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2018
R. Rios, C. Fernandez-Gago, and J. Lopez, "Modelling Privacy-Aware Trust Negotiations",
Computers & Security, vol. 77 , issue August 2018, Elsevier, pp. 773-789, 2018. DOI (I.F.: 2.650)More..

Abstract

Trust negotiations are mechanisms that enable interaction between previously unknown users. After exchanging various pieces of potentially sensitive information, the participants of a negotiation can decide whether or not to trust one another. Therefore, trust negotiations bring about threats to personal privacy if not carefully considered. This paper presents a framework for representing trust negotiations in the early phases of the Software Development Life Cycle (SDLC). The framework can help software engineers to determine the most suitable policies for the system by detecting conflicts between privacy and trust requirements. More precisely, we extend the SI* modelling language and provide a set of predicates for defining trust and privacy policies and a set of rules for describing the dynamics of the system based on the established policies. The formal representation of the model facilitates its automatic verification. The framework has been validated in a distributed social network scenario for connecting drivers with potential passengers willing to share a journey.

Impact Factor: 2.650
Journal Citation Reports® Science Edition (Thomson Reuters, 2017)

PDF icon Ruben2017trust.pdf (425.82 KB)
M. Kolar, C. Fernandez-Gago, and J. Lopez, "Policy Languages and Their Suitability for Trust Negotiation",
32nd Annual IFIP WG 11.3 Conference on Data and Applications Security and Privacy XXXII, 2018, vol. 10980, Springer, Cham, pp. 69-84, 07/2018. DOI More..

Abstract

Entities, such as people, companies, institutions, authorities and web sites live and exist in a conjoined world. In order to live and enjoy social benefits, entities need to share knowledge, resources and to cooperate together. The cooperation brings with it many new challenges and problems, among which one is the problem of trust. This area is also important for the Computer Science. When unfamiliar entities wish to cooperate, they do not know what to expect nor whether they can trust each other. Trust negotiation solves this problem by sequential exchanging credentials between entities, which have decided to establish a trust relationship in order to reach a common goal. Entities specify their own policies that handle a disclosure of confidential information to maintain their security and privacy. Policies are defined by means of a policy language. This paper aims to identify the most suitable policy language for trust negotiation. To do so, policy languages are analysed against a set of criteria for trust negotiation that are first established.

PDF icon kolar2018.pdf (242.31 KB)
D. Ferraris, C. Fernandez-Gago, and J. Lopez, "A Trust-by-Design Framework for the Internet of Things",
2018 9th IFIP International Conference on New Technologies Mobility and Security (NTMS), IEEE, 04/2018. DOI More..

Abstract

The Internet of Things (IoT) is an environment of interconnected entities, that are identifiable, usable and controllable via the Internet. Trust is necessary in a system such as IoT as the entities involved should know the effect of interacting with other entities. Moreover, the entities must also be able to trust a system to reliably use it. An IoT system is composed of different entities from different vendors, each of them with a different purpose and a different lifecycle. So considering trust in the whole IoT system lifecycle is useful and necessary to guarantee a good service for the whole system. The heterogeneity and dynamicity of this field make it difficult to ensure trust in IoT. We propose a trust by design framework for including trust in the development of an IoT entity considering all the phases of the life-cycle. It is composed of the K-Model and transversal activities.

PDF icon 1684.pdf (165.19 KB)
2017
C. Fernandez-Gago, F. Moyano, and J. Lopez, "Modelling Trust Dynamics in the Internet of Things",
Information Sciences, vol. 396, Elsevier, pp. 72-82, 2017. DOI (I.F.: 4.305)More..

Abstract

The Internet of Things (IoT) is a paradigm based on the interconnection of everyday objects. It is expected that the ‘things’ involved in the IoT paradigm will have to interact with each other, often in uncertain conditions. It is therefore of paramount importance for the success of IoT that there are mechanisms in place that help overcome the lack of certainty. Trust can help achieve this goal. In this paper, we introduce a framework that assists developers in including trust in IoT scenarios. This framework takes into account trust, privacy and identity requirements as well as other functional requirements derived from IoT scenarios to provide the different services that allow the inclusion of trust in the IoT.

