X509_get_signature_info
if (!X509_get_signature_info(cert, NULL, NULL, &secbits, NULL))
int X509_get_signature_info(X509 *x, int *mdnid, int *pknid, int *secbits,
if (!X509_get_signature_info(x, &nid, &pknid, &secbits, NULL))
if (!X509_get_signature_info(x, &mdnid, &pknid, NULL, NULL))