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D. Nuñez, and I. Agudo, "BlindIdM: A Privacy-Preserving Approach for Identity Management as a Service",
International Journal of Information Security, vol. 13, issue 2, Springer, pp. 199-215, 2014. DOI (I.F.: 0.963)More..


Identity management is an almost indispensable component of today’s organizations and companies, as it plays a key role in authentication and access control; however, at the same time it is widely recognized as a costly and time-consuming task. The advent of cloud computing technologies, together with the promise of flexible, cheap and efficient provision of services, has provided the opportunity to externalize such a common process, shaping what has been called Identity Management as a Service (IDaaS). Nevertheless, as in the case of other cloud-based services, IDaaS brings with it great concerns regarding security and privacy, such as the loss of control over the outsourced data. In this paper we analyze these concerns and propose BlindIdM, a model for privacy-preserving IDaaS with a focus on data privacy protection. In particular, we describe how a SAML-based system can be augmented to employ proxy re-encryption techniques for achieving data condentiality with respect to the cloud provider, while preserving the ability to supply the identity service. This is an innovative contribution to both the privacy and identity management landscapes.

Impact Factor: 0.963
Journal Citation Reports® Science Edition (Thomson Reuters, 2014)

PDF icon nunez2014blindidm.pdf (628.97 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)
D. Nuñez, C. Fernandez-Gago, and J. Luna, "Eliciting Metrics for Accountability of Cloud Systems",
Computers & Security, vol. 62, Elsevier, pp. 149-164, 08/2016. DOI (I.F.: 2.849)More..


Cloud computing provides enormous business opportunities, but at the same time is a complex and challenging paradigm. The major concerns for users adopting the cloud are the loss of control over their data and the lack of transparency. Providing accountability to cloud systems could foster trust in the cloud and contribute toward its adoption. Assessing how accountable a cloud provider is becomes then a key issue, not only for demonstrating accountability, but to build it. To this end, we need techniques to measure the factors that influence on accountability. In this paper, we provide a methodology to elicit metrics for accountability in the cloud, which consists of three different stages. Since the nature of accountability at- tributes is very abstract and complex, in the first stage we perform a conceptual analysis of the accountability attributes in order to decompose them into concrete practices and mechanisms. Then, we analyze relevant control frameworks designed to guide the implementation of security and privacy mechanisms, and use them to identify measurable factors, related to the practices and mechanisms defined earlier. Lastly, specific metrics for these factors are derived. We also provide some strategies that we consider relevant for the empirical validation of the elicited accountability metrics. 

Impact Factor: 2.849
Journal Citation Reports® Science Edition (Thomson Reuters, 2016)

PDF icon nunez2016eliciting.pdf (460.29 KB)
D. Nuñez, I. Agudo, and J. Lopez, "Escrowed decryption protocols for lawful interception of encrypted data",
IET Information Security, vol. 13, issue 5, IET, pp. 498 -- 507, 09/2019. More..


Escrowed decryption schemes (EDSs) are public-key encryption schemes with an escrowed decryption functionality that allows authorities to decrypt encrypted messages under investigation, following a protocol that involves a set of trusted entities called `custodians'; only if custodians collaborate, the requesting authority is capable of decrypting encrypted data. This type of cryptosystem represents an interesting trade-off to privacy versus surveillance dichotomy. In this study, the authors propose two EDSs where they use proxy re-encryption to build the escrowed decryption capability, so that custodians re-encrypt ciphertexts, in a distributed way, upon request from an escrow authority, and the re-encrypted ciphertexts can be opened only by the escrow authority. Their first scheme, called EDS, follows an all-or-nothing approach, which means that escrow decryption only works when all custodians collaborate. Their second scheme, called threshold EDS, supports a threshold number of custodians for the escrow decryption operation. They propose definitions of semantic security with respect to the authorities, custodians and external entities, and prove the security of their schemes, under standard pairing-based hardness assumptions. Finally, they present a theoretical and experimental analysis of the performance of both schemes, which show that they are applicable to real-world scenarios.

