Drs. Kemal Akkaya and Selcuk Uluagac

While Bitcoin dominates the market for cryptocurrencies, its use in micropayments is still a challenge due to its long transaction validation times and fees. Recently, the concept of off-chain payments was introduced and led to a payment network called Lightning Network (LN). Off-chain links provide the ability to do transactions without writing to blockchain. However, LN’s design still favors fees and is creating hub nodes that defeat the purpose of blockchain. In addition, it is still not reliable as not all the transactions are guaranteed to be transmitted to their destinations. If current vendors would like to use it, these problems might hinder its adoption. To address this issue, in this paper we advocate creating a private payment network among a given set of vendors that will serve their business needs, just like the idea of private blockchains.  The goal is to build a pure peer-to-peer topology that will eliminate the need for relays and increase the robustness of payments. Using off-chain links as edges and retailers as nodes, the problem is formulated as a multi-flow commodity problem where transactions represent the commodities from various sources to destinations. As the multi-flow commodity problem is NP-Complete, we not only develop an optimization model but also propose a heuristic approach that utilizes shortest path algorithms in a dynamic way by changing the edge weights as payments are made.