This thesis focuses on issues related to authentication in low-cost radio frequency identification technology, more commonly referred to as RFID. This technology it is often referred to as the next technological revolution after the Internet. However, due to the very limited resources in terms of computation, memory and energy on RFID tags, conventional security algorithms cannot be implemented on low-cost RFID tags making security and privacy an important research subject today. First of all, we investigate the scalability in low-cost RFID systems by developing a ns-3 module to simulate the universal low-cost RFID standard EPC Class-1 Generation-2 in order to establish a strict framework for secure identification in low-cost RFID systems. We show that, the symmetrical key cryptography is excluded from being used in any scalable low-cost RFID standard. Then, we propose a scalable authentification protocol based on our adaptation of the famous public key cryptosystem NTRU. This protocol is specially designed for low-cost RFID systems, it can be efficiently implemented into low-cost tags. Finally, we consider the zero-knowledge identification i.e. when the no secret sharing between the tag and the reader is needed. Such identification approaches are very helpful in many RFID applications when the tag changes constantly the field of administration. We propose two lightweight zero-knowledge identification approaches based on GPS and randomized GPS schemes. The proposed approaches consist in storing in the back-end precomputed values in the form of coupons. So, the GPS-based variant can be private and the number of coupons can be much higher than in other approaches thus leading to higher resistance to denial of service attacks for cheaper tags

Voting is a fundamental decision making instrument in any consensus-based society. It is employed in various applications from student body elections, reality television shows, shareholder meetings, to national elections. With the motivation of better eciency, scalability, speed, and lower cost, voting is currently shifting from paper-based to the use of electronic medium. This is while aiming to achieve better security, such that voting result reflects true opinions of the voters. Our research focuses on the study of cryptographic voting protocols accommodating a flexible ballot structure as a foundation for building a secure electronic voting system with acceptable voting results. In particular, we search for a solution suitable for the preferential voting system employed in the Australian Federal Election. The outcomes of the research include: improvements and applications of batch proof and verication theorems and techniques, a proposed alternative homomorphic encryption based voting scheme, a proposed Extended Binary Mixing Gate (EBMG) mix-network scheme, a new threshold randomisation technique to achieve receipt-freeness property in voting, and the application of cryptographic voting protocol for preferential voting. The threats and corresponding requirements for a secure secret-ballot voting scheme are rst discussed. There are significant security concerns about the conduct of electronic voting, and it is essential that the voting results re ect the true opinions of the voters - especially in political elections. We examine and extend batch processing proofs and verifications theorems and proposed applications of the theorems useful for voting. Many instances of similar operations can be processed in a single instance using a batch technique based on one of the batch theorems. As the proofs and verications provide formal assurances that the voting process is secure, batch processing offers great efficiency improvements while retaining the security required in a real-world implementation of the protocol. The two main approaches in cryptographic voting protocols, homomorphic encryption based voting and mix-network based voting, are both studied in this research. An alternative homomorphic voting scheme using multiplicative homomorphism property, and a number of novel mix-network schemes are proposed. It is shown that compared to the mix-network approach, homomorphic encryption schemes are not scalable for straight-forward adaptation of preferential systems. One important requirement of secret-ballot voting is receipt-freeness. A randomisation technique to achieve receipt-freeness in voting is examined and applied in an ecient and practical voting scheme employing an optimistic mix-network. A more general technique using threshold randomisation is also proposed. Combination of the primitives, both the homomorphic encryption and mixnetwork approach, yields a hybrid approach producing a secure and ecient secret-ballot voting scheme accommodating a exible ballot structure. The resulting solution oers a promising foundation for secure and practical secret-ballot electronic voting accommodating any type of counting system.

