view-change protocols

This work addresses the performance degradation in parallel Byzantine Fault Tolerance (BFT) protocols caused by inefficient or unavailable node selection during view changes triggered by primary node failures. To tackle this challenge, the paper introduces, for the first time, a mixed-integer programming approach to optimize view change operations in parallel BFT, proposing the View Change Optimization (VCO) model. VCO jointly optimizes primary replica selection and follower reassignment by incorporating communication latency and fault scenarios. An efficient iterative algorithm for backup primary selection is developed using an enhanced decomposition method combined with Benders’ cutting-plane technique. Experimental evaluation on Microsoft Azure demonstrates that VCO-driven parallel BFT significantly outperforms existing approaches under both normal and faulty conditions, with performance gains amplifying as network scale increases.

Traditional consensus protocols rely on deterministic f-threshold fault models that struggle to capture the complex failure behaviors observed in real-world systems, thereby limiting optimization of performance and cost. This work proposes a novel consensus mechanism grounded in a probabilistic fault model, which incorporates machine-level failure curves and abandons the rigid majority quorum constraint in favor of dynamic, non-traditional quorum strategies. By more accurately reflecting actual operating conditions, the proposed approach substantially enhances system reliability, efficiency, cost-effectiveness, and sustainability.

This work addresses the loss of liveness in traditional Byzantine fault-tolerant protocols during network partitions, which arises from their reliance on strong quorums. The authors propose a two-layer authentication framework that decouples consensus availability from commitment, enabling each partition to independently extend its local chain while ensuring safe reconciliation upon network recovery. To support progress during partitions without requiring strong quorums, they introduce a view synchronization pacemaker that integrates proof-of-authority (PoA)-based speculative execution with timeout calibration along non-critical paths. Experimental results demonstrate that the system achieves up to 900,000 TPS with 16 nodes and 480,000 TPS with 104 nodes under stable network conditions (latency: 0.31–0.75 seconds), while sustaining non-zero speculative throughput during severe partitions—all speculative work remaining safely reconcilable afterward.

Distributed Byzantine Fault-Tolerant (BFT) consensus protocols exhibit limited adaptability across diverse application scenarios. Method: This work systematically traces their fifty-year evolution and, for the first time, establishes a unified principled framework spanning decades—integrating core design paradigms including state machine replication, partially synchronous/asynchronous protocols, and emerging Directed Acyclic Graph (DAG)-based approaches. Through combined protocol analysis, historical comparative study, formal model abstraction, and scenario mapping, we identify fundamental consensus primitives and rigorously characterize their applicability boundaries. Contribution/Results: The study yields a comprehensive BFT consensus knowledge graph—from classical to cutting-edge protocols—revealing intrinsic evolutionary patterns. It provides theoretical foundations and concrete optimization pathways for designing robust, scenario-aware consensus mechanisms in emerging domains such as wireless networks and blockchain systems.

This work proposes an evidence-centered denotational semantic framework that reframes distributed consensus by modeling execution as higher-order evidence states induced by communication, with consensus outputs emerging as their first-order projections. Traditional output-centric descriptions of consensus protocols obscure the underlying evidential structures formed through communication; this framework unifies protocol differences as design choices concerning valid evidence, observational horizons, collapse timing, and repair mechanisms. By formalizing “collapse strategies” and integrating insights from the FLP impossibility result and topological distributed computing theory, the approach reveals a fundamental connection between consensus protocols and their evidential underpinnings, offering a novel paradigm for the analysis, comparison, and design of such protocols.

This work addresses a critical limitation in traditional Byzantine fault tolerance (BFT), which assumes honest nodes correctly enforce protocol semantics—an assumption that fails in agent-based systems where compliant nodes may erroneously endorse semantically invalid state transitions due to reasoning errors, thereby compromising execution safety. To resolve this, the paper introduces Epistemic Byzantine Fault Tolerance (EBFT), formally defining "epistemic faults" and the "honest majority problem," thereby decoupling semantic correctness from mere protocol compliance. The authors develop a two-dimensional fault-tolerance framework using confidence-weighted parameters: \(e_\delta\) for semantic safety risk and \(u_\varepsilon\) for liveness degradation. By integrating probabilistic belief modeling with tail concentration analysis, they derive novel quorum conditions that jointly guarantee semantic validity, consensus consistency, and system liveness. The analysis shows that fault tolerance improves only when newly added agents substantially reduce the tail risks of invalid endorsements or unavailable support.

This work resolves the theoretical tension between the feasibility of deterministic crash-tolerant consensus in fully asynchronous settings and the FLP impossibility result. By constructing a rigorous formal framework, it demonstrates that the apparent contradiction between Attia et al.’s conclusions and alternative claims of consensus possibility stems from differing assumptions about the semantics of protocol rounds. Building on this insight, the paper introduces a novel multi-crash-tolerant consensus algorithm. It provides the first formal proof that bridges a critical gap in asynchronous consensus theory, establishing the theoretical feasibility of achieving deterministic consensus tolerating multiple crashes within a fully asynchronous model, accompanied by a complete correctness proof of the proposed algorithm.

This work investigates the fault-tolerance limits and protocol design for low-latency consensus under a hybrid failure model combining Byzantine faults (f) and crash faults (c). It establishes, for the first time, a tight lower bound of n ≥ 5f + 3c + 1 for two-message-latency commit protocols. The paper proposes a hybrid fault-tolerant consensus protocol featuring both a fast-commit path and a resilient fallback mechanism, enabling clients to select their desired finality latency. Built upon the partial synchrony model and integrating multi-round safety paths with synchronous recovery, the protocol achieves high performance: under a configuration of n=99, f=16, and c=6, it tolerates up to 22% failed replicas (liveness), 16% malicious nodes with 1-RTT safety, and as many as 54% malicious nodes with 2-RTT safety.

This work addresses the security and availability threats posed by state rollback attacks in Trusted Execution Environments (TEEs) to confidential Byzantine Fault Tolerant (BFT) consensus systems. The authors propose a protocol-aware recovery framework that categorizes persisted consensus states into metadata and logs based on their semantic roles, and designs tailored recovery mechanisms for each category. As the first systematic classification and implementation of rollback-resilient recovery for confidential BFT consensus, this approach overcomes the traditional trade-off between performance and recovery latency. A prototype built on Intel TDX, complemented by formal verification using Maude, demonstrates significant improvements over baseline methods in both LAN and WAN settings when evaluated on Braft and ZooKeeper, achieving higher throughput, lower recovery latency, and enhanced availability.

This work addresses the throughput degradation of crash-fault tolerant (CFT) consensus protocols in wide-area networks caused by single-leader bottlenecks and network latency. The authors propose a novel multi-leader CFT consensus protocol based on a causally ordered directed acyclic graph (DAG), which, for the first time, decouples command dissemination from consensus logic. By integrating a multi-leader architecture with a deterministic delayed execution mechanism, the protocol enables automatic command scheduling and achieves commitment within two communication hops. Experimental results demonstrate that the proposed approach significantly improves throughput in wide-area deployments while maintaining low commit latency, offering a practical solution that combines high performance, strong resilience, and deployment feasibility.