Personal identity refers to a set of attributes (e.g., name, social insurance number, etc.) that are associated with a person. Identity management is the process of creating, maintaining and destroying identities of individuals in a population. Biometric technologies are technologies developed to use statistical analysis of an individual’s biological or behavioral traits to determine his identity. Biometrics based authentication systems offer a reliable solution for identity management, because of their uniqueness, relative stability over time and security (among other reasons). Public acceptance of biometric systems will depend on their ability to ensure robustness, accuracy and security. Although robustness and accuracy of such systems are rapidly improving, there still remain some issues of security and balancing it with privacy. While the uniqueness of biometric traits offers a convenient and reliable means of identification, it also poses the risk of unauthorized cross-referencing among databases using the same biometric trait. There is also a high risk in case of a biometric database being compromised, since it’s not possible to revoke the biometric trait and re-issue a new one as is the case with passwords and smart keys. This unique attribute of biometric based authentication system poses a challenge that might slow down public acceptance and the use of biometrics for authentication purposes in large scale applications. In this research we investigate the vulnerabilities of biometric systems focusing on template security in iris-based biometric recognition systems. The iris has been well studied for authentication purposes and has been proven accurate in large scale applications in several airports and border crossings around the world. The most widely accepted iris recognition systems are based on Daugman’s model that creates a binary iris template. In this research we develop different systems using watermarking, bio-cryptography as well as feature transformation to achieve revocability and security of binary templates in iris based biometric authentication systems, while maintaining the performance that enables widespread application of these systems. All algorithms developed in this research are applicable on already existing biometric authentication systems and do not require redesign of these existing, well established iris-based authentication systems that use binary templates.

In traditional Wireless Sensor network's (WSN's), the sink is the only unconditionally trusted authority. If the sink is not connected to the nodes for a period of time then the network is considered as unattended. In Unattended Wireless Sensor Network (UWSN), a trusted mobile sink visits each node periodically to collect data. This network differs from the traditional multi hop wireless sensor networks where the nodes close to the sink deplete their power earlier than the other nodes. An UWSN can prolong the life time of the network by saving the battery of the nodes and also it can be deployed in environments where it is not practical for the sink to be online all the time. Saving data in the memory of the nodes for a long time causes security problems due to the lack of tamper-resistant hardware. Data collected by the nodes has to be secured until the next visit of the sink. Securing the data from an adversary in UWSN is a challenging task. We present two non-cryptographic algorithms (DS-PADV and DS-RADV) to ensure data survivability in mobile UWSN. The DS-PADV protects against proactive adversary which compromises nodes before identifying its target. DS-RADV makes the network secure against reactive adversary which compromises nodes after identifying the target. We also propose a data authentication scheme against a mobile adversary trying to modify the data. The proposed data authentication scheme uses inexpensive cryptographic primitives and few message exchanges. The proposed solutions are analyzed both mathematically and using simulations proving that the proposed solutions are better than the previous ones in terms of security and communication overhead.

