Coercion Resistant MIX for Electronic Auction

Abstract

Coercion in sealed-bid auction refers to the problem of bid-rigging, where the adversary (coercer) dictates the bidder (coerced bidder) to bid some low value and also feasible to determine whether the victim has complied with the demands. Therefore uncoerciveness is an essential property to achieve fair and competitive sealed-bid auction. Receipt-free mechanisms are developed to confine the property of uncoerciveness. The prior receipt-free schemes assume an impractical assumption of the availability of an untappable channel between bidders and the auction authorities. Our previous work proposed a sender-side deniable encryption scheme to relax the assumption of the untappable channel where the receiver side is not colluded. However, we examined that neither the untappable channel nor the deniable encryption can provide receipt-freeness in presence of colluded authorities unless the privacy of the bidders are not preserved. MIX (MIX-cascade) is a well known technique for anonymous communication. This paper presents a MIX scheme compatible with deniable encryption to facilitate the receipt-freeness mechanisms to be practical without the assumption of untappable channel and also in the presence of colluded authorities. The proposed MIX may replace the untappable channel without changing the existing receipt-free mechanisms.