OptChain: Achieving Optimal Throughput of Permissionless Blockchains
2026-06-22 • Cryptography and Security
Cryptography and Security
AI summaryⓘ
The authors present OptChain, a new blockchain protocol designed to handle as many transactions as theoretically possible without sacrificing security. They first figure out the maximum speed any blockchain can achieve given some chance of errors, then build OptChain to get very close to that speed. OptChain splits tasks into smaller parts (shards) and uses two key techniques: Shardis, which speeds up communication within each shard, and diffusion mining, which keeps the system secure even if only one node per shard is honest. Their tests on real cloud servers show OptChain works better than current methods and nearly reaches the best possible performance.
blockchainstate machine replicationthroughputshardingverifiable information dispersaldiffusion miningpermissionless protocolssecurityscalabilityAWS EC2
Authors
Chunjiang Che, Songze Li, Xuechao Wang
Abstract
We introduce \textit{OptChain}, a permissionless blockchain state machine replication (SMR) protocol that achieves optimal throughput. We first establish a theoretical upper bound on the throughput of any SMR protocol under a fixed error probability, and OptChain is the first protocol to approach this limit. Conceptually, OptChain is a sharding protocol that optimizes both vertical and horizontal scalability. Vertically, we introduce \textit{Shardis}, a novel permissionless verifiable information dispersal mechanism that maximizes intra-shard throughput to its physical limit, determined by the fastest node's bandwidth within each shard. Horizontally, we propose \textit{diffusion mining}, which ensures security as long as each shard includes at least one honest node, thereby allowing for the maximum number of shards. We provide a formal security and efficiency analysis, demonstrating that OptChain approaches the established upper bound while maintaining robust security. Finally, we implement a full prototype of OptChain and deploy it on AWS EC2 nodes across various regions. Experimental results indicate that OptChain outperforms state-of-the-art permissionless protocols and closely approaches the theoretical optimal throughput.