@article {nunez2017proxy, title = {Proxy Re-Encryption: Analysis of Constructions and its Application to Secure Access Delegation}, journal = {Journal of Network and Computer Applications}, volume = {87}, year = {2017}, month = {06/2017}, pages = {193-209}, publisher = {Elsevier}, abstract = {

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.\ 

}, issn = {1084-8045}, doi = {10.1016/j.jnca.2017.03.005}, author = {David Nu{\~n}ez and Isaac Agudo and Javier Lopez} } @inproceedings {nunez2017sistema, title = {Sistema de Acceso Delegado a Informaci{\'o}n Cifrada para Apache Hadoop}, booktitle = {III Jornadas Nacionales de Investigaci{\'o}n en Ciberseguridad}, year = {2017}, month = {06/2017}, pages = {174-175}, publisher = {URJC}, organization = {URJC}, address = {Madrid}, abstract = {

En este art{\'\i}culo presentamos un sistema que permite delegaci{\'o}n de acceso a informaci{\'o}n cifrada para Apache Hadoop, de forma segura y transparente al usuario. Para ello usamos t{\'e}cnicas criptogr{\'a}ficas avanzadas basadas en el recifrado delegado.\ Con este sistema, es posible almacenar en Hadoop los datos de forma cifrada y delegar de forma segura el acceso a los nodos de computaci{\'o}n.\ El funcionamiento es transparente ya que se integra con la capa del sistema de ficheros nativa HDFS.\ Adem{\'a}s, el recifrado delegado permite hacer rotaci{\'o}n de claves de cifrado de forma segura y r{\'a}pida.

}, keywords = {Big Data, Cryptography, Hadoop, proxy re-encryption}, isbn = {978-84-608-4659-8}, url = {http://hdl.handle.net/10115/14540}, author = {David Nu{\~n}ez and Isaac Agudo and Michael Egorov and MacLane Wilkison} } @inproceedings {agudo2016technique, title = {A Technique for Enhanced Provision of Appropriate Access to Evidence across Service Provision Chains}, booktitle = {10th International IFIP Summer School on Privacy and Identity Management}, year = {2016}, pages = {187-204}, abstract = {

Transparency and verifiability are necessary aspects of accountability, but care needs to be taken that auditing is done in a privacy friendly way. There are situations where it would be useful for certain actors to be able to make restricted views within service provision chains on accountability evidence, including logs, available to other actors with specific governance roles. For example, a data subject or a Data Protection Authority (DPA) might want to authorize an accountability agent to act on their behalf, and be given access to certain logs in a way that does not compromise the privacy of other actors or the security of involved data processors. In this paper two cryptographic-based techniques that may address this issue are proposed and assessed.

}, isbn = {978-3-319-41762-2}, doi = {10.1007/978-3-319-41763-9_13}, author = {Isaac Agudo and Ali El Kaafarani and David Nu{\~n}ez and Siani Pearson} } @incollection {1512, title = {Metrics for Accountability in the Cloud}, booktitle = {Accountability and Security in the Cloud}, volume = {8937}, number = {LNCS Tutorial}, year = {2015}, pages = {129-153}, author = {Carmen Fernandez-Gago and David Nu{\~n}ez} } @incollection {nunez15privacy, title = {Privacy-Preserving Identity Management as a Service}, booktitle = {Accountability and Security in the Cloud}, series = {Lecture Notes in Computer Science}, volume = {8937}, year = {2015}, pages = {114-125}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

In this paper we tackle the problem of privacy and confidentiality in Identity Management as a Service (IDaaS). The adoption of cloud computing technologies by organizations has fostered the externalization of the identity management processes, shaping the concept of Identity Management as a Service. However, as it has happened to other cloud-based services, the cloud poses serious risks to the users, since they lose the control over their data. As part of this work, we analyze these concerns and present a model for privacy-preserving IDaaS, called BlindIdM, which is designed to provide data privacy protection through the use of cryptographic safeguards.

