The introduction of bitcoin and other cryptocurrencies has led the U.S. Treasury and Federal Reserve to ask: Why shouldn’t America roll out digital cash — or Central Bank Digital Currency — with the same technology used for these privately issued currencies? After all, anyone can create a shared digital ledger and issue their own currency on it. But not all cryptocurrencies are created equal. Some, like bitcoin, prioritize the privacy and autonomy of the individual by enabling free transacting without trusted third parties. Other cryptos — including CBDCs — are built to be fully programmable — controllable — by the...