In the Big Data era, personal metadata may will become a new type of corporate asset, however there have already been a growing public concern about user's privacy mined from metadata. In this paper we address the problem of implementing the self-sovereignty of personal metadata on the existing OpenPDS/SafeAnswers framework according to the Windhover Principle. In order to do that, we propose a new framework, called BlocakChain-based Personal Data Store (BCPDS), to realize two basic properties: notary and autonomy. This framework, firstly introduces the BlockChain as a notary, into OpenPDS/SafeAnswers for secure storage of personal meta-data instead of the original database. Next, we present an AutoNomybased Access Control (ANAC) to improve the SafeAnswers module, where ANAC is a new mechanism that enforces access based on the relationship among all authorized users and metadata's owner. In addition, we also propose General Access Structure (GAS) and threshold secret sharing scheme in BlockChain as an implementation method for our BC-PDS framework.
Yupeng Zhang, Jonathan Katz, Charalampos Papamanthou
We present a new construction of an expressive set accumulator. Unlike existing cryptographic accumulators, ours provides succinct proofs for a large collection of operations over accumulated sets, including intersection, union, set difference, SUM, COUNT, MIN, MAX, and RANGE, as well as arbitrary nestings of the above. We also show how to extend our accumulator to be zero-knowledge. The security of our accumulator is based on extractability assumptions and other assumptions that hold in the generic group model. Our construction has asymptotically optimal verification complexity and proof size, constant update complexity, and public verifiability/updatability-namely, any client who knows the public key and the last accumulator value can verify the supported operations and update the accumulator. The expressiveness of our accumulator comes at the cost of quadratic prover time. However, we show that the cryptographic operations involved are cheap compared to those incurred by generic approaches (e.g., SNARKs) that are equally expressive: our prover runs faster for sets of up to 5 million items. Our accumulator serves as a powerful cryptographic tool with many applications. For example, it can be applied to efficiently support verification of a rich collection of SQL queries when used as a drop-in replacement in existing verifiable database systems (e.g., IntegriDB, CCS 2015).
Hubert Ritzdorf, Karl Wüst, Arthur Gervais, Guillaume Felley · 5 authors
An internet user wanting to share observed content is typically restricted to primitive techniques such as screenshots, web caches or share button-like solutions. These acclaimed proofs, however, are either trivial to falsify or require trust in centralized entities (e.g., search engine caches). This motivates the need for a seamless and standardized internet-wide non-repudiation mechanism, allowing users to share data from news sources, social websites or financial data feeds in a provably secure manner. Additionally, blockchain oracles that enable data-rich smart contracts typically rely on a trusted third party (e.g., TLSNotary or Intel SGX). A decentralized method to transfer web-based content into a permissionless blockchain without additional trusted third party would allow for smart contract applications to flourish. In this work, we present TLS-N, the first TLS extension that provides secure non-repudiation and solves both of the mentioned challenges. TLS-N generates non-interactive proofs about the content of a TLS session that can be efficiently verified by third parties and blockchain based smart contracts. As such, TLS-N increases the accountability for content provided on the web and enables a practical and decentralized blockchain oracle for web content. TLS-N is compatible with TLS 1.3 and adds a minor overhead to a typical TLS session. When a proof is generated, parts of the TLS session (e.g., passwords, cookies) can be hidden for privacy reasons, while the remaining content can be verified.
Lei Xu, Lin Chen, Nolan Shah, Zhimin Gao · 6 authors
Since Internet based applications have become the norm for most users, security has become a bigger concern than ever before, especially for applications like social networking and cloud based storage. Access control is one of the key techniques that can mitigate security concerns for web based applications. However, most existing access control mechanisms require a trusted party, which are vulnerable to many threats including malicious insiders and single point failure. In response to these challenges, we propose DL-BAC, a novel access control system based on the distributed ledger. DL-BAC robustly enforces access control policies without depending on a single trusted party. We also provide an extension of DL-BAC that is privacy respecting and evaluate the performance of DL-BAC to show its practicability.