Impact Factor: 4.305
Journal Citation Reports® Science Edition (Thomson Reuters, 2017)

PDF icon Fer_IS17.pdf (1002.43 KB)
2016
F. Moyano, C. Fernandez-Gago, and J. Lopez, "A Model-driven Approach for Engineering Trust and Reputation into Software Services",
Journal of Network and Computer Applications, vol. 69, Elsevier, pp. 134-151, 04/2016. (I.F.: 3.500)More..
Impact Factor: 3.500
Journal Citation Reports® Science Edition (Thomson Reuters, 2016)

PDF icon JNCA16.pdf (613.36 KB)
R. Rios, C. Fernandez-Gago, and J. Lopez, "Privacy-Aware Trust Negotiation",
12th International Workshop on Security and Trust Management (STM), vol. LNCS 9871, Springer, pp. 98-105, 09/2016. DOI More..

Abstract

Software engineering and information security have traditionally followed divergent paths but lately some efforts have been made to consider security from the early phases of the Software Development Life Cycle (SDLC). This paper follows this line and concentrates on the incorporation of trust negotiations during the requirements engineering phase. More precisely, we provide an extension to the SI* modelling language, which is further formalised using answer set programming specifications to support the automatic verification of the model and the detection of privacy conflicts caused by trust negotiations.

PDF icon rios2016b.pdf (237.78 KB)
2015
F. Moyano, C. Fernandez-Gago, K. Beckers, and M. Heisel, "Engineering Trust- and Reputation-based Security Controls for Future Internet Systems",
The 30th ACM/SIGAPP Symposium On Applied Computing (SAC 2015), pp. 1344-1349, 08/2015. DOI More..
PDF icon moyano15SAC.pdf (284.13 KB)
2014
C. Fernandez-Gago, I. Agudo, and J. Lopez, "Building Trust from Context Similarity Measures",
Computer Standards & Interfaces, Special Issue on Security in Information Systems, vol. 36, issue 4, Elsevier, pp. 792-800, 2014. DOI (I.F.: 0.879)More..

Abstract

 Trust is an essential feature of any system where entities have to collaborate among them. Trust can assist entities making decisions about what is the best entity for establishing a certain collaboration. It would be desirable to simulate behaviour of users as in social environments where they tend to establish relationships or to trust users who have common interests or share some of their opinions, i.e., users who are similar to them to some extent. Thus, in this paper we first introduce the concept of context similarity among entities and from it we derive a similarity network which can be seen as a graph. Based on this similarity network we dene a trust model that allows us also to establish trust along a path of entities. A possible applications of our model are proximity-based trust establishment. We validate our model in this scenario.

 

Impact Factor: 0.879
Journal Citation Reports® Science Edition (Thomson Reuters, 2014)

PDF icon CSI13.pdf (573.29 KB)
F. Moyano, C. Fernandez-Gago, B. Baudry, and J. Lopez, "Engineering Trust-Awareness and Self-adaptability in Services and Systems",
Engineering Secure Future Internet Services and Systems, vol. LNCS 8431, no. 8431, Springer, pp. 180-209, 03/2014. DOI More..

Abstract

The Future Internet (FI) comprises scenarios where many heterogeneous and dynamic entities must interact to provide services (e.g., sensors, mobile devices and information systems in smart city scenarios). The dynamic conditions under which FI applications must execute call for self-adaptive software to cope with unforeseeable changes in the application environment. Models@run.time is a promising model-driven approach that supports the runtime adaptation of distributed, heterogeneous systems. Yet frameworks that accommodate this paradigm have limited support to address security concerns, hindering their usage in real scenarios. We address this challenge by enhancing models@run.time with the concepts of trust and reputation. Trust improves decision-making processes under risk and uncertainty and constitutes a distributed and flexible mechanism that does not entail heavyweight administration. This chapter introduces a trust and reputation framework that is integrated into a distributed component model that implements the models@run.time paradigm, thus allowing software components to include trust in their reasoning process. The framework is illustrated in a smart grid scenario.

