Fair exchange in e-commerce and certified e-mail, new scenarios and protocols

We are witnessing a steady growth in the use of Internet in the electronic commerce field. This rise is promoting the migration from traditional processes and applications (paper based) to an electronic model. But the security of electronic transactions continues to pose an impediment to its implementation. Traditionally, most business transactions were conducted in person. Signing a contract required the meeting of all interested parties, the postman delivered certified mail in hand, and when paying for goods or services both customer and provider were present. When all parties are physically present, a transaction does not require a complex protocol. The participants acknowledge the presence of the other parties as assurance that they will receive their parts, whether a signature on a contract, or a receipt, etc. But with e-commerce growing in importance as sales and business channel, all these transactions have moved to its digital counterpart. Therefore we have digital signature of contracts, certified delivery of messages and electronic payment systems. With electronic transactions, the physical presence is not required,moreover, most of the times it is even impossible. The participants in a transaction can be thousands of kilometers away from each other, and they may not even be human participants, they can be machines. Thus, the security that the transaction will be executed without incident is not assured per se, we need additional security measures. To address this problem, fair exchange protocols were developed. In a fair exchange every party involved has an item that wants to exchange, but none of the participants is willing to give his item away unless he has an assurance he will receive the corresponding item from the other participants. Fair exchange has many applications, like digital signature of contracts, where the items to be exchanged are signatures on contracts, certified delivery of messages, where we exchange a message for evidence of receipt, or a payment process, where we exchange a payment (e-cash, e-check, visa, etc.) for digital goods or a receipt. The objective of this dissertation is the study of the fair exchange problem. In particular, it presents two new scenarios for digital contracting, the Atomic Multi- Two Party (AM2P) and the Agent Mediated Scenario (AMS), and proposes one optimistic contract signing protocol for each one. Moreover, it studies the efficiency of Multi-Party Contract Signing (MPCS) protocols from their architecture point of view, presenting a new lower bound for each architecture, in terms of minimum number of transactions needed. Regarding Certified Electronic Mail (CEM), this dissertation presents two optimistic CEMprotocols designed to be deployed on thecurrent e-mail infrastructure, therefore they assume the participation of multiple Mail Transfer Agents (MTAs). In one case, the protocol assumes untrusted MTAs whereas in the other one it assumes each User Agent (UA) trusts his own MTA. Regarding payment systems, this dissertation presents a secure and efficient electronic bearer bank check scheme allowing the electronic checks to be transferred fairly and anonymously.L’ús d’Internet en l’àmbit del comerç electrònic està experimentant un creixement estable. Aquest increment d’ús està promovent lamigració de processos tradicionals i aplicacions (basades en paper) cap a un model electrònic. Però la seguretat de les transaccions electròniques continua impedint la seva implantació. Tradicionalment, la majoria de les transaccions s’han dut a terme en persona. La firma d’un contracte requeria la presència de tots els firmants, el carter entrega les cartes certificades enmà, i quan es paga per un bé o servei ambdós venedor i comprador hi són presents. Quan totes les parts hi són presents, les transaccions no requereixen un protocol complex. Els participants assumeixen la presència de les altres parts com assegurança que rebran el que esperen d’elles, ja sigui la firma d’un contracte, un rebut d’entrega o un pagament. Però amb el creixement del comerç electrònic com a canal de venda i negoci, totes aquestes transaccions s’hanmogut al seu equivalent en el món electrònic. Així doncs tenim firma electrònica de contractes, enviament certificat de missatges, sistemes de pagament electrònic, etc. En les transaccions electròniques la presència física no és necessària, de fet, la majoria de vegades és fins it tot impossible. Els participants poden estar separats permilers de kilòmetres, i no és necessari que siguin humans, podrien sermàquines. Llavors, la seguretat de que la transacció s’executarà correctament no està assegurada per se, necessitem proporcionar mesures de seguretat addicionals. Per solucionar aquest problema, es van desenvolupar els protocols d’intercanvi equitatiu. En un intercanvi equitatiu totes les parts involucrades tenen un objecte que volen intercanviar, però cap de les parts implicades vol donar el seu objecte si no té la seguretat que rebrà els objectes de les altres parts. L’intercanvi equitatiu té multitud d’aplicacions, com la firma electrònica de contractes, on els elements a intercanviar son firmes de contractes, enviament certificat demissatges, on s’intercanvien unmissatge per una evidència de recepció, o un procés de pagament, on intercanviemun pagament (e-cash, visa, e-xec, etc.) per bens digitals o per un rebut. L’objectiu d’aquesta tesi és estudiar el problema de l’intercanvi equitatiu. En particular, la tesi presenta dos nous escenaris per a la firma electrònica de contractes, l’escenari multi-two party atòmic i l’escenari amb agents intermediaris, i proposa un protocol optimista per a cada un d’ells. A més, presenta un estudi de l’eficiència dels protocols de firma electrònica multi-part (Multi-Party Contract Signing (MPCS) protocols) des del punt de vista de la seva arquitectura, presentant una nova fita per a cada una, en termes de mínim nombre de transaccions necessàries. Pel que fa al correu electrònic certificat, aquesta tesi presenta dos protocols optimistes dissenyats per a ser desplegats damunt l’infraestructura actual de correu electrònic, per tant assumeix la participació demúltiples agents de transferència de correu. Un dels protocols assumeix que cap dels agents de transferència de correu participants és de confiança,mentre que l’altre assumeix que cada usuari confia en el seu propi agent. Pel que fa a sistemes de pagament, la tesi presenta un esquema de xec bancari al portador, eficient i segur, que garanteix que la transferència dels xecs es fa demanera anònima i equitativa

