When Bitcoin first launched in 2009, it promised its users a decentralized digital currency that would be free from the prying eyes of financial authorities. That was possible thanks to the blockchain, a digital stone slab where every transaction could be etched into the collective public record.

Of course, Bitcoin and its look-alikes quickly descended into a haven for grifters, drug sales, and money-laundering, enabling anonymous criminals the world over. Then a few confusing things happened. First, it quickly turned out that Bitcoin wasn’t quite as anonymous as initially advertised,…