Colosseum: A Scalable Permissioned Blockchain over Structured Network

Abstract

Permissioned blockchain protocols generally use voting based algorithms to reach consensus. Scaling such protocols is hard because of their high message complexity and thus, have a limited number of applications. Use cases like banking and healthcare blockchain require a scalable distributed protocol to maintain the consistency of the ledger and ensure its safety. This paper presents Colosseum, a scalable consensus protocol designed for permissioned blockchain systems. It is a knockout tournament based protocol over a structured ring network to reach consensus on the next set of block proposers. Participants compete in the rounds of a novel two-player game in each tournament to become eligible to propose block. Colosseum introduces Proof-of-Win as the certificate for the result of matches to have an efficient and easy way to propose trusted blocks and verify them.