Data security and trading framework for smart grids in neighborhood area networks

Due to the drastic increase of electricity prosumers, i.e., energy consumers that are also producers, smart grids have become a key solution for electricity infrastructure. In smart grids, one of the most crucial requirements is the privacy of the final users. The vast majority of the literature addresses the privacy issue by providing ways of hiding user’s electricity consumption. However, open issues in the literature related to the privacy of the electricity producers still remain. In this paper, we propose a framework that preserves the secrecy of prosumers’ identities and provides protection against the traffic analysis attack in a competitive market for energy trade in a Neighborhood Area Network (NAN). In addition, the amount of bidders and of successful bids are hidden from malicious attackers by our framework. Due to the need for small data throughput for the bidders, the communication links of our framework are based on a proprietary communication system. Still, in terms of data security, we adopt the Advanced Encryption Standard (AES) 128bit with Exclusive-OR (XOR) keys due to their reduced computational complexity, allowing fast processing. Our framework outperforms the state-of-the-art solutions in terms of privacy protection and trading flexibility in a prosumer-to-prosumer design

Techniques, Taxonomy, and Challenges of Privacy Protection in the Smart Grid

As the ease with which any data are collected and transmitted increases, more privacy concerns arise leading to an increasing need to protect and preserve it. Much of the recent high-profile coverage of data mishandling and public mis- leadings about various aspects of privacy exasperates the severity. The Smart Grid (SG) is no exception with its key characteristics aimed at supporting bi-directional information flow between the consumer of electricity and the utility provider. What makes the SG privacy even more challenging and intriguing is the fact that the very success of the initiative depends on the expanded data generation, sharing, and pro- cessing. In particular, the deployment of smart meters whereby energy consumption information can easily be collected leads to major public hesitations about the tech- nology. Thus, to successfully transition from the traditional Power Grid to the SG of the future, public concerns about their privacy must be explicitly addressed and fears must be allayed. Along these lines, this chapter introduces some of the privacy issues and problems in the domain of the SG, develops a unique taxonomy of some of the recently proposed privacy protecting solutions as well as some if the future privacy challenges that must be addressed in the future.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111644/1/Uludag2015SG-privacy_book-chapter.pd

Keeping Fairness Alive : Design and formal verification of optimistic fair exchange protocols

Fokkink, W.J. [Promotor]Pol, J.C. van de [Promotor

Diglosia Geolingüística en las Naciones del Consejo de Cooperación para los Estados Árabes del Golfo

