The core technical component of blockchains is consensus: how to reach agreement among
a distributed network of nodes. A plethora of blockchain consensus protocols have been
proposed---ranging from new designs, to novel modifications and extensions of consensus
protocols from the classical distributed systems literature. The inherent complexity of
consensus protocols and their rapid and dramatic evolution makes it hard to contextualize
the design landscape. We address this challenge by conducting a systematization of …

The blockchain initially gained traction in 2008 as the technology underlying bitcoin, but now
has been employed in a diverse range of applications and created a global market worth
over $150 B as of 2017. What distinguishes blockchains from traditional distributed
databases is the ability to operate in a decentralized setting without relying on a trusted third
party. As such their core technical component is consensus: how to reach agreement among
a group of nodes. This has been extensively studied already in the distributed systems …