  The targeted advertising is based on preference profiles inferred via
relationships among individuals, their monitored responses to previous
advertising and temporal activity over the Internet, which has raised critical
privacy concerns. In this paper, we present a novel proposal for a
Blockchain-based advertising platform that provides: a system for privacy
preserving user profiling, privately requesting ads from the advertising
system, the billing mechanisms for presented and clicked ads, the advertising
system that uploads ads to the cloud according to profiling interests, various
types of transactions to enable advertising operations in Blockchain-based
network, and the method that allows a cloud system to privately compute the
access policies for various resources (such as ads, mobile user profiles). Our
main goal is to design a decentralized framework for targeted ads, which
enables private delivery of ads to users whose behavioral profiles accurately
match the presented ads, defined by the ad system. We implement a POC of our
proposed framework i.e. a Bespoke Miner and experimentally evaluate various
components of Blockchain-based in-app advertising system, implementing various
critical components; such as, evaluating user profiles, implementing access
policies, encryption and decryption of users' profiles. We observe that the
processing delay for traversing policies of various tree sizes, the
encryption/decryption time of user profiling with various key-sizes and user
profiles of various interests evaluates to an acceptable amount of processing
time as that of the currently implemented ad systems.
