2 {- OpenSSL::safe::output_do_not_edit_headers(); -}
6 openssl-dhparam - DH parameter manipulation and generation
12 [B<-inform> B<DER>|B<PEM>]
13 [B<-outform> B<DER>|B<PEM>]
24 {- $OpenSSL::safe::opt_engine_synopsis -}{- $OpenSSL::safe::opt_r_synopsis -}
25 {- $OpenSSL::safe::opt_provider_synopsis -}
28 =for openssl ifdef dsaparam engine
32 This command is used to manipulate DH parameter files.
40 Print out a usage message.
42 =item B<-inform> B<DER>|B<PEM>, B<-outform> B<DER>|B<PEM>
44 The input format and output format; the default is B<PEM>.
45 The object is compatible with the PKCS#3 B<DHparameter> structure.
46 See L<openssl(1)/Format Options> for details.
48 =item B<-in> I<filename>
50 This specifies the input filename to read parameters from or standard input if
51 this option is not specified.
53 =item B<-out> I<filename>
55 This specifies the output filename parameters to. Standard output is used
56 if this option is not present. The output filename should B<not> be the same
57 as the input filename.
61 This option is deprecated.
63 If this option is used, DSA rather than DH parameters are read or created;
64 they are converted to DH format. Otherwise, "strong" primes (such
65 that (p-1)/2 is also prime) will be used for DH parameter generation.
67 DH parameter generation with the B<-dsaparam> option is much faster,
68 and the recommended exponent length is shorter, which makes DH key
69 exchange more efficient. Beware that with such DSA-style DH
70 parameters, a fresh DH key should be created for each use to
71 avoid small-subgroup attacks that may be possible otherwise.
75 Performs numerous checks to see if the supplied parameters are valid and
76 displays a warning if not.
78 =item B<-2>, B<-3>, B<-5>
80 The generator to use, either 2, 3 or 5. If present then the
81 input file is ignored and parameters are generated instead. If not
82 present but I<numbits> is present, parameters are generated with the
87 This option specifies that a parameter set should be generated of size
88 I<numbits>. It must be the last option. If this option is present then
89 the input file is ignored and parameters are generated instead. If
90 this option is not present but a generator (B<-2>, B<-3> or B<-5>) is
91 present, parameters are generated with a default length of 2048 bits.
92 The minimim length is 512 bits. The maximum length is 10000 bits.
96 This option inhibits the output of the encoded version of the parameters.
100 This option prints out the DH parameters in human readable form.
104 This option converts the parameters into C code. The parameters can then
105 be loaded by calling the get_dhNNNN() function.
107 {- $OpenSSL::safe::opt_engine_item -}
109 {- $OpenSSL::safe::opt_r_item -}
111 {- $OpenSSL::safe::opt_provider_item -}
117 This command replaces the B<dh> and B<gendh> commands of previous
120 OpenSSL currently only supports the older PKCS#3 DH, not the newer X9.42
123 This command manipulates DH parameters not keys.
127 There should be a way to generate and manipulate DH keys.
132 L<openssl-pkeyparam(1)>,
133 L<openssl-dsaparam(1)>
137 The B<-dsaparam> and B<-engine> options were deprecated in OpenSSL 3.0.
141 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
143 Licensed under the Apache License 2.0 (the "License"). You may not use
144 this file except in compliance with the License. You can obtain a copy
145 in the file LICENSE in the source distribution or at
146 L<https://www.openssl.org/source/license.html>.