Les smooth (ou universal) projective hash functions ont été introduites par Cramer et Shoup, à Eurocrypt'02, comme un outil pour construire des schémas de chiffrement efficaces et sûrs contre les attaques à chiffrés choisis. Depuis, elles ont trouvé de nombreuses applications, notamment pour la construction de schémas d'authentification par mot de passe, d'oblivious transfer, de signatures en blanc, et de preuves à divulgation nulle de connaissance. Elles peuvent êtres vues comme des preuves implicites d'appartenance à certains langages. Un problème important est de caractériser pour quels langages de telles fonctions existent.Dans cette thèse, nous avançons dans la résolution de ce problème en proposant la notion de diverse modules. Un diverse module est une représentation d'un langage, comme un sous-module d'un module plus grand, un module étant un espace vectoriel sur un anneau. À n'importe quel diverse module est associée une smooth projective hash function pour le même langage. Par ailleurs, presque toutes les smooth projective hash functions actuelles sont construites de cette manière.Mais les diverse modules sont aussi intéressants en eux-mêmes. Grâce à leur structure algébrique, nous montrons qu'ils peuvent facilement être combinés pour permettre de nouvelles applications, comme les preuves implicites à divulgation nulle de connaissance (une alternative légère aux preuves non-interactives à divulgation nulle de connaissance), ainsi que des preuves non-interactives à divulgation nulle de connaissance et one-time simulation-sound très efficaces pour les langages linéaires sur les groupes cycliques. / Smooth (or universal) projective hash functions were first introduced by Cramer and Shoup, at Eurocrypt'02, as a tool to construct efficient encryption schemes, indistinguishable under chosen-ciphertext attacks. Since then, they have found many other applications, including password-authenticated key exchange, oblivious transfer, blind signatures, and zero-knowledge arguments. They can be seen as implicit proofs of membership for certain languages. An important question is to characterize which languages they can handle.In this thesis, we make a step forward towards this goal, by introducing diverse modules. A diverse module is a representation of a language, as a submodule of a larger module, where a module is essentially a vector space over a ring. Any diverse module directly yields a smooth projective hash function for the corresponding language, and almost all the known smooth projective hash functions are constructed this way.Diverse modules are also valuable in their own right. Thanks to their algebraic structural properties, we show that they can be easily combined to provide new applications related to zero-knowledge notions, such as implicit zero-knowledge arguments (a lightweight alternative to non-interactive zero-knowledge arguments), and very efficient one-time simulation-sound (quasi-adaptive) non-interactive zero-knowledge arguments for linear languages over cyclic groups.

La sécurité de l’information repose sur la bonne interaction entre différents niveaux d’abstraction : les composants matériels, systèmes d’exploitation, algorithmes, et réseaux de communication. Cependant, protéger ces éléments a un coût ; ainsi de nombreux appareils sont laissés sans bonne couverture. Cette thèse s’intéresse à ces différents aspects, du point de vue de la sécurité et de la cryptographie. Nous décrivons ainsi de nouveaux algorithmes cryptographiques (tels que des raffinements du chiffrement de Naccache–Stern), de nouveaux protocoles (dont un algorithme d’identification distribuée à divulgation nulle de connaissance), des algorithmes améliorés (dont un nouveau code correcteur et un algorithme efficace de multiplication d’entiers),ainsi que plusieurs contributions à visée systémique relevant de la sécurité de l’information et à l’intrusion. En outre, plusieurs de ces contributions s’attachent à l’amélioration des performances des constructions existantes ou introduites dans cette thèse. / Information security relies on the correct interaction of several abstraction layers: hardware, operating systems, algorithms, and networks. However, protecting each component of the technological stack has a cost; for this reason, many devices are left unprotected or under-protected. This thesis addresses several of these aspects, from a security and cryptography viewpoint. To that effect we introduce new cryptographic algorithms (such as extensions of the Naccache–Stern encryption scheme), new protocols (including a distributed zero-knowledge identification protocol), improved algorithms (including a new error-correcting code, and an efficient integer multiplication algorithm), as well as several contributions relevant to information security and network intrusion. Furthermore, several of these contributions address the performance of existing and newly-introduced constructions.

