The importance of constructing reliable and efficient methods for securing digital information in the modern world cannot be overstated. The urgency of this need is reflected in mainstream media--newspapers and websites are full of news about critical user information, be it credit card numbers, medical data, or social security information, being compromised and used illegitimately. According to news reports, hackers probe government computer networks millions of times a day, about 9 million Americans have their identities stolen each year and cybercrime costs large American businesses 3.8 million dollars a year. More than 1 trillion worth of intellectual property has already been stolen from American businesses. It is this evergrowing problem of securing valuable information that our thesis attempts to address (in part). In this thesis, we study methods to secure information that are fast, convenient and reliable. Our overall contribution has four distinct threads. First, we construct efficient, "expressive" Public Key Encryption systems (specifically, Identity Based Encryption systems) based on the hardness of lattice problems. In Identity Based Encryption (IBE), any arbitrary string such as the user's email address or name can be her public key. IBE systems are powerful and address several problems faced by the deployment of Public Key Encryption. Our constructions are secure in the standard model. Next, we study secure communication over the two-user interference channel with an eavesdropper. We show that using lattice codes helps enhance the secrecy rate of this channel in the presence of an eavesdropper. Thirdly, we analyze the security requirements of network coding. Network Coding is an elegant method of data transmission which not only helps achieve capacity in several networks, but also has a host of other benefits. However, network coding is vulnerable to "pollution attacks" when there are malicious users in the system. We design mechanisms to prevent pollution attacks. In this setting, we provide two constructions -- a homomorphic Message Authentication Code (HMAC) and a Digital Signature, to secure information that is transmitted over such networks. Finally, we study the benefits of using Compressive Sensing for secure communication over the Wyner wiretap channel. Compressive Sensing has seen an explosion of interest in the last few years with its elegant mathematics and plethora of applications. So far however, Compressive Sensing had not found application in the domain of secrecy. Given its inherent assymetry, we ask (and answer in the affirmative) the question of whether it can be deployed to enable secure communication. Our results allow linear encoding and efficient decoding (via LASSO) at the legitimate receiver, along with infeasibility of message recovery (via an information theoretic analysis) at the eavesdropper, regardless of decoding strategy. / text

Σε αυτή τη μεταπτυχιακή διπλωματική εργασία μελετήθηκαν, αναπτύχτηκαν και συγκριθήκαν αρχιτεκτονικές για κρυπτογραφικές εφαρμογές που χρησιμοποιούνται στης τεχνικές πιστοποίησης μηνυμάτων. Σε αυτές χρησιμοποιήθηκαν και τεχνικές βελτιστοποίησης της απόδοσης. Στην ασφάλεια μετάδοσης των πληροφοριών, η πιστοποίηση μηνύματος είναι μία θεμελιώδης τεχνική, η οποία χρησιμοποιείται για να επιβεβαιώσει ότι τα ληφθέντα μηνύματα προέρχονται από τον σωστό αποστολέα και ότι δεν έχουν τροποποιηθεί κατά τη μετάδοση. Στην πιστοποίηση μηνύματος, απαιτείται η χρήση ενός κώδικα πιστοποίησης μηνύματος (Message Authentication Code-MAC). Οι τεχνικές για να δημιουργηθεί ένα MAC γίνεται με δύο τρόπους: α)Με χρήση μίας hash συνάρτησης σε συνδυασμό με ένα μυστικό κλειδί και αναφέρεται σαν HMAC (Hash-based MAC). β)Με χρήση ενός block cipher αλγορίθμου κρυπτογράφησης σε συνδυασμό με ένα μυστικό κλειδί και αναφέρεται σαν CMAC (Cipher block-based MAC). Θα υλοποιηθούν οι δύο παραπάνω τρόποι-μέθοδοι παραγωγής MAC, σε πλατφόρμες υλικού με γνώμονα την αύξηση της ρυθμαπόδοσης τους. Θα αποτιμηθεί ο ρόλος τους στα κρυπτογραφικά συστήματα ασφαλείας και σε ποιές περιπτώσεις συνίσταται η χρήση της κάθε μίας τεχνικής. Έτσι θα ξεκαθαριστούν οι διαφορές τους και θα καθοριστεί το προφίλ των εφαρμογών στης οποίες κάθε μια εκ των δύο αυτών τεχνικών ταιριάζει καλύτερα. Οι υλοποιήσεις συγκριθήκαν στην ίδια πλατφόρμα υλικού που χρησιμοποιήθηκε για την τελική υλοποίηση ώστε σε κάθε περίπτωση, ανάλογα με της απαιτήσεις της εκάστοτε εφαρμογής, να βρεθεί και η βέλτιστη λύση από πλευράς κόστους. / In the present M.Sc. thesis, several architectures for message authentication codes were studied, developed and compared to each