Diplomas have high importance in society since they serve as official proofs for education. Therefore, it is not surprising that forgeries of such documents have become commonplace. Thus, employers ordinarily have the diplomas manually verified by the issuer. Blockchain creates opportunities to overcome these obstacles, as it has revolutionized the way in which people interact with each other. Based on this, a holistic solution that includes issuance and verification of diplomas can be realized. This paper presents a proposal of a blockchain based system for managing diplomas called UZHBC (University of ZuricH BlockChain).

Network Functions Virtualization (NFV) is transforming the way in which network operators acquire and manage network services. By using virtualization technologies to move packet processing from dedicated hardware to software, NFV has introduced a new market focused on the offer and distribution of Virtual Network Functions (VNF). Infrastructure Providers (InP) can benefit from an NFV market by providing their infrastructures to fulfill demands of end-users that, in turn, acquire VNFsas-a-Service (VNFaaS). In this context, solutions that promote the competition between InPs can lead to lower prices, while increasing VNF performance to accommodate specific demands of end-users. In this paper, BRAIN, a blockchain-based reverse auction is presented to introduce an auditable solution in which InPs can compete to host VNFs taking into account the demands of each particular end-user. Such a solution helps reduce costs involved in VNF's commercialization and also monetize NFVenabled infrastructures. BRAIN is supported by a case study that provides evidence of the solution's feasibility and effectiveness. A discussion regarding blockchain advantages and drawbacks in this use-case (e.g., , additional costs and time) concludes this paper.

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The blockchain (BC) world is rapidly becoming a universe of several ledgers designed for a specific purpose, holding data previously stored (i.e., siloed) in centralized databases. The use of different BCs for the same purpose could hamper the frictionless exchange of data or value. On one hand, it is natural that there are competing implementations exploring the benefits of BC. On the other hand, the problem of siloed data re-emerges, with respect to isolated chains. In this regard, BC interoperability is necessary to connect different BCs, exchanging information and assets. Moreover, to foster BC employment, developers must be able to interact with such different BCs without knowing the details of each implementation. This paper presents a novel solution, called Bifröst, to store and retrieve data on different BCs. Bifröst employs a notary scheme, which allows for connectivity to different BCs. The presented prototype is highly modular and currently implements seven adapters to popular BC implementations, including Bitcoin, Ethereum, and Stellar. The developed prototype was evaluated concerning performance, security, and data size to verify the feasibility of such an implementation and assess design decisions taken during its development.

Em primeiro lugar, gostaria de agradecer à minha família, a qual é a base de tudo. Ao meu pai e minha mãe, que são exemplo a serem seguidos de integridade, perseverança, honestidade, trabalho duro e por me ensinarem que o estudo é uma fundação essencial no crescimento do indivíduo. Ao meu irmão, companheiro desde sempre, exemplo de dedicação e que sempre torceu por mim e pelo Internacional :). A minha namorada, que esteve presente em todos os momentos, bons ou ruins e sempre acreditou em mim. Sem vocês nunca teria chegado até aqui. Obrigado! Gostaria de também agradecer ao meu orientador, Lisandro, que durante todo o decorrer de meu mestrado contribuiu com diversos elementos essenciais para a conclusão desta dissertação, oportunidades e pela valiosa orientação tanto acadêmica e pessoal. Destaco as reuniões e encontros que foram fonte de esclarecimento para problemas de pesquisa e para indicar a direção na qual seguir durante toda minha formação. Meus agradecimentos ao corpo docente e técnicos administrativos da Universidade Federal do Rio Grande do Sul (UFRGS), em especial aos professores das disciplinas que cursei durante o mestrado, obrigado pelos ensinamentos. Estendo meus agradecimentos à todo o grupo de Redes de Computadores do Instituto de Informática da UFRGS, grupo que mais que colegas, se tornaram amigos. Expresso minha gratidão ao Lab. 210 pela fiel parceria, amizade, e churrascos durante estes dois anos, em especial ao Cristian Machado (Batman), Muriel Franco (Mumu), Ricardo Pfitscher (Tocaio) e Ricardo Santos (Ricardão) pelas múltiplas contribuições nos artigos e nesta dissertação. Valeu, gurizada! Uma menção à todos meus amigos que estão do meu lado até hoje, desde o ensino fundamental, ensino médio e graduação. Espero que toda a amizade que temos continue se perpetuando. Por fim, obrigado à todos as pessoas, departamentos e órgãos federais que contribuíram de alguma maneira, direta ou indireta, para minha formação. "Desire to know why, and how, curiosity; such as is in no living creature but man: so that man is distinguished, not only by his reason, but also by this singular passion from other animals; in whom the appetite of food, and other pleasures of sense, by predominance, take away the care of knowing causes; which is a lust of the mind, that by a perseverance of delight in the continual and indefatigable generation of knowledge, exceedeth the short vehemence of any carnal pleasure".-THOMAS HOBBES-LEVIATHAN.

Due to the growing interest in the blockchain (BC),several applications are being developed, taking advantage ofthe benefits that such technology promises to deliver, such asremoval of Trust Third Parties (TTP) to verify transactions anddata immutability. However, these applications require certainaspects, such as high transaction throughput or data privacy,that early BC implementations (e.g.,Bitcoin) did not provide.Thus, a myriad of novel BC implementations was developed,which introduced the issue of choosing the right implementationfor a specific use-case. This paper presents a framework, calledPleBeuS, to address this selection issue by allowing users tospecify policies that rule the automatic selection of the BC thatdata will be stored. The selection process relies on a costawareapproach and considers both public and private implementationsand their technical characteristics. Moreover,PleBeuScom-municates with a BC-agnostic interoperability API to enforcetransactions. The evaluation of thePleBeuSprototype showedthat it is possible to automatically select a BC-based on userpolicies, considering cost thresholds and technical details (e.g.,BC throughput, deployment), and reduce manual interaction.

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Digitization of electoral processes depends on confident systems that produce verifiable evidence. The design and implementation of voting systems has been widely studied in prior research, bringing together expertise in many fields. Switzerland is organized in a federal, decentralized structure of independent governmental entities. Thus, its decentralized structure is a real-world example for implementing an electronic voting system, where trust is distributed among multiple authorities.This work outlines the design and implementation of a blockchainbased electronic voting system providing cast-as-intended verifiability. The generation of non-interactive zero-knowledge proofs of knowledge enables every voter to verify the encrypted vote, while maintaining the secrecy of the ballot. The Public Bulletin Board (PBB) is a crucial component of every electronic voting system, serving as a publicly verifiable log of communication and ballots -here a blockchain is used as the PBB. Also, the required cryptographic operations are in linear relation to the number of voters, making the outlined system fit for large-scale elections.