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Filología, leída el 06-09-2021This sociolinguistic research falls within the broad field of diglossic cross-cultural communication, the social evaluation of accents and social identity theories. The study of dialectal variations in the pronunciation of Educated Standard Arabic (ESA) is central to the understanding of the degree of agreement that the informants showed regarding their interpersonal evaluations in terms of the standard accented varieties and according to the standardised rating constructs (see Wiggins and Trobst, 1999). The aim of this research was to analyse a specific international reference framework of standard dialectal variations in the Arabic dialectal continuum from Gulf Cooperation Council countries between men and women alike who are likely to attach more prestige to a specific oral language variety. This research proposes that the degree of agreement that the informants showed for a particular accent is a determinant in the implementation of effective communication in order to achieve concord and harmony in interpersonal cross-cultural interactions...El presente estudio sociolingüístico se enmarca dentro del extenso campo de la comunicación diglósica transcultural, la evaluación social de acentos, y las teorías de identidad social. El estudio de las variaciones dialectales de la pronunciación de una misma lengua resulta de vital importancia en sociolingüística para entender hasta qué punto los diferentes acentos influyen en la evaluación personal de acuerdo con determinados valores racionales estimativos estandarizados (ver Wiggins y Tobst, 1999). El propósito de esta investigación reside en analizar un marco específico internacional de referencia sobre las variaciones dialectales comprendidas en las naciones del consejo de cooperación para los estados árabes del golfo entre hombres y mujeres por igual, esperando encontrar la variedad de mayor prestigio. Esta investigación propone que el grado de conformidad expresado por los informantes con respecto a un acento en particular es determinante para la implementación de una comunicación efectiva que aglutine la concordia y la armonía en las interacciones comunicativas transculturales e interpersonales...Fac. de FilologíaTRUEunpu

A user-managed access control model and mechanisms for web based social networks: enhancing expressive power, co-ownership management, interoperability and authorized data exposures

