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DHPARAM(1)                          OpenSSL                         DHPARAM(1)

       dhparam - DH parameter manipulation and generation

       ooppeennssssll ddhhppaarraamm [--iinnffoorrmm DDEERR||PPEEMM] [--oouuttffoorrmm DDEERR||PPEEMM] [--iinn filename]
       [--oouutt filename] [--ddssaappaarraamm] [--nnoooouutt] [--tteexxtt] [--CC] [--22] [--55] [--rraanndd
       file(s)] [--eennggiinnee iidd] [numbits]

       This command is used to manipulate DH parameter files.

       --iinnffoorrmm DDEERR||PPEEMM
           This specifies the input format. The DDEERR option uses an ASN1 DER
           encoded form compatible with the PKCS#3 DHparameter structure. The
           PEM form is the default format: it consists of the DDEERR format
           base64 encoded with additional header and footer lines.

       --oouuttffoorrmm DDEERR||PPEEMM
           This specifies the output format, the options have the same meaning
           as the --iinnffoorrmm option.

       --iinn filename
           This specifies the input filename to read parameters from or stan-
           dard input if this option is not specified.

       --oouutt filename
           This specifies the output filename parameters to. Standard output
           is used if this option is not present. The output filename should
           nnoott be the same as the input filename.

           If this option is used, DSA rather than DH parameters are read or
           created; they are converted to DH format.  Otherwise, "strong"
           primes (such that (p-1)/2 is also prime) will be used for DH param-
           eter generation.

           DH parameter generation with the --ddssaappaarraamm option is much faster,
           and the recommended exponent length is shorter, which makes DH key
           exchange more efficient.  Beware that with such DSA-style DH param-
           eters, a fresh DH key should be created for each use to avoid
           small-subgroup attacks that may be possible otherwise.

       --22, --55
           The generator to use, either 2 or 5. 2 is the default. If present
           then the input file is ignored and parameters are generated

       --rraanndd file(s)
           a file or files containing random data used to seed the random num-
           ber generator, or an EGD socket (see RAND_egd(3)).  Multiple files
           can be specified separated by a OS-dependent character.  The sepa-
           rator is ;; for MS-Windows, ,, for OpenVMS, and :: for all others.

           this option specifies that a parameter set should be generated of
           size numbits. It must be the last option. If not present then a
           value of 512 is used. If this option is present then the input file
           is ignored and parameters are generated instead.

           this option inhibits the output of the encoded version of the

           this option prints out the DH parameters in human readable form.

       --CC  this option converts the parameters into C code. The parameters can
           then be loaded by calling the ggeett_ddhhnumbits(()) function.

       --eennggiinnee iidd
           specifying an engine (by it's unique iidd string) will cause rreeqq to
           attempt to obtain a functional reference to the specified engine,
           thus initialising it if needed. The engine will then be set as the
           default for all available algorithms.

       The program ddhhppaarraamm combines the functionality of the programs ddhh and
       ggeennddhh in previous versions of OpenSSL and SSLeay. The ddhh and ggeennddhh pro-
       grams are retained for now but may have different purposes in future
       versions of OpenSSL.

       PEM format DH parameters use the header and footer lines:

        -----BEGIN DH PARAMETERS-----
        -----END DH PARAMETERS-----

       OpenSSL currently only supports the older PKCS#3 DH, not the newer
       X9.42 DH.

       This program manipulates DH parameters not keys.

       There should be a way to generate and manipulate DH keys.


       The ddhhppaarraamm command was added in OpenSSL 0.9.5.  The --ddssaappaarraamm option
       was added in OpenSSL 0.9.6.

3rd Berkeley Distribution           0.9.7a                          DHPARAM(1)

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