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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
09483c58 | 5 | dhparam - DH parameter manipulation and generation |
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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>] | |
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15 | [B<-noout>] |
16 | [B<-text>] | |
17 | [B<-C>] | |
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18 | [B<-2>] |
19 | [B<-5>] | |
41918458 | 20 | [B<-rand> I<file(s)>] |
bfa35550 | 21 | [B<-engine id>] |
41918458 | 22 | [I<numbits>] |
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23 | |
24 | =head1 DESCRIPTION | |
25 | ||
26 | This command is used to manipulate DH parameter files. | |
27 | ||
28 | =head1 OPTIONS | |
29 | ||
30 | =over 4 | |
31 | ||
32 | =item B<-inform DER|PEM> | |
33 | ||
34 | This specifies the input format. The B<DER> option uses an ASN1 DER encoded | |
35 | form compatible with the PKCS#3 DHparameter structure. The PEM form is the | |
36 | default format: it consists of the B<DER> format base64 encoded with | |
37 | additional header and footer lines. | |
38 | ||
39 | =item B<-outform DER|PEM> | |
40 | ||
41 | This specifies the output format, the options have the same meaning as the | |
42 | B<-inform> option. | |
43 | ||
41918458 | 44 | =item B<-in> I<filename> |
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45 | |
46 | This specifies the input filename to read parameters from or standard input if | |
47 | this option is not specified. | |
48 | ||
41918458 | 49 | =item B<-out> I<filename> |
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50 | |
51 | This specifies the output filename parameters to. Standard output is used | |
52 | if this option is not present. The output filename should B<not> be the same | |
53 | as the input filename. | |
54 | ||
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55 | =item B<-dsaparam> |
56 | ||
57 | If this option is used, DSA rather than DH parameters are read or created; | |
58 | they are converted to DH format. Otherwise, "strong" primes (such | |
59 | that (p-1)/2 is also prime) will be used for DH parameter generation. | |
60 | ||
61 | DH parameter generation with the B<-dsaparam> option is much faster, | |
62 | and the recommended exponent length is shorter, which makes DH key | |
63 | exchange more efficient. Beware that with such DSA-style DH | |
64 | parameters, a fresh DH key should be created for each use to | |
65 | avoid small-subgroup attacks that may be possible otherwise. | |
66 | ||
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67 | =item B<-2>, B<-5> |
68 | ||
69 | The generator to use, either 2 or 5. 2 is the default. If present then the | |
70 | input file is ignored and parameters are generated instead. | |
71 | ||
41918458 | 72 | =item B<-rand> I<file(s)> |
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73 | |
74 | a file or files containing random data used to seed the random number | |
a4cfd178 UM |
75 | generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>). |
76 | Multiple files can be specified separated by a OS-dependent character. | |
b87ef946 | 77 | The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for |
a4cfd178 | 78 | all others. |
09483c58 | 79 | |
41918458 | 80 | =item I<numbits> |
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81 | |
82 | this option specifies that a parameter set should be generated of size | |
41918458 | 83 | I<numbits>. It must be the last option. If not present then a value of 512 |
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84 | is used. If this option is present then the input file is ignored and |
85 | parameters are generated instead. | |
86 | ||
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87 | =item B<-noout> |
88 | ||
89 | this option inhibits the output of the encoded version of the parameters. | |
90 | ||
91 | =item B<-text> | |
92 | ||
93 | this option prints out the DH parameters in human readable form. | |
94 | ||
95 | =item B<-C> | |
96 | ||
97 | this option converts the parameters into C code. The parameters can then | |
41918458 | 98 | be loaded by calling the B<get_dh>I<numbits>B<()> function. |
ef7eaa4c | 99 | |
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100 | =item B<-engine id> |
101 | ||
e5fa864f | 102 | specifying an engine (by its unique B<id> string) will cause B<dhparam> |
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103 | to attempt to obtain a functional reference to the specified engine, |
104 | thus initialising it if needed. The engine will then be set as the default | |
105 | for all available algorithms. | |
106 | ||
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107 | =back |
108 | ||
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109 | =head1 WARNINGS |
110 | ||
111 | The program B<dhparam> combines the functionality of the programs B<dh> and | |
112 | B<gendh> in previous versions of OpenSSL and SSLeay. The B<dh> and B<gendh> | |
113 | programs are retained for now but may have different purposes in future | |
114 | versions of OpenSSL. | |
115 | ||
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116 | =head1 NOTES |
117 | ||
118 | PEM format DH parameters use the header and footer lines: | |
119 | ||
120 | -----BEGIN DH PARAMETERS----- | |
121 | -----END DH PARAMETERS----- | |
122 | ||
123 | OpenSSL currently only supports the older PKCS#3 DH, not the newer X9.42 | |
124 | DH. | |
125 | ||
126 | This program manipulates DH parameters not keys. | |
127 | ||
128 | =head1 BUGS | |
129 | ||
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130 | There should be a way to generate and manipulate DH keys. |
131 | ||
132 | =head1 SEE ALSO | |
133 | ||
bb075f88 | 134 | L<dsaparam(1)|dsaparam(1)> |
ef7eaa4c | 135 | |
41918458 BM |
136 | =head1 HISTORY |
137 | ||
138 | The B<dhparam> command was added in OpenSSL 0.9.5. | |
139 | The B<-dsaparam> option was added in OpenSSL 0.9.6. | |
140 | ||
ef7eaa4c | 141 | =cut |