Aissam Outchakoucht, Hamza Es-Samaali, Jean Philippe
The Internet of Things (IoT) is now destroying the barriers between the real and digital worlds. However, one of the huge problems that can slow down the development of this global wave, or even stop it, concerns security and privacy requirements. The criticality of these latter comes especially from the fact that the smart objects may contain very intimate information or even may be responsible for protecting people’s lives. In this paper, the focus is on access control in the IoT context by proposing a dynamic and fully distributed security policy. Our proposal will be based, on one hand, on the concept of the blockchain to ensure the distributed aspect strongly recommended in the IoT; and on the other hand on machine learning algorithms, particularly on reinforcement learning category, in order to provide a dynamic, optimized and self-adjusted security policy.
Unlinkability and accountability are conflicting yet critical requirements that need to be addressed in order to preserve users' privacy as well as to protect service providers in today identity ecosystems. In this paper we present a pseudonymous identity management system in which users can carry out unlinkable on-line transactions without having to disclose their actual identity information in plain text to the service providers. At the same time, the service providers have strong assurance about the authenticity of the transactions. In our approach, users' identity is cryptographically encoded in pseudonymous identity tokens. % issued by trusted identity providers. Our system includes a lightweight policy language which enables users and service providers to express their requirements pertaining to pseudonymous identity verification and a suite of protocols based on zero-knowledge-proofs which enables the fulfillment of these requirements. We have implemented a prototype of the proposed system and carried out a security and performance analysis.
There has recently been a flood of interest in potential new applications of blockchains, as well as proposals for more generic designs called public ledgers. Most of the novel proposals have been in the financial sector. However, the public ledger is an abstraction that solves several of the fundamental problems in the design of secure distributed systems: global time in the form of a strict linear order of past events, globally consistent and immutable view of the history, and enforcement of some application-specific safety properties. This paper investigates the applications of public ledgers to access control and, more specifically, to group management in distributed systems where entities are represented by their public keys and authorization is encoded into signed certificates. It is particularly difficult to handle negative information, such as revocation of certificates or group membership, in the distributed setting. The linear order of events and global consistency simplify these problems, but the enforcement of internal constraints in the ledger implementation often presents problems. We show that different types of revocation require slightly different properties from the ledger. We compare the requirements with Bitcoin, the best known blockchain, and describe an efficient ledger design for membership revocation that combines ideas from blockchains and from web-PKI monitoring. While we use certificate-based group-membership management as the case study, the same ideas can be applied more widely to rights revocation in distributed systems.
There has recently been a flood of interest in potential new applications of\nblockchains, as well as proposals for more generic designs called public\nledgers. Most of the novel proposals have been in the financial sector.\nHowever, the public ledger is an abstraction that solves several of the\nfundamental problems in the design of secure distributed systems: global time\nin the form of a strict linear order of past events, globally consistent and\nimmutable view of the history, and enforcement of some application-specific\nsafety properties. This paper investigates the applications of public ledgers\nto access control and, more specifically, to group management in distributed\nsystems where entities are represented by their public keys and authorization\nis encoded into signed certificates. It is particularly difficult to handle\nnegative information, such as revocation of certificates or group membership,\nin the distributed setting. The linear order of events and global consistency\nsimplify these problems, but the enforcement of internal constraints in the\nledger implementation often presents problems. We show that different types of\nrevocation require slightly different properties from the ledger. We compare\nthe requirements with Bitcoin, the best known blockchain, and describe an\nefficient ledger design for membership revocation that combines ideas from\nblockchains and from web-PKI monitoring. While we use certificate-based\ngroup-membership management as the case study, the same ideas can be applied\nmore widely to rights revocation in distributed systems.\n
We propose Blind Password Registration (BPR), a new class of cryptographic protocols that is instrumental for secure registration of client passwords at remote servers with additional protection against unwitting password disclosures on the server side that may occur due to the lack of the state-of-the-art password protection mechanisms implemented by the server or due to common server-compromise attacks. The dictionary attack resistance property of BPR protocols guarantees that the only information available to the server during and after the execution of the protocol cannot be used to reveal the client password without performing an offline dictionary attack on a password verifier (e.g. salted hash value) that is stored by the server at the end of the protocol. In particular, at no point in time the server is supposed to work with plain passwords. Our BPR model allows servers to enforce password policies and the requirement on the client to obey them during the execution of the BPR protocol is covered by the policy compliance property.We construct an efficient BPR protocol in the standard model for ASCII-based password policies using some techniques underlying the recently introduced Zero-Knowledge Password Policy Checks (ZKPPC). However, we do not rely on the full power of costly ZKPPC proofs and in fact show that BPR protocols can be modelled and realised simpler and significantly faster (as supported by our implementation) without using them as a building block. Our BPR protocol can directly be used to replace ZKPPC-based registration procedure for existing VPAKE protocols.