PDF icon moyano14esfi.pdf (3.2 MB)
F. Moyano, C. Fernandez-Gago, K. Beckers, and M. Heisel, "Enhancing Problem Frames with Trust and Reputation for Analyzing Smart Grid Security Requirements",
Smart Grid Security - Second International Workshop, J. Cuellar Eds., LNCS 8448, Springer, pp. 166-180, Aug, 2014. DOI More..
PDF icon moyano14smartgridsec.pdf (404.33 KB)
F. Moyano, K. Beckers, and C. Fernandez-Gago, "Trust-Aware Decision-Making Methodology for Cloud Sourcing",
26th International Conference on Advanced Information Systems Engineering (CAiSE 2014), M. Jarke, et al. Eds., LCNS 8484, Springer, pp. 136-149, 06/2014. DOI More..

Abstract

Cloud sourcing consists of outsourcing data, services and infrastructure to cloud providers. Even when this outsourcing model brings advantages to cloud customers, new threats also arise as sensitive data and critical IT services are beyond customers' control. When an organization considers moving to the cloud, IT decision makers must select a cloud provider and must decide which parts of the organization will be outsourced and to which extent. This paper proposes a methodology that allows decision makers to evaluate their trust in cloud providers. The methodology provides a systematic way to elicit knowledge about cloud providers, quantify their trust factors and aggregate them into trust values that can assist the decision-making process. The trust model that we propose is based on trust intervals, which allow capturing uncertainty during the evaluation, and we define an operator for aggregating these trust intervals. The methodology is applied to an eHealth scenario.

PDF icon moyano14caise.pdf (333.6 KB)
2013
F. Moyano, C. Fernandez-Gago, and J. Lopez, "Building Trust and Reputation In: A Development Framework for Trust Models Implementation",
8th International Workshop on Security and Trust Management (STM 2012), A. Jøsang, P. Samarati, and M. Petrocchi Eds., LNCS 7783, Springer, pp. 113-128, 2013. DOI More..

Abstract

During the last years, many trust and reputation models have been proposed, each one targeting different contexts and purposes, and with their own particularities. While most contributions focus on defining ever-increasing complex models, little attention has been paid to the process of building these models inside applications during their implementation. The result is that models have traditionally considered as ad-hoc and after-the-fact solutions that do not always fit with the design of the application. To overcome this, we propose an object-oriented development framework onto which it is possible to build applications that require functionalities provided by trust and reputation models. The framework is extensible and flexible enough to allow implementing an important variety of trust models. This paper presents the framework, describes its main components, and gives examples on how to use it in order to implement three different trust models.

 

PDF icon moyano2012stm.pdf (571.19 KB)
F. Paci, C. Fernandez-Gago, and F. Moyano, "Detecting Insider Threats: a Trust-Aware Framework",
8th International Conference on Availability, Reliability and Security, IEEE, pp. 121-130, Nov 2013. DOI More..

Abstract

The number of insider threats hitting organizations and big enterprises is rapidly growing. Insider threats occur when trusted employees misuse their permissions on organizational assets. Since insider threats know the organization and its processes, very often they end up undetected. Therefore, there is a pressing need for organizations to adopt preventive mechanisms to defend against insider threats. In this paper, we propose a framework for insiders identification during the early requirement analysis of organizational settings and of its IT systems. The framework supports security engineers in the detection of insider threats and in the prioritization of them based on the risk they represent to the organization. To enable the automatic detection of insider threats, we extend the SI* requirement modeling language with an asset model and a trust model. The asset model allows associating security properties and sensitivity levels to assets. The trust model allows specifying the trust level that a user places in another user with respect to a given permission on an asset. The insider threats identification leverages the trust levels associated with the permissions assigned to users, as well as the sensitivity of the assets to which access is granted. We illustrate the approach based on a patient monitoring scenario.

PDF icon moyano2013ares.pdf (552.98 KB)
F. Moyano, C. Fernandez-Gago, and J. Lopez, "A Framework for Enabling Trust Requirements in Social Cloud Applications",
Requirements Engineering, vol. 18, issue 4, Springer London, pp. 321-341, Nov 2013. DOI (I.F.: 1.147)More..