Dans cette thèse, on s'intéresse à des schémas de chiffrement par blocs, c'est-à-dire que le chiffrement (et le déchiffrement) envoie un bloc de n bits sur un bloc de n bits. Il y a essentiellement deux grandes structures utilisées pour un schéma de chiffrement par blocs : la structure de Feistel (utilisée pour le DES) et la structure SPN (utilisée pour l'AES). L'étude de la sécurité de ces différents structures et schémas a permis de nombreuses avancées autant pratiques que théoriques. Nous présentons dans cette thèse des preuves de sécurité pour le schéma d'Even-Mansour itéré, le schéma paramétrable CLRW et le schéma de Feistel à clés alternées. Ces preuves utilisent une technique probabiliste, appelée coupling, introduite en cryptographie en 2002 par Mironov. Nous présentons cette technique dans le cadre des probabilités, puis la façon d'utiliser le coupling pour prouver la sécurité des schémas cités précédemment. Nous présentons également une étude de la sécurité du schéma d'Even-Mansour à deux tours pour certaines minimisations (même clés de tours ou même permutations internes par exemple) et, pour conclure, une comparaison des différentes techniques d'indistinguabilité / In this thesis, we study blockciphers, meaning that the encryption (and decryption) sends a block of n bits on a block of n bits. There is essentially two main structures used for a blockcipher: the Feistel structure (used for DES) and the SPN structure (used for AES). The study of the security of these structures and schemes has led to many practical and theoretical advances. We present in this thesis proofs of security for the iterated Even-Mansour scheme, the tweakable blockcipher CLRW and the key-alternating Feistel cipher. These proofs use a probabilistic technique, called coupling, introduced in cryptography in 2002 by Mironov. We present this technique in the context of probabilities, then we present how to use the coupling to prove the security for the schemes mentioned above. We also present an analysis of the security of the Even-Mansour cipher with two rounds and some properties (same round keys or same internal permutations for example) and, finally, we compare the different techniques to prove indistinguishability

Dans cette thèse, nous nous intéressons à la sécurité de générateurs pseudo-aléatoires et d'implémentations de schémas de signature. Concernant les schémas de signature, nous proposons, dans le cas d'une implémentation répandue de RSA, différentes attaques par injection de faute effectives quelque soit l'encodage du message. Nous présentons par ailleurs une contre-mesure infective prouvée sûre pour protéger le schéma RSA--PSS contre un certain nombre de fautes non aléatoires. Nous étudions également le schéma ECDSA couplé aux techniques d'accélération GLV/GLS. En fonction des implémentations, nous prouvons soit la bonne distribution du nonce utilisé, soit qu'il présente un biais permettant une attaque. Enfin, nous élaborons un outil qui recherche automatiquement des attaques par faute à partir d'une implémentation et d'une politique de faute, outil appliqué avec succès sur des implémentations de RSA et de ECDSA. Concernant les générateurs pseudo-aléatoires algébriques, nous étudions les générateurs non-linéaires et améliorons certaines attaques en diminuant l'information donnée à l'adversaire. Nous nous intéressons également à la sécurité du générateur Micali-Schnorr à travers quelques attaques et une étude statistique de son hypothèse de sécurité. Finalement nous proposons une cryptanalyse de tout schéma à clé publique basé sur la factorisation ou le logarithme discret dont la clé secrète est générée à partir d'un générateur linéaire. / In this thesis, we are interested in the security of pseudorandom number generators and of implementations of signature schemes. Regarding the signature schemes, we propose, in the case of a widespread implementation of RSA, various fault attacks which apply to any padding function. In addition we present a proven secure infective countermeasure to protect the RSA--PSS scheme against some non-random faults. Furthermore we study the ECDSA scheme coupled with the GLV/GLS speed-up techniques. Depending on the implementations, we prove either the good distribution of the used nonce, or that it has a bias, thereby enabling an attack. Finally we develop a tool for automatically finding fault attacks given an implementation and a fault policy, which is successfully applied to some RSA and ECDSA implementations. Regarding pseudorandom number generators, we study the nonlinear ones and improve some attacks by reducing the information available to the adversary. We also are interested in the security of the Micali-Schnorr generator through various attacks and a statistical study of its security assumption. Finally we propose a cryptanalysis of any public-key scheme based on the factorization or the discrete logarithm when the secret key is generated using a linear generator.

