Orientador: Ricardo Miranda Martins / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-25T03:12:47Z (GMT). No. of bitstreams: 1 Spina_AndreVinicius_M.pdf: 1532380 bytes, checksum: 1525ba4a0d466a2c148b8b1a485ccec2 (MD5) Previous issue date: 2014 / Resumo: A pesquisa apresentará uma introdução a Teoria dos Números através de uma abordagem sobre os métodos criptográficos RSA e Diffie-Hellman, onde pode-se constatar situações onde eles são eficientes. A teoria matemática presente nesse trabalho envolve conhecimentos em números primos, aritmética modular, testes de primalidade, grupos e outras questões envolvendo teoria dos números / Abstract: The paper presents a Number Theory introduction, trough a RSA and Diffie-Hellman cryptographic methods approach, where one can observe situations where they are effective. The mathematical theory introduced in this paper encompass prime numbers, Modular arithmetic,Primality test, groups and other Number Theory related branches / Mestrado / Matemática em Rede Nacional - PROFMAT / Mestre em Matemática em Rede Nacional - PROFMAT

M.Ing. (Electrical and Electronic Engineering) / Please refer to full text to view abstract

M.Ing. (Electric and Electrical Engineering) / From the day the first 'apple' was eaten, a species of people existed that wants to misuse other people, This species is normally the first to use new technology to their advantage. It is essential for our own security to restrict the boundaries of their playing-field and to fill the field it self with potholes. This however should be a continuous process, for their dexterity tends to evolveas fast as new techniques are mastered. Firstly this thesis entails the analysis of the boundaries of the playing field of authentication systems without security. The boundaries of authentication systems with security is established with a unique technique. Concluding the first part of the thesis, a new method of code designing for this playing-field is proposed. Reordering the potholes on the playing-field is the subject of the second part of the thesis. Anew public key system is described for this purpose. A novel implementation of insertion/deletion error correcting codes is presented in this new system. To conclude the thesis, a thorough analysis of this public key system is presented.

Today the Internet is used more and more as a transportation for information. Much of the information is confidential and should not be read by those not privileged. To protect the information from unauthorized access cryptography can be applied. The cryptography algorithms in use today all have their pros and cons. They are therefore suited for different applications. We've compared three different cryptography algorithms RSA, DES and IDEA. What we've focused on is the level of security the algorithms give. DES and IDEA are symmetrical algorithms and as such they use the same key for encryption and decryption. RSA on the other hand is an asymmetrical algorithm. Asymmetrical algorithms use two keys, one for encryption and the other for decryption. The factor that is most decisive for the algorithms security is the length of the key that is used. What is interesting concerning the keys is that security increases linearly for the symmetrical algorithms, as the key length increases. For asymmetrical algorithms it increases on an expontiell curve. RSA has got a big advantage compared to DES and IDEA. The advantage is key management. RSA can be used to exchange symmetrical keys in a safe way. The big disadvantage of RSA is that it's very slow to use. According to measurements that we have seen it is about 3 to 4 times slower then DES and IDEA during encryption, when using a key length of 1024 bits. At decryption RSA is about 120 times slower using a key length of 1024 bits. DES on the other hand is slower then newer symmetrical algorithms such as IDEA. This makes it uncalled for to use it in it?s original shape as it?s obsolete and insecure. Using DES will only give a false sense of security, unless the information doesn't need to be secure for more then a short time period. IDEA offers high using it's 128 bits key and it's also the fastest of the two symmetrical algorithms, compared to the level of security that it offers. IDEA today has no known weaknesses and it has not been broken. Of the three IDEA is the best choice to use when it concerns cryptography of information, for example information which is stored on a hard disc, or information that is sent in e-commerce.

Many of the products commercially available today contain some form of encrypted or hashed data. It can involve DRM protection, licenses and certificates, signatures or identification information. Regardless of what the data is intended for, it is protected for a reason and may be worth a great deal of money to the owner. There are numerous examples of products that have been subject to hacking in the form of simple memory attacks. If the keys are made all too easily extracted, the value of the protected data will soon be lost. The aim of the thesis work discussed in this report was to evaluate the vulnerabilities in mobile phones to this sort of attacks and to find possible security enhancements that can be applied. A method is proposed where masking will secure the cryptology keys while they reside in the memory. Different masks are developed and tested - The effects on performance are measured and the security is evaluated. The thesis work concludes that it is possible to implement masking on many of the security functions using keys and that the masks will increase security. The conclusion also states that the time consumption of the masking heavily depends on which mask that is used and that the masking could be applied in such a way that the level of masking can be varied.

