Efficient Passive Clustering and Gateways selection MANETs

Passive clustering does not employ control packets to collect topological information in ad hoc networks. In our proposal, we avoid making frequent changes in cluster architecture due to repeated election and re-election of cluster heads and gateways. Our primary objective has been to make Passive Clustering more practical by employing optimal number of gateways and reduce the number of rebroadcast packets

Themelio: a new blockchain paradigm

Public blockchains hold great promise in building protocols that uphold security properties like transparency and consistency based on internal, incentivized cryptoeconomic mechanisms rather than preexisting trust in participants. Yet user-facing blockchain applications beyond "internal" immediate derivatives of blockchain incentive models, like cryptocurrency and decentralized finance, have not achieved widespread development or adoption. We propose that this is not primarily due to "engineering" problems in aspects such as scaling, but due to an overall lack of transferable endogenous trust—the twofold ability to uphold strong, internally-generated security guarantees and to translate them into application-level security. Yet we argue that blockchains, due to their foundation on game-theoretic incentive models rather than trusted authorities, are uniquely suited for building transferable endogenous trust, despite their current deficiencies. We then engage in a survey of existing public blockchains and the difficulties and crises that they have faced, noting that in almost every case, problems such as governance disputes and ecosystem inflexibility stem from a lack of transferable endogenous trust. Next, we introduce Themelio, a decentralized, public blockchain designed to support a new blockchain paradigm focused on transferable endogenous trust. Here, the blockchain is used as a low-level, stable, and simple root of trust, capable of sharing this trust with applications through scalable light clients. This contrasts with current blockchains, which are either applications or application execution platforms. We present evidence that this new paradigm is crucial to achieving flexible deployment of blockchain-based trust. We then describe the Themelio blockchain in detail, focusing on three areas key to its overall theme of transferable, strong endogenous trust: a traditional yet enhanced UTXO model with features that allow powerful programmability and light-client composability, a novel proof-of-stake system with unique cryptoeconomic guarantees against collusion, and Themelio's unique cryptocurrency "mel", which achieves stablecoin-like low volatility without sacrificing decentralization and security. Finally, we explore the wide variety of novel, partly off-chain applications enabled by Themelio's decoupled blockchain paradigm. This includes Astrape, a privacy-protecting off-chain micropayment network, Bitforest, a blockchain-based PKI that combines blockchain-backed security guarantees with the performance and administration benefits of traditional systems, as well as sketches of further applications

Privacidade em redes de próxima geração

Doutoramento em Engenharia InformáticaIn the modern society, communications and digital transactions are becoming the norm rather than the exception. As we allow networked computing devices into our every-day actions, we build a digital lifestyle where networks and devices enrich our interactions. However, as we move our information towards a connected digital environment, privacy becomes extremely important as most of our personal information can be found in the network. This is especially relevant as we design and adopt next generation networks that provide ubiquitous access to services and content, increasing the impact and pervasiveness of existing networks. The environments that provide widespread connectivity and services usually rely on network protocols that have few privacy considerations, compromising user privacy. The presented work focuses on the network aspects of privacy, considering how network protocols threaten user privacy, especially on next generation networks scenarios. We target the identifiers that are present in each network protocol and support its designed function. By studying how the network identifiers can compromise user privacy, we explore how these threats can stem from the identifier itself and from relationships established between several protocol identifiers. Following the study focused on identifiers, we show that privacy in the network can be explored along two dimensions: a vertical dimension that establishes privacy relationships across several layers and protocols, reaching the user, and a horizontal dimension that highlights the threats exposed by individual protocols, usually confined to a single layer. With these concepts, we outline an integrated perspective on privacy in the network, embracing both vertical and horizontal interactions of privacy. This approach enables the discussion of several mechanisms to address privacy threats on individual layers, leading to architectural instantiations focused on user privacy. We also show how the different dimensions of privacy can provide insight into the relationships that exist in a layered network stack, providing a potential path towards designing and implementing future privacy-aware network architectures.Na sociedade moderna, as comunicações e transacções digitais estão a tornar-se a regra e não a excepção. À medida que permitimos a intromissão de dispositivos electrónicos de rede no nosso quotidiano, vamos construíndo um estilo de vida digital onde redes e dispositivos enrirquecem as nossas interacções. Contudo, ao caminharmos para um ambiente digital em rede, a nossa privacidade vai-se revestindo de maior importãncia, pois a nossa informação pessoal passa a encontrar-se cada vez mais na rede. Isto torna-se particularmente relevante ao adoptarmos redes de próxima geração, que permitem acesso ubíquo a redes, serviços e conteúdos, aumentando o impacte e pervasividade das redes actuais. Os ambientes onde a conectividade e os serviços se tornam uma constante, assentam em protocolos de rede que normalmente contemplam poucas considerações sobre privacidade, comprometendo desta forma o utlizador. O presente trabalho centra-se nos aspectos de privacidade que dizem respeito à rede devido à forma como os protocolos são utilizados nas diferentes camadas, e que resultando em ameaças à privacidade do utilizador. Abordamos especificamente os identificadores presentes nos protocolos de rede, e que são essenciais à sua função. Neste contexto exploramos a possibilidade destes identificadores comprometerem a privacidade do utilizador através da informação neles contida, bem como das relações que podem ser estabelecidas entre identificadores de diferentes protocolos. Após este estudo centrado nos identificadores, mostramos como a privacidade em redes pode ser explorada ao longo de duas dimensões: uma dimensão que acentua as relações verticais de privacidade, cruzando vários protocolos até chegar ao utilizador, e uma dimensão horizontal que destaca as ameaças causadas por cada protocolo, de forma individual, normalmente limitadas a uma única camada. Através destes conceitos, mostramos uma visão integrada de privacidade em redes, abrangendo tanto as interacçoes de privacidade verticais como as horizontais. Esta visão permite discutir vários mecanismos para mitigar ameaças específicas a cada camada de rede, resultando em instânciações arquitecturais orientadas à privacidade do utilizador. Finalmente, mostramos como as diferentes dimensões de privacidade podem fornecer uma visão diferente sobre as relações estabelecidas na pilha protocolar que assenta em camadas, mostrando um caminho possível para o desenvolvimento de futuras arquitecturas de rede com suporte para privacidade