Abstract

Cloud applications entail the provision of a huge amount of heterogeneous, geographically-distributed resources managed and shared by many different stakeholders who often do not know each other beforehand. This raises numerous security concerns that, if not addressed carefully, might hinder the adoption of this promising computational model. Appropriately dealing with these threats gains special relevance in the social cloud context, where computational resources are provided by the users themselves. We argue that taking trust and reputation requirements into account can leverage security in these scenarios by incorporating the notions of trust relationships and reputation into them. For this reason, we propose a development framework onto which developers can implement trust-aware social cloud applications. Developers can also adapt the framework in order to accommodate their application-specific needs.

Impact Factor: 1.147
Journal Citation Reports® Science Edition (Thomson Reuters, 2013)

PDF icon moyano2013re.pdf (1.25 MB)
J. A. Montenegro, M. J. Fischer, J. Lopez, and R. Peralta, "Secure sealed-bid online auctions using discreet cryptographic proofs",
Mathematical and Computer Modelling, vol. 57, Elsevier, pp. 2583–2595, Jun 2013. DOI (I.F.: 2.02)More..

Abstract

This work describes the design and implementation of an auction system using secure multiparty computation techniques. Our aim is to produce a system that is practical under actual field constraints on computation, memory, and communication. The underlying protocol is privacy-preserving, that is, the winning bid is determined without information about the losing bids leaking to either the auctioneer or other bidders. Practical implementation of the protocol is feasible using circuit-based cryptographic proofs along with additively homomorphic bit commitment. Moreover, we propose the development of a Proof Certificatestandard. These certificates convey sufficient information to recreate the cryptographic proofs and verify them offline.

Impact Factor: 2.02
Journal Citation Reports® Science Edition (Thomson Reuters, 2013)

PDF icon MFLR13.pdf (606.16 KB)
F. Moyano, C. Fernandez-Gago, and J. Lopez, "Towards Engineering Trust-aware Future Internet Systems",
3rd International Workshop on Information Systems Security Engineering (WISSE 2013), X. Franch, and P. Soffer Eds., LNBIP 148, Springer-Verlag, pp. 490-501, Jun 2013. DOI More..

Abstract

Security must be a primary concern when engineering Future Internet (FI) systems and applications. In order to achieve secure solutions, we need to capture security requirements early in the Software Development Life Cycle (SDLC). Whereas the security community has traditionally focused on providing tools and mechanisms to capture and express hard security requirements (e.g. confidentiality), little attention has been paid to other important requirements such as trust and reputation. We argue that these soft security requirements can leverage security in open, distributed, heterogeneous systems and applications and that they must be included in an early phase as part of the development process. In this paper we propose a UML extension for specifying trust and reputation requirements, and we apply it to an eHealth case study.

PDF icon moyano13wisse.pdf (505.78 KB)
F. Moyano, B. Baudry, and J. Lopez, "Towards Trust-Aware and Self-Adaptive Systems",
7th IFIP WG 11.11 International Conference on Trust Management (IFIPTM 2013), C. Fernandez-Gago, I. Agudo, F. Martinelli, and S. Pearson Eds., AICT 401, Springer, pp. 255-262, Jun 2013. DOI More..

Abstract

The Future Internet (FI) comprises scenarios where many heterogeneous and dynamic entities must interact to provide services (e.g., sensors, mobile devices and information systems in smart city scenarios). The dynamic conditions under which FI applications must execute call for self-adaptive software to cope with unforeseeable changes in the application environment. Software engineering currently provides frameworks to develop reasoning engines that automatically take reconfiguration decisions and that support the runtime adaptation of distributed, heterogeneous applications. However, these frameworks have very limited support to address security concerns of these application, hindering their usage for FI scenarios. We address this challenge by enhancing self-adaptive systems with the concepts of trust and reputation. Trust will improve decision-making processes under risk and uncertainty, in turn improving security of self-adaptive FI applications. This paper presents an approach that includes a trust and reputation framework into a platform for adaptive, distributed component-based systems, thus providing software components with new abilities to include trust in their reasoning process.  

