During his PhD at the University of Waterloo, he helped design and deploy voting systems that can cryptographically prove the tally is correct. One system, Scantegrity, was the first such system to be used in a real government election (and, little-known fact: the first to use the blockchain). His research on Bitcoin spans time-stamping (CommitCoin), decentralized prediction markets, proofs of solvency (Provisions), anonymity (Mixcoin), and usability. Recently, he has worked on systemizing knowledge on Bitcoin, as well as contextualizing the history of digital cash prior to Bitcoin's emergence.