DSA_generate_parameters(3)  OpenSSL  DSA_generate_parameters(3)





NAME
       DSA_generate_parameters - generate DSA parameters

SYNOPSIS
        #include <openssl/dsa.h>

        DSA *DSA_generate_parameters(int bits, unsigned char *seed,
                       int seed_len, int *counter_ret, unsigned long *h_ret,
                       void (*callback)(int, int, void *), void *cb_arg);

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

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

       If seed is NULL or seed_len < 20, the primes will be
       generated at random. Otherwise, the seed is used to gen-
       erate them. If the given seed does not yield a prime q,
       a new random seed is chosen and placed at seed.

       DSA_generate_parameters() places the iteration count in
       *counter_ret and a counter used for finding a generator
       in *h_ret, unless these are NULL.

       A callback function may be used to provide feedback
       about the progress of the key generation. If callback is
       not NULL, it will be called as follows:

       o   When a candidate for q is generated, callback(0,
           m++, cb_arg) is called (m is 0 for the first candi-
           date).

       o   When a candidate for q has passed a test by trial
           division, callback(1, -1, cb_arg) is called.  While
           a candidate for q is tested by Miller-Rabin primal-
           ity tests, callback(1, i, cb_arg) 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, callback(2, 0,
           cb_arg) and callback(3, 0, cb_arg) are called.

       o   Before a candidate for p (other than the first) is
           generated and tested, callback(0, counter, cb_arg)
           is called.

       o   When a candidate for p has passed the test by trial
           division, callback(1, -1, cb_arg) is called.  While
           it is tested by the Miller-Rabin primality test,
           callback(1, i, cb_arg) is called in the outer loop
           (once for each witness that confirms that the candi-
           date may be prime).  i is the loop counter (starting
           at 0).

       o   When p has been found, callback(2, 1, cb_arg) is
           called.

       o   When the generator has been found, callback(3, 1,
           cb_arg) is called.

RETURN VALUE
       DSA_generate_parameters() returns a pointer to the DSA
       structure, or NULL if the parameter generation fails.
       The error codes can be obtained by ERR_get_error(3).

BUGS
       Seed lengths > 20 are not supported.

SEE ALSO
       dsa(3), ERR_get_error(3), rand(3), DSA_free(3)

HISTORY
       DSA_generate_parameters() appeared in SSLeay 0.8. The
       cb_arg argument was added in SSLeay 0.9.0.  In versions
       up to OpenSSL 0.9.4, callback(1, ...) was called in the
       inner loop of the Miller-Rabin test whenever it reached
       the squaring step (the parameters to callback did not
       reveal how many witnesses had been tested); since
       OpenSSL 0.9.5, callback(1, ...)  is called as in
       BN_is_prime(3), i.e. once for each witness.  =cut



0.9.7c                     2002-09-25DSA_generate_parameters(3)