In the rich literature of secure multi-party computation MPC, several important results rely on whereby protocols from one model of MPC are transformed to protocols from another model. Motivated by the goal of simplifying and unifying results in the area of MPC, we formalize a general notion of black-box protocol transformations that captures previous transformations from the literature as special cases, and present several new transformations. We motivate our study of protocol transformations by presenting the following applications.
Simplifying feasibility results:Easily rederive a result in Goldreich's book 2004, on MPC with full in the presence of an honest majority, from an earlier result in the book, on MPC that offers security with abort.Rederive the classical result of Rabin and Ben-Or 1989 by applying a transformation to the simpler protocols of Ben-Or et al. or Chaum et al. 1988.Efficiency improvements:The first constant-rate MPC protocol for a constant number of parties that offers full information-theoretic with an optimal threshold, improving over the protocol of Rabin and Ben-Or;A fully secure MPC protocol with optimal threshold that improves over a previous protocol of Ben-Sasson et al. 2012 in the case of deep and narrow computations;A fully secure MPC protocol with near-optimal threshold that improves over a previous protocol of Damgard et al. 2010 by improving the dependence on the parameter from linear to polylogarithmic;An efficient new transformation from passive-secure two-party computation in the OT-hybrid and OLE-hybrid model to zero-knowledge proofs, improving over a recent similar transformation of Hazay and Venkitasubramaniam 2016 for the case of static zero-knowledge, which is restricted to the OT-hybrid model and requires a large number of commitments.
Finally, we prove the impossibility of two simple types of black-box protocol transformations, including an unconditional variant of a previous negative result of Rosulek 2012 that relied on the existence of one-way functions.
Succinct non-interactive zero-knowledge arguments of knowledge (Zk-SNARKs) are needed in many applications. Unfortunately, all previous zk-SNARKs for interesting languages are either inefficient for the prover, or are non-adaptive and based on a commitment scheme that depends both on the prover's input and on the language, i.e., they are not commit-and-prove (CaP) SNARKs. We propose a proof-friendly extractable commitment scheme, and use it to construct prover-efficient adaptive CaP succinct zk-SNARKs for different languages, that can all reuse committed data. In new zk-SNARKs, the prover computation is dominated by a linear number of cryptographic operations. We use batch-verification to decrease the verifier's computation; importantly, batch-verification can be used also in QAP-based zk-SNARKs.
The ‘blockchain’ is the core mechanism for the Bitcoin digital payment system. It embraces a set of inter-related technologies: the blockchain itself as a distributed record of digital events, the distributed consensus method to agree whether a new block is legitimate, automated smart contracts, and the data structure associated with each block. We propose a permanent distributed record of intellectual effort and associated reputational reward, based on the blockchain that instantiates and democratises educational reputation beyond the academic community. We are undertaking initial trials of a private blockchain or storing educational records, drawing also on our previous research into reputation management for educational systems.
Authentication is primary process by which you can verify that someone is legitimate user or not. The identification of an entity or person is based on the username and password provided to that entity. In security systems, authentication is playing an important role by which it provides access to the system to an entity based on their identity. Authentication only ensures that the entity who is claims to be, but do not passes any information about the access rights of the entity. The zero- knowledge protocol used to provide data security and zero-knowledge transfer during authentication. The proposed model for node authentication using zero - knowledge proof for secure login is much faster than existing model in terms of execution time, CPU usage, time complexity and performance. It also provides security features likes confidentiality, integrity, authentication and non-repudiation.
