Karel Wouters

Offline NFC payments with electronic vouchers

In this paper a practical offline payment system based on digital vouchers using Near Field Communication (NFC) in mobile phones is presented. This work was performed within the scope of the IBBT NFC-Voucher project. The goal of the project is to assess the feasibility of such a system, from a technical and security perspective, using tangible NFC devices such as the Nokia 6131 NFC mobile phone. This involved an in-depth technical and security analysis of all actors in the system and a rigorous elaboration of the practical security requirements and assumptions. In the architecture implementing and connecting all the different actors of this voucher payment system, no compromises regarding security were made. At device level all sensitive data is stored in a Secure Element (SE) with limited access for non-authorised users. The backbone and voucher transfer system uses a classical Public Key Infrastructure (PKI), such that only trusted and registered parties can handle and transfer vouchers. After having implemented this system, we conclude that it is possible to build an off-line payment system for mobile phones without compromising security, but that it remains quite challenging, given the current limitations on speed, available memory and security functionality.

Threat Modelling for Security Tokens in Web Applications

In the last couple of years, several European countries have started projects which intend to provide their citizens with electronic identity cards, driven by the European Directive on Electronic Signatures. One can expect that within a few years, these smart cards will be used in a wide variety of applications. In this paper, we describe the common threats that can be identified when using security tokens such as smart cards in web applications. We illustrate each of these threats with a few attack scenarios. This paper is part of a series of papers, written by several academic teams. Each paper focuses on one particular technological building block for web applications.

Secure and Privacy-Friendly Logging for eGovernment Services

In this paper we present a scheme for building a logging- trail for processes related to eGovernment services. A citizen can reconstruct the trail of such a process and verify its status if he is the subject of that process. Reconstruction is based on hand-overs, special types of log events, that link data stored by multiple logging servers, which are not necessarily trusted. Our scheme is privacy-friendly in the sense that only the authorised subject, i.e. the citizen, can link the different log entries related to one specific process. The scheme is also auditable; it allows logging servers to show that they behave according to a certain policy.

Introduction to the Belgian EID Card

This article gives a brief introduction to the Belgian EID card project commonly referred to as Belpic. This introduction includes an overview of the history of the project, details on the visual and cryptographic aspects of the EID cards, a discussion of the different sub-CAs involved, together with the card issuing process.

Secure remote reconfiguration of an FPGA-based embedded system

This paper describes the protocol, architecture, and implementation details of an FPGA-based embedded system that is able to remotely reconfigure the FPGA, using a TCP/IP connection, in a secure way. When considering the security aspects, we imply data confidentiality, explicit key authentication and data origin authentication. Since these aspects are overhead for the main application, the system is to be as small as possible. Therefore we have focused on compactness rather than on speed for the implementation. The implemented solution exists out of 2 components: a communication part and a cryptographic part. The system can be easily integrated at any point in the design of an FPGA-based embedded system, due to the simple and modular architecture.

Towards an XML format for time-stamps

XML has become a well-established format for information exchange. Several formats have been defined to secure XML data, such as XML Digital Signatures, XML Encryption and XKMS. In recent work by ETSI on XML digital signatures conforming to European legislation, time-stamps play a key role for qualified digital signatures. Some ASN.1-based formats for time-stamp protocols have been defined within IETF and ISO/IEC. In this paper, we investigate how the wide range of time-stamping protocols in the literature can be embedded into a single XML format; our work is based on existing standardisation efforts. We present our ideas in the form of a concrete XML structure, which can be used as the starting point to develop a mature XML-based time-stamping protocol.

Hardware Strengthening a Distributed Logging Scheme

In the online world, service providers allow users to upload data to be stored or processed. In some cases, privacy will become an essential feature. Sensitive content can be the data provided to or the services used at the service provider. Logging of the actions of the service providers can therefore also generate privacy-sensitive content. However, to enhance transparency towards users, logging can be a very useful tool. In this paper, we build upon the concept of distributed privacy-preserving log trails. The trust in such a system lies in the storage of a vector in a certain register stored in software. With a piece of malicious software, a hacker or curious user could misuse this register to learn about a certain process or to learn for whom a service is performed, although the scheme ensures forward-unlinkability and forward-integrity. In this paper, we strengthen the conventional software approach by implementing the vector in external hardware. This hardens the scheme further, and reduces the level to which the log server has to be trusted, at the cost of additional but solvable security threats.

Enhancing Transparency with Distributed Privacy-Preserving Logging

Transparency of data processing is often a requirement for compliance to legislation and/or business requirements. Furthermore, it has recognised as a key privacy principle, for example in the European Data Protection Directive. At the same time, transparency of the data processing should be limited to the users involved in order to minimise the leakage of sensitive business information and privacy of the employees (if any) performing the data processing.

Secure event logging in sensor networks

This paper proposes protocols for secure logging of events in sensor networks by gathering in a secure and reliable way all information at one central point. Not only the chronological order of logged events sent by the different sensors is guaranteed. Also modification, deletion, and addition of other data is made impossible. As proof of concept, we have designed a prototype of the gateway sensor on an FPGA platform.

EVAWEB: A Web-Based Assessment System to Learn X.509/PKIX-Based Digital Signatures

EVAWEB is a Web-based assessment system that has been developed to evaluate the learning enhancement produced by the use of X.509 Public Key Infrastructure (X.509/PKIX)-based digital signatures in a real environment. EVAWEB allows the students to experience main X.509/PKIX processes related to the digital signature mechanism. In this paper, EVAWEB and its assessment by the students are described