state machine replication

Traditional distributed systems struggle to support modern autonomous infrastructures that integrate stochastic models and autonomous agents. This work proposes the Post-Deterministic Distributed System (PDDS) model, introducing for the first time its five architectural pillars. Its core innovation is a "cognitive state replication" mechanism that extends consistency from data visibility to knowledge visibility, alongside a novel fault classification framework. By leveraging protocol-driven development, verifiable agent infrastructure, and semantic quorum guarantees, PDDS enables coordination among semantically equivalent yet executionally divergent agents. This approach achieves verifiable semantic rollback and cross-agent reasoning consistency, establishing a theoretical foundation for trustworthy autonomous systems.

Designing customized consensus protocols for distributed systems is labor-intensive, error-prone, and difficult to verify; existing Paxos/Raft variants require full reimplementation, hindering scenario-specific adaptability. This paper introduces Protocol Replicated Data Types (PRDTs), the first framework unifying consensus logic by grounding it in monotonic knowledge growth—integrating monotonic replicated data types (RDTs) with epistemic consensus semantics. We propose RDT algebraic composition, enabling modular, composable protocol construction. We formally prove that correctness properties—including safety and liveness—are derivable from PRDT specifications. Empirically, PRDTs faithfully reconstruct canonical protocols (e.g., Paxos, Raft) with performance on par with hand-optimized implementations. PRDTs substantially lower the barrier to custom protocol design while ensuring formal verifiability, flexibility, maintainability, and industrial deployability.

Traditional state machine replication (SMR) suffers from performance limitations in partially or fully asynchronous networks. This paper proposes Chora, an SMR protocol designed to exploit the strong synchronization characteristics of modern datacenter networks, enabling low-overhead, highly parallel replication. Chora employs kernel-bypass networking, a multi-threaded architecture, and relaxed round boundary control—achieving tightly bounded 2-μs rounds—to realize pipelined, multi-instance parallel replication. Crucially, it permits concurrent, coordination-free proposal generation across replicas. Its core innovation lies in directly translating network-level synchronization into protocol-level efficiency gains, thereby eliminating the serialization and coordination overhead inherent in conventional consensus protocols. Experimental results demonstrate that Chora achieves 255% and 109% higher throughput than the best-performing single-leader and multi-leader SMR protocols, respectively, significantly surpassing existing SMR performance bottlenecks.

Existing non-transactional consistency levels in distributed cloud object storage are defined heterogeneously, hindering systematic comparison and formal verification. Method: This paper proposes a unified framework based on the Shared Object Pool (SOP) model, centering on “order” and introducing a novel dual-constraint formalization that jointly captures convergence (via lineage shape) and relational ordering (via operation-relative positions). Contribution/Results: The framework concisely characterizes essential distinctions among mainstream consistency models—including eventual, causal, and read-committed consistency—and establishes, for the first time, their theoretical availability upper bounds. It further provides rigorous semantic mappings of real-world cloud storage protocols, including Amazon S3 and Azure Blob Storage. The resulting framework offers a formally verifiable, engineering-friendly theoretical foundation for the design, verification, and optimization of cloud object storage systems.

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 challenge of ensuring atomicity and consistency in offline-first peer-to-peer systems characterized by sparse connectivity and partial replication. To this end, it introduces— for the first time—the IntersectionAtomicity and IntersectionCC models, which formally capture the constraints on atomicity and consistency under transactional semantics in such environments. By integrating principles from distributed transaction theory with access control mechanisms, the paper develops a reasoning framework tailored to offline-first collaborative systems. Building upon this foundation, it derives practical correctness guarantees that directly inform system design, thereby significantly enhancing the reliability and correctness of applications operating under these challenging conditions.

Traditional CRDTs struggle to ensure state consistency in Byzantine environments due to their reliance on update filtering mechanisms. This work proposes a deterministic state reconstruction approach that decouples update propagation from state derivation: all updates are accepted, but only valid ones contribute to the final state. By structurally rejecting or transforming malicious updates, the system guarantees convergence of replicas under arbitrary update injection and supports a layered security model encompassing authentication, authorization, and confidentiality. Built upon delta-state CRDTs, the resulting Melda system is tailored for JSON documents and formally verified to preserve state consistency despite message reordering, loss, or forgery. Theoretical analysis confirms that identical update sets yield indistinguishable states, achieving coordination-free strong eventual consistency with Byzantine fault tolerance.

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.

This work addresses the inflexibility of static trusted setups in existing zero-knowledge proof systems, which hinder continuous and automated generation of public reference strings (CRS). To overcome this limitation, the authors propose a Layer 2 coordination framework that enables, for the first time within a ZK-rollup architecture, a decentralized, continuous trusted setup without centralized coordination. By decoupling transaction processing from ceremony execution, they design two protocol variants—one based on smart contracts and another on asynchronous peer-to-peer communication—leveraging PBFT consensus, non-interactive zero-knowledge proofs of knowledge (NIZKPoK), and a commit-reveal mechanism. Experimental results demonstrate that the proposed approach maintains ceremony liveness and Layer 2 transaction throughput stability under wide-area network conditions and adversarial settings, tolerating node failures and malicious behavior while effectively mitigating adaptive manipulation risks.

This work addresses the challenge of securely excluding historical updates from compromised nodes in traditional Byzantine fault-tolerant CRDTs without violating causal consistency. The authors propose a fine-grained trust model that, for the first time in Byzantine CRDTs, decouples identity trust from content trust. By integrating deterministic reconstruction, public-key-based identity verification, and a semantics-aware update filtering mechanism, the approach enables selective inclusion or exclusion of updates. This design supports application-level policies and effectively mitigates Byzantine behavior and faulty nodes while strictly preserving causal consistency, thereby significantly enhancing the robustness and flexibility of decentralized systems in post-compromise scenarios.