Rule-based conditional trust with OpenPGP.

This thesis describes a new trust model for OpenPGP encryption. This trust model uses conditional rule-based trust to establish key validity and trust. This thesis describes Trust Rules that may be used to sort and categorize keys automatically without user interaction. Trust Rules are also capable of integrating key revocation status into its calculations so it too is automated. This thesis presents that conditional trust established through Trust Rules can enforce stricter security while reducing the burden of use and automating the process of key validity, trust, and revocation

Properties of nanostructured motherwort extract and its application in fruit jelly candy production

The research paper includes the information on the application of nanostructured motherwort extract in the production of fruit jelly candy, which can be used as a therapeutic functional food product. The size of nanostructured motherwort extract was determined by a nanoparticle tracking analysis (NTA

Security plane for data authentication in information-centric networks

Orientadores: Maurício Ferreira Magalhães, Jussi KangasharjuTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A segurança da informação é responsável pela proteção das informações contra o acesso nãoautorizado, uso, modificação ou a sua destruição. Com o objetivo de proteger os dados contra esses ataques de segurança, vários protocolos foram desenvolvidos, tais como o Internet Protocol Security (IPSEC) e o Transport Layer Security (TLS), provendo mecanismos de autenticação, integridade e confidencialidade dos dados para os usuários. Esses protocolos utilizam o endereço IP como identificador de hosts na Internet, tornando-o referência e identificador no estabelecimento de conexões seguras para a troca de dados entre aplicações na rede. Com o advento da Web e o aumento exponencial do consumo de conteúdos, como vídeos e áudios, há indícios da migração gradual do uso predominante da Internet, passando da ênfase voltada para a conexão entre hosts para uma ênfase voltada para a obtenção de conteúdo da rede, paradigma esse conhecido como information-centric networking. Nesse paradigma, usuários buscam por documentos e recursos na Internet sem se importarem com o conhecimento explícito da localização do conteúdo. Como consequência, o endereço IP que previamente era utilizado como ponto de referência do provedor de dados, torna-se meramente um identificador efêmero do local onde o conteúdo está armazenado, resultando em implicações para a autenticação correta dos dados. Nesse contexto, a simples autenticação de um endereço IP não garante a autenticidade dos dados, uma vez que o servidor identificado por um dado endereço IP não é necessariamente o endereço do produtor do conteúdo. No contexto de redes orientadas à informação, existem propostas na literatura que possibilitam a autenticação dos dados utilizando somente o conteúdo propriamente dito, como a utilização de assinaturas digitais por bloco de dado e a construção de árvores de hash sobre os blocos de dados. A ideia principal dessas abordagens é atrelar uma informação do provedor original do conteúdo nos blocos de dados transportados, por exemplo, uma assinatura digital, possibilitando a autenticação direta dos dados com o provedor, independentemente do host onde o dado foi obtido. Apesar do mecanismo citado anteriormente possibilitar tal verificação, esse procedimento é muito oneroso do ponto de vista de processamento, especialmente quando o número de blocos é grande, tornando-o inviável de ser utilizado na prática. Este trabalho propõe um novo mecanismo de autenticação utilizando árvores de hash com o objetivo de prover a autenticação dos dados de forma eficiente e explícita com o provedor original e, também, de forma independente do host onde os dados foram obtidos. Nesta tese, propomos duas técnicas de autenticação de dados baseadas em árvores de hash, chamadas de skewed hash tree (SHT) e composite hash tree (CHT), para a autenticação de dados em redes orientadas à informação. Uma vez criadas, parte dos dados de autenticação é armazenada em um plano de segurança e uma outra parte permanece acoplada ao dado propriamente dito, possibilitando a verificação baseada no conteúdo e não no host de origem. Além disso, essa tese apresenta o modelo formal, a especificação e a implementação das duas técnicas de árvore de hash para autenticação dos dados em redes de conteúdo através de um plano de segurança. Por fim, esta tese detalha a instanciação do modelo de plano de segurança proposto em dois cenários de autenticação de dados: 1) redes Peer-to-Peer e 2) autenticação paralela de dados sobre o HTTPAbstract: Information security is responsible for protecting information against unauthorized access, use, modification or destruction. In order to protect such data against security attacks, many security protocols have been developed, for example, Internet Protocol Security (IPSec) and Transport Layer Security (TLS), providing mechanisms for data authentication, integrity and confidentiality for users. These protocols use the IP address as host identifier on the Internet, making it as a reference and identifier during the establishment of secure connections for data exchange between applications on the network. With the advent of the Web and the exponential increase in content consumption (e.g., video and audio), there is an evidence of a gradual migration of the predominant usage of the Internet, moving the emphasis on the connection between hosts to the content retrieval from the network, which paradigm is known as information-centric networking. In this paradigm, users look for documents and resources on the Internet without caring about the explicit knowledge of the location of the content. As a result, the IP address that was used previously as a reference point of a data provider, becomes merely an ephemeral identifier of where the content is stored, resulting in implications for the correct authentication data. In this context, the simple authentication of an IP address does not guarantee the authenticity of the data, because a hosting server identified by a given IP address is not necessarily the same one that is producing the requested content. In the context of information-oriented networks, some proposals in the literature proposes authentication mechanisms based on the content itself, for example, digital signatures over a data block or the usage of hash trees over data blocks. The main idea of these approaches is to add some information from the original provider in the transported data blocks, for example, a digital signature, enabling data authentication directly with the original provider, regardless of the host where the data was obtained. Although the mechanism mentioned previously allows for such verification, this procedure is very costly in terms of processing, especially when the number of blocks is large, making it unfeasible in practice. This thesis proposes a new authentication mechanism using hash trees in order to provide efficient data authentication and explicitly with the original provider, and also independently of the host where the data were obtained. We propose two techniques for data authentication based on hash trees, called skewed hash tree (SHT) and composite hash tree (CHT), for data authentication in information-oriented networks. Once created, part of the authentication data is stored in a security plane and another part remains attached to the data itself, allowing for the verification based on content and not on the source host. In addition, this thesis presents the formal model, specification and implementation of two hash tree techniques for data authentication in information-centric networks through a security plane. Finally, this thesis details the instantiation of the security plane model in two scenarios of data authentication: 1) Peer-to-Peer and 2) parallel data authentication over HTTPDoutoradoEngenharia de ComputaçãoDoutor em Engenharia Elétric

