Papers by V. Chrissikopoulos
Traffic engineering and control, 1983
A measure of deceleration of major-road drivers approaching a t-junction (Chrissikopoulos et al, ... more A measure of deceleration of major-road drivers approaching a t-junction (Chrissikopoulos et al, see TRIS 380552), is examined in relation to vehicle speed and in relation to the accepted gap and crossing time of vehicles in the other stream crossing into the junction. A regression analysis shows that there is a negative correlation between the measure of deceleration and the time difference between the accepted gap and crossing time. Data from three rural trunk road sites are used. (Author/TRRL)
In this paper, investigate the use of brain activity for person identification. A biometric syste... more In this paper, investigate the use of brain activity for person identification. A biometric system is a technological system that uses information about a person. Research on brain signals show that each individual has a unique brain wave pattern. Electroencephalography signals generated by mental tasks are acquired to extract the distinctive brain signature of an individual. Electroencephalography signals during four biometric tasks, namely relax, math, read and spell was acquired from 50 subjects. Features are derived from power spectral density. Classification is performed using Feed forward neural network and Recurrent neural network. The performance of the neural model was evaluated in terms of training, performance and classification accuracies. The results confirmed that the proposed scheme has potential in classifying the EEG signals. RNN is considerably better with an average accuracy of 95% for the spell task and 92% for the read tasks in comparison with a feed forward neu...
American Journal of Electroneurodiagnostic Technology, 2003
In the present study the problem of discriminating between interictal epileptic and non-epileptic... more In the present study the problem of discriminating between interictal epileptic and non-epileptic pathological EEG stages, which present episodic loss of consciousness, is investigated. The proposed method is based on a novel algorithm, which produces auto-correlated coefficients from an appropriate, selected EEG segment. The characteristic features of these coefficients are based on a prototype spectral variation of an extended spectrum in which alpha, beta and gamma activities are included. The statistical processing of the results of this method shows that it may be characterized as accurate for recognition purposes.
IFIP Advances in Information and Communication Technology, 1996
Enforcing network security in Telemedicine systems is necessary in order to ensure security of th... more Enforcing network security in Telemedicine systems is necessary in order to ensure security of the information exchanged. In this paper we propose a conference key distribution system that is able to provide the network security services required in an anticipated implementation. The protocol is based on public keys and has a low communication and computation complexity. In addition, a scenario for secure data exchange through the Telemedicine system network based on this protocol is presented.
IFIP Advances in Information and Communication Technology, 1996
Data security in computer networks is becoming increasingly important due to the expanding role o... more Data security in computer networks is becoming increasingly important due to the expanding role of distributed computation, distributed databases and tele-communication applications such as electronic mail and electronic funds transfer. For privacy, information which may be highly sensitive or privileged must be encrypted with secret keys which are shared by the communicating parties. These keys are generated by key agreement protocols. Traditionally such protocols were designed by trial and error. History has proven this method to be unreliable: many protocols were broken or serious flaws were exposed. In this paper we discuss the security aspects of key agreement protocols. In particular, we consider two models for provable security, one based on probabilistic encryption, the other on zero-knowledge. We propose a variant of the Diffie-Hellman key agreement protocol which is provably secure and efficient.
Studies in health technology and informatics
In this paper, a secure medical digital library architecture is presented, that is based on the C... more In this paper, a secure medical digital library architecture is presented, that is based on the CORBA specifications for distributed systems. Special attention is given to the distinguished nature of medical data, whose integrity and confidentiality should be preserved at all costs. This is achieved through the employment of Trusted Third Parties (TTP) technology for the support of the required security services.
IFIP Advances in Information and Communication Technology, 2002
Electronic elections could be a viable alternative for real-life elections in a democratic societ... more Electronic elections could be a viable alternative for real-life elections in a democratic society. In traditional elections, a voting booth does more than allow voters to keep their vote secret. The voting booth actually requires that voters vote secretly. If the privacy of the vote was allowed but not required, then a voter could easily sell his vote to a vote-buyer, or be coerced by a coercer. We present a receipt-free election scheme without making any hardware or physical assumptions about the communication channel between the voter and the voting authorities. Our solution is software-based i.e. voters are able to exercise their electoral rights from their home by using a personal computer with Internet access. The only physical assumption we make use of is an untappable channel between the two voting authorities that are employed in our scheme. This scheme satisfies most requirements of a secure electronic election. We make use of well-known cryptographic techniques such as time-lock puzzles and blind signatures.
