Privacy Preserving Cryptographic Protocols for Secure Heterogeneous Networks

Disertační práce se zabývá kryptografickými protokoly poskytující ochranu soukromí, které jsou určeny pro zabezpečení komunikačních a informačních systémů tvořících heterogenní sítě. Práce se zaměřuje především na možnosti využití nekonvenčních kryptografických prostředků, které poskytují rozšířené bezpečnostní požadavky, jako je například ochrana soukromí uživatelů komunikačního systému. V práci je stanovena výpočetní náročnost kryptografických a matematických primitiv na různých zařízeních, které se podílí na zabezpečení heterogenní sítě. Hlavní cíle práce se zaměřují na návrh pokročilých kryptografických protokolů poskytujících ochranu soukromí. V práci jsou navrženy celkově tři protokoly, které využívají skupinových podpisů založených na bilineárním párování pro zajištění ochrany soukromí uživatelů. Tyto navržené protokoly zajišťují ochranu soukromí a nepopiratelnost po celou dobu datové komunikace spolu s autentizací a integritou přenášených zpráv. Pro navýšení výkonnosti navržených protokolů je využito optimalizačních technik, např. dávkového ověřování, tak aby protokoly byly praktické i pro heterogenní sítě.The dissertation thesis deals with privacy-preserving cryptographic protocols for secure communication and information systems forming heterogeneous networks. The thesis focuses on the possibilities of using non-conventional cryptographic primitives that provide enhanced security features, such as the protection of user privacy in communication systems. In the dissertation, the performance of cryptographic and mathematic primitives on various devices that participate in the security of heterogeneous networks is evaluated. The main objectives of the thesis focus on the design of advanced privacy-preserving cryptographic protocols. There are three designed protocols which use pairing-based group signatures to ensure user privacy. These proposals ensure the protection of user privacy together with the authentication, integrity and non-repudiation of transmitted messages during communication. The protocols employ the optimization techniques such as batch verification to increase their performance and become more practical in heterogeneous networks.

