A Privacy-Friendly Loyalty System Based on Discrete Logarithms over Elliptic Curves

Abstract. Systems for the support of customer relationship management are be-coming increasingly attractive for vendors. Loyalty systems provide an interest-ing possibility for vendors in customer relationship management. This holds for both real world and online vendors. However, beside some potential benefits of a loyalty system, customers may also fear an invasion into their privacy, and may thus refuse to participate in such programs. In this paper, we present a privacy-friendly loyalty system to be used by online vendors to issue loyalty points. The system prevents vendors from exploiting data for the creation of customer profiles by providing unconditional unlinkability of loyalty points with regard to purchases. In the proposed system, we apply the difficulty for the computa-tion of discrete logarithms in a group of prime order to construct a secure and privacy-friendly counter. More precisely, all computations are carried out over special cryptographic groups based on elliptic curves where the decisional Diffie-Hellman problems can be solved easily while the computational Diffie-Hellman is believed to be hard.

Migration in the balance: tight ecological margins and the changing fortunes of shorebird populations

Dependent as they are on rare and remote open habitats for breeding and survival, shorebirds connect continents and hemispheres with their individual movements. Although many of the wetland systems on which shorebirds rely, especially in the rich West, have now some form of protection, two case studies on man-induced declines of Red Knots Calidris canutus in The Netherlands and the USA demonstrate that despite the legislation in these countries, the responsible authorities have tragically failed to provide the necessary safeguards. At the same time, these examples indicate how instructive shorebirds can be in elucidating ecosystem changes at local, and at global, scales. I advocate continued close scientific scrutiny of complementary sets of shorebird species so that we can be informed about their fate, and about the fate of ecosystems world-wide that are so effectively connected by their movements