Desiderata in Mechanism Design

In a direct mechanism, a communication protocol queries agents’ private information in order to determine the outcome. Protocols make a distinction between the information solicited by the mechanism designer and the information revealed to the designer, and thus allow for the formulation of privacy desiderata in mechanism design. One such desideratum is need-to-know privacy, which formalizes a notion of data minimization. A protocol is need-to-know private if every piece of an agent’s private information that is revealed to the designer is needed to determine their outcome. A social choice rule is need-to-know implementable if there is a need-to-know protocol that implements it. Need-to-know implementability depends on the commitment power of the designer. When the designer is able to commit to arbitrary (cryptographic) protocols, any non-bossy social choice rule is need-to-know implementable. When the designer can only commit to personalized queries that correspond to messages sent in an extensive-form game, random serial dictatorship is the unique need-to-know and efficient object assignment rule, and the first price auction is the unique need-to-know and efficient standard auction. When the designer can commit to making some anonymous queries, the second-price auction becomes need-to-know implementable.