Le sujet de cette thèse est la cryptographie et son interconnexions avec la théorie des codes. En particulier, on utilise des techniques issues de la théorie des codes pour construire et analyser des protocoles cryptographiques avec des propriétés nouvelles ou plus avancées. On se concentre d'abord sur le partage de secret ou secret sharing, un sujet important avec de nombreuses applications pour la Cryptographie actuelle. Dans la variante à laquelle on s'intéresse, un schéma de partage de secret reçoit en entrée un élément secret, et renvoie en sortie n parts de telle façon que chaque ensemble de parts de taille suffisamment petite ne donne aucune information sur le secret (confidentialité), tandis que chaque ensemble de taille suffisamment grande permet de reconstituer le secret (reconstruction). Un schéma de partage de secret peut donc être vu comme une solution à un problème de communication où un émetteur Alice est connectée avec un destinataire Bob par n canaux distincts, dont certains sont contrôlés par un adversaire Ève. Alice peut utiliser un schéma de partage de secret pour communiquer un message secret a Bob de telle façon qu'Ève n'apprenne aucune information sur le secret en lisant les données transmises sur les canaux qu'elle contrôle, tandis que Bob peut recevoir le message même si Ève bloque ces dits canaux. Notre contributions au partage de secret concernent ses liens avec la théorie des codes ; comme les deux domaines partagent un même but (récupérer des données à partir d'informations partielles), ce n'est pas surprenant qu'ils aient connu une interaction longue et fertile. Plus précisément, Massey commença une analyse fructueuse à propos de la construction et de l'étude d'un schéma de partage de secret à partir d'un code correcteur. L'inconvénient de cette analyse est que la confidentialité d'un schéma de partage de secret est estimé grâce au dual du code sous-jacent ; cela peut être problématique vu qu'il pourrait ne pas être possible d'obtenir des codes avec des propriétés souhaitables qui aient aussi un bon code dual. On contourne ce problème en établissant une connexion nouvelle entre les deux domaines, telle que la confidentialité d'un schéma de partage de secrets n'est plus contrôlée par le dual du code sous-jacent. Cela nous permet d'exploiter complètement le potentiel de certaines constructions récentes de codes pour obtenir des meilleurs schémas; on illustre ceci avec deux applications. Premièrement, en utilisant des codes avec codage et décodage en temps linéaire on obtient une famille de schémas de partage de secret où le partage (calcul des parts issues du secret) tout comme la reconstruction peuvent s'effectuer en temps linéaire ; pour des seuils de confidentialité et de reconstruction croissants, ceci restait jusqu'à présent un problème ouvert. Deuxièmement, on utilise des codes avec décodage en liste pour construire des schémas de partage de secret robustes, c'est-à-dire des schémas qui peuvent reconstituer le secret même si certaines parts sont incorrectes, sauf avec une petite probabilité d'erreur. etc... / The topic of this dissertation is Cryptography, and its connections with Coding Theory. Concretely, we make use of techniques from Coding Theory to construct and analyze cryptographic protocols with new and/or enhanced properties. We first focus on Secret Sharing, an important topic with many applications to modern Cryptography, which also forms the common ground for most of the concepts discussed in this thesis. In the flavor we are interested in, a secret-sharing scheme takes as input a secret value, and produces as output n shares in such a way that small enough sets of shares yield no information at all on the secret (privacy), while large enough sets of shares allow to recover the secret (reconstruction). A secret-sharing scheme can thus be seen as a solution to a secure communication problem where a sender Alice is connected to a receiver Bob via $n$ distinct channels, some of which are controlled by an adversary Eve. Alice can use a secret-sharing scheme to communicate a secret message to Bob in such a way that Eve learns no information on the message by eavesdropping on the channels she controls, while Bob can receive the message even if Eve blocks the channels under her control. Our contributions to Secret Sharing concern its connection with Coding Theory; since the two fields share the goal of recovering data from incomplete information, it is not surprising that Secret Sharing and Coding Theory have known a long and fruitful interplay. In particular, Massey initiated a very successful analysis on how to construct and study secret-sharing schemes from error-correcting codes. The downside of this analysis is that the privacy of secret-sharing schemes is estimated in terms of the dual of the underlying code; this can be problematic as it might not be possible to obtain codes with desirable properties that have good duals as well. We circumvent this problem by establishing a new connection between the two fields, where the privacy of secret-sharing schemes is no longer controlled by the dual of the underlying code. This allows us to fully harness the potential of recent code constructions to obtain improved schemes; we exemplify this by means of two applications. First, by making use of linear-time encodable and decodable codes we obtain a family of secret-sharing schemes where both the sharing (computation of the shares from the secret) and the reconstruction can be performed in linear time; for growing privacy and reconstruction thresholds, this was an hitherto open problem. Second, we make use of list-decodable codes to construct robust secret-sharing schemes, i.e., schemes that can recover the secret even if some of the shares are incorrect, except with a small error probability. The family we present optimizes the trade-off between the extra data that needs to be appended to the share to achieve robustness and the error probability in the reconstruction, reaching the best possible value. etc...