Anonymous authentication is a mean of authorizing a user without leakage of user personal information. The technology of Anonymous Authentication Systems (AAS) provides privacy of the user and yet preserves the security of the system. This thesis presents the basic cryptographic primitives, which can provide anonymous authentication. Among these primitives there are usually some asymmetric cryptosystems, but an essential part of anonymous authentication is based on zero knowledge protocols, blind signature schemes, threshold group schemes, etc., that are presented in Chapter 1. Generally, Anonymous Authentication Systems have application as electronic coin, electronic cash, group signatures, anonymous access systems, electronic vote, etc., which are analyzed and presented in Chapters 2 and 3. In the practical section, the implementation (in the environment .NET in C#) of the AAS system is presented and described in Chapter 4, which is being developed at the FEEC BUT.

This thesis discusses the possibility of ensuring the safety, integrity and authenticity of data communication with respect to user privacy. This thesis describes the fundamentals of smart grid networks with capabilities of existing forms of security to communications that have been chosen as a target for application deployment of group signatures to ensure the security, integrity and authenticity of data communications. It describes the concept of a zero-knowledge and cryptography primitives. Further, the basic principles are presented, the history of development, and various schemes are compared based on the construction and performance. The second part is given to the deployment and optimization of group signatures for computationally limited devices. Within the draft report were to be implemented in the Java language chosen scheme HLCCN, DP and BBS. They were then tested under various platforms which were measured and evaluated performance parameters of the schemes. The optimization of the work is focused on the times of signatures, which are critical to a smart grid system. Under the platforms are deployed pre-processed pairing optimization methods and other methods resulting from the deployment platform as JPBWrappera and native libraries to deliver more efficient times of sgnaiture. At the end of the thesis are evaluated achievements of optimization methods and the appropriateness of the deployment of smart grids.

Au cours de la dernière décennie, avec la standardisation d’Internet, le développement des réseaux à haut débit, le paiement à l’usage et la quête sociétale de la mobilité, le monde informatique a vu se populariser un nouveau paradigme, le Cloud. Le recours au cloud est de plus en plus remarquable compte tenu de plusieurs facteurs, notamment ses architectures rentables, prenant en charge la transmission, le stockage et le calcul intensif de données. Cependant, ces services de stockage prometteurs soulèvent la question de la protection des données et de la conformité aux réglementations, considérablement due à la perte de maîtrise et de gouvernance. Cette dissertation vise à surmonter ce dilemme, tout en tenant compte de deux préoccupations de sécurité des données, à savoir la confidentialité des données et l’intégrité des données. En premier lieu, nous nous concentrons sur la confidentialité des données, un enjeu assez considérable étant donné le partage de données flexible au sein d’un groupe dynamique d’utilisateurs. Cet enjeu exige, par conséquence, un partage efficace des clés entre les membres du groupe. Pour répondre à cette préoccupation, nous avons, d’une part, proposé une nouvelle méthode reposant sur l’utilisation de la cryptographie basée sur l’identité (IBC), où chaque client agit comme une entité génératrice de clés privées. Ainsi, il génère ses propres éléments publics et s’en sert pour le calcul de sa clé privée correspondante. Grâce aux propriétés d’IBC, cette contribution a démontré sa résistance face aux accès non autorisés aux données au cours du processus de partage, tout en tenant compte de deux modèles de sécurité, à savoir un serveur de stockage honnête mais curieux et un utilisateur malveillant. D’autre part, nous définissons CloudaSec, une solution à base de clé publique, qui propose la séparation de la gestion des clés et les techniques de chiffrement, sur deux couches. En effet, CloudaSec permet un déploiement flexible d’un scénario de partage de données ainsi que des garanties de sécurité solides pour les données externalisées sur les serveurs du cloud. Les résultats expérimentaux, sous OpenStack Swift, ont prouvé l’efficacité de CloudaSec, en tenant compte de l’impact des opérations cryptographiques sur le terminal du client. En deuxième lieu, nous abordons la problématique de la preuve de possession de données (PDP). En fait, le client du cloud doit avoir un moyen efficace lui permettant d’effectuer des vérifications