Establishing Trust in Online Advertising with Signed Transactions.

Programmatic advertising operates one of the most sophisticated and efficient service platforms on the Internet. However, the complexity of this ecosystem is the main cause of one of the most important problems in online advertising, the lack of transparency. This lack of transparency leads to subsequent problems such as advertising fraud, which causes billions of dollars in losses. In this paper we propose Ads.chain, a technological solution to the lack-of-transparency problem in programmatic advertising. Ads.chain extends the current effort of the IAB in providing traceability in online advertising through the Ads.txt and Ads.cert solutions, addressing the limitations of these techniques. Ads.chain is a communication protocol that provides end-to-end cryptographic traceability at the ad transaction level. It can be seamlessly embedded in ad-tags and the OpenRTB protocol, the de-facto standards for communications in online advertising, allowing an incremental adoption by the industry. We have implemented the protocol and made the code publicly available. We assess the performance of Ads.chain through a thorough analysis in a lab environment that emulates a real ad delivery process. The obtained results show that our protocol adds delays lower than 0.25 ms per ad space on the web page and a marginal delay of 0.8 ms on the intermediaries. These results confirm its impact on the user experience and the overall operation of the programmatic ad delivery process can be considered negligible.