Vassilios Chrissikopoulos

Person identification based on parametric processing of the EEG

Person identification based on parametric spectral analysis of the EEG signal is addressed in this work-a problem that has not yet been seen in a signal-processing framework, to the best of our knowledge. AR parameters are estimated from a signal containing only the alpha, rhythm activity of the EEG. These parameters are used as features in the classification step, which employs a learning vector quantizer network. The proposed method was applied on a set of real EEG recordings made on healthy individuals, in an attempt to experimentally investigate the connection between a persons EEG and genetically-specific information. Correct classification scores at the range of 72% to 84% show the potential of our approach for person classification/identification and are in agreement with previous research showing evidence that the EEG carries genetic information.

Secure Transactions with Mobile Agents in Hostile Environments

A major problem of mobile agents is their apparent inability to authenticate transactions in hostile environments. In this paper, we consider a framework for the prevention of agent tampering without compromising the mobility or autonomy of the agent. Our approach uses encrypted functions. We present an RSA implementation which answers affirmatively the open problem on undetachable signatures of Sander and Tschudin.

Parametric person identification from the EEG using computational geometry

Person identification based on features extracted parametrically from the EEG spectrum is investigated in this work. The method proposed utilizes computational geometry algorithms (convex polygon intersections), appropriately modified, in order to classify unknown EEGs. The signal processing step includes EEG spectral analysis for feature extraction, by fitting a linear model of the AR type on the alpha rhythm EEG signal. The correct classification scores obtained on real EEG data experiments (91% in the worst case) are promising in that they corroborate existing evidence that EEG carries genetically specific information and is therefore appropriate as a basis for person identification methods.

Moderating effects of online shopping experience on customer satisfaction and repurchase intentions

Purpose – Satisfaction and experience are essential ingredients for successful customer retention. This study aims to verify the moderating effect of experience on two types of relationships: the relationship of certain antecedents with satisfaction, and the relationship of satisfaction with intention to repurchase. Design/methodology/approach – This paper applies structural equation modelling (SEM) and multi-group analysis to examine the moderating role of experience in a conceptual model estimating the intention to repurchase. Responses from 393 people were used to examine the differences between high- and low-experienced users of online shopping. Findings – The research shows that experience has moderating effects on the relationships between performance expectancy and satisfaction and satisfaction and intention to repurchase. This study empirically demonstrates that prior customer experience strengthens the relationship between performance expectancy and satisfaction, while it weakens the relationship...

Receipt-Freeness in Large-Scale Elections without Untappable Channels

For an electronic election to be fully democratic there is a need for security mechanisms that will assure the privacy of the voters. With receipt-free electronic voting, a voter neither obtains nor is able to construct a receipt proving the content of her vote. In this paper we first consider the minimal requirements for receipt-free elections, without untappable communication channels between the voter and the voting authorities. We then propose a solution, which satisfies these requirements. This solution is based on an encryption blackbox, which uses its own randomness. Finally we present an implementation with smartcards, suitable for Internet voting.

Strengthening Privacy Protection in VANETs

In the not so far future, vehicles are expected to be able to communicate with each other and with the road infrastructure, to enhance driving experience and support road safety, among others. Vehicular ad-hoc networks (VANETs) introduce a number of security challenges to the research community, mainly concerning the tradeoff between the privacy of the drivers and the accountability of misbehaving vehicles. Another challenge is how to satisfy privacy in the presence of an adversary that has access to all communication (a global observer), and that can perform traffic analysis in order to link messages and identify vehicles. In this paper we attempt to address such issues and propose a set of cryptographic mechanisms that balance the tradeoff between privacy and accountability in a VANET. Furthermore, we examine techniques for location privacy against adversaries that perform a Bayesian traffic analysis, and propose a strategy to strengthen location privacy in VANETs.

Modeling security in cyber–physical systems

Abstract This paper describes a framework for modeling the security of a cyber–physical system in which the behavior of the adversary is controlled by a threat model that captures – in a unified manner – the cyber aspects (with discrete values) and the physical aspects (with continuous values) of the cyber–physical system. In particular, the framework addresses combined (dependent) vector attacks and synchronization/localization issues. The framework identifies the cyber–physical features that must be protected according to the prevailing security policy. Also, the framework can be used for formal proofs of the security of cyber–physical systems.

Shiny happy people buying: the role of emotions on personalized e-shopping

Personalized services are diffusing rapidly in online shopping communities. However, the current understanding of the influence of personalization is limited. This study extends personalization literature into the area of emotions related to intention to purchase and into the context of online shopping. Responses from 182 online shoppers were used to examine the impact of personalization on customer emotions and intention to purchase. The results show that there is a direct positive association between personalization and purchase intentions. In addition, provision of personalization features in e-shops may evoke positive emotions to online shoppers but does not evoke nor mitigate negative ones. Finally, our study reports that emotions influence online shopping behavior either positively, through the formulation of positive emotions, or negatively, through negative emotions. These findings indicate that positive emotions mediate the relationship between personalization and purchase intentions. Our study concludes with a critical appraisal of our findings and a discussion of prospective theoretical and managerial implications for e-shop practitioners.

Assessing Emotions Related to Privacy and Trust in Personalized Services

This study explores the dynamics of personalized services in online shopping, with regard to emotions, privacy and trust. The basic emotions of happiness and anxiety were chosen. A sample of 182 online shoppers was used to assess the effect of privacy and trust on their emotions through personalized services, and how these emotions ultimately affect their purchase intentions. The findings indicate that privacy affects anxiety while trust affects happiness, while both emotions have significant influence on customers’ intention to buy through personalized services. The study concludes with theoretical and practical implications, limitations, and future research directions.

Uncoercible e-Bidding Games

The notion of uncoercibility was first introduced in e-voting systems to deal with the coercion of voters. However this notion extends to many other e-systems for which the privacy of users must be protected, even if the users wish to undermine their own privacy. In this paper we consider uncoercible e-bidding games. We discuss necessary requirements for uncoercibility, and present a general uncoercible e-bidding game that distributes the bidding procedure between the bidder and a tamper-resistant token in a verifiable way. We then show how this general game can be used to design provably uncoercible e-auctions and e-elections. Finally, we discuss the practical consequences of uncoercibility in other areas of e-commerce.