PDF icon moyano2013ifiptm.pdf (585.82 KB)
F. Moyano, C. Fernandez-Gago, and J. Lopez, "A Trust and Reputation Framework",
Doctoral Symposium of the International Symposium on Engineering Secure Software and Systems (ESSoS-DS 2013), M. Heisel, and E. Marchetti Eds., CEUR-WS 965, CEUR-WS, pp. 7-12, 2013. More..

Abstract

The Future Internet is posing new security challenges as their scenarios are bringing together a huge amount of stakeholders and devices that must interact under unforeseeable conditions. In addition, in these scenarios we cannot expect entities to know each other beforehand, and therefore, they must be involved in risky and uncertain collaborations. In order to minimize threats and security breaches, it is required that a well-informed decision-making process is in place, and it is here where trust and reputation can play a crucial role. Unfortunately, services and applications developers are often unarmed to address trust and reputation requirements in these scenarios. To overcome this limitation, we propose a trust and reputation framework that allows developers to create trust- and reputation-aware applications.  

PDF icon moyano2013essosds.pdf (217.23 KB)
C. Fernandez-Gago, F. Martinelli, S. Pearson, and I. Agudo Eds., Trust Management VII, 7th WG11.11 International conference , vol. 401, Springer, June 2013. More..
2012
F. Moyano, C. Fernandez-Gago, and J. Lopez, "A Conceptual Framework for Trust Models",
9th International Conference on Trust, Privacy & Security in Digital Business (TrustBus 2012), S. Fischer-Hübner, S. Katsikas, and G. Quirchmayr Eds., LNCS 7449, Springer Verlag, pp. 93-104, Sep 2012. DOI More..

Abstract

During the last twenty years, a huge amount of trust and reputation models have been proposed, each of them with their own particularities and targeting different domains. While much effort has been made in defining ever-increasing complex models, little attention has been paid to abstract away the particularities of these models into a common set of easily understandable concepts. We propose a conceptual framework for computational trust models that will be used for analyzing their features and for comparing heterogeneous and relevant trust models.

PDF icon moyano2012trustbus.pdf (470.63 KB)
F. Moyano, C. Fernandez-Gago, and J. Lopez, "Implementing Trust and Reputation Systems: A Framework for Developers’ Usage",
International Workshop on Quantitative Aspects in Security Assurance, 2012. More..

Abstract

During the last decades, a huge amount of trust and reputation models have been proposed, each of them with their own particularities and targeting different domains. While much effort has been made in defining ever-increasing complex models, little attention has been paid to abstract away the particularities of these models into a common set of easily understandable concepts. We propose a conceptual framework for computational trust models that is used for developing a component-oriented development framework that aims to assist developers during the implementation phase.

PDF icon moyano12qasa.pdf (609.67 KB)
C. Meadows, and C. Fernandez-Gago Eds., Security and Trust Management - 7th International Workshop, STM 2011 , vol. 7170, Springer, July 2012. More..
F. Moyano, C. Fernandez-Gago, and J. Lopez, "Service-Oriented Trust and Reputation Architecture",
Proceedings of the Doctoral Symposium of the International Symposium on Engineering Secure Software and Systems (ESSoS-DS 2012), J. Cuellar, and N. Koch Eds., CEUR-WS 834, CEUR-WS, pp. 41-46, 2012. More..

Abstract

As the Future Internet arrives, more complex, service-based applications are spreading. These applications pose several challenges, including the huge amount of entities that must interact and their het- erogeneity. The success of these applications depends on the collaboration and communication of these entities, that might belong to different or- ganizations and administrative domains. Therefore, trust and reputation become two crucial issues. We propose the specification and design of a service-based security architecture that stresses the delivery of trust and reputation services to any application that might require them.

