Most secure solution for door open by remote

Hi there,

I know it's not a special node red question, but I need some help from the crowd.

I have an standard door opener which is controlled from a "stupid" RFID Modul. Now I search for a solution which I can use by remote from my smartphone ... actually I ordered a Shelly uni which I want to use locally to trigger the RFID Modul.

I don't need a solution to open the door from Hawaii when the postman push the doorbell. ( If I want the I'll use VPN ) A local network solution should be great.
Of course I take a look at the "nubi opener" but then I need a Nubi gateway and that's not what I want.

What's the most easiest and secure way to trigger the opener?

Your opinions?

Thanks in advance