Cryptographic Protection of Digital Identity

Dizertační práce se zabývá kryptografickými schématy zvyšující ochranu soukromí uživatelů v systémech řízení přístupu a sběru dat. V současnosti jsou systémy fyzického řízení přístupu na bázi čipových karet využívány téměř dennodenně většinou z nás, například v zaměstnání, ve veřejné dopravě a v hotelech. Tyto systémy však stále neposkytují dostatečnou kryptografickou ochranu a tedy bezpečnost. Uživatelské identifikátory a klíče lze snadno odposlechnout a padělat. Funkce, které by zajišťovaly ochranu soukromí uživatele, téměř vždy chybí. Proto je zde reálné riziko možného sledovaní lidí, jejich pohybu a chovaní. Poskytovatelé služeb nebo případní útočníci, kteří odposlouchávají komunikaci, mohou vytvářet profily uživatelů, ví, co dělají, kde se pohybují a o co se zajímají. Za účelem zlepšení tohoto stavu jsme navrhli čtyři nová kryptografická schémata založená na efektivních důkazech s nulovou znalostí a kryptografii eliptických křivek. Konkrétně dizertační práce prezentuje tři nová autentizační schémata pro využití v systémech řízení přístupu a jedno nové schéma pro využití v systémech sběru dat. První schéma využívá distribuovaný autentizační přístup vyžadující spolupráci více RFID prvků v autentizačním procesu. Tato vlastnost je výhodná zvláště v případech řízení přístupu do nebezpečných prostor, kdy pro povolení přístupu uživatele je nezbytné, aby byl uživatel vybaven ochrannými pomůckami (se zabudovanými RFID prvky). Další dvě schémata jsou založena na atributovém způsobu ověření, tj. schémata umožňují anonymně prokázat vlastnictví atributů uživatele, jako je věk, občanství a pohlaví. Zatím co jedno schéma implementuje efektivní revokační a identifikační mechanismy, druhé schéma poskytuje nejrychlejší verifikaci držení uživatelských atributů ze všech současných řešení. Poslední, čtvrté schéma reprezentuje schéma krátkého skupinového podpisu pro scénář sběru dat. Schémata sběru dat se používají pro bezpečný a spolehlivý přenos dat ze vzdálených uzlů do řídící jednotky. S rostoucím významem chytrých měřičů v energetice, inteligentních zařízení v domácnostech a rozličných senzorových sítí, se potřeba bezpečných systémů sběru dat stává velmi naléhavou. Tato schémata musí podporovat nejen standardní bezpečnostní funkce, jako je důvěrnost a autentičnost přenášených dat, ale také funkce nové, jako je silná ochrana soukromí a identity uživatele či identifikace škodlivých uživatelů. Navržená schémata jsou prokazatelně bezpečná a nabízí celou řadu funkcí rozšiřující ochranu soukromí a identity uživatele, jmenovitě se pak jedná o zajištění anonymity, nesledovatelnosti a nespojitelnosti jednotlivých relací uživatele. Kromě úplné kryptografické specifikace a bezpečnostní analýzy navržených schémat, obsahuje tato práce také výsledky měření implementací jednotlivých schémat na v současnosti nejpoužívanějších zařízeních v oblasti řízení přístupu a sběru dat.The doctoral thesis deals with privacy-preserving cryptographic schemes in access control and data collection areas. Currently, card-based physical access control systems are used by most people on a daily basis, for example, at work, in public transportation and at hotels. However, these systems have often very poor cryptographic protection. For instance, user identifiers and keys can be easily eavesdropped and counterfeited. Furthermore, privacy-preserving features are almost missing and, therefore, user’s movement and behavior can by easily tracked. Service providers (and even eavesdroppers) can profile users, know what they do, where they go, and what they are interested in. In order to improve this state, we propose four novel cryptographic schemes based on efficient zero-knowledge proofs and elliptic curve cryptography. In particular, the thesis presents three novel privacy-friendly authentication schemes for access control and one for data collection application scenarios. The first scheme supports distributed multi-device authentication with multiple Radio-Frequency IDentification (RFID) user’s devices. This feature is particularly important in applications for controlling access to dangerous areas where the presence of protective equipment is checked during each access control session. The other two presented schemes use attribute-based approach to protect user’s privacy, i.e. these schemes allow users to anonymously prove the ownership of their attributes, such as age, citizenship, and gender. While one of our scheme brings efficient revocation and identification mechanisms, the other one provides the fastest authentication phase among the current state of the art solutions. The last (fourth) proposed scheme is a novel short group signature scheme for data collection scenarios. Data collection schemes are used for secure and reliable data transfer from multiple remote nodes to a central unit. With the increasing importance of smart meters in energy distribution, smart house installations and various sensor networks, the need for secure data collection schemes becomes very urgent. Such schemes must provide standard security features, such as confidentiality and authenticity of transferred data, as well as novel features, such as strong protection of user’s privacy and identification of malicious users. The proposed schemes are provably secure and provide the full set of privacy-enhancing features, namely anonymity, untraceability and unlinkability of users. Besides the full cryptographic specification and security analysis, we also show the results of our implementations on devices commonly used in access control and data collection applications.

An architecture for secure data management in medical research and aided diagnosis

