What mechanism is embedded within, for instance, tram cards that you can use to check in and out of your train ride, that prevents you from copying the signal that is coming from that card ? I could maybe understand this for cards that have an account linked to them (e.g. bank cards or other personalised cards), but what about cards you just [top up](https://en.wikipedia.org/wiki/Stored-value_card?wprov=sfti1) (e.g. [train cards in the Netherlands](https://en.wikipedia.org/wiki/OV-chipkaart?wprov=sfti1)). Why couldn’t you just copy every signal that is coming out of that card and clone it to a different one making a receiving device think you have a topped up card?
In: 0
You can clone the signal, but that wont be enough.
Your error is that you believe there is a “add money on the card signal” when you add money to your account.
There is a lot more than that, along with various identifiers that will make sure the transaction, if any, is unique, and both the emitter and receiver are the ones that are supposed to be.
It is a radio system with authentication, just like a phone and a sim card.
Latest Answers