Sixth IEEE International Symposium on a World of Wireless Mobile and Multimedia Networks
Recent work on key establishment for sensor networks has shown that it is feasible to employ limi... more Recent work on key establishment for sensor networks has shown that it is feasible to employ limited Elliptic Curve Cryptography in sensor networks through hybrid protocols. In this paper, we propose a hybrid key establishment protocol for uniform self-organized sensor networks. The proposed protocol combines the Elliptic Curve Diffie-Hellmann key establishment with implicit certificates and symmetrickey cryptographic techniques. The protocol can be implemented on uniform networks comprised of restricted functional devices. Furthermore, due to its public-key nature, the protocol is resilient to a wide range of passive and active attacks such as known-key attacks, as well as attacks against the confidentiality, integrity and authenticity of the communication. The protocol is scalable and efficient for low-capability devices in terms of storage, communication and computational complexity: the cost per node for a key establishment is reduced to one scalar multiplication with a random point plus one with a fixed point.
Journal in Computer Virology, 2008
A network worm is a specific type of malicious software that self propagates by exploiting applic... more A network worm is a specific type of malicious software that self propagates by exploiting application vulnerabilities in network-connected systems. Worm propagation models are mathematical models that attempt to capture the propagation dynamics of scanning worms as a means to understand their behaviour. It turns out that the emerged scalability in worm propagation plays an important role in order to describe the propagation in a realistic way. On the other hand human-based countermeasures also drastically affect the propagation in time and space. This work elaborates on a recent propagation model (Avlonitis et al. in J Comput Virol 3, 87-92, 2007) that makes use of Partial Differential Equations in order to treat correctly scalability and non-uniform behaviour (e.g., local preference worms). The aforementioned gradient model is extended in order to take into account human-based countermeasures that influence the propagation of local-preference worms in the Internet. Certain aspects of scalability emerged in random and local preference strategies are also discussed by means of random field considerations. As a result the size of a critical network that needs to be studied in order to describe the global propagation of a scanning worm is estimated. Finally, we present simulation results that validate the proposed analytical results and demonstrate the higher propagation rate of local preference worms compared with random scanning worms.
12th International Workshop on Database and Expert Systems Applications
ABSTRACT Mobile agents are an appealing technology for distributed applications in open networks.... more ABSTRACT Mobile agents are an appealing technology for distributed applications in open networks. A major problem is the asymmetric relation of mobile agents and their execution environment in matters of security. The security concerns are even greater in the case where agents are executed autonomously in multiple hosts, and in particular when the environment is hostile. The proposed solutions in the literature for secure autonomous agents are more of theoretic interest since they are inefficient for real applications. In this paper, we propose a cryptographic solution for secure autonomous agents which is based on dynamically generated message-flexible multi-signatures. Our scheme is practical and does not compromise the advantages of the mobile agent paradigm.
Proceedings of the 18th Panhellenic Conference on Informatics, 2014
ICECS'99. Proceedings of ICECS '99. 6th IEEE International Conference on Electronics, Circuits and Systems (Cat. No.99EX357)
Person identification based on parametric spectral analysis of the EEG signal is addressed in thi... more 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
ICECS'99. Proceedings of ICECS '99. 6th IEEE International Conference on Electronics, Circuits and Systems (Cat. No.99EX357)
... 1-6, 1998. [17] Varner, J., Potter, R., Rohrbaugh, J., A proce-dure for automatic classifica... more ... 1-6, 1998. [17] Varner, J., Potter, R., Rohrbaugh, J., A proce-dure for automatic classification of EEG genetic variants, Processing of biological signals, 30.9-3, Annual nternational Conference of the IEEE Engi-neering in Medicine and Biology Society, vol. 13, no. 1, 1991. ...