}, keywords = {Cloud Computing, Cryptography, Identity Management as a Service, privacy}, isbn = {978-3-319-17198-2}, doi = {10.1007/978-3-319-17199-9_5}, url = {http://dx.doi.org/10.1007/978-3-319-17199-9_5}, author = {David Nu{\~n}ez and Isaac Agudo and Javier Lopez}, editor = {Massimo Felici and Carmen Fernandez-Gago} } @inproceedings {1516, title = {Tools for Cloud Accountability: A4Cloud Tutorial}, booktitle = {9th IFIP Summer School on Privacy and Identity Management for the Future Internet in the Age of Globalisation}, volume = {457}, year = {2015}, pages = {219-236}, publisher = {Springer IFIP AICT}, organization = {Springer IFIP AICT}, address = {Patras (Greece)}, abstract = {

Cloud computing is becoming a key IT infrastructure technology being adopted progressively by companies and users. Still, there are issues and uncertainties surrounding its adoption, such as security and how users data is dealt with that require attention from developers, researchers, providers and users. The A4Cloud project tries to help solving the problem of accountability in the cloud by providing tools that support the process of achieving accountability. This paper presents the contents of the first A4Cloud tutorial. These contents include basic concepts and tools developed within the project. In particular, we will review how metrics can aid the accountability process and some of the tools that the A4Cloud project will produce such as the Data Track Tool (DTT) and the Cloud Offering Advisory Tool (COAT).

}, isbn = {978-3-319-18620-7}, issn = {978-3-319-18621-4}, doi = {10.1007/978-3-319-18621-4_15}, author = {Carmen Fernandez-Gago and Vasilis Tountopoulos and Simone Fischer-H{\"u}bner and Rehab Alnemr and David Nu{\~n}ez and Julio Angulo and Tobias Pulls and Theo Koulouris} } @article {nunez2014blindidm, title = {BlindIdM: A Privacy-Preserving Approach for Identity Management as a Service}, journal = {International Journal of Information Security}, volume = {13}, year = {2014}, pages = {199-215}, publisher = {Springer}, abstract = {

Identity management is an almost indispensable component of today{\textquoteright}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 con dentiality 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.

}, issn = {1615-5262}, doi = {10.1007/s10207-014-0230-4}, author = {David Nu{\~n}ez and Isaac Agudo} } @inproceedings {nunez2014delegated, title = {Delegated Access for Hadoop Clusters in the Cloud}, booktitle = {IEEE International Conference on Cloud Computing Technology and Science (CloudCom 2014)}, year = {2014}, month = {12/2014}, pages = {374-379}, publisher = {IEEE}, organization = {IEEE}, address = {Singapore}, abstract = {

Among Big Data technologies, Hadoop stands out for its capacity to store and process large-scale datasets. However, although Hadoop was not designed with security in mind, it is widely used by plenty of organizations, some of which have strong data protection requirements. Traditional access control solutions are not enough, and cryptographic solutions must be put in place to protect sensitive information. In this paper, we describe a cryptographically-enforced access control system for Hadoop, based on proxy re-encryption. Our proposed solution fits in well with the outsourcing of Big Data processing to the cloud, since information can be stored in encrypted form in external servers in the cloud and processed only if access has been delegated. Experimental results show that the overhead produced by our solution is manageable, which makes it suitable for some applications.

}, isbn = {978-1-4799-4093-6}, doi = {10.1109/CloudCom.2014.50}, url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=\&arnumber=7037691}, author = {David Nu{\~n}ez and Isaac Agudo and Javier Lopez} } @inproceedings {nunez2013leveraging, title = {Leveraging Privacy in Identity Management as a Service through Proxy Re-Encryption}, booktitle = {Ph.D Symposium of the European Conference on Service-Oriented and Cloud Computing (ESOCC) 2013}, year = {2013}, month = {September 2013}, address = {M{\'a}laga, Spain}, abstract = {

The advent of cloud computing has provided the opportunity to externalize the identity management processes, shaping what has been called Identity Management as a Service (IDaaS). However, 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. As part of this PhD thesis, we analyze these concerns and propose BlindIdM, a model for privacy-preserving IDaaS with a focus on data privacy protection through the use of proxy re-encryption.

