Vincent Naessens

Analysis of revocation strategies for anonymous Idemix credentials

In an increasing information-driven society, preserving privacy is essential. Anonymous credentials promise a solution to protect the users privacy. However, to ensure accountability, efficient revocation mechanisms are essential. Having classified existing revocation strategies, we implemented one variant for each. In this paper we describe our classification and compare our implementations. Finally, we present a detailed analysis and pragmatic evaluation of the strategies.

Structure preserving CCA secure encryption and applications

In this paper we present the first CCA-secure public key encryption scheme that is structure preserving, i.e., our encryption scheme uses only algebraic operations. In particular, it does not use hash-functions or interpret group elements as bit-strings. This makes our scheme a perfect building block for cryptographic protocols where parties for instance want to prove properties about ciphertexts to each other or to jointly compute ciphertexts. Our scheme is very efficient and is secure against adaptive chosen ciphertext attacks. We also provide a few example protocols for which our scheme is useful. For instance, we present an efficient protocol for two parties, Alice and Bob, that allows them to jointly encrypt a given function of their respective secret inputs such that only Bob learns the resulting ciphertext, yet they are both ensured of the computations correctness. This protocol serves as a building block for our second contribution which is a set of protocols that implement the concept of so-called oblivious trusted third parties. This concept has been proposed before, but no concrete realization was known.

A privacy-preserving ticketing system

Electronic identity (eID) cards are deployed in an increasing number of countries. These cards often provide digital authentication and digital signature capabilities, but have at the same time serious privacy shortcomings. We can expect that ordering and issuing tickets for events (e.g. soccer matches) will be increasingly done using eID cards, hence, severely threatening the user’s privacy. This paper proposes two alternative ticketing systems that are using the eID card in a bootstrap procedure, but still are providing a high degree of privacy to the user.

Performance analysis of accumulator-based revocation mechanisms

Anonymous credentials are discussed as a privacy friendlier replacement for public key certificates. While such a transition would help to protect the privacy of digital citizens in the emerging information society, the wide scale deployment of anonymous credentials still poses many challenges. One of the open technical issues is the efficient revocation of anonymous credentials. Currently, accumulator based revocation is considered to be the most efficient and most privacy friendly mechanism for revoking anonymous credentials. This paper analyses the performance of three accumulator based credential revocation schemes. It identifies the bottlenecks of those implementations and presents guidelines to improve the efficiency in concrete applications.

Commercial Home Assistance Services

In this chapter, the authors describe the software architecture of a commercially run home assistance system that allows patients or elderly people to stay longer at home. Since such systems often have to handle sensitive medical information, the protection of the privacy is a major concern. In addition, legislation often restricts access to health information to qualified persons (i.e. medical personnel), who are not always available in a commercial setting. The home assistance system can offer several services, ranging from scheduling necessary tasks and following up their execution, to monitoring the patient’s health status and responding promptly to requests for help or in case of emergency situations, and all this without the need to maintain personal medical data or identifying information about patients and caregivers in the home assistance centre.Through the use of ICT tools, such as the internet, portals, and telecommunication devices, the quality of healthcare has improved in local and global health; aiding in the development of a sustainable economy. Handbook of Research on ICTs for Quality Improvement in Healthcare and Social Services brings together a valuable research collection on ICT elements needed to improve communication and collaboration between global health institutes, public and private organisations, and foundations. Highlighting the adoption and success factors in the development of technologies for healthcare, this book is essential for IT professionals, technology solution providers, researchers, and students interested in technology and its relationship with healthcare and social services.

Security and Privacy Improvements for the Belgian eID Technology

The Belgian Electronic Identity Card enables Belgian citizens to prove their identity digitally and to sign electronic documents. At the end of 2009, every Belgian citizen older than 12 years will have such an eID card. In the future, usage of the eID card may be mandatory. However, irresponsible use of the card may cause harm to individuals.

A smart card based solution for user-centric identity management

This paper presents a prototype of a previously proposed user-centric identity management system using trusted modules. The trusted module, implemented using a smart card, can retrieve user attributes from identity providers and offer them to service providers, after authentication. This paper allows an evaluation of the practical feasibility of the identity management architecture and provides insight in several design decisions made during the prototype implementation. Also, the cryptographic protocols implemented in the prototype are discussed.

A formal approach for inspecting privacy and trust in advanced electronic services

Advanced information processing technologies are often applied to large profiles and result in detailed behavior analysis. Moreover, under the pretext of increased personalization and strong accountability, organizations exchange information to compile even larger profiles. However, the user is unaware about the amount and type of personal data kept in profiles, partially due to advanced interactions between multiple organizations during service consumption. In this paper, a formal approach to inspect privacy and trust in advanced electronic services is presented. It allows to express access and privacy policies of service providers. Also, the privacy properties of multiple authentication technologies are formally modeled. From this, meaningful privacy properties can be extracted based on varying trust assumptions. Feedback is rendered through automated reasoning, useful for both users and system designers. To demonstrate its practicability, the approach is applied to the design of a travel reservation system.

A Mobile and Reliable Anonymous ePoll Infrastructure

This paper illustrates and scans the limits of the use of anonymous credentials (e.g. Idemix) on smart phones to preserve the user’s privacy. A prototypical application with strong privacy requirements, ePoll, will be presented in detail. To ease the implementation of such applications, a specialized identity management framework has been developed. A first prototype of the ePoll application was built for workstations. Later it was ported to a smart phone to evaluate the performance of anonymous credential protocols in this setting.

PriMan: a privacy-preserving identity framework

PriMan is presented; privacy-preserving user-centric identity management middleware which defines and groups the required functionality. It offers the application developer a uniform technology-agnostic interface to use and combine different types of privacy enhancing technologies. Moreover, the PriMan framework defines all the components and their functionality required to raise the development of privacy enhanced client-server applications to a higher level.