ACS on linux arm to access the premises by pin at a certain time?

Question

linux

There are 8 rooms per floor.
Task: some simple service running on synology arm j213.
The service listens to the com port for certain data and transmits certain data depending on the data in the database table.
For example, client number 1 bought time in room 1 from xx to yy. He receives a pin in the mail and the pin is valid at this time on this day.
Near each door there is a digital panel with rs485 interface. It monitors the reed switch for closing the door and controls the latch of the lock. Those. is essentially a client and initiates the transfer. I'll do it all myself, I'm interested in software.
There is one ready-made solution with battery-powered locks and a common control unit, but the locks do not transmit the state of the batteries, the software does not have an API, and the lock memory is small.
They offered another solution from the office for 12,000 euros, but it's too expensive and I don't know the details.
I would like to do something cheaper and without batteries.
The ideal would be a demon in python or go, so that you can write in regular x86 and collect by arm, because. You don't need a separate server for this either.
From the software, I found only very complex scuds and scuds, but everything is not right and there is no arm.

Answer 1

RS-485 is not secure. All devices hang on a common bus, having access to one panel, you can listen to all the communication of other devices and even control them. Encrypt then all communication.

Answer 2

The task is specific - usually no one puts such developments into the public domain - in order to preserve the principle of the "black box" as an additional protection against hacking.
So it's better to make separate keyboards, separately lock controllers - otherwise all that the Chinese have is cheap for films - where they shoot at the panel and the door opens.
here is an interesting device - two inputs, two outputs ru.aliexpress.com/item/Modbus-RTU-protocol-2-relay...