D. Nuñez, I. Agudo, and J. Lopez, "Proxy Re-Encryption: Analysis of Constructions and its Application to Secure Access Delegation",
Journal of Network and Computer Applications, vol. 87, Elsevier, pp. 193-209, 06/2017. DOI (I.F.: 3.991)More..


This paper analyzes the secure access delegation problem, which occurs naturally in the cloud, and postulate that Proxy Re-Encryption is a feasible cryptographic solution, both from the functional and efficiency perspectives. Proxy re-encryption is a special type of public-key encryption that permits a proxy to transform ciphertexts from one public key to another, without the proxy being able to learn any information about the original message. Thus, it serves as a means for delegating decryption rights, opening up many possible applications that require of delegated access to encrypted data. In particular, sharing information in the cloud is a prime example. In this paper, we review the main proxy re-encryption schemes so far, and provide a detailed analysis of their characteristics. Additionally, we also study the efficiency of selected schemes, both theoretically and empirically, based on our own implementation. Finally, we discuss some applications of proxy re-encryption, with a focus on secure access delegation in the cloud. 

Impact Factor: 3.991
Journal Citation Reports® Science Edition (Thomson Reuters, 2017)

PDF icon nunez2017proxy.pdf (687.13 KB)
N. Nomikos, et al., "Relay Selection for Secure 5G Green Communications",
Telecommunication Systems , vol. 59, issue 1, Springer US, pp. 169-187, 05/2015. DOI (I.F.: 0.822)More..


In this article, we present relay selection policies in applications with secrecy requirements which are of interest in the fifth generation (5G) of wireless networks. More specifically, we provide a classification of relays based on their distinct communication attributes, such as processing, multiple antennas, storage, channel estimation, density and security level. In addition, we discuss the level of efficiency exhibited by each relay class, regarding their impact in delay-critical applications and green communications applications, while aiming at a specific security level at the physical layer. Then, relay selection policies are proposed taking into consideration the goals set by each application. Numerical evaluation of the proposed policies in terms of the average secrecy rate, average delay and power reduction show improved performance compared to other state-of-the-art solutions. 

Impact Factor: 0.822
Journal Citation Reports® Science Edition (Thomson Reuters, 2015)

A. Nieto, "Becoming JUDAS: Correlating Users and Devices during a Digital Investigation",
IEEE Transactions on Information Forensics & Security, vol. 15, IEEE, pp. 3325-3334, 17/04/2020. DOI (I.F.: 7.178)More..


One of the biggest challenges in IoT-forensics is the analysis and correlation of heterogeneous digital evidence, to enable an effective understanding of complex scenarios. This paper defines a methodology for extracting unique objects (e.g., representing users or devices) from the files of a case, defining the context of the digital investigation and increasing the knowledge progressively, using additional files from the case (e.g. network captures). The solution includes external searches using open source intelligence (OSINT) sources when needed. In order to illustrate this approach, the proposed methodology is implemented in the JSON Users and Devices analysis (JUDAS) tool, which is able to generate the context from JSON files, complete it, and show the whole context using dynamic graphs. The approach is validated using the files in an IoT-Forensic digital investigation where an important set of potential digital evidence extracted from Amazon’s Alexa Cloud is analysed.

Impact Factor: 7.178
Journal Citation Reports® Science Edition (Thomson Reuters, 2020)

PDF icon JUDAS2020.pdf (9.25 MB)
A. Nieto, R. Roman, and J. Lopez, "Testificación Digital",
Revista SIC, vol. 122, Ediciones CODA, pp. 94-98, Nov 2016. More..


