How to ensure security in a homemade immobilizer on arduino?

Question

Arduino

I am tormented by the obsession to make an immobilizer on arduino for my car.
The simplest is a key fob with an rfid tag, but, as far as I understand, the tags are easily copied from a distance.
Please advise where to look.

Answer 1

Look towards cryptographic Rfid tags. For example, Mifare DESfire. But, I'm afraid, arduino will not work with them. Firstly, these tags are high-frequency (13 MHz), a separate reader circuit is needed. Secondly, the AVR may not have enough memory and processing power to work with cryptography.
Another option is to make a keychain yourself, on a microcontroller with some kind of radio module. You can make any exchange protocol you like, even with one-time codes.