📝 SummarXiv

Abstract

In this work, we propose Ocior, a practical asynchronous Byzantine fault-tolerant (BFT) consensus protocol that achieves the optimal performance in resilience, communication, computation, and round complexity. Unlike traditional BFT consensus protocols, Ocior processes incoming transactions individually and concurrently using parallel instances of consensus. While leader-based consensus protocols rely on a designated leader to propose transactions, Ocior is a leaderless consensus protocol that guarantees stable liveness. Ocior achieves: 1) Optimal resilience: Ocior tolerates up to $t$ faulty nodes controlled by an adaptive adversary, for $n\geq 3t+1$. 2) Optimal communication complexity: The total expected communication per transaction is $O(n)$. 3) Optimal (or near-optimal) computation complexity: The total computation per transaction is $O(n)$ in the best case, or $O(n \log^2 n)$ in the worst case. 4) Optimal round complexity: A legitimate two-party transaction can be finalized with a good-case latency of two asynchronous rounds, for any $n\geq 3t+1$. The good case in terms of latency refers to the scenario where the transaction is proposed by any (not necessarily designated) honest node. A two-party transaction involves the transfer of digital assets from one user (or group of users) to one or more recipients. To support efficient consensus, we introduce a novel non-interactive threshold signature (TS) scheme called OciorBLSts. It offers fast signature aggregation, and is adaptively secure. OciorBLSts achieves a signature aggregation computation cost of only $O(n)$ for the best case. Moreover, OciorBLSts supports the property of Instantaneous TS Aggregation. This enables real-time aggregation of partial signatures as they arrive, reducing waiting time and improving responsiveness.