Orientador: Julio César López Hernández / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-24T00:18:34Z (GMT). No. of bitstreams: 1 Gouvea_ConradoPortoLopes_D.pdf: 3342900 bytes, checksum: b3a072bdbc369f1a1fffd95e1c1f4365 (MD5) Previous issue date: 2013 / Resumo: A implementação eficiente e segura de esquemas criptográficos é um aspecto importante da criptografia aplicada. Neste trabalho, foca-se na implementação em software de algoritmos relevantes da criptografia de curvas elípticas (CCE), criptografia baseada em emparelhamentos (CBE), e de cifração autenticada (CA). Duas plataformas computacionais modernas foram utilizadas: o microcontrolador MSP430, bastante utilizado em redes de sensores sem fio, e o processador ARM, amplamente empregado por dispositivos móveis como smartphones e tablets que estão se tornando cada vez mais populares. Técnicas para a melhoria de desempenho em software utilizando conjuntos de instruções, periféricos e melhorias algorítmicas são descritas. A implementação segura, cujo objetivo é prevenir certos ataques de canais secundários, também é estudada e novas técnicas são providas para reduzir seu impacto na velocidade em processadores ARM. Tais resultados contribuem para a construção eficiente e segura de sistemas criptográficos em sensores sem fio e processadores móveis / Abstract: The efficient and secure implementation of cryptographic schemes is an important aspect of practical cryptography. In this work, we focus on the software implementation of relevant algorithms in elliptic curve cryptography (ECC), pairing-based cryptography (PBC) and in authenticated encryption (AE). Two modern computational platforms were targeted: the MSP430 microcontroller often used in wireless sensor networks, and the ARM processor, widely employed in mobile devices such as smartphones and tablets which are increasingly becoming ubiquitous. Techniques for improving the software performance by taking advantage of instruction sets, peripherals and algorithmic enhancements are described. The secure implementation, which aims at thwarting common side-channel attacks, is also studied and new techniques are provided for improving its efficiency on ARM processors. These results contribute to the building of efficient and secure cryptographic systems on wireless sensors and mobile processors / Doutorado / Ciência da Computação / Doutor em Ciência da Computação

Historically, cryptographic file systems have been several times slower than non-cryptographic file systems. This paper describes the design and implementation of a fast Cryptographic Log-structured File System on OpenBSD. We experimentally demonstrate that our pro-totype file system performs close to the Fast File System (FFS) and the Log-structured File System (LFS). To increase performance, our file system performs most encryption and decryption work during disk read and write operations. This is possible thanks to the SEAL encryption algorithm, a software optimized stream cipher that allows the en-cryption work to be performed prior to the actual data is available. We believe that our cryptographic file system design is ideal for optimal read and write performance on locally stored confidential data. / Denna uppsats beskriver utvecklingen av ett kryptografiskt log-strukturerat filsystem och vi visar genom experiment att dess prestanda är jämförbar med lokala filsystem. / Karl Knutsson Skiftesgatan 40 332 35 Gislaved Sweden

