Dashing and Star: Byzantine Fault Tolerance with Weak Certificates

State-of-the-art Byzantine fault-tolerant (BFT) protocols assuming partial synchrony such as SBFT and HotStuff use regular certificates obtained from 2f + 1 (partial) signatures. We show that one can use weak certificates obtained from only f + 1 signatures to assist in designing more robust and more efficient BFT protocols. We design and implement two BFT systems: Dashing (a family of two HotStuff-style BFT protocols) and Star (a parallel BFT framework). We first present Dashingl that targets both efficiency and robustness using weak certificates. Dashingl is also network-adaptive in the sense that it can leverage network connection discrepancy to improve performance. We show that Dashing1 outperforms HotStuff in various failure-free and failure scenarios. We then present Dashing2 enabling a one-phase fast path by using strong certificates from 3f + 1 signatures. We then leverage weak certificates to build Star, a highly scalable BFT framework that delivers transactions from n - f replicas. Star compares favorably with existing protocols in terms of liveness, communication, state transfer, scalability, and/or robustness under failures. We demonstrate that Dashing achieves 47%-107% higher peak throughput than HotStuff for experiments on Amazon EC2. Meanwhile, unlike all known BFT protocols whose performance degrades as f grows large, the peak throughput of Star increases as f grows. When deployed in a WAN with 91 replicas across five continents, Star achieves an impressive throughput of 256 ktx/sec, 2.38x that of Narwhal.