LONDON — A digital art piece, tweaked using cryptocurrency technology to make it one-of-a-kind, sold at auction last week for nearly $70 million. That transaction made global headlines and buoyed booming interest in these kinds of digital objects, which have captured the attention of artists and collectors alike.

These non-fungible tokens, or NFTs, solve a problem central to digital collectibles: how to claim ownership of something that can be easily and endlessly duplicated. NFTs confirm an item's ownership by recording the details on a digital ledger known as a blockchain, which is public and stored on computers across the internet.