La transmission de données multimédia sur les réseaux sécurisés a une croissance exponentielle grâce aux progrès scientifique dans les technologies de l'information et de la communication. La sécurité des données dans certaines applications comme le stockage sécurisé, l'authentification, la protection des droits d'auteurs, la communication militaire ou la visioconférence confidentielles, nécessitent de nouvelles stratégies en matière de transmission sécurisée. Deux techniques sont couramment utilisées pour la transmission sécurisée de données visuelles, à savoir : la cryptographie et la stéganographie. La cryptographie sécurise les données en utilisant des clés secrètes afin de rendre les données illisibles, la stéganographie, elle, vise à insérer des données cruciales dans des signaux porteurs anodins.De plus, pour la confiance mutuelle et les systèmes distribués, le partage sécurisé de ressources est souvent une garantie suffisante pour les applications de communication. L'objectif principal de cette thèse est de réaliser une protection des données visuelles, en particulier les images numériques, par le biais des techniques modernes de cryptographie. Dans ce contexte, deux objectifs de recherche ont été développés durant ces travaux de thèse.La première partie de notre travail se concentre sur la sécurité des images numériques dans un environnement partagé. Ensuite, la deuxième partie porte sur l'intégrité des données visuelles pendant une transmission sécurisée.Nous avons proposé un nouveau schéma de partage des images qui exploite les propriétés d'addition et de multiplication homomorphique de deux crypto systèmes à clé publique largement utilisés : les algorithmes RSA et Paillier. Dans les schémas traditionnels de partage sécurisé, le ``dealer'' partitionne le secret en parties et le distribue à chacun des autres acteurs. Ainsi, aucun des acteurs impliqués ne participe à la création du partage sécurisé, mais il est toujours possible que le ``dealer'' transmette des données malveillantes. Au contraire, l'approche proposée utilise le système de partage de secret d'une manière qui limite l'influence du ‘‘dealer'' sur le protocole en permettant à chaque acteur de participer.La deuxième partie de ces travaux de thèse met l'accent sur l'intégrité des données visuelles lors de la transmission. L'intégrité des données signifie que les données gardent leurs structures complètes au cours d'une opération numérique comme le stockage, le transfert ou la récupération. Le changement d'un seul bit de données cryptées peut avoir un impact catastrophique sur les données décryptées. Nous abordons le problème de correction d'erreurs dans les images cryptées en utilisant le chiffrement à clé symétrique AES (Advanced Encryptions Standard) suivant différents modes. Trois mesures sont proposées afin d'exploiter les statistiques locales des données visuelles et l'algorithme de chiffrement, dans l'objectif de corriger les erreurs efficacement. / Due to the advancements in the information and communication technologies, the transmission of multimedia data over secure or insecure communication channels has increased exponentially. The security of data in applications like safe storage, authentications, copyright protection,remote military image communication or confidential video-conferencing require new strategies for secure transmission. Two techniques are commonly used for the secure transmission of visual data, i.e. cryptography and steganography. Cryptography achieves security by using secret keysto make the data illegible while steganography aims to hide the data in some innocent carrier signal. For shared trust and distributed environment, secret sharing schemes provide sufficient security in various communication applications. The principal objective of this thesis is to achieveprotection of visual data especially images through modern cryptographic techniques. In this context, the focus of the work in perspective, is twofolded. The first part of our work focuses on the security of image data in shared environment while the second part focuses on the integrity ofimage data in the encrypted domain during transmission.We proposed a new sharing scheme for images which exploits the additive and multiplicative homomorphic properties of two well known public key cryptosystems, namely, the RSA and the Paillier. In traditional secret sharing schemes, the dealer partitions the secret into shares and distributethe shares to each of the player. Thus, none of the involved players participate in the creation of the shared secret and there is always a possibilitythat the dealer can cheat some player. On the contrary, the proposed approach employs the secret sharing scheme in a way that limits the influence of the dealer over the protocol by allowing each player to participate. The second part of our thesis emphasizes on the integrity of visual data during transmission. Data integrity means that the data have its complete structure during any operation like storage, transfer or retrieval. A single bit change in encrypted data can have catastrophic impact over the decrypted data. We address the problem of error correction in images encrypted using symmetric key cryptosystem of the Advanced Encryption Standard (AES) algorithm. Three methods are proposed to exploit the local statistics of the visual data and the encryption algorithm to successfully correct the errors.