PDF icon moyano2012essosds.pdf (188.61 KB)
F. Moyano, C. Fernandez-Gago, I. Agudo, and J. Lopez, "A Task Ordering Approach for Automatic Trust Establishment",
Proceedings of the 2012 International Symposium on Engineering Secure Software and Systems (ESSoS 2012), G. Barthe, B. Livshits, and R. Scandariato Eds., LNCS 7159, Springer, pp. 76–89, Feb 2012. DOI More..

Abstract

Trust has become essential in computer science as a way of assisting the process of decision-making, such as access control. In any system, several tasks may be performed, and each of these tasks might pose different associated trust values between the entities of the system. For instance, in a file system, reading and overwriting a file are two tasks that pose different trust values between the users who can carry out these tasks. In this paper, we propose a simple model for automatically establishing trust relationships between entities considering an established order among tasks.

PDF icon Moyano_ESSoS12.pdf (526.84 KB)
2011
C. Alcaraz, C. Fernandez-Gago, and J. Lopez, "An Early Warning System based on Reputation for Energy Control Systems",
IEEE Transactions on Smart Grid, vol. 2, no. 4, IEEE, pp. 827-834, Nov 2011. DOI More..

Abstract

Most of energy control or SCADA (Supervisory Control and Data Acquisition) systems are very dependent on advanced technologies and on traditional security mechanisms for protecting the a system against anomalous events. Security mechanisms are not enough to be used in critical systems, since they can only detect anomalous events occurring at a certain moment in time. For this reason it becomes of paramount importance the usage of intelligent systems with capability for preventing anomalous situations and reacting against them on time. This type of systems are, for example, Early Warning Systems (EWS). In this paper, we propose an EWS based on Wireless Sensor Networks (WSNs) (under the ISA100.11a standard) and reputation for controling the network behaviour. The WSN are organized into clusters where a Cluster Head (CH) is designated. This CH will contain a Reputation Manager Module. The usability of this approach is also analyzed considering a Smart Grid scenario.} keywords = {Critical Information Infrastructures, Sensor Networks, Early Warning Systems, Reputation, SCADA Systems, Smart Grid.

PDF icon Alcaraz2011.pdf (495.57 KB)
2010
I. Agudo, C. Fernandez-Gago, and J. Lopez, "A Scale Based Trust Model for Multi-Context Environments",
Computers and Mathematics with Applications, vol. 60, Elsevier, pp. 209-216, July, 2010. DOI (I.F.: 1.472)More..

Abstract

When interactions among users of a system have to take place, for example, over the internet, establishing trust relationships among these users becomes crucial. However, the way this trust is established depends to a certain extent on the context where the interactions take place. Most of the time, trust is encoded as a numerical value that might not be very meaningful for a not very experienced user. In this paper we propose a model that takes into account the semantic and the computational sides of trust. This avoids users having to deal directly with the computational side; they instead deal with meaningful labels such as Bad or Good in a given context.

Impact Factor: 1.472
Journal Citation Reports® Science Edition (Thomson Reuters, 2010)

PDF icon Agudo2010b.pdf (279.77 KB)
J. Lopez, R. Roman, I. Agudo, and C. Fernandez-Gago, "Trust Management Systems for Wireless Sensor Networks: Best practices",
Computer Communications, vol. 33, no. 9, Elsevier, pp. 0140-3664, 2010. DOI (I.F.: 0.816)More..

Abstract

Wireless sensor networks (WSNs) have been proven a useful technology for perceiving information about the physical world and as a consequence has been used in many applications such as measurement of temperature, radiation, flow of liquids, etc. The nature of this kind of technology, and also their vulnerabilities to attacks make the security tools required for them to be considered in a special way. The decision making in a WSN is essential for carrying out certain tasks as it aids sensors establish collaborations. In order to assist this process, trust management systems could play a relevant role. In this paper, we list the best practices that we consider are essential for developing a good trust management system for WSN and make an analysis of the state of the art related to these practices.

Impact Factor: 0.816
Journal Citation Reports® Science Edition (Thomson Reuters, 2010)

PDF icon JavierLopezMunoz2010.pdf (210.98 KB)
2009
C. Alcaraz, et al., "Adaptive Dispatching of Incidences Based on Reputation for SCADA Systems",
6th International Conference on Trust, Privacy and Security in Digital Business (TrustBus’09), Springer-Verlag, pp. 86-94, September, 2009. DOI More..

