Security is a word we hear a lot, especially in conversations about blockchain. But when a project claims security, what guarantees does it provide exactly? Maybe more importantly, are there some critical aspects of security missing from existing blockchains? To answer these questions, a clearer definition is needed. In this post we aim to clarify what security properties current blockchains have, how confidentiality and privacy are a critical missing feature, and ways we intend to fill that gap.