Avec la généralisation d'Internet, l'usage des protocoles cryptographiques est devenu omniprésent. Étant donné leur complexité et leur l'aspect critique, une vérification formelle des protocoles cryptographiques est nécessaire.Deux principaux modèles existent pour prouver les protocoles. Le modèle symbolique définit les capacités de l'attaquant comme un ensemble fixe de règles, tandis que le modèle calculatoire interdit seulement a l'attaquant derésoudre certain problèmes difficiles. Le modèle symbolique est très abstrait et permet généralement d'automatiser les preuves, tandis que le modèle calculatoire fournit des garanties plus fortes.Le fossé entre les garanties offertes par ces deux modèles est dû au fait que le modèle symbolique décrit les capacités de l'adversaire alors que le modèle calculatoire décrit ses limitations. En 2012 Bana et Comon ont proposé unnouveau modèle symbolique dans lequel les limitations de l'attaquant sont axiomatisées. De plus, si la sémantique calculatoire des axiomes découle des hypothèses cryptographiques, la sécurité dans ce modèle symbolique fournit desgaranties calculatoires.L'automatisation des preuves dans ce nouveau modèle (et l'élaboration d'axiomes suffisamment généraux pour prouver un grand nombre de protocoles) est une question laissée ouverte par l'article de Bana et Comon. Dans cette thèse nous proposons une procédure de décision efficace pour une large classe d'axiomes. De plus nous avons implémenté cette procédure dans un outil (SCARY). Nos résultats expérimentaux montrent que nos axiomes modélisant la sécurité du chiffrement sont suffisamment généraux pour prouver une large classe de protocoles. / With the rise of the Internet the use of cryptographic protocols became ubiquitous. Considering the criticality and complexity of these protocols, there is an important need of formal verification.In order to obtain formal proofs of cryptographic protocols, two main attacker models exist: the symbolic model and the computational model. The symbolic model defines the attacker capabilities as a fixed set of rules. On the other hand, the computational model describes only the attacker's limitations by stating that it may break some hard problems. While the former is quiteabstract and convenient for automating proofs the later offers much stronger guarantees.There is a gap between the guarantees offered by these two models due to the fact the symbolic model defines what the adversary may do while the computational model describes what it may not do. In 2012 Bana and Comon devised a new symbolic model in which the attacker's limitations are axiomatised. In addition provided that the (computational semantics) of the axioms follows from the cryptographic hypotheses, proving security in this symbolic model yields security in the computational model.The possibility of automating proofs in this model (and finding axioms general enough to prove a large class of protocols) was left open in the original paper. In this thesis we provide with an efficient decision procedure for a general class of axioms. In addition we propose a tool (SCARY) implementing this decision procedure. Experimental results of our tool shows that the axioms we designed for modelling security of encryption are general enough to prove a large class of protocols.

This dissertation describes a security policy for a distributed utility metering system. The system uses untrusted networks, such as the Internet, to communicate between service providers (water, gas, electricity etc.) and the gateway servers at customer premises. Within a building, the system uses a low-bandwidth mains-borne network, or Field-Area Network (FAN), such as Fieldbus, to communicate between the gateway server and each of the utility meters. The FAN is regarded as untrusted, and communications to and from each utility meter must be protected from all other meters and any possible outsiders on the network. It must also be assumed that the gateway server is physically vulnerable to attack, and that its loss must not jeopardise the security of the system. Each service provider must be able to access each utility meter individually. Service providers can send commands to individual utility meters, and obtain individual meter readings applicable to their service. Service providers must not be able to interfere with one another’s service. However, the gateway must be able to interpret communications initiated by individual meters, to ensure that the alarm can be raised to service providers if a meter reading appears to have been tampered with. On high-bandwidth networks, well known symmetric and public-key cryptography techniques can easily provide the required features. However, with a low-bandwidth network such as FANs, the protocol must be carefully optimised to minimise the amount of data transmitted. This dissertation describes a new architecture, in which well-known cryptography principles are applied in the FAN field in a way that has not been described in the literature. / Dissertation (MEng)--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

