End-to-End Verifiable Quadratic Voting with Everlasting Privacy

Quadratic voting is an intriguing new method for public choice suggested by Lalley and Weyl, which they showed to be utilitarian efficient. Voters are given a budget of credits and can assign each of the candidates a (perhaps negative) value, where the price paid for their voting choice is the sum of the squared values. From a security viewpoint, we generally request elections to be private and have integrity, and even further (end-to-end) verifiability which entails public bulletin boards. Such public data might be troublesome when considering future adversaries capable of breaking current cryptographic primitives, either due to computational power advances, broken primitives or scientific breakthroughs. This calls for election schemes with everlasting privacy and perfectly private audit trails. In the. case of quadratic voting this is even more crucial since budget balances have to be linked between elections in a verifiable way, and revealing old budget values partially break privacy in later elections. In this paper, we suggest an efficient construction of electronic quadratic voting with end-tœend verifiability and a perfectly private audit trail inspired by the methods of Cuveliel', Pereira and ters, but adapted to include the quadratic relations and keeping budget balances everlasting private.