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ef7eaa4c DSH |
1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
09483c58 | 5 | dhparam - DH parameter manipulation and generation |
ef7eaa4c DSH |
6 | |
7 | =head1 SYNOPSIS | |
8 | ||
41918458 | 9 | B<openssl dhparam> |
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10 | [B<-inform DER|PEM>] |
11 | [B<-outform DER|PEM>] | |
41918458 BM |
12 | [B<-in> I<filename>] |
13 | [B<-out> I<filename>] | |
14 | [B<-dsaparam>] | |
fc1d88f0 | 15 | [B<-check>] |
ef7eaa4c DSH |
16 | [B<-noout>] |
17 | [B<-text>] | |
18 | [B<-C>] | |
09483c58 DSH |
19 | [B<-2>] |
20 | [B<-5>] | |
41918458 | 21 | [B<-rand> I<file(s)>] |
bfa35550 | 22 | [B<-engine id>] |
41918458 | 23 | [I<numbits>] |
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24 | |
25 | =head1 DESCRIPTION | |
26 | ||
27 | This command is used to manipulate DH parameter files. | |
28 | ||
29 | =head1 OPTIONS | |
30 | ||
31 | =over 4 | |
32 | ||
33 | =item B<-inform DER|PEM> | |
34 | ||
35 | This specifies the input format. The B<DER> option uses an ASN1 DER encoded | |
36 | form compatible with the PKCS#3 DHparameter structure. The PEM form is the | |
37 | default format: it consists of the B<DER> format base64 encoded with | |
38 | additional header and footer lines. | |
39 | ||
40 | =item B<-outform DER|PEM> | |
41 | ||
42 | This specifies the output format, the options have the same meaning as the | |
43 | B<-inform> option. | |
44 | ||
41918458 | 45 | =item B<-in> I<filename> |
ef7eaa4c DSH |
46 | |
47 | This specifies the input filename to read parameters from or standard input if | |
48 | this option is not specified. | |
49 | ||
41918458 | 50 | =item B<-out> I<filename> |
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51 | |
52 | This specifies the output filename parameters to. Standard output is used | |
53 | if this option is not present. The output filename should B<not> be the same | |
54 | as the input filename. | |
55 | ||
41918458 BM |
56 | =item B<-dsaparam> |
57 | ||
58 | If this option is used, DSA rather than DH parameters are read or created; | |
59 | they are converted to DH format. Otherwise, "strong" primes (such | |
60 | that (p-1)/2 is also prime) will be used for DH parameter generation. | |
61 | ||
62 | DH parameter generation with the B<-dsaparam> option is much faster, | |
63 | and the recommended exponent length is shorter, which makes DH key | |
64 | exchange more efficient. Beware that with such DSA-style DH | |
65 | parameters, a fresh DH key should be created for each use to | |
66 | avoid small-subgroup attacks that may be possible otherwise. | |
67 | ||
fc1d88f0 RS |
68 | =item B<-check> |
69 | ||
70 | check if the parameters are valid primes and generator. | |
71 | ||
09483c58 DSH |
72 | =item B<-2>, B<-5> |
73 | ||
b5a379aa EK |
74 | The generator to use, either 2 or 5. If present then the |
75 | input file is ignored and parameters are generated instead. If not | |
76 | present but B<numbits> is present, parameters are generated with the | |
77 | default generator 2. | |
09483c58 | 78 | |
41918458 | 79 | =item B<-rand> I<file(s)> |
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80 | |
81 | a file or files containing random data used to seed the random number | |
9b86974e | 82 | generator, or an EGD socket (see L<RAND_egd(3)>). |
a4cfd178 | 83 | Multiple files can be specified separated by a OS-dependent character. |
b87ef946 | 84 | The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for |
a4cfd178 | 85 | all others. |
09483c58 | 86 | |
41918458 | 87 | =item I<numbits> |
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88 | |
89 | this option specifies that a parameter set should be generated of size | |
b5a379aa EK |
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> or B<-5>) is | |
93 | present, parameters are generated with a default length of 2048 bits. | |
09483c58 | 94 | |
ef7eaa4c DSH |
95 | =item B<-noout> |
96 | ||
97 | this option inhibits the output of the encoded version of the parameters. | |
98 | ||
99 | =item B<-text> | |
100 | ||
101 | this option prints out the DH parameters in human readable form. | |
102 | ||
103 | =item B<-C> | |
104 | ||
105 | this option converts the parameters into C code. The parameters can then | |
41918458 | 106 | be loaded by calling the B<get_dh>I<numbits>B<()> function. |
ef7eaa4c | 107 | |
bfa35550 RL |
108 | =item B<-engine id> |
109 | ||
e5fa864f | 110 | specifying an engine (by its unique B<id> string) will cause B<dhparam> |
bfa35550 RL |
111 | to attempt to obtain a functional reference to the specified engine, |
112 | thus initialising it if needed. The engine will then be set as the default | |
113 | for all available algorithms. | |
114 | ||
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115 | =back |
116 | ||
09483c58 DSH |
117 | =head1 WARNINGS |
118 | ||
119 | The program B<dhparam> combines the functionality of the programs B<dh> and | |
b0700d2c | 120 | B<gendh> in previous versions of OpenSSL. The B<dh> and B<gendh> |
09483c58 DSH |
121 | programs are retained for now but may have different purposes in future |
122 | versions of OpenSSL. | |
123 | ||
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124 | =head1 NOTES |
125 | ||
126 | PEM format DH parameters use the header and footer lines: | |
127 | ||
128 | -----BEGIN DH PARAMETERS----- | |
129 | -----END DH PARAMETERS----- | |
130 | ||
131 | OpenSSL currently only supports the older PKCS#3 DH, not the newer X9.42 | |
132 | DH. | |
133 | ||
134 | This program manipulates DH parameters not keys. | |
135 | ||
136 | =head1 BUGS | |
137 | ||
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138 | There should be a way to generate and manipulate DH keys. |
139 | ||
140 | =head1 SEE ALSO | |
141 | ||
9b86974e | 142 | L<dsaparam(1)> |
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143 | |
144 | =cut |