Incentivizing cooperative relay in UTXO-based blockchain network

Today’s blockchain system provides two incentives for participants: block reward and transaction fee. However, these incentives benefit block miners more than ordinary participants. Besides, the message propagation relies on the volunteer work of these participants. We consider that there could be a third incentive to reward the relay process in the blockchain network. Nodes should be paid for corresponding relay work and incentives to expedite message propagation. We take advantage of the payment nature of blockchain and the characteristics of the UTXO Model, and propose a relay payment scheme to tackle the relay incentive issue. UTXO (unspent transaction output) is an abstract ownership of cryptocurrency and it represents a chain of payment relations between transactions. Any legal transaction should have valid UTXO(s) and generate new UTXO(s) to accomplish payment process. Native token in blockchain provides a straight and favorable payment method, and the UTXO model binds the interest of relay nodes and message originator. Then we model a cooperative, competitive relay game based on our scheme. We analyze the equilibrium results and run massive simulations on different datasets. This incentive scheme is free-rider resilient and could further expand to meet diverse relay requirement via transaction scripts in UTXO model. Our discussion and results help explore the relay incentives in the blockchain network and draw an example for the design of new blockchain systems.