SoK: DAG-based Consensus Protocols

2024-05-27

International Conference on Blockchain

AI Summary

This SoK paper systematically investigates the CAP trade-offs, security vulnerabilities, and scalability limitations of Directed Acyclic Graph (DAG)-based consensus protocols in distributed ledgers. Methodologically, it establishes a unified evaluation framework integrating CAP theory, functional modeling, and cross-protocol comparative analysis to enable systematic classification and evolutionary trajectory assessment of DAG consensus protocols. Key contributions include: (i) identifying characteristic consistency–availability trade-off patterns inherent to DAG consensus; (ii) uncovering recurrent design deviations and common attack vectors across protocols; (iii) pinpointing critical research gaps—particularly in fairness guarantees, formal verification, and heterogeneous network adaptability; and (iv) proposing a verifiable, forward-looking research roadmap. The study provides both theoretical foundations and practical guidelines for protocol design optimization, standardization efforts, and rigorous security evaluation of DAG-based distributed ledger systems.

Technology Category

• Data Mining & Knowledge Management: Representing, Reasoning, and Using Provenance, Trust
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization
• Multiagent Systems: Mechanism Design

Application Category

• Security and Privacy: Blockchains and distributed ledgers
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics

Abstract

This paper is a Systematization of Knowledge (SoK) that focuses on Directed Acyclic Graph (DAG)-based consensus protocols in Distributed Ledger Technologies (DLTs). Our study evaluates their impact on performance and their tradeoffs concerning consistency, availability, and partition tolerance, as postulated by the CAP theorem. We delineate the key functionalities and tradeoffs of DAGbased consensus protocols, highlighting iterative improvements and deviations from foundational models. Additionally, we identify research gaps and suggest directions for future work to refine DAG-based consensus mechanisms.

Problem

• Analyzes DAG-based consensus protocols' performance and trade-offs
• Classifies protocols into availability-focused vs consistency-focused types
• Identifies security, scalability challenges and future research directions

Innovation

• DAG-based consensus protocols classification
• Analyzing CAP theorem trade-offs
• Exploring security and scalability challenges