Blockmania: from Block DAGs to Consensus

Blockmania is a byzantine consensus protocol. Nodes emit blocks forming a directed acyclic graph (block DAG). The block DAG is subsequently interpreted by each node separately to ensure consensus with safety, liveness and finality. The resulting system has communication complexity $O(N^2)$ even in the worse case, and very low constant factors --- as compared to $O(N^4)$ for PBFT; it is leaderless; and network operations do not depend on the composition of the quorum or node stake. This makes Blockmania ideal for dynamic membership and flexible and non-interrupted proof-of-stake protocols. X-Blockmania, has $O(N)$ communication cost but also higher latency $O(\log N)$.