Unlink ability and accountability are conflicting yet critical requirements for on-line transactions that need to be addressed in order to preserve users' privacy as well as to protect service providers in today identity ecosystems. In this poster paper we introduce a pseudonymous identity management system in which users can carry out unlink able on-line transactions without having to disclose their actual identity to the service providers. At the same time, the service providers have strong assurance about the authenticity of the identity and credentials. In our approach, users' identity is cryptographically encoded in pseudonymous identity tokens issued by trusted identity providers. Our system includes a lightweight policy language which enables users and service providers to express their requirements pertaining to pseudonymous identity verification and a suite of protocols based on zero-knowledge-proofs which enables the fulfillment of these requirements.
The use of security certificates under the Cloud environment is the foundation to establish mutual trust between the Cloud and the user. In this paper, we propose an authentication method based on zero-knowledge proof and the mind of key escrow. With the method, authentication will not only satisfy the requirement anonymity and security but also can recover the real identity information in special circumstances with the cooperation of multiple parties. We will show that this proposed method is more suitable for promotion through analysis and comparison with an existing scheme.
Zero-knowledge proof protocol is a basic cryptographic technique. And zero-knowledge proof of double discrete logarithm has some particular properties, so it has been widely applied in many security systems. But the efficient problem of zero-knowledge proof of double discrete logarithm has not been solved to this day, since there are some special difficulties in computing this kind of knowledge proof. Hence, the time complexity and the space complexity of existing schemes are all O(k), where k is a security parameter. After redesigning the basic construction of knowledge proof, we provide a new zero-knowledge proof of double discrete logarithm, which is the first scheme with O(1) time complexity and O(1) space complexity. If introducing an off-line TTP (trusted third party), we can provide two additional zeroknowledge proof schemes of double discrete logarithm, one is even more efficient than the first one, the other one solves another open problem, which is how to efficiently prove the equality of double discrete logarithms in zero-knowledge way, and the existing techniques cannot solve this problem. We also provide the detailed security proofs of our designs and efficiency analysis, comparing with the existing schemes. The significant improvement in efficiency of this basic cryptographic technique is also helpful for many security systems.
Paul Lajoie-Mazenc, Emmanuelle Anceaume, Gilles Guette, Thomas Sirvent · 5 authors
—Open and large-scale systems do not encourage their users to behave trustworthily, which may entail non-negligible risks when interacting with unknown users, for instance when buying an item on an e-commerce platform. Reputation mech-anisms reduce these risks by associating a reputation score to each user, summarizing their past behavior. To be useful to users, reputation mechanisms need to guarantee two main properties: the non-monotonicity of reputation scores, in order to exactly reflect the users' behavior, and the privacy of their users, so that the history of their transactions is not publicly available. We propose a distributed privacy-preserving reputation mechanism handling non-monotonic ratings. Our proposition relies on two distinct distributed third parties and on cryptographic tools, including zero-knowledge proofs of knowledge, anonymous proxy signatures, and verifiable secret sharing. We show that this proposal is computationally efficient, and thus practical. To the best of our knowledge, this solution is the first one that preserves users' privacy and handles both positive and negative ratings without relying on a central authority.
Entendemos por inteligencia colectiva una forma de inteligencia que surge de la colaboración y la participación de varios individuos o, siendo más estrictos, varias entidades. En base a esta sencilla definición podemos observar que este concepto es campo de estudio de las más diversas disciplinas como pueden ser la sociología, las tecnologías de la información o la biología, atendiendo cada una de ellas a un tipo de entidades diferentes: seres humanos, elementos de computación o animales. Como elemento común podríamos indicar que la inteligencia colectiva ha tenido como objetivo el ser capaz de fomentar una inteligencia de grupo que supere a la inteligencia individual de las entidades que lo forman a través de mecanismos de coordinación, cooperación, competencia, integración, diferenciación, etc. Sin embargo, aunque históricamente la inteligencia colectiva se ha podido desarrollar de forma paralela e independiente en las distintas disciplinas que la tratan, en la actualidad, los avances en las tecnologías de la información han provocado