CommTLC: An Alternative to Reduce the Attack Surface of HTLCs in Lightning Networks

Abstract

The Payment Channel Network is widely recognized as one of the most effective solutions for handling off-chain transactions and addressing blockchain scalability challenges. In the Lightning Network, a popular off-chain mechanism, multi-hop payments are facilitated through Hashed Time-Locked Contracts (HTLCs). However, despite its broad adoption, HTLCs are susceptible to various attacks, such as Fakey, Griefing, and Wormhole attacks. In these attacks, adversaries aim to disrupt transaction throughput by exhausting channel capacity or stealing routing fees from honest nodes along the payment path. We propose a scheme called CommTLC, which leverages Pedersen commitments and signatures to detect and punish/prevent adversaries in Fakey, Griefing and Wormhole attacks. We implement the proposed scheme and analyse its security within the universal composability (UC) framework. Additionally, we compare the performance of CommTLC with the latest schemes, MAPPCN-OR and EAMHL+. The results demonstrate that CommTLC outperforms both MAPPCN-OR and EAMHL+ in communication overhead, with only a slight increase in computational overhead compared to MAPPCN-OR. Furthermore, the adversary detection time for Fakey, Griefing and Wormhole attacks using CommTLC is reduced to just a few milliseconds—specifically, less than 112 ms for a payment path involving five users.