code: public static OpenSslX509KeyManagerFactory newEngineBased(File certificateChain, String password)
              throws CertificateException, IOException,
                     KeyStoreException, NoSuchAlgorithmException, UnrecoverableKeyException {
          return newEngineBased(SslContext.toX509Certificates(certificateChain), password);
      }
docs: Create a new initialized {@link OpenSslX509KeyManagerFactory} which loads its {@link PrivateKey} directly from
  an {@code OpenSSL engine} via the
  <a href="https://www.openssl.org/docs/man1.1.0/crypto/ENGINE_load_private_key.html">ENGINE_load_private_key</a>
  function.