International Association
for Cryptologic Research

Payment Channel Networks (PCNs) are the most scalable and trust-minimized solution to Bitcoin's scalability challenges. Within PCNs, connected payer and payee can make arbitrary off-chain transactions through multi-hop payments (MHPs) over payment channel paths, while intermediate relays charge relay fees by providing liquidity. However, current MHP protocols face critical security threats including fee-stealing attacks and griefing attacks. In this paper, we identify new fee-stealing attacks targeting most existing MHP protocols. Second, we prove that eliminating griefing attacks in current MHP protocols is impossible by reducing the problem to fair secret exchange. Finally, we introduce Zeus, the first Bitcoin-compatible MHP protocol that is secure against fee-stealing attacks and offers bounded griefing protection against $k$-cost-sensitive adversaries—those who only launch griefing attacks when the expected damage exceeds a $k$ fraction of their own cost. These guarantees are established through rigorous proofs in the Global Universal Composability (GUC) framework. Our comprehensive evaluation demonstrates that Zeus reduces worst-case griefing damage to 28\% and 75\% compared to MHP schemes such as AMHL~(NDSS'19) and Blitz~(USENIX SEC'21), respectively. Our results further show that, even under the most adverse configurations within the Lightning Network, Zeus imposes costs on adversaries that are at least ten times greater than their potential damage.