We show how group discounts can be offered without forcing buyers to surrender their anonymity, as long as buyers can use their own computing devices (e.g. smartphone, tablet 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 makes group discounts compatible with buyer privacy (that is, buyer anonymity).


Buyer privacy Group discounts Cryptographic protocols Digital signatures  



Thanks go to Dr Carla Ràfols for advice on IBDT signatures. The following funding sources are acknowledged: Google (Faculty Research Award to the first author), Government of Catalonia (ICREA Acadèmia Prize to the first author and grant 2014 SGR 537), Spanish Government (project TIN2011-27076-C03-01 “CO-PRIVACY”), European Commission (FP7 projects “DwB” and “Inter-Trust”) and Templeton World Charity Foundation (grant TWCF0095/AB60 “Co-Utility”). The authors are with the UNESCO Chair in Data Privacy. The views in this paper are the authors’ own and do not necessarily reflect the views of Google, UNESCO or the Templeton World Charity Foundation.


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Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  1. 1.Department of Computer Engineering and MathematicsUniversitat Rovira i VirgiliTarragonaSpain

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