> It's not about paying by cash but paying by card offline. How is this going to be implemented I wonder.
Considering that the card has memory on it, you can store there how much balance you have when you do an online payment. The bank can send back your available balance, so you cannot spend offline more than you have.
You could store money digitally on a card. Moneo did that until 2015 and it was used in France as a wallet for paying meals in school canteens for tertiary education. That system was phased out just as I left university.
I remember writing an app in Java to read the balance on a card with my laptop which had a built-in smartcard reader, because I was too lazy to go to a station. Everyone in the classroom then promptly asked me to check their balance... and a few asked if I could top it up somehow.
True. But you can have a rule that says something like “after X offline transactions you must insert the card into an ATM for update”.
My thinking is that in this day and and age, unless something bad really happens (war, volcanic erruption), the chances of using a card for offline transactions for an extended period of time are very close to zero.
Considering that the card has memory on it, you can store there how much balance you have when you do an online payment. The bank can send back your available balance, so you cannot spend offline more than you have.
I can't think about anything simpler than this.