Agora: A Privacy-Aware Data Marketplace

Abstract

We propose Agora, the first blockchain-based data marketplace that enables multiple privacy-concerned parties to get compensated for contributing and exchanging data, without relying on a trusted third party during the exchange. Agora achieves data privacy, output verifiability, and atomicity of payments by leveraging cryptographic techniques, and is designed as a decentralized application via smart contracts. Particularly, data generators provide encrypted data to data brokers who use a functional secret key to learn nothing but the output of a specific, agreed upon, function over the raw data. Data consumers can purchase decrypted outputs from the brokers, accompanied by corresponding proofs of correctness. We implement a working prototype of Agora on Ethereum and experimentally evaluate its performance and deployment costs. As a core building block of Agora, we propose a new functional encryption scheme with additional public parameters that operate as a trust anchor for verifying decrypted results.

Privacy-preserving Analytics for Data Markets using MPC

“…Furthermore, our marketplace does neither learn the owners' data content nor the analysis result, but only metadata,. As opposed to Agora [28], where the broker, their market place, gets to know the analysis result. Our security guarantees in terms of privacy analysis, however, depend on the assumption that at least one MPC node behaves honestly.…”

“…As discussed by Koutsos et al [28], a data market has to at least satisfy data privacy and output verifiability which are defined as follows:…”

“…Note that in contrast to Koutsos et al [28] we omit atomicity of payments, which requires that data owners are correctly reimbursed, as for simplicity we do not (yet) consider per-access payments at this stage, but assume that data owners are compensated through a lump sum when uploading their data. However, we consider it important that data owners stay in control of their data, and therefore request that data owners need to be able to define for which (types of) computations their data may be used, and which computations are considered to privacy-invasive by the data owner.…”

“…Mediacalchain [1] among many others facilitates the exchange of medical data end-to-end secured. Agora [28] goes a step further and offers a data market place for privacy-sensitive data built from functional encryption (FE) [7] where data consumers are able to buy evaluations of certain functions on user data. Thereby only the results of the evaluation are exchanged without the need to transfer the original data sets.…”

Data Market Design: A Systematic Literature Review

“…A famous analogy proclaims data as the new oil 1 , and, like oil, it can be traded, processed and used in different contexts and applications. Indeed, the last decade has seen an incredible increase in both the amount of data being collected [3], [4], as well as the development of infrastructure necessary to process and share the vast amounts of collected data in new contexts [5], [6].…”