Context: Secrecy has kept researchers spanning over centuries engaged in the creation of data protection techniques. With the growing rate of data breach and intervention of adversaries in confidential data storage and communication, efficient data protection has found to be a challenge. Homomorphic encryption is one such data protection technique in the cryptographic domain which can perform arbitrary computations on the enciphered data without disclosing the original plaintext or message. The first working fully homomorphic encryption scheme was proposed in the year 2009 and since then there has been a tremendous increase in the development of homomorphic encryption schemes such that they can be applied to a wide range of data services that demand security. All homomorphic encryption schemes can be categorized as partially homomorphic (PHE), somewhat homomorphic (SHE), leveled Homomorphic (LHE), and fully homomorphic encryption (FHE). Each encryption algorithm has its own importance and usage in different realms of security. DHGV, Paillier, HElib, and FHEW are the algorithms chosen in this study considering their wide usage and scope for further advancement in this subject area. A public-key algorithm named RSA is also chosen for comparison of the impact of HE and PKE (Public-key encryption) algorithm on the CPU and Memory. The utilization of various homomorphic schemes and concepts in the trending cloud storage systems is a prevailing field of research and can be expanded further by knowing the current state-of-the-art of homomorphic encryption. Hence, the necessity of comprehending the knowledge of homomorphic encryption schemes and their aspect in cloud security becomes vital. Objectives: The objective of this study is to analytically assess homomorphic encryption and various homomorphic encryption schemes. A comprehensive investigation on working and performance of the selected HE schemes is another objective of this research. Also, an experiment to run publicly available libraries of DGHV, Paillier, HElib, and FHEW is one of the main objectives. In addition to these, comprehending the impact of HE and PKE on CPU and Memory is also among the objectives of the study. The role and practice of homomorphic encryption in the cloud storage system are among the secondary objectives of this research in terms of securing confidential data. These objectives are set based on the research gap identified by conducting an exhaustive literature review. Methods: The objectives of this study are achieved by adopting the methods exhaustive literature review and experiment. Scientific databases such as IEEE Xplore, ACM Digital Library, Inspec, Springer Link etc. are used and literature is accordingly selected based on the relevance to the research topic. An exhaustive literature review is conducted and extensive bibliographic research is done to accomplish the objective of comprehending the working, applications, significance of homomorphic encryption. Apart from literature review, bibliographic research, an experiment is also conducted to run the publicly available homomorphic encryption libraries to evaluate, compare, and analyze the performance of DGHV, Paillier, HElib, and FHEW schemes. Experiment to run publicly available PKE algorithm is also conducted. Finally, the conclusion and outcome by adopting these research methods for accomplishing the objectives are theoretically presented in detail. Results: By conducting an exhaustive literature review, the importance, working, application of homomorphic encryption and its schemes is discerned. And by conducting an experiment, the impact of HE and PKE is also discerned. Apart from this, the limitations of HE and selected HE schemes along with the distinction between public and private key cryptography is understood by finding and mapping in connection with each other. From the experiment conducted, it is examined that despite the encryption libraries being publicly available for use, the possibility of running and employing few libraries successfully is remarkably low inferring that there is much improvement needed in this cryptographic discipline. Conclusions: From this research, it can be concluded that homomorphic encryption has a wide scope of extending towards efficiency and application in various fields concerned with data protection. It can also me concluded that the experimental assessment of state of the art of few HE schemes libraries that are available online are remarkably impractical for real-time practice. By analyzing the selected ii schemes, it can be concluded few HE schemes do not support any other operations on encrypted data other than addition and multiplication due to which chances of increasing noise for each encryption is relatively high. From the experiment conducted for Paillier encryption (HE) and RSA (PKE) encryption, it is concluded that both the schemes increase linearly with an increase in the input size when CPU and Memory utilization is measured. Apart from these conclusions, it can also be inferred that not all the homomorphic encryption algorithms are IND-CCA1 and IND-CCA2 secure. From this study, it can be deduced that more empirical validation and analysis of HE algorithms is required in terms of their performance and security. In order to address these problems, much research and improvement are required as it inferred from the results of this research that Homomorphic encryption is still in its early stage of development and enormous utility can be anticipated when enhanced correctly.

This thesis describes the system design and implementation of the secure Ephemerizer System that was first introduced by Radia Perlman in 2005. The system is designed to enable users to keep data for a finite period of time before making the data unrecoverable by destroying the keys with which the data was encrypted. The task of the Ephemerizer System service is to create, advertise, and destroy keys required for the Ephemerizer System's functionalities. We designed the Ephemerizer System Service's security by placing the sensitive key management modules into a Trusted Computing Base (TCB). Our compartmentalized approach distributes security requirements at different sensitivity levels into different protection domains. In our approach, we implement the trusted protection domain (our TCB) on a tamper-resistant Javacard. We placed the key storage database into the partly trusted protection domain to improve scalability and availability of the Ephemerizer System. The partly trusted protection domain requires memory isolation and other security mechanisms provided by the underlying operating system. We implemented several mechanisms on the TCB, such as the signature engine, cryptographic modules, the on-card expiration validator, and on-card time verification. We make the Ephemerizer System available to users as a web service and expose it though a uniform API. This approach enables the seamless integration of the Ephemerizer System into business processes on heterogeneous platforms.

