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Decentralised cryptocurrencies such as Bitcoin offer a new paradigm of electronic payment systems that do not rely on a trusted third-party. Instead, the peers forming the network handle the task traditionally left to the third-party, preventing attackers from spending twice the same resource, and do so in a publicly verifiable way through Bitcoin's main innovation, the blockchain. However, due to a lack of synchrony in the network, Bitcoin peers may transiently have conflicting views of the system: the blockchain is forked. This can happen purely by accident but attackers can also voluntarily create forks to mount other attacks on the system. In this work, we describe Bitcoin and its underlying blockchain protocol; we introduce a formal model to capture the normal operations of the system as well as forks and double-spending attacks. We use it to define Bitcoin's fundamental properties in terms of safety, liveness and validity. We present the current state of the system: first, we analyse some of the most prominent works that academia has produced between 2008 and 2016, as well as some promising leads to improve the system; then, we use the results of a measurement campaign to show that the size of the network is relatively stable because join and leave operations compensate each other, and that blocks propagate to most of the network in a matter of seconds. We further compare our results to those usually accepted by the community. We introduce a Bitcoin network simulator that we have implemented and present the experiment we have performed to validate it. Finally, we propose a modification to Bitcoin's operations that can prevent double-spending attacks and forks without giving up on its main ideological principles, decentralisation and the absence of source of trust.

Smart grid is a power supply system that uses digital communication technology to detect and react to local changes for power demand. Modern and future power supply system requires a distributed system for effective communication and management. Blockchain, a distributed technology, has been applied in many fields, e.g., cryptocurrency exchange, secure sharing of medical data, and personal identity security. Much research has been done on the application of blockchain to smart grid. While blockchain has many advantages, such as security and no interference from third parties, it also has inherent disadvantages, such as untrusted network environment, lacking data source privacy, and low network throughput.In this research, three systems are designed to tackle some of these problems in blockchain technology. In the first study, Information-Centric Blockchain Model, we focus on data privacy. In this model, the transactions created by nodes in the network are categorized into separate groups, such as billing transactions, power generation transactions, etc. In this model, all transactions are first encrypted by the corresponding pairs of asymmetric keys, which guarantees that only the intended receivers can see the data so that data confidentiality is preserved. Secondly, all transactions are sent on behalf of their groups, which hides the data sources to preserve the privacy. Our preliminary implementation verified the feasibility of the model, and our analysis demonstrates its effectiveness in securing data source privacy, increasing network throughput, and reducing storage usage. In the second study, we focus on increasing the network’s trustworthiness in an untrusted network environment. A reputation system is designed to evaluate all node’s behaviors. The reputation of a node is evaluated on its computing power, online time, defense ability, function, and service quality. The performance of a node will affect its reputation scores, and a node’s reputation scores will be used to assess its qualification, privileges, and job assignments. Our design is a relatively thorough, self-operated, and closed-loop system. Continuing evaluation of all node’s abilities and behaviors guarantees that only nodes with good scores are qualified to handle certain tasks. Thus, the reputation system helps enhance network security by preventing both internal and external attacks. Preliminary implementation and security analysis showed that the reputation model is feasible and enhances blockchain system’s security. In the third research, a countermeasure was designed for double spending. Double spending is one of the two most concerned security attacks in blockchain. In this study, one of the most reputable nodes was selected as detection node, which keeps checking for conflict transactions in two consecutive blocks. Upon a problematic transaction was discovered, two punishment transactions were created to punish the current attack behavior and to prevent it to happen in future. The experiment shows our design can detect the double spending effectively while using much less detection time and resources.

There have been extensive debates on the factors that influence local policy decisions. Although many researchers have contributed to uncovering various influences such as political, economic, institutional, and demographic factors on local policy decisions, however, the concept of QoL rarely has used in extant literature. Local government spending is likely to be affected by citizen demands for achieving community well-being. Additionally, given that different policy functions variably affect local circumstances, the impact of QoL on local policy decisions will depend on the policy area. Hence, this study examined the relationship between QoL and local budgetary decisions based on Peterson's (1981) policy scheme of, three distinct policy arenas (developmental, allocational, and redistributive policy). In examining the relationship of QoL and city spending across policy functions, I also considered economic, political, institutional, and demographic factors, derived from various theoretical perspectives on local policy decisions. The relative influences of community QoL as well as other factors on local policy decisions were estimated by two-stage least squares regression analysis (2SLS) for developmental spending and by ordinary least squares (OLS) for allocational and redistributive spending. To measure community QoL, this study used 89,066 completed surveys from 167 communities in the United States for 2002-2008 are used. QoL appeared as a critical factor influencing local government expenditures in the three policy areas. The impact of QoL on local spending in the three areas differed depending on city income levels; city income levels then moderated local policy decisions. These findings suggest that local policy priorities adjusted in accordance with economic growth. Allocational policy functions also should be thought to be functions of cities geared toward giving them a competitive edge over other cities by meeting evolved citizen preferences for city amenities. These findings also point to distinct patterns of political activities in each policy arena. Given that community QoL reflects adjusted citizens' demands, I contend that community QoL can contribute to performance management by providing additional public information and a complementary performance indicator. / Ph. D.

