Deadlock Prevention in Payment Channel Networks

Abstract

The use of blockchain-based cryptocurrencies has significantly increased over the last ten years; nevertheless, the broader acceptance of these currencies is hindered by scaling challenges. Payment Channel Networks (PCN), which operates as a layer two solution, presents itself as a viable option for augmenting the scalability of a blockchain network. In order to reduce the time and cost associated with the on-chain settlement, users have the option to conduct off-chain transactions through payment channels within their network. The growth of the PCN is expected to be accompanied by a corresponding increase in the number of transactions. However, the current distributed routing algorithms are unable to manage several simultaneous transactions due to deadlocks efficiently. We illustrate the possibility of deadlock in distributed routing algorithms. We prove that routing two transactions in PCN is NP-complete by reducing it from a two-commodity flow problem. In contrast to earlier work that avoided deadlock by exploiting locking or priority queues, our work emphasizes routing algorithms to avoid conditions for deadlock. We enhance the routing choices to minimize the number of saturated links that can cause deadlock. Resource allocation graphs are used to illustrate the necessary and sufficient conditions required for transactions to be in a deadlock. We also show how the dynamic behavior of resources can affect the deadlock situation in future timestamps. The deadlock trilemma and the relation between concurrency, resources, and deadlocks have also been discussed. The experimental evaluation shows that the proposed methodology yields an improvement in transaction count in the Speedy and the Webflow algorithms by 41% and 27%, respectively.