  Governments around the world are trying to build large data registries for
effective delivery of a variety of public services. However, these efforts are
often undermined due to serious concerns over privacy risks associated with
collection and processing of personally identifiable information. While a rich
set of special-purpose privacy-preserving techniques exist in computer science,
they are unable to provide end-to-end protection in alignment with legal
principles in the absence of an overarching operational architecture to ensure
purpose limitation and protection against insider attacks. This either leads to
weak privacy protection in large designs, or adoption of overly defensive
strategies to protect privacy by compromising on utility.
  In this paper, we present an operational architecture for privacy-by-design
based on independent regulatory oversight stipulated by most data protection
regimes, regulated access control, purpose limitation and data minimisation. We
briefly discuss the feasibility of implementing our architecture based on
existing techniques. We also present some sample case studies of
privacy-preserving design sketches of challenging public service applications.