}, author = {David Nu{\~n}ez and Isaac Agudo and Javier Lopez} } @inproceedings {nunez2013metamodel, title = {A Metamodel for Measuring Accountability Attributes in the Cloud}, booktitle = {2013 IEEE International Conference on Cloud Computing Technology and Science (CloudCom 2013)}, year = {2013}, month = {12/2013}, pages = {355-362}, publisher = {IEEE}, organization = {IEEE}, address = {Bristol, UK}, abstract = {

Cloud governance, and in particular data governance in the cloud, relies on different technical and organizational practices and procedures, such as policy enforcement, risk management, incident management and remediation. The concept of accountability encompasses such practices, and is essential for enhancing security and trustworthiness in the cloud. Besides this, proper measurement of cloud services, both at a technical and governance level, is a distinctive aspect of the cloud computing model. Hence, a natural problem that arises is how to measure the impact on accountability of the procedures held in practice by organizations that participate in the cloud ecosystem. In this paper, we describe a metamodel for addressing the problem of measuring accountability properties for cloud computing, as discussed and defined by the Cloud Accountability Project (A4Cloud). The goal of this metamodel is to act as a language for describing: (i) accountability properties in terms of actions between entities, and (ii) metrics for measuring the fulfillment of such properties. It also allows the recursive decomposition of properties and metrics, from a high-level and abstract world to a tangible and measurable one. Finally, we illustrate our proposal of the metamodel by modelling the transparency property, and define some metrics for it.

}, isbn = {978-0-7685-5095-4}, doi = {10.1109/CloudCom.2013.53}, author = {David Nu{\~n}ez and Carmen Fernandez-Gago and Siani Pearson and Massimo Felici} } @inproceedings {nunez2012integrating, title = {Integrating OpenID with Proxy Re-Encryption to enhance privacy in cloud-based identity services}, booktitle = {IEEE CloudCom 2012}, year = {2012}, month = {Dec 2012}, pages = {241 - 248}, publisher = {IEEE Computer Society}, organization = {IEEE Computer Society}, address = {Taipei, Taiwan}, abstract = {

The inclusion of identity management in the cloud computing landscape represents a new business opportunity for providing what has been called Identity Management as a Service (IDaaS). Nevertheless, IDaaS introduces the same kind of problems regarding privacy and data confidentiality as other cloud services; on top of that, the nature of the outsourced information (users{\textquoteright} identity) is critical. Traditionally, cloud services (including IDaaS) rely only on SLAs and security policies to protect the data, but these measures have proven insufficient in some cases; recent research has employed advanced cryptographic mechanisms as an additional safeguard. Apart from this, there are several identity management schemes that could be used for realizing IDaaS systems in the cloud; among them, OpenID has gained crescent popularity because of its open and decentralized nature, which makes it a prime candidate for this task. In this paper we demonstrate how a privacy-preserving IDaaS system can be implemented using OpenID Attribute Exchange and a proxy re-encryption scheme. Our prototype enables an identity provider to serve attributes to other parties without being able to read their values. This proposal constitutes a novel contribution to both privacy and identity management fields. Finally, we discuss the performance and economical viability of our proposal.

}, keywords = {Cloud Computing, Cryptography, identity management, OpenID, privacy, proxy re-encryption}, isbn = {978-1-4673-4511-8}, issn = {978-1-4673-4509-5}, doi = {10.1109/CloudCom.2012.6427551}, author = {David Nu{\~n}ez and Isaac Agudo and Javier Lopez} } @inproceedings {neumann2012strong, title = {Strong Authentication of Humans and Machines in Policy Controlled Cloud Computing Environment Using Automatic Cyber Identity}, booktitle = {Information Security Solutions Europe 2012}, year = {2012}, month = {2012}, pages = {195-206}, publisher = {Springer Vieweg}, organization = {Springer Vieweg}, address = {Brussels, Belgium}, abstract = {

The paper describes the experience with integration of automatic cyber identity technology with policy controlled virtualisation environment. One identity technology has been used to enable strong authentication of users (human beings) as well as machines (host systems) to the virtualization management system. The real experimental evaluation has been done in PASSIVE project (Policy-Assessed system-level Security of Sensitive Information processing in Virtualised Environments - SEVENTH FRAMEWORK PROGRAMME THEME ICT-2009.1.4 INFORMATION AND COMMUNICATION TECHNOLOGIES - Small or medium-scale focused research project - Grant agreement no.: 257644).

