On sybil-proof mechanisms (2407.14485v2)

Abstract: We show that in the single-parameter mechanism design environment, the only non-wasteful, symmetric, incentive compatible and sybil-proof mechanism is a second price auction with symmetric tie-breaking. Thus, if there is private information, lotteries or other mechanisms that do not always allocate to a highest-value bidder are not sybil-proof or not incentive compatible.