que esto ya no sea suficiente. Hoy en día seres humanos y máquinas a través de todo tipo de redes de comunicación e interfaces, conviven en un entorno en el que la inteligencia colectiva ha cobrado una nueva dimensión: ya no sólo puede intentar obtener un comportamiento superior al de sus entidades constituyentes sino que ahora, además, estas inteligencias individuales son completamente diferentes unas de otras y aparece por lo tanto el doble reto de ser capaces de gestionar esta gran heterogeneidad y al mismo tiempo ser capaces de obtener comportamientos aún más inteligentes gracias a las sinergias que los distintos tipos de inteligencias pueden generar. Dentro de las áreas de trabajo de la inteligencia colectiva existen varios campos abiertos en los que siempre se intenta obtener unas prestaciones superiores a las de los individuos. Por ejemplo: consciencia colectiva, memoria colectiva o sabiduría colectiva. Entre todos estos campos nosotros nos centraremos en uno que tiene presencia en la práctica totalidad de posibles comportamientos inteligentes: la toma de decisiones. El campo de estudio de la toma de decisiones es realmente amplio y dentro del mismo la evolución ha sido completamente paralela a la que citábamos anteriormente en referencia a la inteligencia colectiva. En primer lugar se centró en el individuo como entidad decisoria para posteriormente desarrollarse desde un punto de vista social, institucional, etc. La primera fase dentro del estudio de la toma de decisiones se basó en la utilización de paradigmas muy sencillos: análisis de ventajas e inconvenientes, priorización basada en la maximización de algún parámetro del resultado, capacidad para satisfacer los requisitos de forma mínima por parte de las alternativas, consultas a expertos o entidades autorizadas o incluso el azar. Sin embargo, al igual que el paso del estudio del individuo al grupo supone una nueva dimensión dentro la inteligencia colectiva la toma de decisiones colectiva supone un nuevo reto en todas las disciplinas relacionadas. Además, dentro de la decisión colectiva aparecen dos nuevos frentes: los sistemas de decisión centralizados y descentralizados. En el presente proyecto de tesis nos centraremos en este segundo, que es el que supone una mayor atractivo tanto por las posibilidades de generar nuevo conocimiento y trabajar con problemas abiertos actualmente así como en lo que respecta a la aplicabilidad de los resultados que puedan obtenerse. Ya por último, dentro del campo de los sistemas de decisión descentralizados existen varios mecanismos fundamentales que dan lugar a distintas aproximaciones a la problemática propia de este campo. Por ejemplo el liderazgo, la imitación, la prescripción o el miedo. Nosotros nos centraremos en uno de los más multidisciplinares y con mayor capacidad de aplicación en todo tipo de disciplinas y que, históricamente, ha demostrado que puede dar lugar a prestaciones muy superiores a otros tipos de mecanismos de decisión descentralizados: la confianza y la reputación. Resumidamente podríamos indicar que confianza es la creencia por parte de una entidad que otra va a realizar una determinada actividad de una forma concreta. En principio es algo subjetivo, ya que la confianza de dos entidades diferentes sobre una tercera no tiene porqué ser la misma. Por otro lado, la reputación es la idea colectiva (o evaluación social) que distintas entidades de un sistema tiene sobre otra entidad del mismo en lo que respecta a un determinado criterio. Es por tanto una información de carácter colectivo pero única dentro de un sistema, no asociada a cada una de las entidades del sistema sino por igual a todas ellas. En estas dos sencillas definiciones se basan la inmensa mayoría de sistemas colectivos. De hecho muchas disertaciones indican que ningún tipo de organización podría ser viable de no ser por la existencia y la utilización de los conceptos de confianza y reputación. A partir de ahora, a todo sistema que utilice de una u otra forma estos conceptos lo denominaremos como sistema de confianza y reputación (o TRS, Trust and Reputation System). Sin embargo, aunque los TRS son uno de los aspectos de nuestras vidas más cotidianos y con un mayor campo de aplicación, el conocimiento que existe actualmente sobre ellos no podría ser más disperso. Existen un gran número de trabajos científicos en todo tipo de áreas de conocimiento: filosofía, psicología, sociología, economía, política, tecnologías de la información, etc. Pero el principal problema es que no existe una visión completa de la confianza y reputación en su sentido más amplio. Cada disciplina focaliza sus estudios en unos aspectos u otros dentro de los TRS, pero ninguna de ellas trata de explotar el conocimiento generado en el resto para mejorar sus prestaciones en su campo de aplicación concreto. Aspectos muy detallados en algunas áreas de conocimiento son completamente obviados por otras, o incluso aspectos tratados por distintas disciplinas, al ser estudiados desde distintos puntos de vista arrojan resultados complementarios que, sin embargo, no son aprovechados fuera de dichas áreas de conocimiento. Esto nos lleva a una dispersión de conocimiento muy elevada y a una falta