$\mathtt{SFPoW}$SFPoW: Constructing Secure and Flexible Proof-of-Work Sidechains for Cross-Chain Interoperability With Wrapped Assets

Sidechain techniques enhance blockchain scalability and interoperability, enabling decentralized exchanges and cross-chain operations for wrapped digital assets. However, existing PoW sidechains face challenges, including centralization, high communication costs, and incomplete PoW-based security proofs. This paper introduces $\mathtt{SFPoW}$, a Secure and Flexible Proof-of-Work sidechains for cross-chain interoperability with wrapped assets. $\mathtt{SFPoW}$ facilitates decentralized asset transfers and token swaps across nearly all PoW-based cryptocurrencies without requiring soft or hard forks or fixed PoW targets. It establishes a decentralized, fair validation set within the sidechain, improving adaptability and reducing competition and confirmation periods. A pluggable cross-chain proof generation method is proposed, effectively filtering lazy nodes, incentivizing active participation, and minimizing on-chain verification overhead to a proof size of 200.5 bytes. Through mining behavior analysis and cryptographic reductions, $\mathtt{SFPoW}$ satisfies weak and strong atomicity. Experiments on the Ronin blockchain and an Ethereum testnet demonstrate a round-trip cost of $6.55 and latency of 372.1–382.6 seconds, confirming its practicality and efficiency.