Web servers are increasingly being used in embedded devices as a communication medium. As more systems connect to the Internet, the need for security is increasing. The Transport Layer Protocol (TLS) is the successor of Secure Socket Layer (SSL) and provides security in almost all secure Internet transactions. This thesis aims to investigate if TLS can be adapted to embedded systems without sacrificing much of the system resources available. A literature study and an implementation of TLS have been performed. The literature study determined resource intense parts of TLS, hardware support as well as export laws applicable to TLS. The different parts of the implementation are evaluated on an ARM7-core to determine the execution times. The results for the symmetric ciphers AES and 3DES are compared when measuring execution times using both software and hardware solutions. The size of the implementation is also measured. TLS was shown to be able to integrate on embedded systems. Practical issues such as certificates and keys can be solved in different ways to suite the target environment. The largest remaining issue is the execution time for asymmetric algorithms. The results that are provided clearly illustrates that the RSA used for key exchange is very time consuming. Alternative solutions to gain better performance are discussed.

Le retrait d’information privé que nous nommons PIR, désigne un groupe de protocoles qui s’inscrit dans un ensemble plus vaste des technologies d’amélioration de la vie privée. Sa fonctionnalité principale est de dissimuler l’index d’un élément d’une liste accédée par un client au regard de son hôte. Sans négliger l’appart de leurs auteurs à la communauté scientifique, l’utilisabilité de ce groupe de protocoles semble limitée, car pour un client, télécharger l’intégralité de la liste est plus efficient. À ce jour, les PIR, se fondent sur des serveurs répliqués mutuellement méfiants, des périphériques de confiance ou bien des systèmes cryptographiques. Nous considérerons ici les retraits d’informations privés computationnels et plus particulièrement ceux reposant sur les réseaux euclidiens qui n’offrent des propriétés particulières, comme l’homomorphisme. Afin d’en démontrer l’utilisabilité, nous proposons un retrait d’information privé reposant sur un système cryptographique homomorphe performant et aisé d’utilisation / Private information retrieval, named PIR, is a set of protocols that is a part of privacy enhancement technologies.Its major feature is to hide the index of a record that a user retrieved from the host.Without neglecting the scientific contributions of its authors, the usability of this protocol seems hard since that, for a user, it seems more and more efficient to receive all the records.Thus far, PIR can be achieved using mutually distrustful databases replicated databases, trusted hardware, or cryptographic systems.We focus on computational private information retrieval, and specifically on thus based on cryptographic systems.This decision is contingent to the spread of cryptographic systems based on lattices who provide specific properties.To demonstrate it usability, we offer an efficient and easy-to-use private Information retrieval based on homomorphic encryption.

Today, the most frequently used signaling system for telecommunication is called Signaling System No. 7 (SS7). The growing usage of mobile telephones and mobile data communica-tion, and the development of new services mean that the risk of intrusion and exploitation of the SS7 signaling networks increases. The increasing problem with unauthorized access to sensitive information and the operators’ growing demand for security is the origin of our work. This thesis presents a prototype design and implementation of a Security Gateway (SEG), which is a fundamental part of the TCAP user security (TCAPsec) concept. TCAPsec is a security concept for introducing security mechanisms to the signaling system. The proto-type includes three different protection modes that provide security services, ranging from almost no protection to full protection with the use of encryption algorithms. The thesis also contains an evaluation study of the delay penalties caused by the use of these security services. With regards to the restrictions on the prototype, the conclusion drawn from the evaluation results was that the protection mechanisms in the different protection modes did not inflict any significant time penalties. Instead, the results of the study indicate that the routing process of messages in the network is a more significant delaying part in the communication between different nodes. This result implies that the routing process takes longer time than the security services. The thesis also presents a number of discovered features that will require further investigation and development before the TCAPsec concept can be realized.

