Thesis (M.S.)--Florida State University, 2006. / Advisor: Mike Burmester, Florida State University,College of Arts amd Sciences, Dept. of Computer Science. Title and description from dissertation home page (viewed June 19, 2006). Document formatted into pages; contains viii, 40 pages. Includes bibliographical references.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 117-122). Also available in electronic version.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 88-92). Also available in electronic version.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 61-64). Also available in electronic version.

Thesis (M.S. in Electrical Engineering)--Vanderbilt University, Aug. 2007. / Title from title screen. Includes bibliographical references.

Constructing advanced cryptographic applications often requires the ability of privately embedding messages or functions in the code of a program. As an example, consider the task of building a searchable encryption scheme, which allows the users to search over the encrypted data and learn nothing other than the search result. Such a task is achievable if it is possible to embed the secret key of an encryption scheme into the code of a program that performs the "decrypt-then-search" functionality, and guarantee that the code hides everything except its functionality. This thesis studies two cryptographic primitives that facilitate the capability of hiding secrets in the program of random functions. 1. We first study the notion of a private constrained pseudorandom function (PCPRF). A PCPRF allows the PRF master secret key holder to derive a public constrained key that changes the functionality of the original key without revealing the constraint description. Such a notion closely captures the goal of privately embedding functions in the code of a random function. Our main contribution is in constructing single-key secure PCPRFs for NC^1 circuit constraints based on the learning with errors assumption. Single-key secure PCPRFs were known to support a wide range of cryptographic applications, such as private-key deniable encryption and watermarking. In addition, we build reusable garbled circuits from PCPRFs. 2. We then study how to construct cryptographic hash functions that satisfy strong random oracle-like properties. In particular, we focus on the notion of correlation intractability, which requires that given the description of a function, it should be hard to find an input-output pair that satisfies any sparse relations. Correlation intractability captures the security properties required for, e.g., the soundness of the Fiat-Shamir heuristic, where the Fiat-Shamir transformation is a practical method of building signature schemes from interactive proof protocols. However, correlation intractability was shown to be impossible to achieve for certain length parameters, and was widely considered to be unobtainable. Our contribution is in building correlation intractable functions from various cryptographic assumptions. The security analyses of the constructions use the techniques of secretly embedding constraints in the code of random functions.

L’émergence d’internet et l’amélioration des infrastructures de com- munication ont considérablement encouragé l’explosion des flux d’in- formations au niveau mondial. Cette évolution a été accompagnée par l’apparition de nouveaux besoins et de nouvelles attentes de la part des consommateurs. Communiquer avec ses proches ou ses collaborateurs, stocker des documents de travail, des fichiers mul- timédia, utiliser des services innovants traitant nos documents per- sonnels, tout cela se traduit immanquablement par le partage, avec des tiers, d’informations potentiellement sensibles. Ces tiers, s’ils ne sont pas de confiance, peuvent réutiliser à notre insu les données sensibles que l’on leur a confiées. Dans ce contexte, le chiffrement homomorphe apporte une bonne solution. Il permet de cacher aux yeux des tiers les données qu’ils sont en train de manipuler. Cependant, à l’heure actuelle, le chif- frement homomorphe reste complexe. Pour faire des opérations sur des données de quelques bits (données en clair), il est nécessaire de manipuler des opérandes sur quelques millions de bits (données chiffrées). Ainsi, une opération normalement simple devient longue en termes de temps de calcul. Dans cette étude, nous avons cherché à rendre le chiffrement ho- momorphe plus pratique en concevant un accélérateur spécifique. Nous nous sommes basés sur une approche de type co-conception logicielle/matérielle utilisant l’algorithme de Karatsuba. En particulier, notre approche est compatible avec le batching, qui permet de sto- cker plusieurs bits d’informations dans un même chiffré. Notre étude démontre que le batching peut être implémenté sans surcoût important comparé à l’approche sans batching, et permet à la fois de réduire les temps de calcul (calculs effectués en parallèle) et de réduire le rapport entre la taille des données chiffrées et des données en clair. / The emergence of internet and the improvement of communica- tion infrastructures have considerably increased the information flow around the world. This development has come with the emergence of new needs and new expectations from consumers. Communicate with family or colleagues, store documents or multimedia files, using innovative services which processes our personal data, all of this im- plies sharing with third parties some potentially sensitive data. If third parties are untrusted, they can manipulate without our agreement data we share with them. In this context, homomorphic encryption can be a good solution. Ho- momorphic encryption can hide to the third parties the data they are processing. However, at this point, homomorphic encryption is still complex. To process a few bits of clear data (cleartext), one needs to manage a few million bits of encrypted data (ciphertext). Thus, a computation which is usually simple becomes very costly in terms of computation time. In this work, we have improved the practicability of homomorphic en- cryption by implementing a specific accelerator. We have followed a software/hardware co-design approach with the help of Karatsuba algorithm. In particular, our approach is compatible with batching, a technique that “packs" several messages into one ciphertext. Our work demonstrates that the batching can be implemented at no important additional cost compared to non-batching approaches, and allows both reducing computation time (operations are processed in parallel) and the ciphertext/cleartext ratio.

