameters from or standard input if
     54 this option is not specified.
     55 
     56 =item B<-out> I<filename>
     57 
     58 This specifies the output file to write parameters to.
     59 Standard output is used if this option is not present.
     60 The output filename can be the same as the input filename,
     61 which leads to replacing the file contents.
     62 Note that file I/O is not atomic. The output file is truncated and then written.
     63 
     64 =item B<-dsaparam>
     65 
     66 If this option is used, DSA rather than DH parameters are read or created;
     67 they are converted to DH format.  Otherwise, safe primes (such
     68 that (p-1)/2 is also prime) will be used for DH parameter generation.
     69 
     70 DH parameter generation with the B<-dsaparam> option is much faster.
     71 Beware that with such DSA-style DH parameters, a fresh DH key should be
     72 created for each use to avoid small-subgroup attacks that may be possible
     73 otherwise.
     74 
     75 =item B<-check>
     76 
     77 Performs numerous checks to see if the supplied parameters are valid and
     78 displays a warning if not.
     79 
     80 =item B<-2>, B<-3>, B<-5>
     81 
     82 The generator to use, either 2, 3 or 5. If present then the
     83 input file is ignored and parameters are generated instead. If not
     84 present but I<numbits> is present, parameters are generated with the
     85 default generator 2.
     86 
     87 =item I<numbits>
     88 
     89 This option specifies that a parameter set should be generated of size
     90 I<numbits>. It must be the last option. If this option is present then
     91 the input file is ignored and parameters are generated instead. If
     92 this option is not present but a generator (B<-2>, B<-3> or B<-5>) is
     93 present, parameters are generated with a default length of 2048 bits.
     94 The minimum length is 512 bits. The maximum length is 10000 bits.
     95 
     96 =item B<-noout>
     97 
     98 This option inhibits the output of the encoded version of the parameters.
     99 
    100 =item B<-text>
    101 
    102 This option prints out the DH parameters in human readable form.
    103 
    104 {- $OpenSSL::safe::opt_engine_item -}
    105 
    106 {- $OpenSSL::safe::opt_r_item -}
    107 
    108 {- $OpenSSL::safe::opt_provider_item -}
    109 
    110 =item B<-verbose>
    111 
    112 This option enables the output of progress messages, which is handy when
    113 running commands interactively that may take a long time to execute.
    114 
    115 =item B<-quiet>
    116 
    117 This option suppresses the output of progress messages, which may be
    118 undesirable in batch scripts or pipelines.
    119 
    120 =back
    121 
    122 =head1 NOTES
    123 
    124 This command replaces the B<dh> and B<gendh> commands of previous
    125 releases.
    126 
    127 =head1 SEE ALSO
    128 
    129 L<openssl(1)>,
    130 L<openssl-pkeyparam(1)>,
    131 L<openssl-dsaparam(1)>,
    132 L<openssl-genpkey(1)>.
    133 
    134 =head1 HISTORY
    135 
    136 The B<-engine> option was deprecated in OpenSSL 3.0.
    137 
    138 The B<-C> option was removed in OpenSSL 3.0.
    139 
    140 =head1 COPYRIGHT
    141 
    142 Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.
    143 
    144 Licensed under the Apache License 2.0 (the "License").  You may not use
    145 this file except in compliance with the License.  You can obtain a copy
    146 in the file LICENSE in the source distribution or at
    147 L<https://www.openssl.org/source/license.html>.
    148 
    149 =cut
    150