}, isbn = {978-3-658-00332-6}, doi = {10.1007/978-3-658-00333-3_19}, author = {Neumann Libor and Tomas Halman and Rotek Pavel and Alexander Boettcher and Julian Stecklina and Michal Sojka and David Nu{\~n}ez and Isaac Agudo}, editor = {Norbert Pohlmann and Helmut Reimer and Wolfgang Schneider} } @inproceedings {agudo2011cryptography, title = {Cryptography Goes to the Cloud}, booktitle = {1st International Workshop on Security and Trust for Applications in Virtualised Environments (STAVE 2011)}, series = {Communications in Computer and Information Science}, volume = {187}, year = {2011}, month = {June}, pages = {190-197}, publisher = {Springer}, organization = {Springer}, abstract = {

In this paper we identify some areas where cryptography can help a rapid adoption of cloud computing. Although secure storage has already captured the attention of many cloud providers, offering a higher level of protection for their customer{\textquoteright}s data, we think that more advanced techniques such as searchable encryption and secure outsourced computation will become popular in the near future, opening the doors of the Cloud to customers with higher security requirements.

}, isbn = {978-3-642-22364-8}, doi = {10.1007/978-3-642-22365-5_23}, author = {Isaac Agudo and David Nu{\~n}ez and Gabriele Giammatteo and Panagiotis Rizomiliotis and Costas Lambrinoudakis}, editor = {Changhoon Lee and Jean-Marc Seigneur and James J. Park and Roland R. Wagner} } @inproceedings {DNunez11, title = {Identity Management Challenges for Intercloud Applications}, booktitle = {1st International Workshop on Security and Trust for Applications in Virtualised Environments (STAVE 2011)}, volume = {187}, year = {2011}, month = {June}, pages = {198-204}, address = {Crete (Greece)}, abstract = {

Intercloud notion is gaining a lot of attention lately from both enterprise and academia, not only because of its benefits and expected results but also due to the challenges that it introduces regarding interoperability and standardisation. Identity management services are one of the main candidates to be outsourced into the Intercloud, since they are one of the most common services needed by companies and organisations. This paper addresses emerging identity management challenges that arise in intercloud formations, such as naming, identification, interoperability, identity life cycle management and single sign-on.

}, doi = {10.1007/978-3-642-22365-5_24}, author = {David Nu{\~n}ez and Isaac Agudo and Prokopios Drogkaris and Stefanos Gritzalis} } @inproceedings {1643, title = {Managing Incidents in Smart Grids {\`a} la Cloud}, booktitle = {IEEE CloudCom 2011}, year = {2011}, month = {Nov-Dec 2011}, pages = {527-531}, publisher = {IEEE Computer Society}, organization = {IEEE Computer Society}, address = {Athens, Greece}, abstract = {

During the last decade, the Cloud Computing paradigm has emerged as a panacea for many problems in traditional IT infrastructures. Much has been said about the potential of Cloud Computing in the Smart Grid context, but unfortunately it is still relegated to a second layer when it comes to critical systems. Although the advantages of outsourcing those kind of applications to the cloud is clear, data confidentiality and operational privacy stand as mayor drawbacks. In this paper, we try to give some hints on which security mechanisms and more specific, which cryptographic schemes, will help a better integration of Smart Grids and Clouds. We propose the use of Virtual SCADA in the Cloud (VS-Cloud) as a mean to improve reliability and efficiency whilst maintaining the same protection level as in traditional SCADA architectures.

}, keywords = {Cloud Computing, Cryptography, Incident Management, SCADA Systems, Searchable Encryption, Smart Grid}, isbn = {978-0-7695-4622-3}, doi = {10.1109/CloudCom.2011.79}, author = {Cristina Alcaraz and Isaac Agudo and David Nu{\~n}ez and Javier Lopez} }