other. Performance optimization techniques were exploited as well. Message Authentication Codes (MACs) are widely used in order to protect both a message's integrity -by ensuring that a different MAC will be produced if the message has changed - as well as its authenticity (only someone who knows the secret key could have generated a valid MAC). A message authentication code is an authentication tag (also called a checksum) derived by applying an authentication scheme, together with a secret key, to a message. Typically MACs are produced through: α) HMAC mechanism which is based on a FIPS approved collision-resistant hash function in combination with a secret key (Hash-based MAC). β)CMAC mechanism which is based on a block cipher algorithm in combination with a secret key (Cipher block-based MAC). The above two ways (mechanisms) for producing MACs were designed and implemented in hardware taking into consideration the increase of their throughput. The cryptographic systems in which the above two are exploited were described. Their key role in these systems was valued through an investigation concerning the way of their incorporation. Thus, the differences between them were clarified determining the applications where each one is better befitted. HMAC and CMAC designs are implemented in the same hardware FPGA platform and compared to each other in terms of operating frequency, area consumption and throughput. In this way, the best solution between them concerning their overall cost can be designated.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-08-01T20:10:46Z No. of bitstreams: 1 REX ANTONIO COSTA MEDEIROS - DISSERTAÇÃO PPGEE 2004..pdf: 14601327 bytes, checksum: 5e8b5fae1a59cd77236adc8cc0655c17 (MD5) / Made available in DSpace on 2018-08-01T20:10:46Z (GMT). No. of bitstreams: 1 REX ANTONIO COSTA MEDEIROS - DISSERTAÇÃO PPGEE 2004..pdf: 14601327 bytes, checksum: 5e8b5fae1a59cd77236adc8cc0655c17 (MD5) Previous issue date: 2004-06-22 / CNPq / Nos dias atuais, os sistemas de criptografia e autenticação desempenham um papel fundamental em aplicações que envolvem a manipulação de informações sigilosas, tais como movimentações financeiras, comércio eletrônico, aplicações militares e proteção de arquivos digitais. A popularização do uso dos sistemas de criptografia e autenticação se deve, em grande parte, a descrição de esquema de criptografia por chave pública. A segurança de tais sistemas é baseada na intratabilidade computacional (clássica) de problemas da teoria dos números, como a fatoração em produtos de primos e o problema do logaritmo discreto. A partir da formulação da Mecânica Quântica, foram demonstrados algoritmos que, executados em um computador quântico e consumindo tempo e recursos polinomiais, são capazes de resolver tais problemas. A construção de um computador quântico inviabilizaria, portanto, o uso de sistemas de criptografia e autenticação por chave pública. Nesta dissertação é discutido o problema da autenticação quântica de mensagens clássicas. É proposto um protocolo híbrido que alcança segurança incondicional, mesmo que um criptoanalista disponha de recursos computacionais infinitos, sejam eles clássicos ou quânticos. Através de uma prova matemática formal, é mostrado que o nível de segurança pode ser feito tão alto quanto desejado. Tal segurança é-garantida pelos princípios fundamentais da mecânica quântica. / Nowadays, cryptography and authentication play a central role in applications that manipulates confidential information, like financial transactions, e-commerce, military applications and digital data protection. The explosive growth of cryptosystems is mostly due to the discovery of the so-called public-kcy cryptosystems. The security of such systcms is based on the intractability of some problems from number theory, like factorization and the discrete logarithm problem. After the formulation of the quantum mechanics, several protocols wcre described in order to solve these problems in time and resources polynomials in their argumente. So, one can conclude that public-key cryptosystems are not secure in a scenario where an eavesdropper makes use of quantum computers. In this work it is discussed the problem of quantum authenticating classical messages. It is proposed a non-interactive hybrid protocol reaching information-theoretical security, even when an eavesdropper possesses both infinite quantum and classical computei- power. It is presented a mathematical proof that it is always possible to reach a desirable levei of security. This security is due to the quantum mechanics proprieties of non-orthogonal quantum states.

