| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame^] | 1 | =pod |
| 2 | |
| 3 | =head1 NAME |
| 4 | |
| 5 | openssl-dhparam, |
| 6 | dhparam - DH parameter manipulation and generation |
| 7 | |
| 8 | =head1 SYNOPSIS |
| 9 | |
| 10 | B<openssl dhparam> |
| 11 | [B<-help>] |
| 12 | [B<-inform DER|PEM>] |
| 13 | [B<-outform DER|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<-C>] |
| 21 | [B<-2>] |
| 22 | [B<-5>] |
| 23 | [B<-rand file...>] |
| 24 | [B<-writerand file>] |
| 25 | [B<-engine id>] |
| 26 | [I<numbits>] |
| 27 | |
| 28 | =head1 DESCRIPTION |
| 29 | |
| 30 | This command is used to manipulate DH parameter files. |
| 31 | |
| 32 | =head1 OPTIONS |
| 33 | |
| 34 | =over 4 |
| 35 | |
| 36 | =item B<-help> |
| 37 | |
| 38 | Print out a usage message. |
| 39 | |
| 40 | =item B<-inform DER|PEM> |
| 41 | |
| 42 | This specifies the input format. The B<DER> option uses an ASN1 DER encoded |
| 43 | form compatible with the PKCS#3 DHparameter structure. The PEM form is the |
| 44 | default format: it consists of the B<DER> format base64 encoded with |
| 45 | additional header and footer lines. |
| 46 | |
| 47 | =item B<-outform DER|PEM> |
| 48 | |
| 49 | This specifies the output format, the options have the same meaning and default |
| 50 | as the B<-inform> option. |
| 51 | |
| 52 | =item B<-in> I<filename> |
| 53 | |
| 54 | This specifies the input filename to read parameters from or standard input if |
| 55 | this option is not specified. |
| 56 | |
| 57 | =item B<-out> I<filename> |
| 58 | |
| 59 | This specifies the output filename parameters to. Standard output is used |
| 60 | if this option is not present. The output filename should B<not> be the same |
| 61 | as the input filename. |
| 62 | |
| 63 | =item B<-dsaparam> |
| 64 | |
| 65 | If this option is used, DSA rather than DH parameters are read or created; |
| 66 | they are converted to DH format. Otherwise, "strong" primes (such |
| 67 | that (p-1)/2 is also prime) will be used for DH parameter generation. |
| 68 | |
| 69 | DH parameter generation with the B<-dsaparam> option is much faster, |
| 70 | and the recommended exponent length is shorter, which makes DH key |
| 71 | exchange more efficient. Beware that with such DSA-style DH |
| 72 | parameters, a fresh DH key should be created for each use to |
| 73 | avoid small-subgroup attacks that may be possible 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<-5> |
| 81 | |
| 82 | The generator to use, either 2 or 5. If present then the |
| 83 | input file is ignored and parameters are generated instead. If not |
| 84 | present but B<numbits> is present, parameters are generated with the |
| 85 | default generator 2. |
| 86 | |
| 87 | =item B<-rand file...> |
| 88 | |
| 89 | A file or files containing random data used to seed the random number |
| 90 | generator. |
| 91 | Multiple files can be specified separated by an OS-dependent character. |
| 92 | The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for |
| 93 | all others. |
| 94 | |
| 95 | =item [B<-writerand file>] |
| 96 | |
| 97 | Writes random data to the specified I<file> upon exit. |
| 98 | This can be used with a subsequent B<-rand> flag. |
| 99 | |
| 100 | =item I<numbits> |
| 101 | |
| 102 | This option specifies that a parameter set should be generated of size |
| 103 | I<numbits>. It must be the last option. If this option is present then |
| 104 | the input file is ignored and parameters are generated instead. If |
| 105 | this option is not present but a generator (B<-2> or B<-5>) is |
| 106 | present, parameters are generated with a default length of 2048 bits. |
| 107 | |
| 108 | =item B<-noout> |
| 109 | |
| 110 | This option inhibits the output of the encoded version of the parameters. |
| 111 | |
| 112 | =item B<-text> |
| 113 | |
| 114 | This option prints out the DH parameters in human readable form. |
| 115 | |
| 116 | =item B<-C> |
| 117 | |
| 118 | This option converts the parameters into C code. The parameters can then |
| 119 | be loaded by calling the get_dhNNNN() function. |
| 120 | |
| 121 | =item B<-engine id> |
| 122 | |
| 123 | Specifying an engine (by its unique B<id> string) will cause B<dhparam> |
| 124 | to attempt to obtain a functional reference to the specified engine, |
| 125 | thus initialising it if needed. The engine will then be set as the default |
| 126 | for all available algorithms. |
| 127 | |
| 128 | =back |
| 129 | |
| 130 | =head1 WARNINGS |
| 131 | |
| 132 | The program B<dhparam> combines the functionality of the programs B<dh> and |
| 133 | B<gendh> in previous versions of OpenSSL. The B<dh> and B<gendh> |
| 134 | programs are retained for now but may have different purposes in future |
| 135 | versions of OpenSSL. |
| 136 | |
| 137 | =head1 NOTES |
| 138 | |
| 139 | PEM format DH parameters use the header and footer lines: |
| 140 | |
| 141 | -----BEGIN DH PARAMETERS----- |
| 142 | -----END DH PARAMETERS----- |
| 143 | |
| 144 | OpenSSL currently only supports the older PKCS#3 DH, not the newer X9.42 |
| 145 | DH. |
| 146 | |
| 147 | This program manipulates DH parameters not keys. |
| 148 | |
| 149 | =head1 BUGS |
| 150 | |
| 151 | There should be a way to generate and manipulate DH keys. |
| 152 | |
| 153 | =head1 SEE ALSO |
| 154 | |
| 155 | L<dsaparam(1)> |
| 156 | |
| 157 | =head1 COPYRIGHT |
| 158 | |
| 159 | Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved. |
| 160 | |
| 161 | Licensed under the OpenSSL license (the "License"). You may not use |
| 162 | this file except in compliance with the License. You can obtain a copy |
| 163 | in the file LICENSE in the source distribution or at |
| 164 | L<https://www.openssl.org/source/license.html>. |
| 165 | |
| 166 | =cut |