-of the key generation. If B<callback> is not B<NULL>, it will be
-called as described in L<BN_generate_prime(3)|BN_generate_prime(3)> while a random prime
-number is generated, and when a prime has been found, B<callback(3,
-0, cb_arg)> is called.
+of the key generation. If B<cb> is not B<NULL>, it will be
+called as described in L<BN_generate_prime(3)> while a random prime
+number is generated, and when a prime has been found, B<BN_GENCB_call(cb, 3, 0)>
+is called. See L<BN_generate_prime(3)> for information on
+the BN_GENCB_call() function.