Programa Oficial de Doutoramento en Tecnoloxías da Información e as Comunicacións. 5032V01[Resumo] O Regulamento Xeral de Proteccion de Datos (GDPR) implantouse o 25 de maio de 2018 e considerase o desenvolvemento mais importante na regulacion da privacidade de datos dos ultimos 20 anos. As multas fortes definense por violar esas regras e non e algo que os centros sanitarios poidan permitirse ignorar. O obxectivo principal desta tese e estudar e proponer unha capa segura/integracion para os curadores de datos sanitarios, onde: a conectividade entre sistemas illados (localizacions), a unificacion de rexistros nunha vision centrada no paciente e a comparticion de datos coa aprobacion do consentimento sexan as pedras angulares de a arquitectura controlar a sua identidade, os perfis de privacidade e as subvencions de acceso. Ten como obxectivo minimizar o medo a responsabilidade legal ao compartir os rexistros medicos mediante o uso da anonimizacion e facendo que os pacientes sexan responsables de protexer os seus propios rexistros medicos, pero preservando a calidade do tratamento do paciente. A nosa hipotese principal e: os conceptos Distributed Ledger e Self-Sovereign Identity son unha simbiose natural para resolver os retos do GDPR no contexto da saude? Requirense solucions para que os medicos e investigadores poidan manter os seus fluxos de traballo de colaboracion sen comprometer as regulacions. A arquitectura proposta logra eses obxectivos nun ambiente descentralizado adoptando perfis de privacidade de datos illados.[Resumen] El Reglamento General de Proteccion de Datos (GDPR) se implemento el 25 de mayo de 2018 y se considera el desarrollo mas importante en la regulacion de privacidad de datos en los ultimos 20 anos. Las fuertes multas estan definidas por violar esas reglas y no es algo que los centros de salud puedan darse el lujo de ignorar. El objetivo principal de esta tesis es estudiar y proponer una capa segura/de integración para curadores de datos de atencion medica, donde: la conectividad entre sistemas aislados (ubicaciones), la unificacion de registros en una vista centrada en el paciente y el intercambio de datos con la aprobacion del consentimiento son los pilares de la arquitectura propuesta. Esta propuesta otorga al titular de los datos un rol central, que le permite controlar su identidad, perfiles de privacidad y permisos de acceso. Su objetivo es minimizar el temor a la responsabilidad legal al compartir registros medicos utilizando el anonimato y haciendo que los pacientes sean responsables de proteger sus propios registros medicos, preservando al mismo tiempo la calidad del tratamiento del paciente. Nuestra hipotesis principal es: .son los conceptos de libro mayor distribuido e identidad autosuficiente una simbiosis natural para resolver los desafios del RGPD en el contexto de la atencion medica? Se requieren soluciones para que los medicos y los investigadores puedan mantener sus flujos de trabajo de colaboracion sin comprometer las regulaciones. La arquitectura propuesta logra esos objetivos en un entorno descentralizado mediante la adopcion de perfiles de privacidad de datos aislados.[Abstract] The General Data Protection Regulation (GDPR) was implemented on 25 May 2018 and is considered the most important development in data privacy regulation in the last 20 years. Heavy fines are defined for violating those rules and is not something that healthcare centers can afford to ignore. The main goal of this thesis is to study and propose a secure/integration layer for healthcare data curators, where: connectivity between isolated systems (locations), unification of records in a patientcentric view and data sharing with consent approval are the cornerstones of the proposed architecture. This proposal empowers the data subject with a central role, which allows to control their identity, privacy profiles and access grants. It aims to minimize the fear of legal liability when sharing medical records by using anonymisation and making patients responsible for securing their own medical records, yet preserving the patient’s quality of treatment. Our main hypothesis is: are the Distributed Ledger and Self-Sovereign Identity concepts a natural symbiosis to solve the GDPR challenges in the context of healthcare? Solutions are required so that clinicians and researchers can maintain their collaboration workflows without compromising regulations. The proposed architecture accomplishes those objectives in a decentralized environment by adopting isolated data privacy profiles

Key management for wireless sensor network security

Wireless Sensor Networks (WSNs) have attracted great attention not only in industry but also in academia due to their enormous application potential and unique security challenges. A typical sensor network can be seen as a combination of a number of low-cost sensor nodes which have very limited computation and communication capability, memory space, and energy supply. The nodes are self-organized into a network to sense or monitor surrounding information in an unattended environment, while the self-organization property makes the networks vulnerable to various attacks.Many cryptographic mechanisms that solve network security problems rely directly on secure and efficient key management making key management a fundamental research topic in the field of WSNs security. Although key management for WSNs has been studied over the last years, the majority of the literature has focused on some assumed vulnerabilities along with corresponding countermeasures. Specific application, which is an important factor in determining the feasibility of the scheme, has been overlooked to a large extent in the existing literature.This thesis is an effort to develop a key management framework and specific schemes for WSNs by which different types of keys can be established and also can be distributed in a self-healing manner; explicit/ implicit authentication can be integrated according to the security requirements of expected applications. The proposed solutions would provide reliable and robust security infrastructure for facilitating secure communications in WSNs.There are five main parts in the thesis. In Part I, we begin with an introduction to the research background, problems definition and overview of existing solutions. From Part II to Part IV, we propose specific solutions, including purely Symmetric Key Cryptography based solutions, purely Public Key Cryptography based solutions, and a hybrid solution. While there is always a trade-off between security and performance, analysis and experimental results prove that each proposed solution can achieve the expected security aims with acceptable overheads for some specific applications. Finally, we recapitulate the main contribution of our work and identify future research directions in Part V

