Cryptocurrencies, such as Bitcoin and Ethereum, have seen widespread adoption as a method of distributed trust supporting commerce and cloud computing. In this talk, we will go over the basics of how they work and what their limitations are. In many ways, the talk will be an introduction to CS490P Secure Distributed Systems, which discusses blockchains in depth as well as related topics in systems and network security. As part of the talk, there will be time to answer any questions you might have about this space. This talk be be given by Prof. Brian Levine from the College of Information and Computer Sciences. His research and teaching focus on security, privacy, and forensics in the context of mobile systems, cellular networks, and the Internet. https://people.cs.umass.edu/~brian/