Hi so I am a student in a large city, I have to take on a project and I have been toying with the idea of working with RFID. I wish to take the local bus companies student bus pass that operates on RFID and try and show that the cards are able to be updates from reading/writing to the card. My problem is I don't know how feasible this idea is, my main concern is that the buses find out if a card is valid through an external source and not the card itself. The information I have so far is this: You receive a card which is updated when you wish to purchase another month The card reader on the bus looks like this. Spoiler The card has to be pressed up real close to the reader to authenticate. So if someone with a bit more experience could comment that would be great. All I wish to know is before I go and start buying readers and stuff, would I be able to for example write to the card a date in the future lets say 5 days, and the card would be valid until then?