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J. Lopez, and J. E. Rubio, "Access control for cyber-physical systems interconnected to the cloud",
Computer Networks, vol. 134, Elsevier, pp. 46 - 54, 2018. DOI (I.F.: 3.03)More..
Impact Factor: 3.03
Journal Citation Reports® Science Edition (Thomson Reuters, 2018)

PDF icon LOPEZ201846.pdf (311.96 KB)
D. Nuñez, I. Agudo, and J. Lopez, "On the Application of Generic CCA-Secure Transformations to Proxy Re-Encryption",
Security and Communication Networks, vol. 9, issue 12, Wiley, pp. 1769-1785, 08/2016. DOI (I.F.: 1.067)More..


Several generic methods exist for achieving chosen-ciphertext attack (CCA)-secure public-key encryption schemes from weakly secure cryptosystems, such as the Fujisaki–Okamoto and REACT transformations. In the context of proxy re-encryption (PRE), it would be desirable to count on analogous constructions that allow PRE schemes to achieve better security notions. In this paper, we study the adaptation of these transformations to proxy re-encryption and find both negative and positive results. On the one hand, we show why it is not possible to directly integrate these transformations with weakly secure PRE schemes because of general obstacles coming from both the constructions themselves and the security models, and we identify 12 PRE schemes that exhibit these problems. On the other hand, we propose an extension of the Fujisaki–Okamoto transformation for PRE, which achieves a weak form of CCA security in the random oracle model, and we describe the sufficient conditions for applying it

Impact Factor: 1.067
Journal Citation Reports® Science Edition (Thomson Reuters, 2016)

PDF icon nunez2016application.pdf (437.22 KB)
L. Cazorla, C. Alcaraz, and J. Lopez, "Awareness and Reaction Strategies for Critical Infrastructure Protection",
Computers and Electrical Engineering, vol. 47, issue October, Elsevier, pp. 299-317, 2015. DOI (I.F.: 1.084)More..


Current Critical Infrastructures (CIs) need intelligent automatic active reaction mechanisms to protect their critical processes against cyber attacks or system anomalies, and avoid the disruptive consequences of cascading failures between interdependent and interconnected systems. In this paper we study the Intrusion Detection, Prevention and Response Systems (IDPRS) that can offer this type of protection mechanisms, their constituting elements and their applicability to critical contexts. We design a methodological framework determining the essential elements present in the IDPRS, while evaluating each of their sub-components in terms of adequacy for critical contexts. We review the different types of active and passive countermeasures available, categorizing them and assessing whether or not they are suitable for Critical Infrastructure Protection (CIP). Through our study we look at different reaction systems and learn from them how to better create IDPRS solutions for CIP. 

Impact Factor: 1.084
Journal Citation Reports® Science Edition (Thomson Reuters, 2015)

PDF icon cazorla2015b.pdf (469.16 KB)
A. Nieto, and J. Lopez, "Analysis and Taxonomy of Security/QoS tradeoff solutions for the Future Internet",
Security and Communication Networks (SCN) Journal, vol. 7, issue 12, Wiley-Blackwell, pp. 2778-2803, 2013. DOI (I.F.: 0.433)More..


Motivated by the growing convergence of diverse types of networks and the rise of concepts such as Future Internet (FI), in this paper we analyse the coexistence of security mechanisms and Quality of Service (QoS) mechanisms in resourceconstrained networks, that are relevant types of networks within the FI environment. More precisely, we analyse the current state of the research on security and QoS in the integration of Wireless Sensor Networks (WSNs), Mobile Ad-Hoc Networks (MANETs) and cellular networks. Furthermore, we propose a taxonomy to identify similarities among these technologies, as well as the requirements for network interconnection. As a result, we define a dependency-based model for the analysis of Security and QoS tradeoff, and also define a high-level integration architecture for networks in the FI setting. The final goal is to provide a critical point of view that allows to assess whether such an integration of networks can be both secure and efficient.

Impact Factor: 0.433
Journal Citation Reports® Science Edition (Thomson Reuters, 2013)

PDF icon nietoscn13.pdf (1.67 MB)
R. Roman, et al., "Advanced Secure Multimedia Services for Digital Homes",
Information Systems Frontiers, vol. 14, Springer, pp. 527-540, July 2012. DOI (I.F.: 0.851)More..


Our society is becoming increasingly more IT-oriented, and the images and sounds that reflect our daily life are being stored mainly in a digital form. This digital personal life can be part of the home multimedia contents, and users demand access and possibly share these contents (such as photographs, videos, and music) in an ubiquitous way: from any location and with any device. The purpose of this article is twofold. First, we introduce the Feel@Home system, whose main objective is to enable the previously mentioned vision of an ubiquitous digital personal life. Second, we describe the security architecture of Feel@Home, analyzing the security and privacy requirements that identify which threats and vulnerabilities must be considered, and deriving the security building blocks that can be used to protect both IMS-based and VPN-based solutions.

