When you walked into the store, a sensor identified you, perhaps from a ring or watch you were wearing that transmitted the information. Or perhaps you didn’t need to wear anything special. Maybe a device in the store figured out who you were using a combination of facial recognition, 3-D body shape identification and your gait.Your unique identifier is attached to your digital wallet, which transmits payment for the groceries directly to the store. But you don’t pay in dollars. Your wallet has a dozen digital currencies in it, all with different values based on a variety of factors, including loyalty programs. At certain stores, you might pay with their version of frequent-flier miles. At others, you might pay with the equivalent of a virtual credit card — except the credit card isn’t issued by a traditional bank.

You might also pay with credit that you received through a peer-to-peer online exchange that connects investors with people seeking short- and long-term loans. That’s how you got your mortgage and financed your self-driving car, too.