Lecture Notes in Computer Science, 2013
We propose an efficient anonymous authentication scheme that provides untraceability and unlinkab... more We propose an efficient anonymous authentication scheme that provides untraceability and unlinkability of mobile devices, while accessing Location-Based Services. Following other recent approaches for mobile anonymity, in our scheme the network operator acts as an anonymous credential issuer for its users. However, our scheme supports credential non-transferability, without requiring embedded hardware security features. In addition it supports fairness characteristics. On one hand, it reduces the trust assumptions for the issuer by supporting nonframeability: the issuer, even in collaboration with the LBS provider, cannot simulate a transaction that opens back to an honest user. On the other hand, it supports anonymity revocation for illegally used credentials. Our scheme uses standard primitives such as zero-knowledge proofs, MACs and challenge/responses. We provide formal security proofs based on the intractability of the Divisible Diffie-Hellman assumption.
Lecture Notes in Computer Science, 2000
ABSTRACT We present a sealed-bid electronic auction scheme that is equitably fair for the bidders... more ABSTRACT We present a sealed-bid electronic auction scheme that is equitably fair for the bidders and the seller. In this scheme, the interests of both the bidders and the seller are safeguarded: the identity of the non-winning bidders and their bidding behavior are protected (anonymity), and the bidders cannot withdraw their bids without being detected (non-repudiation). The scheme fulfills the requirements of a secure auction scheme and is verifiable. It extends the Stubblebine & Syverson auction scheme that is not equitably fair (it does not prevent bid withdrawals). Our scheme employs a Registrar and an Auctioneer for which no special trust assumptions are made.
Library Management, 2005
The most promising vision of the Web as a place where information is not only human readable but ... more The most promising vision of the Web as a place where information is not only human readable but also computer understandable, together with recent trends in management of diverse, large and computational intensive data resources through distributed grid applications motivated the authors of this paper to introduce a semantic digital library framework based on grid technology. It follows the OGSA specifications for the development of grid infrastructures capable of efficiently handling such information. It is a service-oriented approach based on common Web technologies such as the Web browser and Web server. The design principles of the proposed framework take into account the emerging need to exploit the semantics of its underlying information through the employment of adequate open standard technologies such as RDF and OWL.
Journal of Information and Optimization Sciences, 2005
ABSTRACT We apply digital image processing techniques using the onion algorithm of computational ... more ABSTRACT We apply digital image processing techniques using the onion algorithm of computational geometry to develop fingerprint verification. This paper describes the design and implementation of a fingerprint verification system, which operates in two stages: (i) pre-processing stage (ii) feature extraction using a Computational Geometry Algorithm (CCA). This method may be characterized as an alternative method to well-known minutiae extraction algorithms. In particular, the proposed method is based on specific features, which depend exclusively on the pixels brightness degree of the fingerprint image. These were extracted from a specific geometric area (convex layer) in which the dominant brightness value of the fingerprint ranges. The proposed algorithm is also compared to a well-known commercial verification system which is based on a minutiae extraction algorithm proposed by Jain et al. In the experimental part 2256 verification on tests for each of the two methods took place. The results of this comparison showed that the proposed method yields correct positive and correct negative verification scores greater than 99%. In particular, the proposed CGA method produced extremely reliable results even in cases where the tested fingerprints were complete specimens yet the position or pressure applied wa not consistent. The computational complexity of the proposed aigorithm may also he characterized as extreme competitive.
International Journal of Medical Informatics, 2001
In this paper, a secure medical digital library is presented. It is based on the CORBA specificat... more In this paper, a secure medical digital library is presented. It is based on the CORBA specifications for distributed systems. The described approach relies on a three-tier architecture. Interaction between the medical digital library and its users is achieved through a Web server. The choice of employing Web technology for the dissemination of medical data has many advantages compared to older approaches, but also poses extra requirements that need to be fulfilled. Thus, special attention is paid to the distinguished nature of such medical data, whose integrity and confidentiality should be preserved at all costs. This is achieved through the employment of Trusted Third Parties (TTP) technology for the support of the required security services. Additionally, the proposed digital library employs smartcards for the management of the various security tokens that are used from the above services.
Electronic Commerce Research, 2004
The notion of uncoercibility was first introduced in e-voting systems to deal with the coercion o... more 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 esystems 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 scheme can be used to design provably uncoercible e-auctions and e-voting systems. Finally, we discuss the practical consequences of uncoercibility in other areas of e-commerce.
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Papers by V. Chrissikopoulos