Ethereum-based smart contracts hold tremendous potential - but only if those contracts can be secured. More than 10% of the 3.7B raised in ICOs has been lost or stolen to hackers. It's easy to take the nihilistic approach, and just say that smart contract hacks are inevitable. But it's straightforward to secure smart contracts, at least against known vulnerabilities. (Straightforward but not fast or easy.) In this talk, we'll learn about the most common and most devastating smart contract vulnerabilities - and how to build secure smart contracts.