dhparam

 

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 DHPARAM(1)                   OpenSSL                   DHPARAM(1)
 
 
 
 NAME
        dhparam - DH parameter manipulation and generation
 
 SYNOPSIS
        openssl dhparam [-inform DER|PEM] [-outform DER|PEM] [-in
        filename] [-out filename] [-dsaparam] [-noout] [-text]
        [-C] [-2] [-5] [-rand file(s)] [numbits]
 
 DESCRIPTION
        This command is used to manipulate DH parameter files.
 
 OPTIONS
        -inform DER|PEM
            This specifies the input format. The DER 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 DER format base64 encoded
            with additional header and footer lines.
 
        -outform DER|PEM
            This specifies the output format, the options have the
            same meaning as the -inform option.
 
        -in filename
            This specifies the input filename to read parameters
            from or standard input if this option is not
            specified.
 
        -out filename
            This specifies the output filename parameters to.
            Standard output is used if this option is not present.
            The output filename should not be the same as the
            input filename.
 
        -dsaparam
            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 parameter generation.
 
            DH parameter generation with the -dsaparam 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 parameters, a fresh
            DH key should be created for each use to avoid small-
            subgroup attacks that may be possible otherwise.
 
        -2, -5
            The generator to use, either 2 or 5. 2 is the default.
            If present then the input file is ignored and
            parameters are generated instead.
 
        -rand file(s)
            a file or files containing random data used to seed
            the random number generator, or an EGD socket (see
            RAND_egd(3)).  Multiple files can be specified
            separated by a OS-dependent character.  The separator
            is ; for MS-Windows, , for OpenVMS, and : for all
            others.
 
        numbits
            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.
 
        -noout
            this option inhibits the output of the encoded version
            of the parameters.
 
        -text
            this option prints out the DH parameters in human
            readable form.
 
        -C  this option converts the parameters into C code. The
            parameters can then be loaded by calling the
            get_dhnumbits() function.
 
 WARNINGS
        The program dhparam combines the functionality of the
        programs dh and gendh in previous versions of OpenSSL and
        SSLeay. The dh and gendh programs are retained for now but
        may have different purposes in future versions of OpenSSL.
 
 NOTES
        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.
 
 BUGS
        There should be a way to generate and manipulate DH keys.
 
 SEE ALSO
        dsaparam(1)
 
 HISTORY
        The dhparam command was added in OpenSSL 0.9.5.  The
        -dsaparam option was added in OpenSSL 0.9.6.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 12/Apr/2000                   0.9.6b                   DHPARAM(1)

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