A Secure Channel for Attribute-Based Credentials [Short Paper] ∗ Gergely Alpár Jaap-Henk Hoepman Radboud University Nijmegen, ICIS DS Radboud University Nijmegen, ICIS DS Nijmegen, The Netherlands Nijmegen, The Netherlands
[email protected] [email protected] ABSTRACT Keywords Attribute-based credentials (ABCs) are building blocks for identity management; cryptography; secure channel; mutual user-centric identity management. They enable the disclo- authentication; anonymous credential; attribute-based cre- sure of a minimum amount of information about their owner dential to a verifier, typically a service provider, to authorise the credential owner for some service, application, or resource. By directly applying attribute-disclosure protocols, the 1. INTRODUCTION data is revealed not only to the verifier, but anyone who As individuals perform an increasing amount of transac- has access to the communication channel. Moreover, as ver- tions online, privacy is of primary importance in the dig- ifiers are not intrinsically authenticated, one can accidentally ital world. For many of these transactions, for instance, reveal attributes to the wrong party. Therefore, a secure the full identity of a user is not essential, only a few non- channel has to be established between the prover and the identifying attributes are sufficient to be revealed (e.g., “over verifier. 18” for buying alcoholic drinks). Traditionally, authentica- Although efficient ABC smart-card implementations exist, tion means the process of proving the ownership of one’s not always can they perform all prover features. An equality identity. A more general notion of authentication is the pro- proof, for instance, is essential in creating pseudonyms that cess of proving that certain predicates, or attributes, hold enable temporary identification and eventually establishing for an entity.