Cette thèse traite des problèmes et des défis de sécurité dans l’Internet des Objets (IdO). L’évolution de l’Internet classique vers l’Internet des Objets crée de nombreux challenges dans la manière de sécuriser les communications et soulève des problèmes liés au contraintes de l’internet des objets à savoir : objets à faibles ressources d’énergie et de calculs, hétérogénéité nuisant à l’interopérabilité des objets, taille du réseau de plus en plus grande, ... etc. En effet, Internet s’est développé d’un réseau d’ordinateurs personnels et de serveurs vers un immense réseau connectant des milliards d’objets intelligents communicants. Ces objets seront intégrés dans des systèmes complexes et utiliseront des capteurs et actionneurs pour observer et interagir avec leur environnement physique. Les exigences des interactions entre objets communicants en termes de sécurité dépendent du contexte qui évolue dans l’espace et le temps. Par conséquent, la définition de la politique de sécurité doit être adaptative et sensible au contexte. Un des problèmes auxquels nous nous sommes intéressés est le contrôle d’accès efficace à base de cryptographie d’attributs : « Attributes Based Encryption (ABE) ». Les schémas ABE (CP-ABE et KP-ABE) présentent plusieurs atouts pour l’implémentation d’un contrôle d’accès cryptographique. Par contre, ces schémas posent des défis opérationnels à cause de leurs complexités et leur surcoût élevé en termes de temps d’exécution et consommation énergétique. Pour pallier cet inconvénient, nous avons exploité l’hétérogénéité d’environnement Internet des Objets pour proposer des versions collaboratives et distribuées de ces schémas de contrôle d’accès cryptographique. Nos solutions réduisent considérablement le coût en termes d’énergie nécessaire à l’exécution. Le deuxième inconvénient des schémas ABE est l’inexistence de mécanismes efficaces de gestion de clés. Nous avons proposé des solutions pour le problème de révocation d’attributs dans le schéma CP-ABE, Ces solutions, en plus de leur efficacité, répondent à des exigences de sécurité différentes selon le cas d’applications. Nous avons proposé également, une solution à base de CP-ABE pour le problème du « grouping proof ». Le « grouping proof » consiste à fournir une preuve sur la coexistence, dans le temps et l’espace, d’un ensemble d’objets. Parmi les applications de notre solution, on peut citer le payement NFC et la sécurisation de l’accès aux locaux sensibles. / In this thesis, we deal with security challenges in the Internet of Things. The evolution of the Internet toward an Internet of Things created new challenges relating to the way to secure communications given the new constraints of IoT, namely: resource constrained objects, heterogeneity of network components, the huge size of the network, etc. Indeed, the Internet evolved from a network of computers and servers toward a huge network connecting billions of smart communicating objects. These objects will be integrated into complex systems and use sensors and actuators to observe and interact with their physical environment. The security requirements of the interactions between smart objects depend on the context which evolves in time and space. Consequently, the definition of the security policies should be adaptive and context-aware. In this thesis, we were interested in the problem of access control in IoT relying on Attribute based Encryption (ABE). Indeed, ABE schemes present many advantages in implementing a cryptographic fine-grained access control. However, these schemes raise many implementation challenges because of their complexity and high computation and energy overheads. To overcome this challenge, we leveraged the heterogeneity of IoT to develop collaborative and distributed versions of ABE schemes. Our solutions reduce remarkably the overhead in terms of energy consumption and computation. The second limitation of ABE schemes is the absence of efficient attribute/key revocation techniques. We have proposed batch based mechanisms for attribute/key revocation in CP-ABE. We demonstrated the efficiency of the proposed solutions through simulations. Finally, we have proposed a CP-ABE based solution for the problem of grouping proof. This problem consists of providing the proof that a set of objects are present simultaneously (same time and same location). The propose solution has many applications such as enforcing the security of NFC based payments and the access to sensitive locations.

