DSAgenerateparameters(3) OpenSSL DSAgenerateparameters(3)

NAME
       DSAgenerateparameters - generate DSA parameters

SYNOPSIS
        #include 

        DSA *DSAgenerateparameters(int bits, unsigned char *seed,
                       int seedlen, int *counterret, unsigned long *hret,
                       void (*callback)(int, int, void *), void *cbarg);

DESCRIPTION
       DSAgenerateparameters() generates primes p and q and a generator g
       for use in the DSA.

       bbiittss is the length of the prime to be generated; the DSS allows a
       maximum of 1024 bits.

       If sseeeedd is NNUULLLL or sseeeeddlleenn < 20, the primes will be generated at
       random. Otherwise, the seed is used to generate them. If the given seed
       does not yield a prime q, a new random seed is chosen and placed at
       sseeeedd.

       DSAgenerateparameters() places the iteration count in *ccoouunntteerrrreett
       and a counter used for finding a generator in *hhrreett, unless these are
       NNUULLLL.

       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
       follows:

       +o   When a candidate for q is generated, ccaallllbbaacckk((00,, mm++++,, ccbbaarrgg)) is
           called (m is 0 for the first candidate).

       +o   When a candidate for q has passed a test by trial division,
           ccaallllbbaacckk((11,, -11,, ccbbaarrgg)) is called.  While a candidate for q is
           tested by Miller-Rabin primality tests, ccaallllbbaacckk((11,, ii,, ccbbaarrgg)) is
           called in the outer loop (once for each witness that confirms that
           the candidate may be prime); i is the loop counter (starting at 0).

       +o   When a prime q has been found, ccaallllbbaacckk((22,, 00,, ccbbaarrgg)) and
           ccaallllbbaacckk((33,, 00,, ccbbaarrgg)) are called.

       +o   Before a candidate for p (other than the first) is generated and
           tested, ccaallllbbaacckk((00,, ccoouunntteerr,, ccbbaarrgg)) is called.

       +o   When a candidate for p has passed the test by trial division,
           ccaallllbbaacckk((11,, -11,, ccbbaarrgg)) is called.  While it is tested by the
           Miller-Rabin primality test, ccaallllbbaacckk((11,, ii,, ccbbaarrgg)) is called in
           the outer loop (once for each witness that confirms that the
           candidate may be prime).  i is the loop counter (starting at 0).

       +o   When p has been found, ccaallllbbaacckk((22,, 11,, ccbbaarrgg)) is called.

       +o   When the generator has been found, ccaallllbbaacckk((33,, 11,, ccbbaarrgg)) is
           called.

RREETTUURRNN VVAALLUUEE
       DSAgenerateparameters() returns a pointer to the DSA structure, or
       NNUULLLL if the parameter generation fails. The error codes can be obtained
       by ERRgeterror(3).

BUGS
       Seed lengths > 20 are not supported.

SEE ALSO
       dsa(3), ERRgeterror(3), rand(3), DSAfree(3)

HISTORY       DSAgenerateparameters() appeared in SSLeay 0.8. The ccbbaarrgg argument
       was added in SSLeay 0.9.0.  In versions up to OpenSSL 0.9.4,
       ccaallllbbaacckk((11,, ......)) was called in the inner loop of the Miller-Rabin test
       whenever it reached the squaring step (the parameters to ccaallllbbaacckk did
       not reveal how many witnesses had been tested); since OpenSSL 0.9.5,
       ccaallllbbaacckk((11,, ......))  is called as in BNisprime(3), i.e. once for each
       witness.



0.9.7l                            2002-09-25        DSAgenerateparameters(3)