périodiques d’intégrité à distance, sans garder les données localement. La preuve de possession se base sur trois aspects : le niveau de sécurité, la vérification publique, et les performances. Cet enjeu est amplifié par des contraintes de stockage et de calcul du terminal client et de la taille des données externalisées. Afin de satisfaire à cette exigence de sécurité, nous définissons d’abord un nouveau protocole PDP, sans apport de connaissance, qui fournit des garanties déterministes de vérification d’intégrité, en s’appuyant sur l’unicité de la division euclidienne. Ces garanties sont considérées comme intéressantes par rapport à plusieurs schémas proposés, présentant des approches probabilistes. Ensuite, nous proposons SHoPS, un protocole de preuve de possession de données capable de traiter les trois relations d’ensembles homomorphiques. SHoPS permet ainsi au client non seulement d’obtenir une preuve de la possession du serveur distant, mais aussi de vérifier que le fichier, en question, est bien réparti sur plusieurs périphériques de stockage permettant d’atteindre un certain niveau de la tolérance aux pannes. En effet, nous présentons l’ensemble des propriétés homomorphiques, qui étend la malléabilité du procédé aux propriétés d’union, intersection et inclusion / Recent technological advances have given rise to the popularity and success of cloud. This new paradigm is gaining an expanding interest, since it provides cost efficient architectures that support the transmission, storage, and intensive computing of data. However, these promising storage services bring many challenging design issues, considerably due to the loss of data control. These challenges, namely data confidentiality and data integrity, have significant influence on the security and performances of the cloud system. This thesis aims at overcoming this trade-off, while considering two data security concerns. On one hand, we focus on data confidentiality preservation which becomes more complex with flexible data sharing among a dynamic group of users. It requires the secrecy of outsourced data and an efficient sharing of decrypting keys between different authorized users. For this purpose, we, first, proposed a new method relying on the use of ID-Based Cryptography (IBC), where each client acts as a Private Key Generator (PKG). That is, he generates his own public elements and derives his corresponding private key using a secret. Thanks to IBC properties, this contribution is shown to support data privacy and confidentiality, and to be resistant to unauthorized access to data during the sharing process, while considering two realistic threat models, namely an honest but curious server and a malicious user adversary. Second, we define CloudaSec, a public key based solution, which proposes the separation of subscription-based key management and confidentiality-oriented asymmetric encryption policies. That is, CloudaSec enables flexible and scalable deployment of the solution as well as strong security guarantees for outsourced data in cloud servers. Experimental results, under OpenStack Swift, have proven the efficiency of CloudaSec in scalable data sharing, while considering the impact of the cryptographic operations at the client side. On the other hand, we address the Proof of Data Possession (PDP) concern. In fact, the cloud customer should have an efficient way to perform periodical remote integrity verifications, without keeping the data locally, following three substantial aspects : security level, public verifiability, and performance. This concern is magnified by the client’s constrained storage and computation capabilities and the large size of outsourced data. In order to fulfill this security requirement, we first define a new zero-knowledge PDP proto- col that provides deterministic integrity verification guarantees, relying on the uniqueness of the Euclidean Division. These guarantees are considered as interesting, compared to several proposed schemes, presenting probabilistic approaches. Then, we propose SHoPS, a Set-Homomorphic Proof of Data Possession scheme, supporting the 3 levels of data verification. SHoPS enables the cloud client not only to obtain a proof of possession from the remote server, but also to verify that a given data file is distributed across multiple storage devices to achieve a certain desired level of fault tolerance. Indeed, we present the set homomorphism property, which extends malleability to set operations properties, such as union, intersection and inclusion. SHoPS presents high security level and low processing complexity. For instance, SHoPS saves energy within the cloud provider by distributing the computation over multiple nodes. Each node provides proofs of local data block sets. This is to make applicable, a resulting proof over sets of data blocks, satisfying several needs, such as, proofs aggregation