El creciente número de dispositivos interconectados trae consigo problemas de seguridad bien conocidos; por ejemplo, aquellos debidos a las vulnerabilidades en protocolos muy diversos –muchos de ellos propietarios– y al factor de error humano introducido por los usuarios. Sin embargo, cabe preguntarse cómo podemos usar el despliegue de tales dispositivos en beneficio de la ciberseguridad. En el proyecto IoTest se está desarrollando una solución, el Testigo Digital, que permitirá a los dispositivos personales con arquitectura de seguridad embebida reaccionar ante ataques virtuales, protegiéndonos de los ciberataques emergentes.

PDF icon nrlSIC16.pdf (476.98 KB)
A. Nieto, N. Nomikos, J. Lopez, and C. Skianis, "Dynamic Knowledge-based Analysis in non-Secure 5G Green Environments using Contextual Data",
IEEE Systems Journal, vol. 11, issue 4, no. 99, IEEE, pp. 2479-2489, 12/2017. DOI (I.F.: 4.337)More..


The growing number of parameters in heteroge- neous networks, as is the case of the fifth generation (5G) Green networks, greatly complicates the analysis of the Security and Quality of Service Tradeoff (SQT). However, studying these types of relationships is crucial in Future Internet scenarios to prevent potential points of failure and to enhance the use of limited resources, increasing the user’s experience. Therefore, it is fundamental to provide tools and models for training, so that the users understand these dependencies and solve them prior to deploying new solutions. In this paper, a Recommendation System for SQT (SQT-RS) is deployed in 5G Green systems, considering the particular case of relay networks and the impact of eavesdropping and jamming contexts on the models generated by the user, aided by SQT-RS. With this goal in mind, we provide a component for the user to automatically select specific contexts based on 5G Green capabilities. 

Impact Factor: 4.337
Journal Citation Reports® Science Edition (Thomson Reuters, 2017)

PDF icon NietNLS15.pdf (1.13 MB)
A. Nieto, and R. Rios, "Cybersecurity Profiles based on Human-Centric IoT Devices",
Human-centric Computing and Information Sciences, vol. 9, no. 1, Springer, pp. 1-23, 2019. DOI (I.F.: 3.7)More..
Impact Factor: 3.7
Journal Citation Reports® Science Edition (Thomson Reuters, 2019)

PDF icon HFNR2019.pdf (2.92 MB)
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)
A. Nieto, R. Roman, and J. Lopez, "Digital Witness: Safeguarding Digital Evidence by using Secure Architectures in Personal Devices",
IEEE Network, IEEE Communications Society, pp. 12-19, 2016. DOI (I.F.: 7.230)More..


Personal devices contain electronic evidence associated with the behaviour of their owners and other devices in their environment, which can help clarify the facts of a cyber-crime scene. These devices are usually analysed as containers of proof. However, it is possible to harness the boom of personal devices to define the concept of digital witnesses, where personal devices are able to actively acquire, store, and transmit digital evidence to an authorised entity, reliably and securely. This article introduces this novel concept, providing a preliminary analysis on the management of digital evidence and the technologies that can be used to implement it with security guarantees in IoT environments. Moreover, the basic building blocks of a digital witness are defined.

Impact Factor: 7.230
Journal Citation Reports® Science Edition (Thomson Reuters, 2016)

PDF icon ieeenet16-nrl.pdf (1002.02 KB)
A. Nieto, and J. Lopez, "Contextualising Heterogeneous Information in Unified Communications with Security Restrictions",
Computer Communications, vol. 68, Elsevier, pp. 33-46, 09/2015. DOI (I.F.: 2.099)More..


The lack of abstraction in a growing semantic, virtual and abstract world poses new challenges for assessing security and QoS tradeoffs. For example, in Future Internet scenarios, where Unified Communications (UC) will take place, being able to predict the final devices that will form the network is not always possible. Without this information the analysis of the security and QoS tradeoff can only be based on partial information to be completed when more information about the environment is available. In this paper, we extend the description of context-based parametric relationship model, providing a tool for assessing the security and QoS tradeoff (SQT) based on interchangeable contexts. Our approach is able to use the heterogeneous information produced by scenarios where UC is present.