A proposta apresentada nesta dissertaÃÃo representa uma expansÃo do conceito original de assinatura em anel. Um esquema de assinatura em anel permite que um membro de um grupo divulgue uma mensagem anonimamente, de tal forma que cada um dos membros do grupo seja considerado o possÃvel autor da mensagem. A ideia principal de uma assinatura em anel à garantir o anonimato do assinante e ainda garantir a autenticidade da informaÃÃo, mostrando que a mensagem partiu de um dos membros do referido grupo. Esta dissertaÃÃo apresenta um esquema de assinatura em anel baseado no esquema de Rivest et al. (2001), em que o assinante pode, mais tarde, revogar seu anonimato apresentando valores secretos que provam que somente ele seria capaz de gerar tal assinatura. Esta propriedade serà chamada aqui de resgate de autoria. A principal diferenÃa em relaÃÃo ao trabalho de Rivest et al. (2001) à apresentada antes mesmo de comeÃar a geraÃÃo da assinatura. Os valores utilizados como entrada para a funÃÃo trapdoor serÃo cÃdigos de autenticaÃÃo de mensagem - MACs gerados pelo algoritmo HMAC, um algoritmo de autenticaÃÃo de mensagem baseado em funÃÃo hash resistente à colisÃo. Essa modificaÃÃo simples permitirà que, no futuro, o assinante revele-se como o verdadeiro autor da mensagem apresentando os valores secretos que geraram os MACs. / The proposal presented in this thesis represents an expansion of the original concept of ring signature. A ring signature scheme allows a member of a group to publish a message anonymously, so that each member of the group can be considered the author of the message. The main idea of a ring signature is to guarantee the anonymity of the subscriber also ensure the authenticity of information, showing that the message came from one of the members of that group. This thesis presents a signature scheme based on (RIVEST et al., 2001), where the subscriber can later revoke anonymity presenting secret values that prove that he would only be able to generate such a signature. This property will be referred to here as rescue of authorship. The main difference to the proposal of Rivest et al. (2001) is presented before we even begin signature generation. The values used as input to the trapdoor function are message authentication codes - MACs generated by the HMAC algorithm, an algorithm for message authentication based on hash function collision resistant. This simple modification will allow, in the future, the subscriber to reveal itself as the true author of the message by showing the secret values to generate those MACs.

