Interopera: An Efficient Cross-Chain Trading Protocol

Abstract With the rapid development of blockchains, blockchain systems are moving on from a stand-alone manner to cross-chain interactions, and achieving interoperability is emerging as one of the essential features of blockchains. Unfortunately, existing mechanisms such as XCLAIM mostly focus on exchanging assets between two blockchains and it is slow and expensive to process each cross-chain trade among more than two blockchains as multiple transactions are required. In this paper, we present Interopera, a decentralized and efficient cross-chain trading protocol among two or more blockchains. Interopera atomically processes each cross-chain trade faster and more cheaply with fewer transactions by a two-phase lock/unlock process. Interopera also achieves efficient cross-chain communication by our presented Partitioned-FlyClient and Tx-FlyClient. Partitioned-FlyClient is based on FlyClient but more efficient with smaller proof size, reducing the storage and bandwidth overheads. Tx-FlyClient maintains efficiency even when cross-chain trades become frequent, instead of other mechanisms only being effective under low cross-chain trades volumes. We also develop a proof-of-concept implementation and the results demonstrate high efficiency of our protocol.