Impact Factor: 2.099
Journal Citation Reports® Science Edition (Thomson Reuters, 2015)

PDF icon NL-COMCOM15.pdf (2 MB)
A. Nieto, A. Acien, and G. Fernandez, "Crowdsourcing analysis in 5G IoT: Cybersecurity Threats and Mitigation",
Mobile Networks and Applications (MONET), Springer US, pp. 881-889, 10/2018. DOI (I.F.: 2.39)More..


Crowdsourcing can be a powerful weapon against cyberattacks in 5G networks. In this paper we analyse this idea in detail, starting from the use cases in crowdsourcing focused on security, and highlighting those areas of a 5G ecosystem where crowdsourcing could be used to mitigate local and remote attacks, as well as to discourage criminal activities and cybercriminal behaviour. We pay particular attention to the capillary network, where an infinite number of IoT objects coexist. The analysis is made considering the different participants in a 5G IoT ecosystem.

Impact Factor: 2.39
Journal Citation Reports® Science Edition (Thomson Reuters, 2018)

PDF icon NAFMONET2018.pdf (1.04 MB)
A. Nieto, R. Rios, and J. Lopez, "IoT-Forensics meets Privacy: Towards Cooperative Digital Investigations",
Sensors, vol. 18, issue 2, no. 492, MDPI, 02/2018. DOI (I.F.: 3.031)More..


IoT-Forensics is a novel paradigm for the acquisition of electronic evidence whose operation is conditioned by the peculiarities of the Internet of Things (IoT) context. As a branch of computer forensics, this discipline respects the most basic forensic principles of preservation, traceability, documentation, and authorization. The digital witness approach also promotes such principles in the context of the IoT while allowing personal devices to cooperate in digital investigations by voluntarily providing electronic evidence to the authorities. However, this solution is highly dependent on the willingness of citizens to collaborate and they may be reluctant to do so if the sensitive information within their personal devices is not sufficiently protected when shared with the investigators. In this paper, we provide the digital witness approach with a methodology that enables citizens to share their data with some privacy guarantees. We apply the PRoFIT methodology, originally defined for IoT-Forensics environments, to the digital witness approach in order to unleash its full potential. Finally, we show the feasibility of a PRoFIT-compliant digital witness with two use cases.

Impact Factor: 3.031
Journal Citation Reports® Science Edition (Thomson Reuters, 2018)

PDF icon nrlSensors2018.pdf (14.4 MB)
A. Nieto, and J. Lopez, "A Model for the Analysis of QoS and Security Tradeoff in Mobile Platforms",
Mobile Networks and Applications (MONET) Journal, vol. 19, issue 1, Springer US, pp. 64-78, 02/2014. DOI (I.F.: 1.045)More..


Today, mobile platforms are multimedia devices that provide different types of traffic with the consequent particular performance demands and, besides, security concerns (e.g. privacy). However, Security and QoS requirements quite often conflict to a large degree; the mobility and heterogeneous paradigm of the Future Internet makes coexistence even more difficult, posing new challenges to overcome. Probably, one of the main challenges is to identify the specific reasons why Security and QoS mechanisms are so related to each other. In this paper, we present a Parametric Relationship Model (PRM) to identify the Security and QoS dependencies, and to elaborate on the Security and QoS tradeoff. In particular, we perform an analysis that focus on the mobile platform environment and, consequently, also considers subjective parameters such user’s experience, that is crucial for increasing the usability of new solutions in the Future Internet. The final aim of our contribution is to facilitate the development of secure and efficient services for mobile platforms.

Impact Factor: 1.045
Journal Citation Reports® Science Edition (Thomson Reuters, 2014)

PDF icon nieto2013mone.pdf (666.18 KB)
A. Nieto, R. Roman, and J. Lopez, "Digital Witness: Digital Evidence Management Framework for the Internet of Things",
ERCIM News, no. 106, ERCIM EEIG, pp. 9-9, 07/2016.
P. Najera, and J. Lopez, "Real-time Location and Inpatient Care Systems Based on Passive RFID",
Journal of Network and Computer Applications, vol. 34, Elsevier, pp. pp. 980-989, 2011. DOI (I.F.: 1.065)More..