The concept of wireless sensor network (WSN) is where tiny devices (sensor nodes), positioned fairly close to each other, are used for sensing and gathering data from its environment and exchange information through wireless connections between these nodes (e.g. sensor nodes distributed through out a bridge for monitoring the mechanical stress level of the bridge continuously). In order to easily deploy a relatively large quantity of sensor nodes, the sensor nodes are typically designed for low price and small size, thereby causing them to have very limited resources available (e.g. energy, processing power). Over the years, different security (cryptographic) primitives have been proposed and refined aiming at utilizing modern processor’s power e.g. 32-bit or 64-bit operation, architecture such as MMX (Multi Media Extension) and etc. In other words, security primitives have targeted at high-end systems (e.g. desktop or server) in software implementations. Some hardware-oriented security primitives have also been proposed. However, most of them have been designed aiming only at large message and high speed hashing, with no power consumption or other resources (such as memory space) taken into considerations. As a result, security mechanisms for ultra-low power (<500µW) devices such as the wireless sensor nodes must be carefully selected or designed with their limited resources in mind. The objective of this project is to provide implementations of security primitives (i.e. encryption and authentication) suitable to the WSN environment, where resources are extremely limited. The goal of the project is to provide an efficient building block on which the design of WSN secure routing protocols can be based on, so it can relieve the protocol designers from having to design everything from scratch. This project has provided three main contributions to the WSN field.  Provides analysis of different tradeoffs between cryptographic security strength and performances, which then provide security primitives suitable for the needs in a WSN environment. Security primitives form the link layer security and act as building blocks for higher layer protocols i.e. secure routing protocol.  Implements and optimizes several security primitives in a low-power microcontroller (TI MSP430F1232) with very limited resources (256 bytes RAM, 8KB flash program memory). The different security primitives are compared according to the number of CPU cycles required per byte processed, specific architectures required (e.g. multiplier, large bit shift) and resources (RAM, ROM/flash) required. These comparisons assist in the evaluation of its corresponding energy consumption, and thus the applicability to wireless sensor nodes.  Apart from investigating security primitives, research on various security protocols designed for WSN have also been conducted in order to optimize the security primitives for the security protocols design trend. Further, a new link layer security protocol using optimized security primitives is also proposed. This new protocol shows an improvement over the existing link layer security protocols. Security primitives with confidentiality and authenticity functions are implemented in the TinyMote sensor nodes from the Technical University of Vienna in a wireless sensor network. This is to demonstrate the practicality of the designs of this thesis in a real-world WSN environment. This research has achieved ultra-low power security primitives in wireless sensor network with average power consumption less than 3.5 µW (at 2 second packet transmission interval) and 700 nW (at 5 second packet transmission interval). The proposed link layer security protocol has also shown improvements over existing protocols in both security and power consumption. / Dissertation (MEng (Computer Engineering))--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / unrestricted

Diversas aplicações de redes de sensores sem fio necessitam de serviços de segurança, como confidencialidade, integridade e autenticação de origem de dados. Contudo, dadas as limitações de processamento, memória e suprimento de energia dos dispositivos, os mecanismos de segurança tradicionais podem causar efeitos indesejáveis na rede, como atraso na comunicação e aumento no consumo de energia, impondo obstáculos para seu uso na tecnologia em questão. Muitas propostas de esquemas de segurança baseados em criptografia simétrica projetados especificamente para redes de sensores sem fio são encontradas na literatura. Contudo, essas soluções são focadas na segurança salto-a-salto. Tal abordagem é adequada para garantir a segurança dos enlaces deste tipo de rede, mas não garante a segurança na comunicação fim-a-fim. Neste trabalho são apresentados cenários e desafios de implementação de segurança neste tipo de rede, e a concepção, o projeto e a implementação de uma arquitetura de segurança para redes de sensores sem fio, que tem como objetivos: prover segurança na comunicação fim-a-fim; permitir a interoperabilidade entre diferentes sistemas; e possibilitar uma maior flexibilidade em relação à utilização de chaves criptográficas em diferentes cenários e topologias. Adicionalmente, a solução proposta suporta ativação e desativação de seus serviços em tempo de execução. O projeto da referida arquitetura, atuante na camada de aplicação da pilha de protocolos de rede, foi construído com base na análise das características de arquiteturas encontradas na literatura, bem como de estratégias adotadas por estas. Para a construção da implementação foram selecionados mecanismos e algoritmos criptográficos a partir da avaliação de desempenho que considerou assimétricas de uso de memória, tempo de execução e consumo de energia. Como resultados são apresentados a especificação da arquitetura, a avaliação qualitativa da mesma e a avaliação de desempenho da implementação desenvolvida como prova de conceito. Além disso, é apresentada uma análise do impacto de diferentes topologias e características de disposição na tarefa de distribuição de chaves criptográficas em redes de sensores sem fio. / Many wireless sensor networks applications need security services, such as confidentiality, data integrity and data source authentication. On the other hand, because of device limitations, security mechanisms may affect the network energy consumption and communication delay, which impose a great challenge for practical implementation of security mechanisms in such scenario. Many solutions based on symmetric cryptography were proposed for the specific challenges of wireless sensor networks. Nevertheless, they are focused on hop-by-hop security. Such approach is suited to provide link-layer security, but it cannot guarantee end-to-end security. This work presents scenarios and challenges to implement security in wireless sensor networks, and the conception, design and implementation of a security architecture, which aims to provide: security in end-to-end communication; interoperability between different systems, and enable greater flexibility in cryptographic keys distribution in different scenarios and topologies. Additionally, the proposed solution supports on-the-y adjustment of its security services. The architecture design, which targets the application layer of the network protocol stack, was based on the main properties of the architectures found in literature as well as adopted strategies. For the implementation, mechanisms and cryptographic algorithms were selected through the performance evaluation that considers memory usage, execution time and power consumption as metrics. The results were the architecture specification and its qualitative analysis, and the performance evaluation of the implementation developed as proof of concept. Furthermore, we present an analysis of topology and deployment impact on key distribution task.

