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149 lines
4.0 KiB
149 lines
4.0 KiB
=pod |
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=head1 NAME |
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dhparam - DH parameter manipulation and generation |
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=head1 SYNOPSIS |
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B<openssl dhparam> |
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[B<-inform DER|PEM>] |
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[B<-outform DER|PEM>] |
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[B<-in> I<filename>] |
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[B<-out> I<filename>] |
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[B<-dsaparam>] |
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[B<-check>] |
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[B<-noout>] |
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[B<-text>] |
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[B<-C>] |
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[B<-2>] |
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[B<-5>] |
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[B<-rand> I<file(s)>] |
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[B<-engine id>] |
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[I<numbits>] |
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=head1 DESCRIPTION |
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This command is used to manipulate DH parameter files. |
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=head1 OPTIONS |
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=over 4 |
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=item B<-inform DER|PEM> |
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This specifies the input format. The B<DER> option uses an ASN1 DER encoded |
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form compatible with the PKCS#3 DHparameter structure. The PEM form is the |
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default format: it consists of the B<DER> format base64 encoded with |
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additional header and footer lines. |
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=item B<-outform DER|PEM> |
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This specifies the output format, the options have the same meaning as the |
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B<-inform> option. |
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=item B<-in> I<filename> |
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This specifies the input filename to read parameters from or standard input if |
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this option is not specified. |
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=item B<-out> I<filename> |
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This specifies the output filename parameters to. Standard output is used |
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if this option is not present. The output filename should B<not> be the same |
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as the input filename. |
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=item B<-dsaparam> |
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If this option is used, DSA rather than DH parameters are read or created; |
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they are converted to DH format. Otherwise, "strong" primes (such |
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that (p-1)/2 is also prime) will be used for DH parameter generation. |
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DH parameter generation with the B<-dsaparam> option is much faster, |
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and the recommended exponent length is shorter, which makes DH key |
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exchange more efficient. Beware that with such DSA-style DH |
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parameters, a fresh DH key should be created for each use to |
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avoid small-subgroup attacks that may be possible otherwise. |
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=item B<-check> |
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check if the parameters are valid primes and generator. |
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=item B<-2>, B<-5> |
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The generator to use, either 2 or 5. If present then the |
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input file is ignored and parameters are generated instead. If not |
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present but B<numbits> is present, parameters are generated with the |
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default generator 2. |
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=item B<-rand> I<file(s)> |
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a file or files containing random data used to seed the random number |
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generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>). |
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Multiple files can be specified separated by a OS-dependent character. |
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The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for |
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all others. |
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=item I<numbits> |
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this option specifies that a parameter set should be generated of size |
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I<numbits>. It must be the last option. If this option is present then |
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the input file is ignored and parameters are generated instead. If |
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this option is not present but a generator (B<-2> or B<-5>) is |
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present, parameters are generated with a default length of 2048 bits. |
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=item B<-noout> |
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this option inhibits the output of the encoded version of the parameters. |
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=item B<-text> |
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this option prints out the DH parameters in human readable form. |
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=item B<-C> |
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this option converts the parameters into C code. The parameters can then |
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be loaded by calling the B<get_dh>I<numbits>B<()> function. |
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=item B<-engine id> |
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specifying an engine (by its unique B<id> string) will cause B<dhparam> |
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to attempt to obtain a functional reference to the specified engine, |
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thus initialising it if needed. The engine will then be set as the default |
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for all available algorithms. |
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=back |
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=head1 WARNINGS |
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The program B<dhparam> combines the functionality of the programs B<dh> and |
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B<gendh> in previous versions of OpenSSL and SSLeay. The B<dh> and B<gendh> |
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programs are retained for now but may have different purposes in future |
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versions of OpenSSL. |
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=head1 NOTES |
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PEM format DH parameters use the header and footer lines: |
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-----BEGIN DH PARAMETERS----- |
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-----END DH PARAMETERS----- |
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OpenSSL currently only supports the older PKCS#3 DH, not the newer X9.42 |
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DH. |
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This program manipulates DH parameters not keys. |
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=head1 BUGS |
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There should be a way to generate and manipulate DH keys. |
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=head1 SEE ALSO |
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L<dsaparam(1)|dsaparam(1)> |
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=head1 HISTORY |
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The B<dhparam> command was added in OpenSSL 0.9.5. |
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The B<-dsaparam> option was added in OpenSSL 0.9.6. |
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=cut
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