This thesis focused on testing whether persistent encryption of Fibre Channel is doable and what kind of security it provides. It has been shown that intercepting, analysing and modifying Fibre Channel traffic is possible without any noticeable performance loss as long as latency is kept within certain boundaries. If latency are outside those boundaries extreme performance loss are to be expected. This latency demand puts further restrictions on the cryptography to be used. Two platforms were simulated, implemented and explained. One for intercepting and modifying Fibre Channel and one for analysing Fibre Channel traffic using Linux and Wireshark.

The generation of random number sequences, that is, of unpredictable sequences free from any structure, has found numerous applications in the field of information technologies. One of the most sensitive applications is cryptography, whose modern practice makes use of secret keys that must indeed be unpredictable for any potential adversary. This type of application demands highly secure randomness generators.This thesis contributes to the device-independent approach to quantum random number generation (DIRNG, for Device-Independent Random Number Generation). Those methods of randomness generation exploit the fundamental unpredictability of the measurement of quantum systems. In particular, the security of device-independent methods does not appeal to a specific model of the device itself, which is treated as a black box. This approach therefore stands in contrast to more traditional methods whose security rests on a precise theoretical model of the device, which may lead to vulnerabilities caused by hardware malfunctions or tampering by an adversary.Our contributions are the following. We first introduce a family of robust self-testing criteria for a class of quantum systems that involve partially entangled qubit pairs. This powerful form of inference allows us to certify that the contents of a quantum black box conforms to one of those systems, on the sole basis of macroscopically observable statistical properties of the black box.That result leads us to introduce and prove the security of a protocol for randomness generation based on such partially entangled black boxes. The advantage of this method resides in its low shared entanglement cost, which allows to reduce the use of quantum resources (both entanglement and quantum communication) compared to existing DIRNG protocols.We also present a protocol for randomness generation based on an original estimation of the black-box correlations. Contrary to existing DIRNG methods, which summarize the accumulated measurement data into a single quantity---the violation of a unique Bell inequality---, our method exploits a complete, multidimensional description of the black-box correlations that allows it to certify more randomness from the same number of measurements. We illustrate our results on a numerical simulation of the protocol using partially entangled states. / La génération de suites de nombres aléatoires, c'est-à-dire de suites imprévisibles et dépourvues de toute structure, trouve de nombreuses applications dans le domaine des technologies de l'information. L'une des plus sensibles est la cryptographie, dont les pratiques modernes font en effet appel à des clés secrètes qui doivent précisément être imprévisibles du point de vue d'adversaires potentiels. Ce type d'application exige des générateurs d'aléa de haute sécurité.Cette thèse s'inscrit dans le cadre de l'approche indépendante des appareils des méthodes quantiques de génération de nombres aléatoires (en anglais, Device-Independent Random Number Generation ou DIRNG). Ces méthodes exploitent la nature fondamentalement imprévisible de la mesure des systèmes quantiques. En particulier, l'appellation "indépendante des appareils" implique que la sécurité de ces méthodes ne fait pas appel à un modèle théorique particulier de l'appareil lui-même, qui est traité comme une boîte noire. Cette approche se distingue donc de méthodes plus traditionnelles dont la sécurité repose sur un modèle théorique précis de l'appareil et peut donc être compromise par un dysfonctionnement matériel ou l'intervention d'un adversaire.Les contributions apportées sont les suivantes. Nous démontrons tout d'abord une famille de critères de "self-testing" robuste pour une classe de systèmes quantiques impliquant des paires de systèmes à deux niveaux (qubits) partiellement intriquées. Cette forme d'inférence particulièrement puissante permet de certifier que le contenu d'une boîte noire quantique est conforme à l'un de ces systèmes, sur base uniquement de propriétés statistiques de la boîte observables macroscopiquement.Ce résultat nous amène à introduire et à prouver la sécurité d'une méthode de génération d'aléa basée sur ces boîtes noires partiellement intriquées. L'intérêt de cette méthode réside dans son faible coût en intrication, qui permet de réduire l'usage de ressources quantiques (intrication ou communication quantique) par rapport aux méthodes de DIRNG existantes.Nous présentons par ailleurs une méthode de génération d'aléa basée sur une estimation statistique originale des corrélations des boîtes noires. Contrairement aux méthodes de DIRNG existantes, qui résument l'ensemble des mesures observées à une seule grandeur (la violation d'une inégalité de Bell unique), notre méthode exploite une description complète (et donc multidimensionnelle) des corrélations des boîtes noires qui lui permet de certifier une plus grande quantité d'aléa pour un même nombre de mesures. Nous illustrons ensuite cette méthode numériquement sur un système de qubits partiellement intriqués. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Data security plays a central role in the design of Internet of Things (IoT). Since most of the "things" in IoT are embedded computing devices it is appropriate to talk about cryptography in embedded of systems. This kind of devices is based on microcontrollers, which have limited resources (processing power, memory, storage, and energy). Therefore, we can apply only lightweight cryptography. The goal of this work is to find the optimal cryptographic solution for IoT devices. It is expected that perception of this solution would be useful for implementation on “limited” devices. In this study, we investigate which lightweight algorithm is better to implement. Also, how we can combine two different algorithms in a hybrid scheme and modify this scheme due to data sending scenario. Compendex, Inspec, IEEE Xplore, ACM Digital Library, and Springer Link databases are used to conduct a comprehensive literature review. Experimental work adopted in this study involves implementations, measurements, and observations from the results. The experimental research covers implementations of different algorithms and experimental hybrid scheme, which includes additional function. Results show the performance of the considered algorithms and proposed hybrid scheme. According to our results, security solutions for IoT have to utilize algorithms, which have good performance. The combination of symmetric and asymmetric algorithms in the hybrid scheme can be a solution, which provides the main security requirements: confidentiality, integrity, and authenticity. Adaptation of this scheme to the possible IoT scenarios shows the results acceptable for implementation due to limited resources of hardware.

