FACT: Sealed-Bid Auction With Full Privacy via Threshold Fully Homomorphic Encryption

Sealed-bid auction is a common mechanism for selling and buying commodities. However, existing auction schemes to protect bids require at least squared computation and communication complexity for the bidders or rely on trusted auctioneers or third parties. To address the above problems, we propose a secure and efficient sealed-bid auction framework, called FACT. We design a lightweight threshold fully homomorphic encryption scheme as the building block. Our framework does not rely on any trusted auctioneer and fulfills a stronger security guarantee, called full privacy, i.e., only the seller and the winning bidder can determine the auction result. While our framework applies to first-price sealed-bid, it can easily be extended to support second-price sealed-bid (i.e., Vickrey auction) with the same security guaranteed. Our framework also supports the dynamic joining and exiting of sellers and bidders. Meanwhile, our framework reduces the bidders’ overhead and the number of interactions to a constant level. We formally prove the security of our framework in the semi-honest adversary model. We implement FACT and run experiments comparing its performance against existing schemes. We find that our framework not only achieves a stronger security guarantee but also shows significant performance improvement compared to existing schemes.