Abstract

SCADA systems represent a challenging scenario where the management of critical alarms is crucial. Their response to these alarms should be efficient and fast in order to mitigate or contain undesired effects. This work presents a mechanism, the Adaptive Assignment Manager (AAM) that will aid to react to incidences in a more efficient way by dynamically assigning alarms to the most suitable human operator. The mechanism uses various inputs for identifying the operators such as their availability, workload and reputation. In fact, we also define a reputation component that stores the reputation of the human operators and uses feedback from past experiences.

PDF icon Alcaraz2009.pdf (289.68 KB)
I. Agudo, C. Fernandez-Gago, and J. Lopez, "Concurrent access control for multi-user and multi-processor systems based on trust relationships",
Concurrency and Computation: Practice and Experience, vol. 21, John Wiley & Sons, pp. 1389-1403, July, 2009. DOI (I.F.: 1.004)More..

Abstract

Concurrent access control is an old problem in many fields in Computer Science. It has been solved in many languages and systems, using mechanisms like monitors or priority queues. Nowadays computers implement multi-core capabilities. This means that they are virtually capable of execution of processes in parallel. This requires new techniques and open new issues in the field of concurrent access control. Moreover, most operating systems are multi-user; thus, we have to focus on a multi-processor multi-user scenario. Trust becomes a paramount aspect when building distributed applications; the same applies on a lower scale in modern computers. We propose the use of a trust graph that keeps record of the trust relationships of the system and helps in deciding on concurrent access requests. The information encoded in the graph will be used both in order to decide on the access requests and to order granted requests in terms of their associated trust level

Impact Factor: 1.004
Journal Citation Reports® Science Edition (Thomson Reuters, 2009)

PDF icon Agudo2009.pdf (180.3 KB)
I. Agudo, C. Fernandez-Gago, and J. Lopez, "A Multidimensional Reputation Scheme for Identity Federations",
Sixth European Workshop on Public Key Services, Applications and Infrastructures (EuroPKI’09), LNCS 6391, Springer, pp. 225-238, 2009. DOI More..

Abstract

Deciding who to trust in the internet of services paradigm is an important and open question. How to do it in an optimal way is not always easy to determine. Trust is usually referred to a particular context whereas a single user may interact in more than one given context. We are interested in investigating how a Federated Reputation System can help exporting trust perceptions from one context to another. We propose a model for deriving trust in online services. In this context, trust is defined as the level of confidence that the service provider holds on the subject interacting with it to behave in a proper way while using the service. Thus, we derive trust by using the reputation values that those users have gained for interacting with these services.

PDF icon Agudo2009a.pdf (238.71 KB)
R. Roman, C. Fernandez-Gago, J. Lopez, and H. Hwa Chen, "Trust and Reputation Systems for Wireless Sensor Networks",
Security and Privacy in Mobile and Wireless Networking, S. Gritzalis, T. Karygiannis, and C. Skianis Eds., Troubador Publishing Ltd, pp. 105-128, 2009. More..

Abstract

The concept of trust has become very relevant in the late years as a consequence of the growth of fields such as internet transactions or electronic commerce. In general, trust has become of paramount importance for any kind of distributed networks, such as wireless sensor networks (WSN in the following). In this chapter of the book, we try to give a general overview of the state of the art on trust management systems for WSN and also try to identify the main features of the architectures of these trust management systems.

PDF icon Roman2009b.pdf (291.67 KB)
2008
I. Agudo, C. Fernandez-Gago, and J. Lopez, "Delegating Privileges over Finite Resources: A Quota Based Delegation Approach",
5th International Workshop on Formal Aspects in Security and Trust (FAST’08), LNCS 5491, Springer, pp. 302-315, 2008. DOI More..

