FlagThis

Abstract

Decentralized Finance (DeFi) applications rely heavily on the order in which transactions are executed, making them susceptible to reordering attacks that enable adversaries to extract Blockchain Extractable Value (BEV). While linear blockchain systems such as Ethereum have inspired extensive research into fair ordering mechanisms, DAG-based consensus protocols have remained largely unprotected despite their growing adoption for scalability and performance. In this paper, we introduce Tilikum, a DAG-based ledger protocol that ensures fair transaction ordering without relying on weak edges. Tilikum achieves ordering linearizability by leveraging median-based timestamp aggregation, or batch order fairness, while maintaining low data redundancy and robust garbage collection. We implemented Tilikum in RustNarwhal/Tusk,and evaluatedPompite, againstThemis representativeand FairDAG. baselines,Our resultsnamelyshow that Tilikum achieves up to 39 __ higher throughput than other fair-ordering baselines, while fully blocking state-of-the-art DAGspecific reordering attacks.