de reutilización de metodologías, políticas de actuación y técnicas de una disciplina a otra. Debido su vital importancia, esta alta dispersión de conocimiento se trata de uno de los principales problemas que se pretenden resolver con el presente trabajo de tesis. Por otro lado, cuando se trabaja con TRS, todos los aspectos relacionados con la seguridad están muy presentes ya que muy este es un tema vital dentro del campo de la toma de decisiones. Además también es habitual que los TRS se utilicen para desempeñar responsabilidades que aportan algún tipo de funcionalidad relacionada con el mundo de la seguridad. Por último no podemos olvidar que el acto de confiar está indefectiblemente unido al de delegar una determinada responsabilidad, y que al tratar estos conceptos siempre aparece la idea de riesgo, riesgo de que las expectativas generadas por el acto de la delegación no se cumplan o se cumplan de forma diferente. Podemos ver por lo tanto que cualquier sistema que utiliza la confianza para mejorar o posibilitar su funcionamiento, por su propia naturaleza, es especialmente vulnerable si las premisas en las que se basa son atacadas. En este sentido podemos comprobar (tal y como analizaremos en más detalle a lo largo del presente documento) que las aproximaciones que realizan las distintas disciplinas que tratan la violación de los sistemas de confianza es de lo más variado. únicamente dentro del área de las tecnologías de la información se ha intentado utilizar alguno de los enfoques de otras disciplinas de cara a afrontar problemas relacionados con la seguridad de TRS. Sin embargo se trata de una aproximación incompleta y, normalmente, realizada para cumplir requisitos de aplicaciones concretas y no con la idea de afianzar una base de conocimiento más general y reutilizable en otros entornos. Con todo esto en cuenta, podemos resumir contribuciones del presente trabajo de tesis en las siguientes. • La realización de un completo análisis del estado del arte dentro del mundo de la confianza y la reputación que nos permite comparar las ventajas e inconvenientes de las diferentes aproximación que se realizan a estos conceptos en distintas áreas de conocimiento. • La definición de una arquitectura de referencia para TRS que contempla todas las entidades y procesos que intervienen en este tipo de sistemas. • La definición de un marco de referencia para analizar la seguridad de TRS. Esto implica tanto identificar los principales activos de un TRS en lo que respecta a la seguridad, así como el crear una tipología de posibles ataques y contramedidas en base a dichos activos. • La propuesta de una metodología para el análisis, el diseño, el aseguramiento y el despliegue de un TRS en entornos reales. Adicionalmente se exponen los principales tipos de aplicaciones que pueden obtenerse de los TRS y los medios para maximizar sus prestaciones en cada una de ellas. • La generación de un software que permite simular cualquier tipo de TRS en base a la arquitectura propuesta previamente. Esto permite evaluar las prestaciones de un TRS bajo una determinada configuración en un entorno controlado previamente a su despliegue en un entorno real. Igualmente es de gran utilidad para evaluar la resistencia a distintos tipos de ataques o mal-funcionamientos del sistema. Además de las contribuciones realizadas directamente en el campo de los TRS, hemos realizado aportaciones originales a distintas áreas de conocimiento gracias a la aplicación de las metodologías de análisis y diseño citadas con anterioridad. • Detección de anomalías térmicas en Data Centers. Hemos implementado con éxito un sistema de deteción de anomalías térmicas basado en un TRS. Comparamos la detección de prestaciones de algoritmos de tipo Self-Organized Maps (SOM) y Growing Neural Gas (GNG). Mostramos como SOM ofrece mejores resultados para anomalías en los sistemas de refrigeración de la sala mientras que GNG es una opción más adecuada debido a sus tasas de detección y aislamiento para casos de anomalías provocadas por una carga de trabajo excesiva. • Mejora de las prestaciones de recolección de un sistema basado en swarm computing y odometría social. Gracias a la implementación de un TRS conseguimos mejorar las capacidades de coordinación de una red de robots autónomos distribuidos. La principal contribución reside en el análisis y la validación de las mejoras increméntales que pueden conseguirse con la utilización apropiada de la información existente en el sistema y que puede ser relevante desde el punto de vista de un TRS, y con la implementación de algoritmos de cálculo de confianza basados en dicha información. • Mejora de la seguridad de Wireless Mesh Networks contra ataques contra la integridad, la confidencialidad o la disponibilidad de los datos y / o comunicaciones soportadas por dichas redes. • Mejora de la seguridad de Wireless Sensor Networks contra ataques avanzamos, como insider attacks, ataques desconocidos, etc. Gracias a las metodologías presentadas implementamos contramedidas contra este tipo de ataques en entornos complejos. En base a los experimentos realizados, hemos demostrado que nuestra aproximación es capaz de detectar y confinar varios tipos de ataques que