Bid opening in e-auction is efficient when a homomorphic secret sharing function is employed to seal the bids and homomorphic secretudreconstruction is employed to open the bids. However, this high efficiency is based on an assumption: the bids are valid (e.g., within audspecial range). An undetected invalid bid can compromise correctness and fairness of the auction. Unfortunately, validity verification ofudthe bids is ignored in the auction schemes employing homomorphic secret sharing (called homomorphic auction in this paper). In thisudpaper, an attack against the homomorphic auction in the absence of bid validity check is presented and a necessary bid validity checkudmechanism is proposed. Then a batch cryptographic technique is introduced and applied to improve the efficiency of bid validity check.
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