Colosseum

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.