Les polynômes modulaires sont utilisés dans le calcul de graphes d’isogénies, le calcul des polynômes de classes ou le comptage du nombre de points d’une courbe elliptique, et sont donc fondamentaux pour la cryptographie basée sur les courbes elliptiques. Des polynômes analogues sur les surfaces abéliennes principalement polarisées ont été introduits par Régis Dupont en 2006, qui a également proposé un algorithme pour les calculer, et des résultats théoriques sur ces polynômes ont été donnés dans un article de Bröker–Lauter, en 2009. Mais les polynômes sont très gros et ils n’ont pu être calculés que pour l’exemple minimal p = 2. Dans cette thèse, nous poursuivons les travaux de Dupont et Bröker–Lauter en permettant de calculer des polynômes modulaires pour des invariants basés sur les thêta constantes, avec lesquels nous avons pu calculer les polynômes jusqu’à p = 7, tout en démontrant des propriétés de ces polynômes. Mais des exemples plus grands ne semblent pas envisageables. Ainsi, nous proposons une nouvelle définition des polynômes modulaires dans laquelle l’on se restreint aux surfaces abéliennes principalement polarisées qui ont multiplication réelle par l’ordre maximal d’un corps quadratique réel afin d’obtenir des polynômes plus petits. Nous présentons alors de nombreux exemples de polynômes et des résultats théoriques. / Modular polynomials on elliptic curves are a fundamental tool used for the computation of graph of isogenies, class polynomials or for point counting. Thus, they are fundamental for the elliptic curve cryptography. A generalization of these polynomials for principally polarized abelian surfaces has been introduced by Régis Dupont in 2006, who has also described an algorithm to compute them, while theoretical results can been found in an article of Bröker– Lauter of 2009. But these polynomials being really big, they have been computed only in the minimal case p = 2. In this thesis, we continue the work of Dupont and Bröker–Lauter by defining and giving theoretical results on modular polynomials with new invariants, based on theta constants. Using these invariants, we have been able to compute the polynomials until p = 7 but bigger examples look intractable. Thus we define a new kind of modular polynomials where we restrict on the surfaces having real multiplication by the maximal order of a real quadratic field. We present many examples and theoretical results.

Avec la possibilité de l’existence d’un ordinateur quantique, les primitives cryptographiques basées sur la théorie des nombres risquent de devenir caduques. Il devient donc important de concevoir des schémas résistants à ce nouveau type de menaces. Les réseaux euclidiens et les codes correcteurs d’erreurs sont deux outils mathématiques permettant de construire des problèmes d’algèbre linéaire, pour lesquels il n’existe aujourd’hui pas d’algorithme quantique permettant d’accélérer significativement leur résolution. Dans cette thèse, nous proposons quatre primitives cryptographiques de ce type : deux schémas de signatures (dont une signature traçable) basés sur les réseaux, un protocole de délégation de signature utilisant du chiffrement complètement homomorphe, et une nouvelle approche permettant de construire des cryptosystèmes très efficaces en pratique basés sur les codes. Ces contributions sont accompagnées de paramètres concrets permettant de jauger les coûts calculatoires des primitives cryptographique dans un monde post-quantique. / In the likely event where a quantum computer sees the light, number theoretic based cryptographic primitives being actually in use might become deciduous. This results in an important need to design schemes that could face off this new threat. Lattices and Error Correcting Codes are mathematical tools allowing to build algebraic problems, for which – up to-date – no quantum algorithm significantly speeding up their resolution is known. In this thesis, we propose four such kind cryptographic primitives: two signatures schemes (among those a traceable one) based on lattices, a signature delegation protocol using fully homomorphic encryption, and a new framework for building very efficient and practical code-based cryptosystems. These contributions are fed with concrete parameters allowing to gauge the concrete costs of security in a post-quantum world.