7 Digital Rights Management for PIR

Abstract

This chapter considers the problem of providing digital rights management (DRM) for goods sold by means of PIR. Section 7.1 shows that DRM and PIR cannot coexist perfectly. Furthermore, Section 7.2 demonstrates how applying a straightforward DRM scheme violates user privacy. We construct a protocol that provides for both DRM and user privacy in Section 7.3. In Section 7.4, we expose a trade-off between the quality of DRM and the amount of privacy provided, borrowing the relaxed privacy definition from the previous chapter. Section 7.6 proves that a certain negative property of the proposed privacy–preserving DRM scheme is unavoidable. This result is of independent interest, bringing new insight into the research area of electronic voting.