Web Based Social Networks (WBSNs) are well-known applications which are used by thousands of people worldwide. However, privacy issues, and access control in particular, cannot be disregarded. WBSNs consist of users who upload data to be shared with other users and the management of who is able to access to the uploaded data is a subject to study. In this respect, this thesis focuses on four aspects. First, WBSN users have to specify their privacy preferences in a fine-grained way. Second, WBSN data is not usually related to a single user, who uploads it and who is considered the owner, but to multiple users who are referred to as co-owners. Then, access control has to be managed preserving the privacy of both, owners and co-owners, such that all their privacy preferences are satisfied without restrictions. Thirdly, the great quantity of WBSNs forces users upon being enrolled in many of them, though being access control management a cumbersome task. Lastly, users upload data to WBSNs and providers store it and may use it for unnoticed or unauthorized purposes. The widespread development of WBSNs has contributed to the enhancement of these applications. The demanding necessity of providing users with tools to control accesses to their data, has boosted the development of proposals in this regard. Nonetheless, a general lack of fine-grained management is detected. The goal of this thesis is to facilitate fine-grained access control management along the whole usage process within and among different WBSNs in a privacy preserving way. Firstly, an expressive usage control model, together with its administrative model, is proposed to achieve the definition of fine-grained access control preferences. Based on previous models, a mechanism to manage co-ownership corresponds to the second contribution of this thesis. Data is decomposed in parts and each of them is assigned to the owner or to a co-owner who establishes access control preferences. Then, these preferences are jointly evaluated and the privacy of all users is completely preserved. Having the right tools to manage access control in a fine-grained way, the third and last contribution of this thesis is a pair of protocols, one being based on an extension of the other, to attain interoperability, reusability and unauthorized data exposures among different WBSNs. Also taking the proposed usage control model as the underlying base to manage access control, these protocols reduce the burden of managing access control in different applications and thus, they help to increase users' control over their data. As a result, this thesis aims to be a challenging step towards the enhancement of access control management procedures in the social networking field.Las Redes Sociales (RSs) son aplicaciones conocidas y utilizadas a lo largo y ancho del mundo. Sin embargo, los problemas de privacidad, y de control de acceso en particular, no pueden menospreciarse. Las RSs se basan en usuarios que comparten datos entre sí, siendo la gestión de quién puede acceder a dichos datos un tema al que hay que prestar especial interés. En base a esto, la presente Tesis estudia cuatro cuestiones. Primero, los usuarios de las RSs tienen que especificar sus preferencias con alta granularidad. Segundo, los datos de las RSs no se asocian a un único usuario, considerado el propietario y quien sube los datos a las RSs, sino que pueden estar asociados a múltiples usuarios, los cuales reciben el nombre de copropietarios. Por ello, el control de acceso tiene que preservar la privacidad de todos los usuarios, tanto de los propietarios como de los copropietarios, consiguiendo satisfacer las preferencias de control de acceso de todos ellos. Tercero, la gran cantidad de RSs existentes obliga a los usuarios a crear cuentas en cada una de ellas en las que quieran participar, siendo la gestión del control de acceso una tarea tediosa. En último lugar, los usuarios suben sus datos a las RSs y los proveedores de servicio los almacenan, pudiéndolos utilizar para su propio beneficio. La necesidad de proporcionar a los usuarios las herramientas adecuadas para que puedan controlar sus datos ha acelerado el desarrollo de propuestas para la mejora de las RSs. Sin embargo, se detecta una falta de granularidad en la gestión del control de acceso. El objetivo de esta Tesis es facilitar la gestión del control de acceso con alta granularidad entre distintas RSs a lo largo de todo el proceso de uso y preservando la privacidad. En primer lugar se propone un modelo de uso expresivo, junto con el modelo administrativo complementario, para conseguir la definición de preferencias de control de acceso con alta granularidad. Basado en los modelos anteriores, la segunda de las contribuciones se corresponde con el desarrollo de un mecanismo para la gestión de la copropiedad. Los datos son descompuestos en partes y cada parte asignada al propietario o a un copropietario para que éste establezca las preferencias de privacidad deseadas. Posteriormente, en cada solicitud de acceso a un dato se evalúan todas las preferencias, preservándose así la privacidad de todos los usuarios. Disponiendo de las herramientas adecuadas para gestionar el control de acceso con alta granularidad, la tercera y última de las contribuciones de esta tesis consiste en el desarrollo de un par de protocolos, uno extendiendo el otro. Estos protocolos facilitan la interoperabilidad, la reusabilidad y la minimización del acceso a los datos de forma no autorizada entre distintas RSs. Igualmente, aplicando el modelo de uso propuesto para la gestión del control de acceso, estos protocolos reducen las tareas a realizar para gestionar el acceso en distintas aplicaciones y por tanto, ayudan a incrementar el control que los usuarios tienen sobre sus datos. En resumen, esta tesis pretende dar un paso en la mejora del control de acceso en las RSs.Programa en Ciencia y Tecnología InformáticaPresidente: Juan Manuel Estévez Tapiador; Vocal: Flavio Lombardi; Secretario: María Isabel González Vasc