afectan a los protocoles esenciales de la red. La propuesta ofrece unas velocidades de detección muy altas así como demuestra que la inclusión de estos mecanismos de actuación temprana incrementa significativamente el esfuerzo que un atacante tiene que introducir para comprometer la red. Finalmente podríamos concluir que el presente trabajo de tesis supone la generación de un conocimiento útil y aplicable a entornos reales, que nos permite la maximización de las prestaciones resultantes de la utilización de TRS en cualquier tipo de campo de aplicación. De esta forma cubrimos la principal carencia existente actualmente en este campo, que es la falta de una base de conocimiento común y agregada y la inexistencia de una metodología para el desarrollo de TRS que nos permita analizar, diseñar, asegurar y desplegar TRS de una forma sistemática y no artesanal y ad-hoc como se hace en la actualidad. ABSTRACT By collective intelligence we understand a form of intelligence that emerges from the collaboration and competition of many individuals, or strictly speaking, many entities. Based on this simple definition, we can see how this concept is the field of study of a wide range of disciplines, such as sociology, information science or biology, each of them focused in different kinds of entities: human beings, computational resources, or animals. As a common factor, we can point that collective intelligence has always had the goal of being able of promoting a group intelligence that overcomes the individual intelligence of the basic entities that constitute it. This can be accomplished through different mechanisms such as coordination, cooperation, competence, integration, differentiation, etc. Collective intelligence has historically been developed in a parallel and independent way among the different disciplines that deal with it. However, this is not enough anymore due to the advances in information technologies. Nowadays, human beings and machines coexist in environments where collective intelligence has taken a new dimension: we yet have to achieve a better collective behavior than the individual one, but now we also have to deal with completely different kinds of individual intelligences. Therefore, we have a double goal: being able to deal with this heterogeneity and being able to get even more intelligent behaviors thanks to the synergies that the different kinds of intelligence can generate. Within the areas of collective intelligence there are several open topics where they always try to get better performances from groups than from the individuals. For example: collective consciousness, collective memory, or collective wisdom. Among all these topics we will focus on collective decision making, that has influence in most of the collective intelligent behaviors. The field of study of decision making is really wide, and its evolution has been completely parallel to the aforementioned collective intelligence. Firstly, it was focused on the individual as the main decision-making entity, but later it became involved in studying social and institutional groups as basic decision-making entities. The first studies within the decision-making discipline were based on simple paradigms, such as pros and cons analysis, criteria prioritization, fulfillment, following orders, or even chance. However, in the same way that studying the community instead of the individual meant a paradigm shift within collective intelligence, collective decision-making means a new challenge for all the related disciplines. Besides, two new main topics come up when dealing with collective decision-making: centralized and decentralized decision-making systems. In this thesis project we focus in the second one, because it is the most interesting based on the opportunities to generate new knowledge and deal with open issues in this area, as well as these results can be put into practice in a wider set of real-life environments. Finally, within the decentralized collective decision-making systems discipline, there are several basic mechanisms that lead to different approaches to the specific problems of this field, for example: leadership, imitation, prescription, or fear. We will focus on trust and reputation. They are one of the most multidisciplinary concepts and with more potential for applying them in every kind of environments. Besides, they have historically shown that they can generate better performance than other decentralized decision-making mechanisms. Shortly, we say trust is the belief of one entity that the outcome of other entities’ actions is going to be in a specific way. It is a subjective concept because the trust of two different entities in another one does not have to be the same. Reputation is the collective idea (or social evaluation) that a group of entities within a system have about another entity based on a specific criterion. Thus, it is a collective concept in its origin. It is important to say that the behavior of most of the collective systems are based on these two simple definitions. In fact, a lot of articles and essays describe how any organization would not be viable if the ideas of trust and reputation did not exist. From now on, we