Research on security and privacy in vehicular ad hoc networks

Los sistemas de redes ad hoc vehiculares (VANET) tienen como objetivo proporcionar una plataforma para diversas aplicaciones que pueden mejorar la seguridad vial, la eficiencia del tráfico, la asistencia a la conducción, la regulación del transporte, etc. o que pueden proveer de una mejor información y entretenimiento a los usuarios de los vehículos. Actualmente se está llevando a cabo un gran esfuerzo industrial y de investigación para desarrollar un mercado que se estima alcance en un futuro varios miles de millones de euros. Mientras que los enormes beneficios que se esperan de las comunicaciones vehiculares y el gran número de vehículos son los puntos fuertes de las VANET, su principal debilidad es la vulnerabilidad a los ataques contra la seguridad y la privacidad.En esta tesis proponemos cuatro protocolos para conseguir comunicaciones seguras entre vehículos. En nuestra primera propuesta empleamos a todas las unidades en carretera (RSU) para mantener y gestionar un grupo en tiempo real dentro de su rango de comunicación. Los vehículos que entren al grupo de forma anónima pueden emitir mensajes vehículo a vehículo (V2V) que inmediatamente pueden ser verificados por los vehículos del mismo grupo (y grupos de vecinos). Sin embargo, en la primera fase del despliegue de este sistema las RSU pueden no estar bien distribuídas. Consecuentemente, se propone un conjunto de mecanismos para hacer frente a la seguridad, privacidad y los requisitos de gestión de una VANET a gran escala sin la suposición de que las RSU estén densamente distribuidas. La tercera propuesta se centra principalmente en la compresión de las evidencias criptográficas que nos permitirán demostrar, por ejemplo, quien era el culpable en caso de accidente. Por último, investigamos los requisitos de seguridad de los sistemas basados en localización (LBS) sobre VANETs y proponemos un nuevo esquema para la preservación de la privacidad de la localización en estos sistemas sobre dichas redes.Vehicular ad hoc network (VANET) systems aim at providing a platform for various applications that can improve traffic safety and efficiency, driver assistance, transportation regulation, infotainment, etc. There is substantial research and industrial effort to develop this market. It is estimated that the market for vehicular communications will reach several billion euros. While the tremendous benefits expected from vehicular communications and the huge number of vehicles are strong points of VANETs, their weakness is vulnerability to attacks against security and privacy.In this thesis, we propose four protocols for secure vehicle communications. In our first proposal, we employ each road-side unit (RSU) to maintain and manage an on-the-fly group within its communication range. Vehicles entering the group can anonymously broadcast vehicle-to-vehicle (V2V) messages, which can be instantly verified by the vehicles in the same group (and neighbor groups). However, at the early stage of VANET deployment, the RSUs may not be well distributed. We then propose a set of mechanisms to address the security, privacy, and management requirements of a large-scale VANET without the assumption of densely distributed RSUs. The third proposal is mainly focused on compressing cryptographic witnesses in VANETs. Finally, we investigate the security requirements of LBS in VANETs and propose a new privacy-preserving LBS scheme for those networks

