Instant Function Calls Using Synchronized Cross-Blockchain Smart Contracts

Most current cross-blockchain approaches focus on exchanging or transferring tokens between networks. While some concepts foster smart contract invocations across blockchains, they require multiple transactions and operate asynchronously. We present a concept enabling instant smart contract calls by creating synchronized client contracts on arbitrary blockchains. Other smart contracts can query these client contracts on the target blockchain for retrieving information without requiring cross-chain message queues. With this, we reduce the dependency of smart contracts on their host blockchain, as remote contracts become available as read-only instances. The synchronization process does not require trust in the executing intermediary since Merkle proofs based on shared state roots are utilized to guarantee correct execution. We propose a novel concept called transition proofs for efficiently proving the correctness of state updates. The prototypical implementation permits smart contract synchronization between EVM-compatible blockchains. Our evaluation shows the approach's applicability regarding execution costs and delay. Further, we conduct a case study by synchronizing one of the largest decentralized exchanges deployed to the Ethereum network.