A centrality analysis of the Lightning Network

Blockchain technology has a huge impact on our digital society by enabling a more decentralized economy and policy making. This decentralization is also pivotal in payment Payment channel networks (PCNs), including the Lightning Network, have emerged as a promising solution to the scalability challenges that many blockchain-based cryptocurrencies, like Bitcoin, grapple with. These PCNs, while innovative, also inherit the rigorous dependability demands of the blockchain. A pivotal aspect of this dependability is the need for a high degree of decentralization, essential for mitigating liquidity bottlenecks and on-path attacks.

Driven by this imperative, our research embarks on an empirical centrality analysis of the Lightning Network, with a keen focus on the betweenness centrality distribution of its routing system. Utilizing an extensive dataset, sourced from several millions of broadcasted messages via the gossip protocol, we introduce the TimeMachine tool, an innovative method that allows for a temporal exploration of the network’s evolution.

Our findings reveal that while the Lightning Network exhibits a commendable level of decentralization, there is a discernible skew: a limited set of nodes command a significant portion of the transactions. Alarmingly, over the past two years, the network’s centrality has surged, with the inequality, as gauged by the Gini index, rising by over 15 uptick of approximately 5 in. This research not only uncovers critical insights into the Lightning Network’s structural dynamics but also raises the question about strategies and policies that ensure its sustained decentralization in the face of evolving challenges such as security vulnerabilities, potential monopolistic tendencies, liquidity bottlenecks, the risk of transaction censorship and many more.