As banks explore the potential of blockchains, they’ve been quick to surmise that the technology, as it was originally designed, does not provide robust privacy. When Satoshi Nakamoto invented bitcoin in 2009, he (or she or they) provided a way for multiple participants, who have no reason to trust each other, to work together in maintaining a canonical, tamperproof history of transactions and digital messages. But the design required that all activity be exposed for anyone to see.