ClearChart: Ensuring integrity of consumer ratings in online marketplaces

In this paper, we propose ClearChart, a transparency-enhancing mechanism to discourage this misbehavior in today's centralized marketplaces. Our protocol employs a novel distributed version of homomorphic MAC along with cryptographic accumulators and digital signatures to protect integrity of the ratings and improves verifiability of the ratings list. ClearChart introduces only a minimal storage overhead to the buyers and sellers, and can also tolerate collusion among sellers, the service provider and a subset of buyers. We have implemented ClearChart and demonstrated its practicality with an empirical evaluation.