RFID technology meets identification and tracking requirements in healthcare environments with potential to speed up and increase reliability of involved processes. Due to this, high expectations for this integration have emerged, but hospital and medical centers interested in adoption of RFID technology require prior knowledge on how to squeeze RFID capabilities, real expectations and current challenges. In this paper, we show our lab tested solutions in two specific healthcare scenarios. On the one hand, we analyze the case of a medical equipment tracking system for healthcare facilities enabling both real-time location and theft prevention. Worth-noting aspects such as possible EMI interferences, technology selection and management of RFID data from hospital information system are analyzed. Lab testing of system reliability based on passive UHF RFID is provided for this case. On the other hand, we analyze and provide a solution for care and control of patients in a hospital based on passive HF RFID with the result of a fully functional demonstrator. Our prototype squeezes RFID features in order to provide a backup data source from patient’s wristband. It also provides an offline working mode aiming to increase application reliability under network fail down and therefore, improving patient’s safety. Considerations regarding lessons learned and challenges faced are exposed.

Impact Factor: 1.065
Journal Citation Reports® Science Edition (Thomson Reuters, 2011)

PDF icon Najera2010.pdf (241.66 KB)
P. Najera, R. Roman, and J. Lopez, "User-centric secure integration of personal RFID tags and sensor networks",
Security and Communication Networks, vol. 6, Wiley-Blackwell, pp. 1177–1197, Oct 2013. DOI (I.F.: 0.433)More..


A personal network (PN) should enable the collaboration of user’s devices and services in a flexible, self-organizing and friendly manner. For such purpose, the PN must securely accommodate heterogeneous technologies with uneven computational and communication resources. In particular, personal RFID tags can enable seamless recognition of user’s context, provide user authentication and enable novel services enhancing the quality and quantity of data handled by the PN. However, the highly constrained features of common RFID tags and their passive role in the network highlights the need of an adequate secure communication model with personal tags which enables their participation as a member of the PN. In this paper, we present our concept of PN, with special emphasis on the role of RFID and sensor networks, and define a secure architecture for PNs including methods for the secure access to context-aware technologies from both local PN members and the Internet of Things. The PN architecture is designed to support differentiated security mechanisms to maximize the level of security for each type of personal device. Furthermore, we analyze which security solutions available in the literature can be adapted for our architecture, as well as the challenges and security mechanisms still necessary in the secure integration of personal tags.

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

P. Najera, F. Moyano, and J. Lopez, "Security Mechanisms and Access Control Infrastructure for e-Passports and General Purpose e-Documents",
Journal of Universal Computer Science, vol. 15, pp. 970-991, 2009. DOI (I.F.: 0.669)More..


Traditional paper documents are not likely to disappear in the near future as they are present everywhere in daily life, however, paper-based documentation lacks the link with the digital world for agile and automated processing. At the same time it is prone to cloning, alteration and counterfeiting attacks. E-passport defined by ICAO and implemented in 45 countries is the most relevant case of hybrid documentation (i.e. paper format with electronic capabilities) to date, but, as the advantages of hybrid documentation are recognized more and more will undoubtedly appear. In this paper, we present the concept and security requirements of general-use e-documents, analyze the most comprehensive security solution (i.e. ePassport security mechanisms) and its suitability for general-purpose e-documentation. Finally, we propose alternatives for the weakest and less suitable protocol from ePassports: the BAC (Basic Access Control). In particular, an appropriate key management infrastructure for access control to document memory is discussed in conjunction with a prototype implementation.

Impact Factor: 0.669
Journal Citation Reports® Science Edition (Thomson Reuters, 2009)

PDF icon Najera2009.pdf (293.84 KB)