Diversas aplicações de redes de sensores sem fio necessitam de serviços de segurança, como confidencialidade, integridade e autenticação de origem de dados. Contudo, dadas as limitações de processamento, memória e suprimento de energia dos dispositivos, os mecanismos de segurança tradicionais podem causar efeitos indesejáveis na rede, como atraso na comunicação e aumento no consumo de energia, impondo obstáculos para seu uso na tecnologia em questão. Muitas propostas de esquemas de segurança baseados em criptografia simétrica projetados especificamente para redes de sensores sem fio são encontradas na literatura. Contudo, essas soluções são focadas na segurança salto-a-salto. Tal abordagem é adequada para garantir a segurança dos enlaces deste tipo de rede, mas não garante a segurança na comunicação fim-a-fim. Neste trabalho são apresentados cenários e desafios de implementação de segurança neste tipo de rede, e a concepção, o projeto e a implementação de uma arquitetura de segurança para redes de sensores sem fio, que tem como objetivos: prover segurança na comunicação fim-a-fim; permitir a interoperabilidade entre diferentes sistemas; e possibilitar uma maior flexibilidade em relação à utilização de chaves criptográficas em diferentes cenários e topologias. Adicionalmente, a solução proposta suporta ativação e desativação de seus serviços em tempo de execução. O projeto da referida arquitetura, atuante na camada de aplicação da pilha de protocolos de rede, foi construído com base na análise das características de arquiteturas encontradas na literatura, bem como de estratégias adotadas por estas. Para a construção da implementação foram selecionados mecanismos e algoritmos criptográficos a partir da avaliação de desempenho que considerou assimétricas de uso de memória, tempo de execução e consumo de energia. Como resultados são apresentados a especificação da arquitetura, a avaliação qualitativa da mesma e a avaliação de desempenho da implementação desenvolvida como prova de conceito. Além disso, é apresentada uma análise do impacto de diferentes topologias e características de disposição na tarefa de distribuição de chaves criptográficas em redes de sensores sem fio. / Many wireless sensor networks applications need security services, such as confidentiality, data integrity and data source authentication. On the other hand, because of device limitations, security mechanisms may affect the network energy consumption and communication delay, which impose a great challenge for practical implementation of security mechanisms in such scenario. Many solutions based on symmetric cryptography were proposed for the specific challenges of wireless sensor networks. Nevertheless, they are focused on hop-by-hop security. Such approach is suited to provide link-layer security, but it cannot guarantee end-to-end security. This work presents scenarios and challenges to implement security in wireless sensor networks, and the conception, design and implementation of a security architecture, which aims to provide: security in end-to-end communication; interoperability between different systems, and enable greater flexibility in cryptographic keys distribution in different scenarios and topologies. Additionally, the proposed solution supports on-the-y adjustment of its security services. The architecture design, which targets the application layer of the network protocol stack, was based on the main properties of the architectures found in literature as well as adopted strategies. For the implementation, mechanisms and cryptographic algorithms were selected through the performance evaluation that considers memory usage, execution time and power consumption as metrics. The results were the architecture specification and its qualitative analysis, and the performance evaluation of the implementation developed as proof of concept. Furthermore, we present an analysis of topology and deployment impact on key distribution task.

