SoK: Concurrency in Blockchain -- A Systematic Literature Review and the Unveiling of a Misconception

2025-06-02

AI Summary

This paper systematically exposes a fundamental modeling misconception in blockchain concurrent execution: mainstream research has long erroneously assumed “inherent determinism” in smart contract execution, overlooking concurrency-induced race conditions, non-determinism, and deadlock risks arising from transaction validation, cross-shard processing, and miner competition. Through a systematic literature review (SLR) and attack-surface modeling, we propose the first comprehensive blockchain concurrency taxonomy spanning the consensus, execution, and sharding layers. This taxonomy identifies three canonical concurrency vulnerability patterns and reveals critical gaps in formal verification. Our contributions are threefold: (i) correcting a pervasive conceptual misuse regarding determinism; (ii) establishing the first theoretical benchmark for blockchain concurrency security; and (iii) providing an evolvable research framework and practical guidelines for designing high-throughput, strongly consistent, and formally verifiable smart contract execution systems.

Technology Category

• Data Mining & Knowledge Management: Scalability, Parallel & Distributed Systems
• Reasoning under Uncertainty: Other Foundations of Reasoning under Uncertainty
• Multiagent Systems: Multiagent Systems under Uncertainty

Application Category

• Security and Privacy: Cryptocurrency and smart contracts
• Economics, Online Markets and Human Computation: Economic aspects of blockchain and cryptocurrencies
• Semantics and Knowledge: Provenance, trust, security and privacy, and ethical issues in managing semantic data

Abstract

Smart contracts, the cornerstone of blockchain technology, enable secure, automated distributed execution. Given their role in handling large transaction volumes across clients, miners, and validators, exploring concurrency is critical. This includes concurrent transaction execution or validation within blocks, block processing across shards, and miner competition to select and persist transactions. Concurrency and parallelism are a double-edged sword: while they improve throughput, they also introduce risks like race conditions, non-determinism, and vulnerabilities such as deadlock and livelock. This paper presents the first survey of concurrency in smart contracts, offering a systematic literature review organized into key dimensions. First, it establishes a taxonomy of concurrency levels in blockchain systems and discusses proposed solutions for future adoption. Second, it examines vulnerabilities, attacks, and countermeasures in concurrent operations, emphasizing the need for correctness and security. Crucially, we reveal a flawed concurrency assumption in a major research category, which has led to widespread misinterpretation. This work aims to correct that and guide future research toward more accurate models. Finally, we identify gaps in each category to outline future research directions and support blockchain's advancement.

Problem

• Analyzing concurrency levels and solutions in blockchain systems
• Investigating vulnerabilities and attacks in concurrent smart contract operations
• Correcting a widespread flawed concurrency assumption in blockchain research

Innovation

• Systematic review of blockchain concurrency levels
• Analyzes vulnerabilities in concurrent smart contracts
• Corrects flawed concurrency assumption in research