NAME    [Toc]    [Back]

       DSA_generate_parameters - generate DSA parameters

LIBRARY    [Toc]    [Back]

       libcrypto, -lcrypto

SYNOPSIS    [Toc]    [Back]

        #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    [Toc]    [Back]

       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, call-
           back(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 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    [Toc]    [Back]

       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    [Toc]    [Back]

       Seed lengths > 20 are not supported.

SEE ALSO    [Toc]    [Back]

       openssl_dsa(3), openssl_err(3), openssl_rand(3),
       DSA_free(3)

HISTORY    [Toc]    [Back]

       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



2000-07-22                    0.9.6g   DSA_generate_parameters(3)