Impact Factor: 0.851
Journal Citation Reports® Science Edition (Thomson Reuters, 2012)

PDF icon Roman2010a.pdf (1.36 MB)
C. Alcaraz, and J. Lopez, "Analysis of Requirements for Critical Control Systems",
International Journal of Critical Infrastructure Protection (IJCIP), vol. 5, Elsevier, pp. 137–145, 2012. DOI (I.F.: 0.63)More..


The use of modern information and communications technologies in supervisory control and data acquisition (SCADA) systems used in the critical infrastructure has become an important topic of research. The modernization significantly enhances operational performance, but also introduces security issues and the associated risks. This paper formally analyzes how the introduction of new technologies can impact control systems and ultimately affect the performance of the critical infrastructure systems being controlled. Five control system requirements are identified with the goal of proposing new operational requirements that trade-off performance and security.

Impact Factor: 0.63
Journal Citation Reports® Science Edition (Thomson Reuters, 2012)

PDF icon 1730.pdf (705.14 KB)
R. Rios, and J. Lopez, "Analysis of Location Privacy Solutions in Wireless Sensor Networks",
IET Communications, vol. 5, Institution of Engineering and Technology, pp. 2518 - 2532, Nov 2011. DOI (I.F.: 0.829)More..


Extensive work has been done on the protection of Wireless Sensor Networks (WSNs) from the hardware to the application layer. However, only recently, the privacy preservation problem has drawn the attention of the research community because of its challenging nature. This problem is exacerbated in the domain of WSNs due to the extreme resource limitation of sensor nodes. In this paper we focus on the location privacy problem in WSNs, which allows an adversary to determine the location of nodes of interest to him. We provide a taxonomy of solutions based on the power of the adversary and the main techniques proposed by the various solutions. In addition, we describe and analyse the advantages and disadvantages of different approaches. Finally, we discuss some open challenges and future directions of research.

Impact Factor: 0.829
Journal Citation Reports® Science Edition (Thomson Reuters, 2011)

PDF icon Rios2011a.pdf (597.01 KB)
D. G. Rosado, E. Fernandez-Medina, J. Lopez, and M. Piattini, "Analysis of Secure Mobile Grid Systems: A Systematic Approach",
Information and Software Technology, vol. 52, Elsevier, pp. 517-536, May 2010. DOI (I.F.: 1.527)More..


Developing software through systematic processes is becoming more and more important due to the growing complexity of software development. It is important that the development process used integrates security aspects from the first stages at the same level as other functional and non-functional requirements. Systems which are based on Grid Computing are a kind of systems that have clear differentiating features in which security is a highly important aspect. The Mobile Grid, which is relevant to both Grid and Mobile Computing, is a full inheritor of the Grid with the additional feature that it supports mobile users and resources. A development methodology for Secure Mobile Grid Systems is proposed in which the security aspects are considered from the first stages of the life-cycle and in which the mobile Grid technological environment is always present in each activity. This paper presents the analysis activity, in which the requirements (focusing on the grid, mobile and security requirements) of the system are specified and which is driven by reusable use cases through which the requirements and needs of these systems can be defined. These use cases have been defined through a UML-extension for security use cases and Grid use cases which capture the behaviour of this kind of systems. The analysis activity has been applied to a real case.

Impact Factor: 1.527
Journal Citation Reports® Science Edition (Thomson Reuters, 2010)

Y.. Qiu, J.. Zhou, J.. Baek, and J. Lopez, "Authentication and Key Establishment in Dynamic Wireless Sensor Networks",
Sensors, vol. 10, pp. 3718-3731, 2010. More..
PDF icon 1694.pdf (325.85 KB)
V. Benjumea, J. Lopez, and J. M. Troya, "Anonymity Analysis in Credentials-based Systems: A Formal Framework",
Computer Standards & Interfaces, vol. 30, no. 4, Elsevier, pp. 253-261, 2008. (I.F.: 1.074)More..


  Anonymity has been formalized and some metrics have been defined in the scope of anonymizing communication channels. In this paper, such formalization has been extended to cope with anonymity in those scenarios where users must anonymously prove that they own certain privileges to perform remote transactions. In these types of scenarios, the authorization policy states the privileges required to perform a given remote transaction. The paper presents a framework to analyze the actual degree of anonymity reached in a given transaction and allows its comparison with an ideal anonymity degree as defined by the authorization policy, providinga tool to model, design and analyze anonymous systems in different scenarios.    

Impact Factor: 1.074
Journal Citation Reports® Science Edition (Thomson Reuters, 2008)

PDF icon VicenteBenjumea2008.pdf (248.09 KB)
V. Benjumea, J. Lopez, and J. M. Troya, "Anonymous Attribute Certificates based on Traceable Signatures",
Internet Research, vol. 16, no. 2, Elsevier, pp. 120-139, 2006. (I.F.: 0.607)More..