Field area networks are rapidly expanding to include a wide range of applications. Intelligent nodes on the network will be installed in a small to medium geographical area to monitor and control processes. Such nodes are generally connected to a centralized gateway used by a service provider to monitor and control various applications. The growth in popularity of ubiquitous computing requires the use of embedded network processors in everyday objects. Even though the idea of interaction between the digital devices around us could bring a great deal of convenience it also introduces great risks. Therefore such applications would not only require measurement, control and communication functionality but also a high level of security. Smart cards offer a simple, inexpensive method of incorporating a cryptographic processor into an embedded system that will allow for the implementation of security services. A field area network has resource limitations that influence security service implementation, such as low bandwidth, limited processing power, limited storage capacity and limited communication protocols. This dissertation discussed the implementation of a security policy for embedded field area networks used in distributed real-time applications, using smart card technology. The primary objective is to formulate a policy that can be implemented to secure a field area network. The secondary objective is to determine whether this policy can be implemented using mechanisms provided by smart card technology, while maintaining reasonable system performance. It states the approach taken to finding a viable solution to the problem defined above. A comprehensive literature study provides background on relevant technology and possible solutions. In a system overview the system’s boundaries and functional requirements are defined. The implementation section outlines possible solutions and describes how these can be implemented. Evaluation, verification and quantification of the performance of the proposed system are performed according to the experimental procedures described. The results obtained are documented and discussed. In the conclusion the proposed solution and the findings from the results are placed in context. Future topics of research in this field are suggested. / Dissertation (MSc)--University of Pretoria, 2006. / Computer Science / unrestricted