Physical attacks on pairing-based cryptography

In dieser Dissertation analysieren wir Schwächen paarungsbasierter kryptographischer Verfahren gegenüber physikalischen Angriffen wie Seitenkanalangriffen und Fehlerangriffen. Verglichen mit weitverbreiteten Primitiven, beispielsweise basierend auf elliptischen Kurven, ist noch relativ wenig über Angriffsmöglichkeiten aufpaarungsbasierte Verfahren bekannt. Ein Grund dafür ist die hohe Komplexität paarungsbasierter Kryptographie und fehlende Standards für die Festlegung von Parametern, Algorithmen und Verfahren. Des Weiteren läßt sich Wissen aus dem Zusammenhang mit elliptischen Kurven aufgrundstruktureller Unterschiede nicht direkt übertragen. Um ein besseres Verständnis des Problems zu erlangen, präsentieren wir in dieser Arbeit neue physikalische Angriffe auf paarungsbasierte Kryptographie. Unsere Ergebnisse, einschließlich deren praktische Umsetzung, machen deutlich, dass physikalische Angriffe eine Gefahr für die Implementierung paarungsbasierter kryptographischer Verfahren darstellen. Diese Gefahr sollte weiter untersucht und bei der Realisierung dieser Verfahren berücksichtig werden. Weiterhin zeigen unsere Ergebnisse, dass eine Einigung über verwendete Parameter, Algorithmen und Verfahren erzielt werden sollte, um die Komplexität von paarungsbasierter Kryptographie hinischtlich physikalische rAngriffe zu vermindern.In this thesis, we analyze the vulnerability of pairing-based cryptographic schemes against physical attacks like side-channel attacks (SCAs) or fault attacks (FAs). Compared to well-established cryptographic schemes, for example, from standard elliptic curve cryptography (ECC), less is known about weaknesses of pairing-based cryptography (PBC) against those attacks. Reasons for this shortcoming are the complexity of PBC and a missing consensus on parameters, algorithms, and schemes,e.g., in the form of standards. Furthermore, the structural difference between ECC and PBC prevents a direct application of the results from ECC. To get a better understanding of the subject, we present new physical attacks on PBC. Our results, including the practical realizations of our attacks, show that physical attacks are a threat for PBC and need further investigation. Our work also shows that the community should agree on parameters, algorithms, and schemes to reduce the complexity of PBC with respect to physical attacks.Peter Günther ; Supervisor: Prof. Dr. rer. nat. Johannes BlömerTag der Verteidigung: 14.03.2016Universität Paderborn, Univ., Dissertation, 201

EL PASSO: Efficient and Lightweight Privacy-preserving Single Sign On

Anonymous credentials are a solid foundation for privacy-preserving Single Sign-On (SSO). They enable unlinkable authentication across domains and allow users to prove their identity without revealing more than necessary. Unfortunately, anonymous credentials schemes remain difficult to use and complex to deploy. They require installation and use of complex software at the user side, suffer from poor performance, and do not support security features that are now common, such as two-factor authentication, secret recovery, or support for multiple devices. In contrast, Open ID Connect (OIDC), the de facto standard for SSO is widely deployed and used despite its lack of concern for users’ privacy. We present EL PASSO, a privacy-preserving SSO system based on anonymous credentials that does not trade security for usability, and can be incrementally deployed at scale alongside Open ID Connect with no significant changes to end-user operations. EL PASSO client-side operations leverage a WebAssembly module that can be downloaded on the fly and cached by users’ browsers, requiring no prior software installation or specific hardware. We develop automated procedures for managing cryptographic material, supporting multi-device support, secret recovery, and privacy-preserving two-factor authentication using only the built-in features of common Web browsers. Our implementation using PS Signatures achieves 39x to 180x lower computational cost than previous anonymous credentials schemes, similar or lower sign-on latency than Open ID Connect and is amenable for use on mobile devices