Abstract

When delegation in real world scenarios is considered, the delegator (the entity that posses the privileges) usually passes the privileges on to the delegatee (the entity that receives the privileges) in such a way that the former looses these privileges while the delegation is effective. If we think of a physical key that opens a door, the privilege being delegated by the owner of the key is opening the door. Once the owner of the key delegates this privilege to another entity, by handing over the key, he is not able to open the door any longer. This is due to the fact that the key is not copied and handed over but handed over to the delegatee. When delegation takes place in the electronic world, the delegator usually retains also the privileges. Thus, both users have them simultaneously. This situation, which in most cases is not a problem, may be undesirable when dealing with certain kind of resources. In particular, if we think of finite resources, those in which the number of users accessing simultaneously is finite, we can not allow that a user delegating his access privilege is also granted access when the delegation if effective. In this paper we propose an approach where each user is delegated an access quota for a resource. If further delegating of the delegated quota occurs, this is subtracted from his quota. That is, when delegating, part of the quota remains with the delegator and another part goes to the delegatee. This allows a more fairly access to the resource. Moreover, we show that this approach can also be applied to any kind of resources by defining appropriate authorization policies.

PDF icon Agudo2008.pdf (304.18 KB)
I. Agudo, C. Fernandez-Gago, and J. Lopez, "A Model for Trust Metrics Analysis",
5th International Conference on Trust, Privacy and Security in Digital Business (TrustBus’08), LNCS 5185, Springer, pp. 28-37, 2008. DOI More..

Abstract

Trust is an important factor in any kind of network essential, for example, in the decision-making process. As important as the definition of trust is the way to compute it. In this paper we propose a model for defining trust based on graph theory and show examples of some simple operators and functions that will allow us to compute trust.

PDF icon Agudo2008a.pdf (129.8 KB)
2007
J. Lopez, and B. M. H"ammerli Eds., "Critical Information Infrastructures Security, Second International Workshop, CRITIS 2007, Málaga, Spain, October 3-5, 2007. Revised Papers",
CRITIS, vol. 5141, Springer, 2007. DOI More..
R. Roman, C. Fernandez-Gago, and J. Lopez, "Featuring Trust and Reputation Management Systems for Constrained Hardware Devices",
1st International Conference on Autonomic Computing and Communication Systems (Autonomics’07), ICST, October, 2007. More..

Abstract

Research on trust management systems for wireless sensor networks is still at a very early stage and few works have done so far. It seems that for those works which deal with the topic general features of how these systems should be are not clearly identified. In this paper we try to identify the main features that a trust management system should have and justify their importance for future developments.

PDF icon Roman2007c.pdf (110.26 KB)
C. Fernandez-Gago, R. Roman, and J. Lopez, "A Survey on the Applicability of Trust Management Systems for Wireless Sensor Networks",
3rd International Workshop on Security, Privacy and Trust in Pervasive and Ubiquitous Computing (SecPerU’07), IEEE Computer Society, pp. 25-30, 2007. DOI More..

Abstract

Trust plays an important role in human life environments and virtual organizations. In the context of a network, trust may help its elements to decide whether another member of the same network is being uncooperative or malicious. Trust becomes quite important in self-configurable and autonomous systems, such as wireless sensor networks (WSN). However, very little effort has been done in the field of trust management in WSN. On the other hand, some efforts have been made in quite related fields such as Ad-hoc and P2P networks. In this paper we give an overview of existing trust management solutions, mainly those developed for Ad-Hoc and P2P networks and, more importantly, investigate their suitability to WSN. We also provide some guidelines to aid the development of trust management systems for WSN according to the nature of these networks.

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2005
I. Agudo, J. Lopez, and J. A. Montenegro, "A Representation Model of Trust Relationships with Delegation Extensions",
3th International Conference on Trust Management (iTRUST’05), LNCS 3477, Springer, pp. 9-22, May, 2005. DOI More..

Abstract

Logic languages establish a formal framework to solve authorization and delegation conflicts. However, we consider that a visual representation is necessary since graphs are more expressive and understandable than logic languages. In this paper, and after overviewing previous works using logic languages, we present a proposal for graph representation of authorization and delegation statements. Our proposal is based on Varadharajan et al. solution, though improve several elements of that work. We also discuss about the possible implementation of our proposal using attribute certificates.

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