This dissertation presents the findings of a generic model aimed at providing secure communication with remote computers via the Internet, based on smart cards. The results and findings are analysed and presented in great detail, in particular the behaviour and performance of smart cards when used to provide the cryptographic functionality. Two implemented models are presented. The first model uses SSL to secure the communication channel over the Internet while using smart cards for user authentication and storage of cryptographic keys. The second model presents the SSH for channel security and smart cards for user authentication, key storage and actual encryption and decryption of data. The model presented is modular and generic by nature, meaning that it can easily be modified to accept the newer protocol by simply including the protocols in a library and with a minor or no modification to both server and client application software. For example, any new algorithm for encryption, key exchange, signature, or message digest, can be easily accommodated into the system, which proves that the model is generic and can easily be integrated into newer technologies. Similarly, smart cards are used for cryptography. Two options are presented: first the smart cards only store the algorithm keys and user authentication, and secondly, smart cards are used for storing the algorithm keys, user authentication, and actual data encryption or decryption, as the requirement may dictate. This is very useful, for example, if data to be transferred is limited to a few bytes, then actual data encryption and decryption is performed using smart cards. On the other hand, if a great deal of data is to be transferred, then only authentication and key storage are performed with smart cards. The model currently uses 3DES with smart card encryption and decryption, because this is faster and consumes fewer resources when compared to RSA. Once again, the model design is flexible to accommodate new algorithms such as AES or IDEA. Important aspects of the dissertation are the study and analysis of the security attacks on smart card use. Several smart card attack scenarios are presented in CHAPTER 3, and their possible prevention is also discussed in detail. AFRIKAANS : Hierdie verhandeling bied die bevindinge van 'n generiese model wat daarop gemik is om veilige kommunikasie te voorsien met 'n afstandsrekenaar via die Internet en op slimkaarte gebaseer. Die resultate en bevindings word ontleed en breedvoerig aangebied, veral die gedrag en werkverrigting van slimkaarte wanneer hulle gebruik word om die kriptografiese funksionaliteit te voorsien. Daar word twee geïmplementeerde modelle aangebied. Die eerste model gebruik SSL om die kommunikasiekanaal oor die Internet te beveilig terwyl slimkaarte vir gebruikerbekragtiging en stoor van kriptografiese sleutels gebruik word. Die tweede model bied die SSH vir kanaalsekuriteit en slimkaarte vir gebruikergeldigheidvasstelling, sleutelstoor en werklike kodering en dekodering van data. Die model wat aangebied word, is modulêr en generies van aard, wat beteken dat dit maklik gewysig kan word om die jongste protokolle te aanvaar deur bloot die protokolle by 'n programbiblioteek met geringe of geen wysiging van beide die bediener- en kliënttoepassingsagteware in te sluit. Byvoorbeeld, enige nuwe algoritme vir kodering, sleuteluitruiling, handtekening of boodskapbondeling kan maklik in die stelsel gehuisves word, wat bewys dat die model generies is en maklik in jonger tegnologieë geïntegreer kan word. Slimkaarte word op soortgelyke wyse vir kriptografie gebruik. Daar word twee keuses aangebied: eerstens stoor die slimkaarte slegs die algoritmesleutels en gebruikergeldigheidvasstelling en tweedens word slimkaarte gebruik om die algoritmesleutels, gebruikergeldigheidvasstelling en werklike datakodering en –dekodering te stoor na gelang van wat vereis word. Dit is baie nuttig, byvoorbeeld, wanneer data wat oorgedra moet word, tot 'n paar grepe beperk is, word die eintlike datakodering en – dekodering uitgevoer deur slimkaarte te gebruik. Andersyds, indien 'n groot hoeveelheid data oorgedra moet word, word slegs geldigheidvasstelling en stoor met slimkaarte uitgevoer. Die model gebruik tans 3DES met slimkaartkodering en –dekodering omdat dit vinniger is en minder hulpbronne gebruik vergeleke met RSA. Die modelontwerp is weer eens buigsaam om nuwe algoritmes soos AES of IDEA te huisves. Nog 'n belangrike aspek van die verhandeling is om die sekuriteitaanvalle op slimkaartgebruik te ondersoek en te ontleed. Verskeie slimkaartaanvalscenario's word in Hoofstuk 3 aangebied en die moontlike voorkoming daarvan word ook breedvoerig bespreek. / Dissertation (MEng)--University of Pretoria, 2011. / Electrical, Electronic and Computer Engineering / unrestricted

