Integrating Anonymous Credentials with eIDs for Privacy-Respecting Online Authentication

Electronic Identity (eID) cards are rapidly emerging in Europe and are gaining user acceptance. As an authentication token, an eID card is a gateway to personal information and as such it is subject to privacy risks. Several European countries have taken extra care to protect their citizens against these risks. A notable example is the German eID card, which we take as a case study in this paper. We first discuss important privacy and security threats that remain in the German eID system and elaborate on the advantages of using privacy attribute-based credentials (Privacy-ABCs) to address these threats. Then we study two approaches for integrating Privacy-ABCs with eID systems. In the first approach, we show that by introducing a new entity in the current German eID system, the citizen can get a lot of the Privacy-ABCs advantages, without further modifications. Then we concentrate on putting Privacy-ABCs directly on smart cards, and we present new results on performance, which demonstrate that it is now feasible for smart cards to support the required computations these mechanisms require.