When we think of "electronic payments", there are a lot of different interpretations: bank cards, credit cards, PayPal and the likes, mobile money, and cryptocurrencies. But they all work in widely different ways. Lately, many central banks – including the European Central Bank – have started investigating or piloting digital currencies to introduce yet another way to pay electronically. In this talk, I will explain the technical (and social) differences between those payment methods and give insights into how such a digital currency platform could be designed.