    @inproceedings {morales2023metacom,
	title = {Integration of MPC into Besu through an extended private transaction model},
	booktitle = {IEEE International Conference on Metaverse Computing, Networking and Applications},
	year = {2023},
	month = {06/2023},
	address = {Kyoto, Japan},
	abstract = {In the last few years we have seen many different approaches to incorporate privacy features to blockchains. In the area of cryptocurrencies that would normally mean protecting the identity of the owner of some funds, but there are other applications where privacy is even more important, especially in permissioned blockchains.
Permissioned blockchain platforms, such as Hyperledger Besu or Hyperledger Fabric, already include the concept of private transactions, which essentially defines a sub-group of the blockchain where their participants share some private data.
We want to go one step ahead and propose an extended model for private transactions where the different participants can have a separated view of the same transaction, allowing the integration of Multi-party Computation protocols in the blockchain.
Our work extends Hyperledger Besu{\textquoteright}s design for private transactions, offering better security properties and a finer grain customization. We cover two specific MPC examples, Private Set Intersection and Byzantine Fault-Tolerant Random Number Generation, and propose a mechanism to run them using smart contract interfaces.
},
	keywords = {blockchain, hyperledger besu, privacy, secure multi-party computation},
	author = {Daniel Morales and Isaac Agudo and Javier Lopez}
}
@article {morales2023psi,
	title = {Private set intersection: A systematic literature review},
	journal = {Computer Science Review},
	volume = {49},
	number = {100567},
	year = {2023},
	month = {05/2023},
	publisher = {Elsevier},
	type = {Review},
	address = {ScienceDirect},
	abstract = {Secure Multi-party Computation (SMPC) is a family of protocols which allow some parties to compute a function on their private inputs, obtaining the output at the end and nothing more. In this work, we focus on a particular SMPC problem named Private Set Intersection (PSI). The challenge in PSI is how two or more parties can compute the intersection of their private input sets, while the elements that are not in the intersection remain private. This problem has attracted the attention of many researchers because of its wide variety of applications, contributing to the proliferation of many different approaches. Despite that, current PSI protocols still require heavy cryptographic assumptions that may be unrealistic in some scenarios. In this paper, we perform a Systematic Literature Review of PSI solutions, with the objective of analyzing the main scenarios where PSI has been studied and giving the reader a general taxonomy of the problem together with a general understanding of the most common tools used to solve it. We also analyze the performance using different metrics, trying to determine if PSI is mature enough to be used in realistic scenarios, identifying the pros and cons of each protocol and the remaining open problems.},
	keywords = {privacy, Private set intersection, Secure Multiparty computation, security},
	issn = {1574-0137},
	doi = {https://doi.org/10.1016/j.cosrev.2023.100567},
	url = {https://www.sciencedirect.com/science/article/pii/S1574013723000345},
	author = {Daniel Morales and Isaac Agudo and Javier Lopez}
}
@inproceedings {morales2022cc,
	title = {Real-time Crowd Counting based on Wearable Ephemeral IDs},
	booktitle = {19th International Conference on Security and Cryptography (SECRYPT 2022)},
	year = {2022},
	month = {07/2022},
	pages = {249-260},
	publisher = {Scitepress},
	organization = {Scitepress},
	address = {Lisbon},
	abstract = {Crowd Counting is a very interesting problem aiming at counting people typically based on density averages and/or aerial images. This is very useful to prevent crowd crushes, especially on urban environments with high crowd density, or to count people in public demonstrations. In addition, in the last years, it has become of paramount importance for pandemic management. For those reasons, giving users automatic mechanisms to anticipate high risk situations is essential. In this work, we analyze ID-based Crowd Counting, and propose a real-time Crowd Counting system based on the Ephemeral ID broadcast by contact tracing applications on wearable devices. We also performed some simulations that show the accuracy of our system in different situations.
},
	keywords = {Crowd Counting, IDS, Pandemics, privacy, Secure Multiparty computation},
	isbn = {978-989-758-590-6},
	issn = {2184-7711},
	doi = {10.5220/0011327200003283},
	author = {Daniel Morales and Isaac Agudo and Javier Lopez}
}
@inproceedings {morales2019,
	title = {Prueba de concepto de Autoridad de Certificaci{\'o}n usando Computaci{\'o}n Segura  Multiparte},
	booktitle = {XIV Jornadas de Ingenier{\'\i}a Telem{\'a}tica},
	year = {2019},
	month = {10/2019},
	pages = {50-53},
	address = {Zaragoza},
	abstract = {Este trabajo pretende analizar el paradigma de la Computaci{\'o}n Segura Multiparte y sus posibles aplicaciones en el campo de la criptograf{\'\i}a. Se plantea como modelo alternativo, mas escalable y seguro al uso de m{\'o}dulos hardware de seguridad para aplicaciones que requieran de Terceras Partes Confiables. Concretamente, se ha integrado un protocolo de criptograf{\'\i}a RSA multiparte con la librer{\'\i}a certbuilder, para la creaci{\'o}n de certificados X.509. De esta forma se asegura que la creaci{\'o}n de los certificados ra{\'\i}z de la Infraestructura de Clave Publica se realiza de forma que la generaci{\'o}n de claves y firma de este se ejecute {\'\i}ntegramente sobre el sistema multiparte, con un modelo de tres partes que trabaja con circuitos aritm{\'e}ticos, sin que ninguna de ellas, de forma aislada, tenga posibilidad de comprometer la clave privada correspondiente. Para comprobar la viabilidad del sistema se han realizado pruebas de generaci{\'o}n de certificados con diferentes longitudes de clave, siendo el proceso determinante la creaci{\'o}n de las claves. Los elevados tiempos hacen que una aplicaci{\'o}n como esta no sea asumible en otros escenarios, pero creemos que para el caso de la creaci{\'o}n de los certificados ra{\'\i}z de una infraestructura de clave p{\'u}blica las garant{\'\i}as avanzadas de seguridad compensan el tiempo extra.
},
	keywords = {privacy, Secure Multiparty computation},
	isbn = {978-84-09-21112-8},
	doi = {10.26754/uz.978-84-09-21112-8},
	author = {Daniel Morales and Isaac Agudo}
}
@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 = {<p>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.</p>
},
	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 {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 = {<p>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.</p>
},
	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}
}
