Private Public Choice

The fields of social choice theory and mechanism design deal with the aggregation of conflicting preferences in a group of agents, may they be electronic or human. Two central problems in these areas are the social choice problem and the mechanism design problem. We argue that the protection of individual preferences has not been considered so far and introduce the preference protection problem, which we aim to solve by applying a fruitful subfield of cryptography called secure multiparty computation. Similar to the implementation of social choice functions in mechanisms, our new view on public choice adds another level to the model by introducing the emulation of mechanisms by cryptographic protocols. This enables the private and secure execution of mechanisms without trusted third-parties by distributing the computation of the mechanism outcome on the participating agents. It is shown that security against computationally bounded adversaries is possible whereas general mechanisms can not be emulated by protocols that are secure against unbounded adversaries. We then investigate how to construct efficient special-purpose protocols, such as a protocol that emulates the Clarke tax mechanism.