Consensus, state machine replication (SMR) and total order broadcast (TOB) protocols are notorious for being poorly scalable with the number of participating nodes. Despite the recent race to reduce overall message complexity of leader-driven SMR/TOB protocols, scalability remains poor and the throughput is typically inversely proportional to the number of nodes. We present Insanely Scalable State Machine Replication, a generic construction to turn leader-driven protocols into scalable multi-leader ones. For our scalable SMR construction we use a novel primitive called Sequenced (Total Order) Broadcast (SB) which we wrap around PBFT, HotStuff and Raft leader-driven protocols to make them scale. Our construction is general enough to accommodate most leader-driven ordering protocols (BFT or CFT) and make them scale. Our implementation improves the peak throughput of PBFT, HotStuff, and Raft by 37x, 56x, and 55x, respectively, at a scale of 128 nodes.

This paper presents Fairy: a modular system that augments any Total Order Broadcast (TOB) protocol with fairness properties, namely input (request) causality and sender obfuscation. With these properties, Fairy helps to prevent front-running attacks where an adversary can interfere with the order of requests depending on request payload and sender identity, allowing for substantial application-level consequences. Fairy leverages Trusted Execution Environments (TEEs) to implement fairness on top of a TOB-based ordering service. Fairy collocates TEEs with ordering service nodes effectively making them run as trusted proxies of actual TOB clients. TEEs help Fairy to achieve both input causality and sender obfuscation - previous related systems addressing only input causality. We evaluate Fairy on top of a recent, efficient Byzantine Fault-Tolerant (BFT) TOB protocol and compare it to state-of-the-art BFT TOB with input causality. We show that Fairy improves state-of-the-art throughput by 66% and reduces latency by 50%.

Fabric is a modular and extensible open-source system for deploying and operating permissioned blockchains and one of the Hyperledger projects hosted by the Linux Foundation (www.hyperledger.org).