Privacy engineering for social networks

In this dissertation, I enumerate several privacy problems in online social networks (OSNs) and describe a system called Footlights that addresses them. Footlights is a platform for distributed social applications that allows users to control the sharing of private information. It is designed to compete with the performance of today's centralised OSNs, but it does not trust centralised infrastructure to enforce security properties. Based on several socio-technical scenarios, I extract concrete technical problems to be solved and show how the existing research literature does not solve them. Addressing these problems fully would fundamentally change users' interactions with OSNs, providing real control over online sharing. I also demonstrate that today's OSNs do not provide this control: both user data and the social graph are vulnerable to practical privacy attacks. Footlights' storage substrate provides private, scalable, sharable storage using untrusted servers. Under realistic assumptions, the direct cost of operating this storage system is less than one US dollar per user-year. It is the foundation for a practical shared filesystem, a perfectly unobservable communications channel and a distributed application platform. The Footlights application platform allows third-party developers to write social applications without direct access to users' private data. Applications run in a confined environment with a private-by-default security model: applications can only access user information with explicit user consent. I demonstrate that practical applications can be written on this platform. The security of Footlights user data is based on public-key cryptography, but users are able to log in to the system without carrying a private key on a hardware token. Instead, users authenticate to a set of authentication agents using a weak secret such as a user-chosen password or randomly-assigned 4-digit number. The protocol is designed to be secure even in the face of malicious authentication agents.This work was supported by the Rothermere Foundation and the Natural Sciences and Engineering Research Council of Canada (NSERC)

The role of Sry-Box (Sox) transcription factors in epithelial stem cell biology of the gastrointestinal tract

Stem cell biology, though a well-established concept in the scientific zeitgeist, is only beginning to emerge as an independent field of study. An understanding of basic stem cell biology and its translation into clinically applicable therapies holds the potential to direct a paradigm shift in modern medical practice. However, in order to realize this potential, the scientific community must first understand the genetic and molecular mechanisms by which cells acquire and maintain 'stemness', specifically, multipotency and the ability to self-renew. Studying the transcriptional machinery that controls these properties could lead to a greater understanding of stem cells as a component of physiology as a whole. Due to its critical importance to homeostasis, the gastrointestinal tract is an attractive system for the study of stem cell biology. Sox factors, a group of transcription factors that have previously been associated with embryonic and neural stem cells, are rapidly emerging as central to maintaining 'stemness' in the gastrointestinal tract as well. This work reviews the known role of Sox factors in the gastrointestinal epithelium and describes our novel findings regarding Sox9 as a marker of stem cells in the adult intestinal epithelium

A new security extension for SCTP

In 2000, the Signaling Transport (SIGTRAN) working group of the IETF defined the Stream Control Transmission Protocol (SCTP) as a new transport protocol. SCTP is a new multi-purpose reliable transport protocol. Due to its various features and easy extensibility it is a valid option not only for already standardised applications but also in many new application scenarios. SCTP has several advantages over TCP and UDP. The analysis of already standardised as well as potential SCTP application scenarios clearly indicates that secure end-to-end transport is one of the crucial requirements for SCTP in the future. Up to now there exist two standardised SCTP security solutions which are called TLS over SCTP [37] and SCTP over IPSec [12]. The goal of this thesis was to evaluate existing SCTP security solutions and find an optimised and efficient security solution. Several drawbacks of the standardised SCTP security solutions identified during the analysis are mainly related to features distinguishing SCTP from TCP and UDP. To avoid these drawbacks a new security solution for SCTP, called Secure SCTP (S-SCTP), is proposed which integrates the cryptographic functions into SCTP. One main requirement was that S-SCTP should be fully compatible with standard SCTP while additionally providing strong security i.e. data confidentiality, integrity and authentication. This also means that all features, options and extensions available for standard SCTP have to be supported. Furthermore, S-SCTP should have advantages with respect to performance over all parameter ranges of SCTP and be user-friendly. To specify the S-SCTP protocol extension several new control messages and new message parameters have been defined. Furthermore, procedures for initialisation, rekeying, and termination of secure sessions have been specified and modelled in SDL. Based on an SCTP implementation available in our group and an open source implementation of TLS, TLS over SCTP and S-SCTP have been implemented. These implementations as well as an SCTP over IPSec configuration were used to do comparative performance studies in a lab testbed. These experiments show that the S-SCTP concept achieves its design goals. It supports all features and current extensions of SCTP. Furthermore, it avoids the inefficiencies of the other solutions over a wide range of application scenarios and protocol parameter settings