Bitcoin, Ethereum and other cryptocurrencies have attracted widespread media attention. Interestingly, their advent has also triggered reflection among central bankers. Their first reaction was, unsurprisingly, to warn consumers against the dangers of unregulated private money. However, almost ten years after the creation of Bitcoin, central bankers now see the huge potential of these currencies for monetary policy and the control of payments. Is this enthusiasm justified? Should central banks create their own digital currency?