<p>Quantum key growing, often called quantum cryptography or quantum key distribution, is a method using some properties of quantum mechanics to create a secret shared cryptography key even if an eavesdropper has access to unlimited computational power. A vital but often neglected part of the method is unconditionally secure message authentication. This thesis examines the security aspects of authentication in quantum key growing. Important concepts are formalized as Python program source code, a comparison between quantum key growing and a classical system using trusted couriers is included, and the chain rule of entropy is generalized to any Rényi entropy. Finally and most importantly, a security flaw is identified which makes the probability to eavesdrop on the system undetected approach unity as the system is in use for a long time, and a solution to this problem is provided.</p>

Quantum key growing, often called quantum cryptography or quantum key distribution, is a method using some properties of quantum mechanics to create a secret shared cryptography key even if an eavesdropper has access to unlimited computational power. A vital but often neglected part of the method is unconditionally secure message authentication. This thesis examines the security aspects of authentication in quantum key growing. Important concepts are formalized as Python program source code, a comparison between quantum key growing and a classical system using trusted couriers is included, and the chain rule of entropy is generalized to any Rényi entropy. Finally and most importantly, a security flaw is identified which makes the probability to eavesdrop on the system undetected approach unity as the system is in use for a long time, and a solution to this problem is provided. / ICG QC

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-03-08T12:29:03Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) JOAO VICTOR DE CARVALHO EVANGELISTA_DISSERTACAO_VERSAO_FINAL_2016.pdf: 4051425 bytes, checksum: c53a5039b8aa3054c77f2ee82a10849f (MD5) / Made available in DSpace on 2017-03-08T12:29:03Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) JOAO VICTOR DE CARVALHO EVANGELISTA_DISSERTACAO_VERSAO_FINAL_2016.pdf: 4051425 bytes, checksum: c53a5039b8aa3054c77f2ee82a10849f (MD5) Previous issue date: 2016-08-16 / Message authentication, which ensures that a received message comes from its acclaimed sender, is of fundamental importance for secure communication systems. We consider in this work a physical layer authentication system employing tag signals embedded in the message to provide a robust authentication method. This work diverges from previous work in the area when it comes to the tag generation method. While the previous works use methods based on cryptographic hash functions or on the channel side information our system employs unidimensional chaotic maps to generate these tags. Due to the loss of information about the initial condition of chaotic maps, we show that they are strong candidates for the tag generation process. We prove that chaotic tags provide a positive lower bound on the unconditional security of the system. Additionally, we calculate the probability of success for three possible attacks to the authentication system: impersonation, substitution and replay.Finally, we analyze how the system parameters affect these probabilities and some performance metrics (bit error rate, outage probability, probability of false negative) and explore the tradeoff between security and performance in order to provide guidelines to design the system. / A autenticação de mensagem, o que garante que uma mensagem recebida vem de seu aclamado remetente, é de fundamental importância para sistemas de comunicação seguros. Neste contexto, considera-se neste trabalho um sistema de autenticação em camada física empregando tags embutidos nas mensagens proporcionando um robusto método de autenticação. Este trabalho diverge de trabalhos anteriores na área no que se refere ao método de geração de tags. Enquanto os trabalhos anteriores utilizam métodos baseados em funções criptográficas de hash e na informação do estado do canal, nosso sistema emprega mapas caóticos unidimensionais para gerar os tags. Devido ao fato de que a informação sobre a condição inicial se perde ao longo de uma órbita caótica mostraremos que elas são fortes candidatas para o processo de geração de tags. Provamos que tags caóticos garantem um limitante inferior positivo na segurança incondicional do sistema. Adicionalmente, nós calculamos a probabilidade de sucesso de três tipos de ataque: de personificação, de substituição e de repetição. Para finalizar, analisamos como os parâmetros do sistema afetam essas probabilidades e algumas métricas de performance (taxa de erro por bit, probabilidade de interrupção e probabilidade de falso negativo) e os compromissos entre segurança e performance para prover um guia de projeto do sistema.