Privads: Privacy Preserving Targeted Advertising

Helen Nissenbaum and others on the PORTIA and PRESIDIO projects have released a white paper describing Privads, a client-side behavioral advertising system designed to protect users’ privacy:

Online behavioral advertising (OBA) refers to the practice of tracking users across web sites in order to infer user interests and preferences. These interests and preferences are then used for selecting ads to present to the user. There is great concern that behavioral advertising in its present form infringes on user privacy. The resulting public debate — which includes consumer advocacy organizations, professional associations, and government agencies — is premised on the notion that OBA and privacy are inherently in conflict.

Privads is a practical architecture that enables targeting without compromising user privacy. Behavioral profiling and targeting in Privads takes place in the user’s browser.

Our technical paper discusses the effectiveness of the system as well as potential social engineering and web-based attacks on the architecture. One complication is billing; ad-networks must bill the correct advertiser without knowing which ad was displayed to the user. We describe a cryptographic billing system that directly solves the problem. We implemented the core targeting system as a Firefox extension and report on its effectiveness.

While some are skeptical about whether Privads will be fully effective and/or embraced by the online advertising industry, this is the kind of innovative, values-based design that we need to mitigate the growing threats to privacy online.

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