This repository contains the prototypes and measurements code for the client and smart contract to run THEMIS, a novel privacy-by-design ad platform that is decentralized and requires zero trust from users.
This implementation is based on THEMIS: Decentralized and Trustless Ad Platform with Reporting Integrity, by the Brave Research team.
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THEMIS client implementation: Implementation of the client-side logic which interacts with the sidechain. This folder also includes benchmarks, tests and end-to-end examples of how the protocol works.
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THEMIS policy smart contract: Implementation of the THEMIS policy smart contract, which calculates the user ad rewards based on the user's encrypted input.
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Payment measurements: Setup used to calculate scalability of confidential payments using AZTEC in the context of THEMIS.
Abstract: Online advertising fuels the (seemingly)free internet. However, although users can access most websites free of charge, they need to pay a heavy cost on their privacy and blindly trust third parties and intermediaries that absorb great amounts of ad revenues and user data. This is one of the reasons users opt out from advertising by resorting ad blockers that in turn cost publishers millions of dollars in lost ad revenues. Existing privacy-preserving advertising approaches(e.g., Adnostic, Privad, Brave Ads) from both industry and academia cannot guarantee the integrity of the performance analytics they provide to advertisers, while they also rely on centralized management that users have to trust without being able to audit.In this paper, we propose THEMIS, a novel privacy-by-design ad platform that is decentralized and requires zero trust from users. THEMIS (i) provides auditability to all participants, (ii) rewards users for viewing ads,and (iii) allows advertisers to verify the performance and billing reports of their ad campaigns. To demonstrate the feasibility and practicability of our approach,we implemented a prototype of THEMIS using a combination of smart contracts and zero-knowledge schemes.Performance evaluation results show that during ad reward payouts, THEMIS can support more than 51M concurrent users on a single-sidechain setup or 153Musers on a multi-sidechain setup, thus proving that THEMIS scales linearly.