Strategic Analysis of Griefing Attack in Lightning Network
Subhra Mazumdar, Prabal Banerjee, Abhinandan Sinha, Sushmita Ruj, Bimal Kumar Roy · IEEE Transactions on Network and Service Management · 2022
Hashed Timelock Contract (HTLC) in Lightning Network is susceptible to agriefing attack. An attacker can block several channels and stall payments by mounting this attack. A state-of-the-art countermeasure, Hashed Timelock Contract with Griefing-Penalty (HTLC-GP) is found to work under the classical assumption of participants being either honest or malicious but fails for rational participants. To address the gap, we introduce a game-theoretic model for analyzing griefing attacks inHTLC. We use this model to analyze griefing attacks inHTLC-GPand conjecture that it is impossible to design an efficient protocol that will penalize a malicious participant with the current Bitcoin scripting system. We study the impact of the penalty on the cost of mounting the attack and observe thatHTLC-GPisweakly effectivein disincentivizing the attacker in certain conditions. To further increase the cost of attack, we introduce the concept ofguaranteed minimum compensation, denoted as$\zeta $, and modifyHTLC-GPinto$\mathrm {HTLC{-}GP}^{\zeta }$. By experimenting on several instances of Lightning Network, we observe that the total coins locked in the network drops to 28% for$\mathrm {HTLC{-}GP}^{\zeta }$, unlike inHTLC-GPwhere total coins locked does not drop below 40%. These results justify that$\mathrm {HTLC{-}GP}^{\zeta }$is better thanHTLC-GPto counter griefing attacks.