Security is always a big problem in IoT (internet of things),when it comes to IoT, there must have cloud computing because many devices in IoT are small embedded devices and they don’t always have enough power to finish some complex calculations. Then, they need to take advantage of a third party system especially cloud at present to finish some operations, but the cloud is not safe enough now, in which some important and private information may be leaked, then people introduce homomorphic encryption which can do calculation on encrypted data. To meet the modern needs for random calculations in which the operation can have random times’ addition and multiplication, researchers are trying to make fully homomorphic encryption practical. So in my thesis, I would choose one fully homomorphic encryption scheme to implement a detailed IoT scenario using some IoT devices such as laptop and raspberry pi. Then I would use performance measurements such as response time calculations to do the performance evaluation such as effectiveness and scalability for this technique. Finally, I find some relationship between different parameters and response time, and also effectiveness, scalability in results and conclusion part.

Este trabalho apresenta a combinação de uma série de mecanismos de segurança baseados em criptografia com conceitos de sistemas operacionais. Esta combinação cria uma arquitetura inovadora,que aproveita características do funcionamento do sistema operacional para protegê-lo de vulnerabilidades relacionadas com a adulteração de programas e bibliotecas. Esta arquitetura consiste em um mecanismo de geração de assinaturas digitais integradas a programas e bibliotecas, para garantir a autenticidade e a integridade dos mesmos e de cada parte do sistema operacional em execução. O sistema funciona de forma transparente para programadores, e possibilita que o software com assinaturas digitais seja compatível com sistemas que não tenham suporte a verificação de assinatura, simplificando o processo de distribuição. A verificação de assinaturas é integrada com o mecanismo de paginação do microprocessador, de forma a efetuar uma verificação sob demanda somente da parte dos programas e bibliotecas que é efetivamente utilizada. Esta integração diminui o impacto sobre o desempenho e proporciona transparência para os usuários finais e administradores de sistemas. A validação do modelo proposto foi realizada como uma extensão à interface binária de aplicação Unix ELF, implementada na plataforma GNU/Linux. O impacto da assinatura digital para desenvolvedores e distribuidores de sistemas operacionais sob a ótica de complexidade de uso, efeitos do sistema para usuários finais e a sobrecarga no desempenho do sistema foram verificados. / This work discusses a series of security mechanisms based in cryptography, combining them with concepts of operating systems, in order to create an innovative architecture that uses some functionalities characteristics of operating system to protect it against vulnerabilities related with the adulteration of computer programs and libraries. This architecture consists in a mechanism for generation of digital signatures integrated into the computer programs and libraries, in order to guarantee the software and operating system authenticity and integrity while in execution by the target machine. The system is transparent to programmers, and it is also possible that software with digital signatures can be executed on systems without support to verification of signature, what simplifies the software distribution process. The verification of signatures is integrated with the paging mechanism of the microprocessor, making on-demand verification only in the part of the programs and libraries that is going to be effectively used, diminishing the impact on the performance and providing transparency for final users and system administrators. The validation of the model was carried through as an extension to the application binary interface Unix ELF, implemented in the GNU/Linux platform. The impact of the digital signature for developers and distributors of operating systems under the point of view of complexity, effect for final users and overload in performance of the system was verified. xix

Este trabalho apresenta a combinação de uma série de mecanismos de segurança baseados em criptografia com conceitos de sistemas operacionais. Esta combinação cria uma arquitetura inovadora,que aproveita características do funcionamento do sistema operacional para protegê-lo de vulnerabilidades relacionadas com a adulteração de programas e bibliotecas. Esta arquitetura consiste em um mecanismo de geração de assinaturas digitais integradas a programas e bibliotecas, para garantir a autenticidade e a integridade dos mesmos e de cada parte do sistema operacional em execução. O sistema funciona de forma transparente para programadores, e possibilita que o software com assinaturas digitais seja compatível com sistemas que não tenham suporte a verificação de assinatura, simplificando o processo de distribuição. A verificação de assinaturas é integrada com o mecanismo de paginação do microprocessador, de forma a efetuar uma verificação sob demanda somente da parte dos programas e bibliotecas que é efetivamente utilizada. Esta integração diminui o impacto sobre o desempenho e proporciona transparência para os usuários finais e administradores de sistemas. A validação do modelo proposto foi realizada como uma extensão à interface binária de aplicação Unix ELF, implementada na plataforma GNU/Linux. O impacto da assinatura digital para desenvolvedores e distribuidores de sistemas operacionais sob a ótica de complexidade de uso, efeitos do sistema para usuários finais e a sobrecarga no desempenho do sistema foram verificados. / This work discusses a series of security mechanisms based in cryptography, combining them with concepts of operating systems, in order to create an innovative architecture that uses some functionalities characteristics of operating system to protect it against vulnerabilities related with the adulteration of computer programs and libraries. This architecture consists in a mechanism for generation of digital signatures integrated into the computer programs and libraries, in order to guarantee the software and operating system authenticity and integrity while in execution by the target machine. The system is transparent to programmers, and it is also possible that software with digital signatures can be executed on systems without support to verification of signature, what simplifies the software distribution process. The verification of signatures is integrated with the paging mechanism of the microprocessor, making on-demand verification only in the part of the programs and libraries that is going to be effectively used, diminishing the impact on the performance and providing transparency for final users and system administrators. The validation of the model was carried through as an extension to the application binary interface Unix ELF, implemented in the GNU/Linux platform. The impact of the digital signature for developers and distributors of operating systems under the point of view of complexity, effect for final users and overload in performance of the system was verified. xix