Orientador: Julio César López Hernández / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-18T13:36:05Z (GMT). No. of bitstreams: 1 Oliveira_ThomazEduardodeFigueiredo_M.pdf: 4175073 bytes, checksum: 14d147ca37955c85736d05e60182a583 (MD5) Previous issue date: 2011 / Resumo: Os algoritmos de resumo criptográfico são uma importante ferramenta usada em muitas aplicações para o processamento seguro e eficiente de informações. Na década de 2000, sérias vulnerabilidades encontradas em funções de resumo tradicionais, como o SHA-1 e o MD5, levou a comunidade a repensar o desenvolvimento da criptanálise destes algoritmos e projetar novas estratégias para a sua construção. Como resultado, o instituto NIST anunciou em novembro de 2007 um concurso público para o desenvolvimento de um novo padrão de funções de resumo, o SHA-3, contando com a participação de autores de todo o mundo. Esta dissertação foca nos aspectos da implementação em software de alguns algoritmos submetidos no concurso SHA-3, buscando compreender a forma como os autores desenvolveram a questão do custo computacional de seus projetos em diversas plataformas, além de entender os novos paradigmas de implementação introduzidos pela tecnologia presente nos processadores atuais. Como consequência, propusemos novas técnicas algorítmicas para a implementação em software de alguns algoritmos, como o Luffa e o Keccak, levando aos mesmos melhorias significativas de desempenho / Abstract: Hash algorithms are an important tool of cryptography used in many applications for secure and efficient information processing. During the 2000 decade, serious vulnerabilities found at some traditional hash functions like SHA-1 and MD5 prompted the cryptography community to review the advances in the cryptanalysis of these algorithms and their design strategies. As a result, on November, 2007, NIST announced a public competition to develop a new cryptographic hash function, the SHA-3, which involved competitors throughout the world. This work focuses on the software implementation aspects of some of the SHA-3 submitted algorithms, seeking to comprehend how the authors resolved the computational cost issues at distinct platforms and to understand the new paradigms introduced by the present processors technology. As a consequence, we proposed new algorithmic techniques for the software implementation of Luffa and Keccak hash algorithms, improving their performance significantly / Mestrado / Teoria da Computação / Mestre em Ciência da Computação

A tecnologia atual não oferece prevenção contra cópia, adulteração ou plágio de uma imagem estática em meio digital sem autorização do verdadeiro autor. Dado que tais mal feitos não podem ser evitados, resta ao criador da obra original lutar a posteriori por seus direitos nos fóruns adequados (no tribunal, por exemplo). Na época da fotografia analógica com filme, o negativo poderia ser utilizado como prova. Hoje este recurso raramente está disponível e se faz necessária uma solução alternativa. A técnica de Marca d´Água é uma das possibilidades criptográficas existentes para apoiar o autor em sua defesa. O principio da Marca d´Água é o encapsulamento de informações relevantes, preferencialmente de forma imperceptível, na imagem a ser protegida. Tais informações, quando extraídas da imagem marcada, devem revelar o verdadeiro autor num processo de disputa. Soluções de Marca d´Água combinada com Criptografia Visual são encontradas na literatura. A principal vantagem deste caminho é a propriedade Imperceptível por segurança perfeita que a Marca d´Água assume quando tratada por Criptografia Visual. O segredo (neste caso, a Marca d´Água) é segmentado via Criptografia Visual em 2 transparências: uma delas é encapsulada na imagem a ser protegida e a outra é mantida pelo verdadeiro autor. Basta a sobreposição de tais transparências para que a Marca d´Água seja revelada. Nesta pesquisa propomos um novo método, denominado MACV, que combina Marca d´Água, Criptografia Visual e um algoritmo de hashing. O MACV apresenta, entre outras, as seguintes propriedades desejáveis de Marca d´Água: imperceptível por segurança perfeita, alta entropia, armazenamento na própria imagem e sem ambiguidade. Veremos em nossa pesquisa bibliográfica que há uma lacuna de soluções que apresentem, simultaneamente, todas estas propriedades. Esta lacuna torna o MACV único em sua categoria. / Current technology does not prevent copy, tamper or plagiarism of a still image in digital media without authorization of the true author. Since such misdeeds can not be avoided, the creator of the original work has to defend his rights a posteriori in the appropriate forum (in court, for example). A negative could be used as evidence in the era of analog photography. Currently this feature is rarely available and an alternative solution is needed. Watermark is one of the existing cryptographic possibilities to support the author in his defense. A Watermark is embedded into the image to be protected, preferably imperceptibly. Such information when extracted from the watermarked image should reveal the true author in a dispute process. Solutions using Watermark with Visual Cryptography are found in the literature. The main advantage of this way is the property Imperceptible by perfect secrecy that the Water- mark assumes when treated by Visual Cryptography. The key (in this case, the Watermark) is partitioned by Visual Cryptography in 2 transparencies: one is embedded in the image to be protected and the other is kept by the true author. The Watermark is revealed by overlapping such transparencies. In this research we propose a new method, called MACV, combining Watermark, Vi- sual Cryptography and a hashing algorithm. The MACV has, among others, the following desirable properties of Watermark: invisible by perfect secrecy, high entropy, stored into the image itself and unambiguously. We will see in our research that there is no solution that presents, simultaneously, all these properties. This fact makes the MACV the first one to show all these properties