DSA_generate_parameters(3)

     DSA_generate_parameters0.9.6h (2002-09-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 generate
          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 candidate).

          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 primality
              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

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     DSA_generate_parameters0.9.6h (2002-09-DSA_generate_parameters(3)

              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, 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

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