  In Benjumea et. al (Benjumea, 2004) we introduced the concept of anonymousattribute certificates in order to integrate anonymity capabilities in the standardizedX.509 attribute certificates. That solution was based on the use of fair-blind signatures(Stadler, 1995), but did not explore further possibilities of constructing similar datastructures based on more advanced signature schemes. In this new work, we propose anew type of anonymous attribute certificates that is based on the more recently proposedtraceable signature scheme (Kiayias, 2004a), providing a new anonymous authorizationsolution with interesting features that were not covered in the aforementioned scheme.Thus, this new solution allows users to make use of their attribute certificates in ananonymous way, but under certain circumstances it allows to disclose the users’ identities,trace the transactions carried out by any specific user, or revoke any anonymousattribute certificate. An additional contribution of this work is that it pays special attentionto the preservation of the unlinkability property between transactions, makingimpossible the creation of anonymous user profiles.

Impact Factor: 0.607
Journal Citation Reports® Science Edition (Thomson Reuters, 2006)

PDF icon VicenteBenjumea2006a.pdf (320.1 KB)
R. Roman, J. Zhou, and J. Lopez, "An Anti-spam Scheme Using Pre-challenges",
Computer Communications, vol. 29, no. 15, Elsevier, pp. 2739-2749, 2006. DOI (I.F.: 0.444)More..


Unsolicited Commercial Email, or Spam, is nowadays an increasingly serious problem to email users. A number of anti-spam schemes have been proposed in the literature and some of them have been deployed in email systems, but the problem has yet been well addressed. One of those schemes is challenge-response, in which a challenge, ranging from a simple mathematical problem to a hard-AI problem, is imposed on an email sender in order to forbid machine-based spam reaching receivers’ mailboxes. However, such a scheme introduces new problems for the users, e.g., delay of service and denial of service. In this paper, we introduce the pre-challenge scheme, which is based on the challenge-response mechanism and takes advantage of some features of email systems. It assumes each user has a challenge that is defined by the user himself/herself and associated with his/her email address, in such a way that an email sender can simultaneously retrieve a new receiver’s email address and challenge before sending an email in the first contact. Some new mechanisms are employed in our scheme to reach a good balance between security against spam and convenience to normal email users. Our scheme can be also used for protecting other messaging systems, like Instant Messaging and Blog comments.

Impact Factor: 0.444
Journal Citation Reports® Science Edition (Thomson Reuters, 2006)

PDF icon Roman2006a.pdf (355.8 KB)
J. A. Onieva, J. Zhou, J. Lopez, and M. Carbonell, "Agent-mediated non-repudiation protocols",
Electronic Commerce Research and Applications, vol. 3, no. 2, Elsevier, pp. 152-162, 2004. More..


Non-repudiation is a security service that provides cryptographic evidence to support the settlement of disputes in electronic commerce. In commercial transactions, an intermediary (or agent) might be involved to help transacting parties to conduct their business. Nevertheless, such an intermediary may not be fully trusted. In this paper, we propose agent-mediated non-repudiation protocols and analyze their security requirements. We first present a simple scenario with only one recipient, followed by a more complicated framework where multiple recipients are involved and collusion between them is possible. We also identify applications that could take advantage of these agent-mediated non-repudiation protocols.

PDF icon Onieva2004a.pdf (196.82 KB)
J. Lopez, R. Oppliger, and G. Pernul, "Authentication and Authorization Infrastructures (AAIs): A Comparative Survey",
Computers & Security, vol. 23, no. 7, Elsevier, pp. 578-590, 2004. (I.F.: 0.412)More..


In this article, we argue that traditional approaches for authorization and access control in computer systems (i.e., discretionary, mandatory, and role-based access controls) are not appropriate to address the requirements of networked or distributed systems, and that proper authorization and access control requires infrastructural support in one way or another. This support can be provided, for example, by an authentication and authorization infrastructure (AAI). Against this background, we overview, analyze, discuss, and put into perspective some technologies that can be used to build and operate AAIs. More specifically, we address Microsoft .NET Passport and some related activities (e.g. the Liberty Alliance Project), Kerberos-based solutions, and AAIs that are based on digital certificates and public key infrastructures (PKIs). We conclude with the observation that there is no single best approach for providing an AAI, that every approach has specific advantages and disadvantages, and that a comprehensive AAI must combine various technologies and approaches.

Impact Factor: 0.412
Journal Citation Reports® Science Edition (Thomson Reuters, 2004)

PDF icon JavierLopez2004.pdf (2.22 MB)
S. Gurgens, J. Lopez, and R. Peralta, "Analysis of E-commerce Protocols: Adapting a Traditional Technique",
International Journal of Information Security, vol. 2, no. 1, Springer, pp. 21-36, 2003. More..


We present the adaptation of our model for the validation of key distribution and authentication protocols to address some of the specific needs of protocols for electronic commerce. The two models defer in both the threat scenario and in the protocol formalization. We demonstrate the suitability of our adaptation by analyzing a specific version of the Internet Billing Server protocol introduced by Carnegie MellonUniversity. Our analysis shows that, while the security properties a key distribution or authentication protocol shall provide are well understood, it is often not clear which properties an electronic commerce protocol can or shall provide. We use the automatic theorem proving software ‘‘Otter’’ developed at Argonne National Laboratories for state space exploration.

PDF icon SigridGuergens2003.pdf (222.22 KB)
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