_hx509_find_extension_subject_key_id
ret = _hx509_find_extension_subject_key_id(certificate, &si);
ret = _hx509_find_extension_subject_key_id(c, &si);
ret_si = _hx509_find_extension_subject_key_id(issuer, &si);
ret = _hx509_find_extension_subject_key_id(_hx509_get_cert(cert),
_hx509_find_extension_subject_key_id (