You are standing in front of a building with 3 rooms and have a NXP Mifare Classic 1k card.
In the first room is a device (device1) that can do the following things:
- Shows how much money is on the card.
- Increase the value of the card, by depositing money.
In the second room is a device (device2) which can do the following things:
- Deduct a fixed amount of the card.
- Opens a door and allows the passage to the third room.
If you have enough money on the card, you can enter the third room.
- Is the amount saved on the card or at other places?
- When the whole system is online, is it possible to change the amount, without access to the program?
I don't want to break the law. I'm only interested in the possibilities. I am looking forward to your opinions and some thought-provokings!