/usr/man/cat.3/DSA_generate_parameters.3

DSA_generate_parameters(3)   OpenSSL   DSA_generate_parameters(3)

NAME

     DSA_generate_parameters_ex, DSA_generate_parameters -
     generate DSA parameters

SYNOPSIS

      #include <openssl/dsa.h>

      int DSA_generate_parameters_ex(DSA *dsa, int bits,
                     const unsigned char *seed,int seed_len,
                     int *counter_ret, unsigned long *h_ret, BN_GENCB *cb);

     Deprecated:

      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_ex() generates primes p and q and a
     generator g for use in the DSA and stores the result in 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 generate
     them. If the given seed does not yield a prime q, a new
     random seed is chosen.

     DSA_generate_parameters_ex() 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 cb is not NULL, it
     will be called as shown below. For information on the
     BN_GENCB structure and the BN_GENCB_call function discussed
     below, refer to BN_generate_prime(3).

     o   When a candidate for q is generated, BN_GENCB_call(cb,
         0, m++) is called (m is 0 for the first candidate).

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

1.0.2t               Last change: 2019-09-10                    1

DSA_generate_parameters(3)   OpenSSL   DSA_generate_parameters(3)

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

     o   When a candidate for p has passed the test by trial
         division, BN_GENCB_call(cb, 1, -1) is called.  While it
         is tested by the Miller-Rabin primality test,
         BN_GENCB_call(cb, 1, i) 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, BN_GENCB_call(cb, 2, 1) is
         called.

     o   When the generator has been found, BN_GENCB_call(cb, 3,
         1) is called.

     DSA_generate_parameters() (deprecated) works in much the
     same way as for DSA_generate_parameters_ex, except that no
     dsa parameter is passed and instead a newly allocated DSA
     structure is returned. Additionally "old style" callbacks
     are used instead of the newer BN_GENCB based approach.
     Refer to BN_generate_prime(3) for further information.

RETURN VALUE

     DSA_generate_parameters_ex() returns a 1 on success, or 0
     otherwise.

     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),
     BN_generate_prime(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

1.0.2t               Last change: 2019-09-10                    2

See also DSA_generate_parameters_ex(3)