Security and privacy in RFID systems

Vu que les tags RFID sont actuellement en phase de large déploiement dans le cadre de plusieurs applications (comme les paiements automatiques, le contrôle d'accès à distance, et la gestion des chaînes d approvisionnement), il est important de concevoir des protocoles de sécurité garantissant la protection de la vie privée des détenteurs de tags RFID. Or, la conception de ces protocoles est régie par les limitations en termes de puissance et de calcul de la technologie RFID, et par les modèles de sécurité qui sont à notre avis trop forts pour des systèmes aussi contraints que les tags RFID. De ce fait, on limite dans cette thèse le modèle de sécurité; en particulier, un adversaire ne peut pas observer toutes les interactions entre tags et lecteurs. Cette restriction est réaliste notamment dans le contexte de la gestion des chaînes d approvisionnement qui est l application cible de ce travail. Sous cette hypothèse, on présente quatre protocoles cryptographiques assurant une meilleure collaboration entre les différents partenaires de la chaîne d approvisionnement. D abord, on propose un protocole de transfert de propriété des tags RFID, qui garantit l authentification des tags en temps constant alors que les tags implémentent uniquement des algorithmes symétriques, et qui permet de vérifier l'authenticité de l origine des tags. Ensuite, on aborde le problème d'authenticité des produits en introduisant deux protocoles de sécurité qui permettent à un ensemble de vérificateurs de vérifier que des tags sans capacité de calcul ont emprunté des chemins valides dans la chaîne d approvisionnement. Le dernier résultat présenté dans cette thèse est un protocole d appariement d objets utilisant des tags sans capacité de calcul , qui vise l automatisation des inspections de sécurité dans la chaîne d approvisionnement lors du transport des produits dangereux. Les protocoles introduits dans cette thèse utilisent les courbes elliptiques et les couplages bilinéaires qui permettent la construction des algorithmes de signature et de chiffrement efficaces, et qui minimisent donc le stockage et le calcul dans les systèmes RFID. De plus, la sécurité de ces protocoles est démontrée sous des modèles formels bien définis qui prennent en compte les limitations et les contraintes des tags RFID, et les exigences strictes en termes de sécurité et de la protection de la vie privée des chaines d approvisionnement.While RFID systems are one of the key enablers helping the prototype of pervasive computer applications, the deployment of RFID technologies also comes with new privacy and security concerns ranging from people tracking and industrial espionage to produ ct cloning and denial of service. Cryptographic solutions to tackle these issues were in general challenged by the limited resources of RFID tags, and by the formalizations of RFID privacy that are believed to be too strong for such constrained devices. It follows that most of the existing RFID-based cryptographic schemes failed at ensuring tag privacy without sacrificing RFID scalability or RFID cost effectiveness. In this thesis, we therefore relax the existing definitions of tag privacy to bridge the gap between RFID privacy in theory and RFID privacy in practice, by assuming that an adversary cannot continuously monitor tags. Under this assumption, we are able to design sec ure and privacy preserving multi-party protocols for RFID-enabled supply chains. Namely, we propose a protocol for tag ownership transfer that features constant-time authentication while tags are only required to compute hash functions. Then, we tackle the problem of product genuineness verification by introducing two protocols for product tracking in the supply chain that rely on storage only tags. Finally, we present a solution for item matching that uses storage only tags and aims at the automation of safety inspections in the supply chain.The protocols presented in this manuscript rely on operations performed in subgroups of elliptic curves that allow for the construction of short encryptions and signatures, resulting in minimal storage requirements for RFID tags. Moreover, the privacy and the security of these protocols are proven under well defined formal models that take into account the computational limitations of RFID technology and the stringent privacy and security requirements of each targeted supply chain application.PARIS-Télécom ParisTech (751132302) / SudocSudocFranceF

Pairing-based cryptosystems and key agreement protocols.

For a long time, pairings on elliptic curves have been considered to be destructive in elliptic curve cryptography. Only recently after some pioneering works, particularly the well-known Boneh-Franklin identity-based encryption (IBE), pairings have quickly become an important tool to construct novel cryptographic schemes. In this thesis, several new cryptographic schemes with pairings are proposed, which are both efficient and secure with respect to a properly defined security model, and some relevant previous schemes are revisited. IBE provides a public key encryption mechanism where a public key can be an arbitrary string such as an entity identifier and unwieldy certificates are unnecessary. Based on the Sakai-Kasahara key construction, an IBE scheme which is secure in the Boneh-Franklin IBE model is constructed, and two identity-based key encapsulation mechanisms are proposed. These schemes achieve the best efficiency among the existing schemes to date. Recently Al-Riyami and Paterson introduced the certificateless public key encryption (CL-PKE) paradigm, which eliminates the need of certificates and at the same time retains the desirable properties of IBE without the key escrow problem. The security formulation of CL-PKE is revisited and a strong security model for this type of mechanism is defined. Following a heuristic approach, three efficient CL-PKE schemes which are secure in the defined strong security model are proposed. Identity-based two-party key agreement protocols from pairings are also investigated. The Bellare-Rogaway key agreement model is enhanced and within the model several previously unproven protocols in the literature are formally analysed. In considering that the user identity may be sensitive information in many environments, an identity-based key agreement protocol with unilateral identity privacy is proposed