Privacy-Preserving Group Discounts

Abstract

How can a buyer legitimately benefit from group discounts while preserving his privacy? We show how this can be achieved when buyers can use their own computing device (e.g. smartphone or computer) to perform a purchase. Specifically, we present a protocol for privacy-preserving group discounts. The protocol allows a group of buyers to prove how many they are without disclosing their identities. Coupled with an anonymous payment system, this allows group discounts to be compatible with buyer privacy. ; This work was partly funded by Google through a Faculty Research Award to the first author, who is also partially supported by the Government of Catalonia through an ICREA Acadèmia Prize. The following partial supports are also gratefully acknowledged: the Spanish Government under projects TIN2011-27076-C03-01 "CO-PRIVACY" and CONSOLIDER INGENIO 2010 CSD2007-00004 "ARES", and the European Commission under FP7 projects "DwB" and "Inter-Trust".