Techniques for Improving Security and Trustworthiness of Integrated Circuits

The integrated circuit (IC) development process is becoming increasingly vulnerable to malicious activities because untrusted parties could be involved in this IC development flow. There are four typical problems that impact the security and trustworthiness of ICs used in military, financial, transportation, or other critical systems: (i) Malicious inclusions and alterations, known as hardware Trojans, can be inserted into a design by modifying the design during GDSII development and fabrication. Hardware Trojans in ICs may cause malfunctions, lower the reliability of ICs, leak confidential information to adversaries or even destroy the system under specifically designed conditions. (ii) The number of circuit-related counterfeiting incidents reported by component manufacturers has increased significantly over the past few years with recycled ICs contributing the largest percentage of the total reported counterfeiting incidents. Since these recycled ICs have been used in the field before, the performance and reliability of such ICs has been degraded by aging effects and harsh recycling process. (iii) Reverse engineering (RE) is process of extracting a circuit’s gate-level netlist, and/or inferring its functionality. The RE causes threats to the design because attackers can steal and pirate a design (IP piracy), identify the device technology, or facilitate other hardware attacks. (iv) Traditional tools for uniquely identifying devices are vulnerable to non-invasive or invasive physical attacks. Securing the ID/key is of utmost importance since leakage of even a single device ID/key could be exploited by an adversary to hack other devices or produce pirated devices. In this work, we have developed a series of design and test methodologies to deal with these four challenging issues and thus enhance the security, trustworthiness and reliability of ICs. The techniques proposed in this thesis include: a path delay fingerprinting technique for detection of hardware Trojans, recycled ICs, and other types counterfeit ICs including remarked, overproduced, and cloned ICs with their unique identifiers; a Built-In Self-Authentication (BISA) technique to prevent hardware Trojan insertions by untrusted fabrication facilities; an efficient and secure split manufacturing via Obfuscated Built-In Self-Authentication (OBISA) technique to prevent reverse engineering by untrusted fabrication facilities; and a novel bit selection approach for obtaining the most reliable bits for SRAM-based physical unclonable function (PUF) across environmental conditions and silicon aging effects

Authorisation Issues for Mobile Code in Mobile Systems

This thesis is concerned with authorisation issues for mobile code in mobile systems. It is divided into three main parts. Part I covers the development of a policy-based framework for the authorisation of mobile code and agents by host systems. Part II addresses the secure download, storage and execution of a conditional access application, used in the secure distribution of digital video broadcast content. Part III explores the way in which trusted computing technology may be used in the robust implementation of OMA DRM version 2. In part I of this thesis, we construct a policy-based mobile code and agent authorisation framework, with the objective of providing both mobile devices and service providers with the ability to assign appropriate privileges to incoming executables. Whilst mobile code and agent authorisation mechanisms have previously been considered in a general context, this thesis focuses on the special requirements resulting from mobile code and agent authorisation in a mobile environment, which restrict the types of solutions that may be viable. Following the description and analysis of a number of architectural models upon which a policy-based framework for mobile code and agent authorisation may be constructed, we outline a list of features desirable in the definitive underlying architecture. Specific implementation requirements for the capabilities of the policy and attribute certificate specification languages and the associated policy engine are then extracted. Candidate policy specification languages, namely KeyNote (and Nereus), Ponder (and (D)TPL) and SAML are then examined, and conclusions drawn regarding their suitability for framework expression. Finally, the definitive policy based framework for mobile code and agent authorisation is described. In the second part of this thesis, a flexible approach that allows consumer products to support a wide range of proprietary content protection systems, or more specifically digital video broadcast conditional access systems, is proposed. Two protocols for the secure download of content protection software to mobile devices are described. The protocols apply concepts from trusted computing to demonstrate that a platform is in a sufficiently trustworthy state before any application or associated keys are securely downloaded. The protocols are designed to allow mobile devices to receive broadcast content protected by proprietary conditional access applications. Generic protocols are first described, followed by an analysis of how well the downloaded code is protected in transmission. How the generic protocols may be implemented using specific trusted computing technologies is then investigated. For each of the selected trusted computing technologies, an analysis of how the conditional access application is protected while in storage and while executing on the mobile host is also presented. We then examine two previously proposed download protocols, which assume a mobile receiver compliant with the XOM and AEGIS system architectures. Both protocols are then analysed against the security requirements defined for secure application download, storage and execution. We subsequently give a series of proposed enhancements to the protocols which are designed to address the identified shortcomings. In the final section of this thesis, we examine OMA DRM version 2, which defines the messages, protocols and mechanisms necessary in order to control the use of digital content in a mobile environment. However, an organisation, such as the CMLA, must specify how robust implementations of the OMA DRM version 2 specification should be, so that content providers can be confident that their content will be safe on OMA DRM version 2 devices. We take the requirements extracted for the robust implementation of the OMA DRM version 2 specification and propose an implementation which meets these requirements using the TCG architecture and TPM/TSS version 1.2 commands