An Anonymous Credit Card System

Credit cards have many important benefits; however, these same benefits often carry with them many privacy concerns. In particular, the need for users to be able to monitor their own transactions, as well as bank's need to justify its payment requests from cardholders, entitle the latter to maintain a detailed log of all transactions its credit card customers were involved in. A bank can thus build a profile of each cardholder even without the latter's consent. In this paper, we present a practical and accountable anonymous credit system based on ecash, with a privacy preserving mechanism for error correction and expense-reporting

Horizon formation and far-from-equilibrium isotropization in supersymmetric Yang-Mills plasma

Using gauge/gravity duality, we study the creation and evolution of anisotropic, homogeneous strongly coupled $\mathcal N=4$ supersymmetric Yang-Mills plasma. In the dual gravitational description, this corresponds to horizon formation in a geometry driven to be anisotropic by a time-dependent change in boundary conditions.Comment: 4 pages, typos corrected, published versio

On the Portability of Generalized Schnorr Proofs

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Concepts Around Privacy-Preserving Attribute-Based Credentials

Part 1: Invited PapersInternational audienceThis article provides a short overview of the concepts around privacy-preserving attribute-based authentication. It then briefly discusses the cryptographic realisation of these concepts and describes an architecture implementing them

Revocable Anonymity

Anonymity services in the EU may be forced by the new EU data retention directive to collect connection data and deanonymise some of their users in case of serious crimes. For this purpose, we propose a new privacy-friendly solution for incorporating revocation in an anonymous communication system. In contrast to other known methods, our scheme does not reveal the identity of a user to any other entity involved in the revocation procedure but the law enforcement agency. Another advantage is, that no user will need to provide more identifying information than his connection (IP) address, that is what he needs to communicate with the system anyway. The proposed scheme is based mainly on threshold group signatures and threshold atomic proxy re-encryption

Privacy Respecting ICT Innovations in Education: Electronic Course Evaluations in Higher Education and Beyond

Part 1: Invited PapersInternational audienceIn this paper we present our institute’s vision towards the introduction of privacy respecting innovative ICT services in the Greek educational sector and, gradually, to other sectors of public interest as well. This vision was shaped during our work within the scope of the EU funded research project ABC4Trust in which our institute implemented a pilot system, based on Privacy-ABCs (Attribute Based Credentials) for the support of anonymous course evaluations in Universities. Privacy-ABCs support cryptographic primitives and tools for eIdentity management that allow users to take full control of what personal information they reveal towards the services they use, providing only the information required to satisfy the service policy. We, first, discuss the set-up of the ABC4Trust pliot and then we explain how we plan to extend the pilot scenarios and characteristics in order to boost eParticipation of members of the educational community of Greece, through the Greek School Network (GSN), in a privacy respecting manner. In particular, we discuss a number of scenarios in which Privacy-ABCs play an important role in ascertaining that users of the GSN only reveal their identity elements which are necessary in order to use a school service. Finally, based on the experiences gathered from our pilot, we present our views with respect to the factors that can inhibit or advance the widespread use of innovations, such as the Privacy-ABCs and the systems based on them, in society. We argue that there are two key factors that affect widespread adoption of innovations: (i) initial introduction of the innovation within groups whose members are linked, somehow, with each other and (ii) gradual introduction to more user groups, of progressively increasing size. This was the model the ABC4Trust project actually adopted in the case of the pilot we discuss in this paper