Streamlet: Textbook Streamlined Blockchains

Abstract

In the past five years or so, numerous blockchain projects have made tremendous progress towards improving permissioned consensus protocols (partly due to their promised applications in Proof-of-Stake cryptocurrencies). Although a significant leap has silently taken place in our understanding of consensus protocols, it is rather difficult to navigate this body of work, and knowledge of the new techniques appears scattered. In this paper, we describe an extremely simple and natural paradigm called Streamlet for constructing consensus protocols. Our protocols are inspired by the core techniques that have been uncovered in the past five years of work; but to the best of our knowledge our embodiment is simpler than ever before and we accomplish this by taking a "streamlining"idea to its full potential. We hope that our textbook constructions will help to decipher the past five years of work on consensus partly driven by the cryptocurrency community - - in particular, how remarkably simple the new generation of consensus protocols has become in comparison with classical mainstream approaches such as PBFT and Paxos.