DHgenerateparameters(3) OpenSSL DHgenerateparameters(3)

NAME
       DHgenerateparameters, DHcheck - generate and check Diffie-Hellman
       parameters

SYNOPSIS
        #include 

        DH *DHgenerateparameters(int primelen, int generator,
            void (*callback)(int, int, void *), void *cbarg);

        int DHcheck(DH *dh, int *codes);

DESCRIPTION
       DHgenerateparameters() generates Diffie-Hellman parameters that can
       be shared among a group of users, and returns them in a newly allocated
       DDHH structure. The pseudo-random number generator must be seeded prior
       to calling DHgenerateparameters().

       pprriimmeelleenn is the length in bits of the safe prime to be generated.
       ggeenneerraattoorr is a small number > 1, typically 2 or 5.

       A callback function may be used to provide feedback about the progress
       of the key generation. If ccaallllbbaacckk is not NNUULLLL, it will be called as
       described in BNgenerateprime(3) while a random prime number is
       generated, and when a prime has been found, ccaallllbbaacckk((33,, 00,, ccbbaarrgg)) is
       called.

       DHcheck() validates Diffie-Hellman parameters. It checks that pp is a
       safe prime, and that gg is a suitable generator. In the case of an
       error, the bit flags DHCHECKPNOTSAFEPRIME or
       DHNOTSUITABLEGENERATOR are set in **ccooddeess.
       DHUNABLETOCHECKGENERATOR is set if the generator cannot be checked,
       i.e. it does not equal 2 or 5.

RETURN VALUES
       DHgenerateparameters() returns a pointer to the DH structure, or NULL
       if the parameter generation fails. The error codes can be obtained by
       ERRgeterror(3).

       DHcheck() returns 1 if the check could be performed, 0 otherwise.

NNOOTTEESS
       DHgenerateparameters() may run for several hours before finding a
       suitable prime.

       The parameters generated by DHgenerateparameters() are not to be used
       in signature schemes.

BUGS
       If ggeenneerraattoorr is not 2 or 5, ddhh->>gg=ggeenneerraattoorr is not a usable generator.

SEE ALSO
       dh(3), ERRgeterror(3), rand(3), DHfree(3)

HISTORY       DHcheck() is available in all versions of SSLeay and OpenSSL.  The
       ccbbaarrgg argument to DHgenerateparameters() was added in SSLeay 0.9.0.

       In versions before OpenSSL 0.9.5, DHCHECKPNOTSTRONGPRIME is used
       instead of DHCHECKPNOTSAFEPRIME.



0.9.7l                            2002-09-25         DHgenerateparameters(3)