call Trust an Reputation System (TRS) to any kind of system that uses these concepts. Even though TRSs are one of the most common everyday aspects in our lives, the existing knowledge about them could not be more dispersed. There are thousands of scientific works in every field of study related to trust and reputation: philosophy, psychology, sociology, economics, politics, information sciences, etc. But the main issue is that a comprehensive vision of trust and reputation for all these disciplines does not exist. discipline its studies on a specific set of topics but of them to of the knowledge in the other disciplines to its behavior or topics in are completely in and even though the study of topics within several disciplines these results are not the discipline where they were This to a knowledge and to a in the of and among disciplines. to its this of trust and reputation knowledge is one of the main problems this thesis to we with all the aspects related to are a it is a vital within the decision-making systems. Besides, TRS are to related to Finally, we that the of is to the of a specific when we deal with these the idea of is always This to the of not being accomplished or being accomplished in a different way we Thus, we can see that any system trust to or its because of its is vulnerable if the it is based on are to this we can see that the approaches of the different disciplines that study of trust and reputation are of approaches of other disciplines have been within the information science of but these approaches are not and to achieve specific of specific They try to a common base of knowledge that could be in other Based on all these this the following to the field of • The of the most existing knowledge related to trust and reputation systems on and • We a for TRS, the main entities and • We a for TRS. We the main and a of for TRS. • We and a to and TRS in real-life environments. we the principal kind of we can with TRS and how TRS can a specific • We a software to and the behavior of a TRS in to achieve a specific or In to the to the field of the TRS, we have to different areas of knowledge thanks to the of the analysis, and • of in Data Centers. to the of the TRS and we a system based on a the performance of Maps and Growing Neural Gas We how SOM better results for of in with We also that GNG better and for the when to • the performance of a system based on swarm computing and social the of a TRS, we to the of a of The main in the and of the that can be with information that in the system and that are for the TRS, and the of the trust based on such • Wireless Mesh Networks the or of and these to the of a TRS we the these kind of and we potential the • We the of Wireless Sensor Networks attacks, such as insider attacks, attacks, etc. to the TRS and we such in a In our we have that our system is of and that the We have also that our is of it has been that the of the mechanisms the the has to in to the we can to all and this thesis a and knowledge in real-life environments that to the performance of any system based on a TRS. Thus, we deal with the main of this the of a common and base of knowledge and the of a for the of TRS that to and TRS in a way.
The role-based access control (RBAC) is a natural and versatile model of the access control principle. In the real world, it is common that an organization provides a service to a user who owns a certain role that was issued by a different organization. However, such a trans-organizational RBAC is not common in a computer network because it is difficult to establish both the security that prohibits malicious impersonation of roles and the flexibility that allows small organizations/individual users to fully control their own roles. This study proposes a system that makes use of Bitcoin technology to realize a trans-organizational RBAC mechanism. Bitcoin, the first decentralized digital currency, is a payment network that has become a platform for innovative ideas. Bitcoin’s technology, including its protocol, cryptography, and open-source nature, has built a good reputation and has been applied in other applications, such as trusted timestamping. The proposed system uses Bitcoin technology as a versatile infrastructure to represent the trust and endorsement relationship that are essential in RBAC and to realize a challenge-response authentication protocol that verifies a user's ownership of roles.
Trust has always been important in electronic commerce. Prior research in MIS has mainly focused on trust-building mechanisms and insurance against opportunistic behavior. We suggest a âtrust-free systemâ approach, which addresses trust issues by eliminating the need for trust. Using Bitcoin, a decentralized electronic cash system, we illustrate how a system can solve trust issues by becoming âtrust-freeâ through design. We discuss the design features of this approach, and explore research questions for generalizing the design to other information systems. The idea of a trust-free system opens a new way of thinking about trust issues in information systems. We believe that there is an untapped potential for new ideas and research on how to design and evaluate information systems.