FHE-Based Publicly Verifiable Sealed-Bid Auction Protocol Atop Cross-Blockchain

Online auctions, which are widely used on Internet advertising platforms, reduce the participation costs for buyers and sellers, and promote the flow of tens of billions of dollars in the global economy. However, Internet advertising platforms tend to be monopolistic and adopt a sealed bidding model. Therefore, when price is the sole determinant of the winner, how to publicly verify the correctness of auction results without disclosing bidding information has become a challenge. To address these issues, we propose a fully homomorphic encryption (FHE)-based sealed-bid auction protocol with public verifiability atop cross-blockchain. Through an approximate comparison algorithm, the proof of the winner consists of ${m} \,\, -1$ (or 1) homomorphic ciphertexts, significantly reducing communication costs, where m represents the number of bidders. Thus, anyone can check the winner’s proof and complete the public verification of correctness. Moreover, this paper designs a cross-blockchain auction system model, breaking the monopoly of platforms, and proposes a distributed private key sharing method, which realizes the auditing function of the relay chain. Finally, we formalize the security model, and verify the correctness, public verifiability and privacy of our scheme. The off-chain time overhead and on-chain gas consumption demonstrate the strong practicability of our protocol in large-scale auctions.