blockchain platform engineers

Abstract: The consensus protocols of most high-performance blockchains use quorum certificates, which bundle the signatures of a quorum of validators. Signature schemes such as BLS can aggregate the signatures of a whole quorum into a single short signature, which keeps these certificates small. A large-scale quantum computer would break these schemes, and no post-quantum scheme with comparable aggregate size and aggregation time is known. Without aggregation, a certificate holds one large post-quantum signature per member of the quorum, so it becomes infeasible for each validator to broadcast certificates, as modern consensus protocols often require. We present Quantum Cadence, a post-quantum consensus protocol with multiple concurrent proposers that avoids certificates altogether: every validator counts quorums among the messages it has received itself. Its safety and liveness do not even depend on signatures, although we add signatures to obtain accountability. Quantum Cadence builds on Cadence and replaces its slot consensus, Chorus, with Quantum Chorus, which keeps the optimal fast-path latency of Chorus: dissemination followed by two rounds of votes. When its fast path fails, Quantum Chorus runs Coda, our signature-free Byzantine agreement for multiple proposers. We also outline how the Conductor, which schedules the slots of Cadence, can be adapted to Quantum Cadence. In simulations with 200 validators, Quantum Chorus has a latency comparable to that of Chorus and scales better with the number of proposers.

Abstract: Layer 2 (L2) rollups have become the dominant scaling solution in Ethereum. At the core of these systems lies the rollup sequencer, a component that orders, executes, and submits L2 transaction blocks to the main Ethereum blockchain. The centralization of this sequencer introduces security risks, including censorship and malicious manipulation of transactions to extract maximum extractable value (MEV). Trusted execution environments (TEEs) provide strong hardware-enforced confidentiality and integrity guarantees for code and data. TEEs are strong candidates for strengthening security and ensuring verifiable neutrality in rollup sequencer operations, but multiple TEE-based designs are possible, offering different trade-offs among modularity, performance, and security guarantees. Among them, the separation of proposer and builder logic (PBS) into independent services is a strong contender against the monolithic approach that bundles all sequencer logic. Despite several proposed theoretical frameworks, there is a lack of experimental evaluation of the practicality and security trade-offs of integrating TEEs into rollup sequencers. This work addresses this gap through a comprehensive empirical study of TEE-enabled rollup designs under both PBS and monolithic sequencer models. Our experimental evaluations show that the impact of TEEs on rollup performance is small and that PBS does not significantly amplify it. We also show that PBS can lead to significant performance improvements by enabling more specialized, efficient builder logic implementations.

Abstract: We present GridSMR, a sharded blockchain that scales execution horizontally while allowing dependent cross-shard operations to progress within a single block. Existing sharded systems typically place coordination between dependent cross-shard steps, making latency grow with causal depth. GridSMR localizes atomicity to individual accounts and executes cross-account work asynchronously. Using an execute-before-agree architecture, dependent operations execute across shards as they become available, while consensus later validates and commits the resulting schedule. This enables Causal Compression: cross-shard latency need not grow with the causal depth of a computation. GridSMR scales single-validator execution to 1.07M requests/s and four-validator execution to 193K committed requests/s, while reducing 16-hop causal-chain latency by 8.2x versus deferred execution.

Abstract: Distributed data management systems deployed in untrusted environments rely on Byzantine Fault-Tolerant (BFT) consensus protocols to tolerate malicious failures. DAG-based BFT protocols improve throughput by letting validators disseminate transactions concurrently and by scaling execution across multiple workers. However, imbalances in workload or resource capacity can still degrade performance significantly. This paper presents Flamingo, a load-balancing protocol for certified DAG-based BFT protocols that addresses imbalance at both the ordering and execution layers. At the ordering layer, Flamingo periodically migrates client accounts away from overloaded validators, adapting to skewed submissions and heterogeneous validator capacity while preserving correctness under Byzantine faults, with migrations taking effect only through the committed log. At the execution layer, Flamingo redistributes committed transactions across executor workers using a deterministic, order-preserving scheduler that balances load and minimizes cross-worker data movement, without centralized coordination or costly distributed commit. Built on top of Narwhal and Tusk, our prototype shows that Flamingo recovers throughput and latency under workload skew, validator heterogeneity, and shifting hotspots, adds negligible overhead when the system is balanced, and needs load balancing in both layers, since resolving only one shifts the bottleneck to the other.