Non-state-backed, decentralized “cryptocurrencies” such as bitcoin have introduced new paradigms for money movement in which transfers are public but the identities of the individuals behind the transfers are masked. This presents both opportunities and challenges. On the one hand, cryptocurrencies have important speed, efficiency and (in some respects) security advantages over traditional approaches. Yet, all mechanisms for moving and storing money—new and old—involve risks and the potential for misuse. This presentation will discuss what bitcoin is, how it works, and the broader implications of systems built on the concept of decentralized trust. John Villasenor is a professor of electrical engineering and public policy at UCLA, a nonresident senior fellow at the Brookings Institution, and a national fellow at the Hoover Institution.