turn 1 on success or 0 on error.</p>

<p>BN_is_prime_ex(), BN_is_prime_fasttest_ex(), BN_is_prime(), BN_is_prime_fasttest() and BN_check_prime return 0 if the number is composite, 1 if it is prime with an error probability of less than 0.25^<b>nchecks</b>, and -1 on error.</p>

<p>BN_generate_prime() returns the prime number on success, <b>NULL</b> otherwise.</p>

<p>BN_GENCB_new returns a pointer to a BN_GENCB structure on success, or <b>NULL</b> otherwise.</p>

<p>BN_GENCB_get_arg returns the argument pre