Cob: a Leaderless Protocol for Parallel Byzantine Agreement in Incomplete Networks
This work addresses the problem of achieving Byzantine agreement in practical, incomplete networks for applications like blockchain sharding, representing an incremental extension of existing protocols.
The paper extends the Multidimensional Byzantine Agreement (MBA) Protocol into Cob, a leaderless Byzantine agreement protocol for incomplete networks with non-synchronized clocks, enabling consensus without requiring all nodes to be active in every step. It proves correctness and security under a supermajority of honest nodes and compares performance with Algorand, maintaining a Bernoulli-like step distribution similar to MBA.
In this paper we extend the \emph{Multidimensional Byzantine Agreement (MBA) Protocol}, a {leaderless} Byzantine agreement for lists of arbitrary values, into a protocol suitable for wide gossiping networks: \emph{Cob}. This generalization allows the consensus process to be run by an incomplete network of nodes provided with (non-synchronized) same-speed clocks. Not all nodes are active in every step, so the network size does not hamper the efficiency, as long as the gossiping broadcast delivers the messages to every node in reasonable time. These network assumptions model more closely real-life communication channels, so the Cob protocol may be applicable to a variety of practical problems, such as blockchain platforms implementing sharding. Cob has the same Bernoulli-like distribution that upper-bounds the number of steps as the MBA protocol. We prove its correctness and security assuming a supermajority of honest nodes in the network, and compare its performance with Algorand.