Black Box Accumulation: Collecting Incentives in a Privacy Preserving Way
Abstract We formalize and construct black box accumulation (BBA) a useful building block for numerous important user centric protocols including loyalty systems, refund systems, and incentive systems (as, e.g. employed in participatory sensing and vehicle to grid scenarios) A core requirement all these systems share is a mechanism to let users collect and sum up values (call it incentives, bonus points, reputation points, etc. issued by some other parties in a privacy preserving way such that curious operators may not be able to link the different transactions of a user. At the same time, a group of malicious users may not be able to cheat the system by pretending to have collected a higher amount than what was actually issued to them. As a first contribution, we fully formalize the core functionality and properties of this important building block. Furthermore, we present a generic and non interactive construction of a BBA system based on homomorphic commitments, digital signatures, and non interactive zero knowledge proofs of knowledge. For our construction, we formally prove security and privacy properties. Finally, we propose a concrete instantiation of our construction using Groth Sahai commitments and proofs as well as the optimal structure preserving signature scheme of Abe et al. and analyze its efficiency.
Proc. Priv. Enhancing Technol.