Rapido: Scaling blockchain with multi-path payment channels

Abstract

One of the fundamental problems that hinders the current blockchain systems for industrial use is scalability. Lightning Network has been proposed to address this challenge, which executes massive amount of transactions off-chain via pre-constructed payment channels, and only records the final state when a payment channel is closed. However, current Lightning Network heavily rely on the single path payment. When the payment value exceeds the deposit of each individual path, the customer has to close all the existing payment channels and construct a new one from scratch, which we term as the overload issue. In addition, the single path payment bears the inherent risk of sensitive information (e.g., payment value) leaking.In this paper, we propose a multi-path off-chain payment mechanism, termed Rapido, which explicitly addresses the overload and privacy leaking issues by splitting and distributing payment to multiple paths. Specifically, a new smart contract, D-HTLC, is equipped with Rapido to encode multi-path payment protocol. We also theoretically prove that the VDP (Value Distributing Problem) is NP-hard. Finally, extensive experiments show that our approach not only resolves the overload issue but also mitigates the skewness of payment channels. Quantitative results further reveal that with the restriction of no adding new payment channels, the success rate of Rapido is more than 3 times higher than that of the Lightning Network. The implementation will be released upon acceptance.