Yes / Drawing on collective contributions and group performance perspectives, this paper examines the role of board diversity in firms’ R&D investment decisions. Building on a fault-line argument about a team’s demographic attributes, this study also decomposes the impact of demographic and cognitive diversity on R&D spending. The study sample contains UK data of non-financial companies covering the period between 2005 and 2018. We employ panel data analysis techniques and control for potential endogeneity issues through the application of the two-step system Generalised Method of Moments (GMM) estimations. The findings demonstrate a positive and significant relationship between board diversity and level of corporate R&D spending. The findings also show cognitive diversity as significantly positively associated with corporate R&D investments. Demographic diversity, however, has an insignificant relationship with corporate spending on R&D. The results further show that demographic diversity negatively moderates the relationship between cognitive diversity and spending on R&D. Our main findings document that the board’s attributes as a group significantly influence decisions of strategic importance such as, investment in R&D projects. The findings on sub-dimensions of board diversity imply that as compared to demographic diversity, functional/cognitive diversity is more relevant to strategic decisions and related outcomes. The study has practical implications for shareholders in documenting the importance of board diversity, and policy implications for regulators in highlighting the separate roles of behavioural and cognitive diversity in shaping firms’ strategic investment decisions.

An extensive literature examines how distributive (i.e., “pork barrel”) spending is allocated among congressional districts. Much of this research finds evidence that intra-chamber factors like ideology, party, and committee membership are the primary determinants of various forms of distributive spending. However, we know much less about how extra-chamber factors such as district-level demand and the economy impact the distribution of federal outlays. In this study, I find that district-level demand and variation in economic factors, in particular, income and unemployment, significantly predict the distribution of new bureaucratic awards in the 110th Congress. The results support the contention that districts get what they need, and this raises questions about the ability of members of powerful committees to steer awards selectively to their districts. It also provides evidence for the economic “law of increasing state activity,” by which districts with higher income levels receive a larger share of federal assistance.

published_or_final_version / Public Administration / Master / Master of Public Administration

Esta dissertação tem como objetivo explorar a relação entre gastos com educação e desempenho escolar, a partir de informações de gastos no nível das escolas. O debate em torno da relação entre gastos e desempenho, em geral, tem se baseado em estimativas que utilizam dados agregados de gastos municipais com educação. Dessa forma, como pouco se sabe a respeito do que é feito, na prática, com os recursos destinados às escolas, as pesquisas se restringem ao apontamento da existência ou não de uma relação entre gastos agregados com educação e desempenho. Neste trabalho, indicamos a relevância da informação de gastos no nível da escola, segundo categorias de agregação dos gastos que apontem para determinadas funções ou atividades escolares, para que se possa avançar no sentido de compreender não somente se gastos com educação estão ou não associados ao desempenho, mas como diferentes tipos de gastos, associados a diferentes atividades escolares, estão relacionados de diferentes formas ao desempenho dos alunos. Assim, com base na revisão da literatura pertinente, elaboramos uma proposta de categorias de gastos com pessoal, para as escolas da rede municipal de São Bernardo do Campo, que esteja alinhada às atividades desenvolvidas pelas escolas, sendo as categorias de maior agregação as que dizem respeito ao que consideramos Gastos diretamente relacionados ao ensino e Gastos indiretamente relacionados ao ensino. A partir das categorias delimitadas, baseadas nas informações de gastos por escola, exploramos a relação entre gasto por aluno e desempenho em matemática na prova Brasil de 2013, por meio de análise de regressão. As estimativas revelaram que a relação entre gastos e desempenho não é homogênea entre as diferentes categorias de gasto e que a especificação dos modelos melhora na medida em que os gastos são desagregados. Dentre os resultados obtidos, destacamos aquele que indica uma relação positiva e significante entre os gastos com Coordenação pedagógica e o desempenho em matemática. / This dissertation aims to explore the relationship between the money spent on education and school performance, based on the information about spending at the school-level. The debate on the relationship between expense and performance has been mostly based on estimates using the aggregated data of municipal spending on education. Thus, as little is known about what is actually done with the resources allocated to schools, researches on this subject are restricted to indicating the existence or the lack of a relationship between aggregate spending and performance. In this study, we show the relevance of the information on spending at the school level, according to categories of aggregate spending that point to certain functions or school activities. With this, we intend not only to understand if education expenses are or are not associated with performance, but also to observe how different types of costs associated with different school activities are related in different ways to the performance of students. Thus, based on literature review, we have proposed categories of personnel expenses for the municipal schools of São Bernardo do Campo, which are aligned to the activities developed by the schools. Categories of higher aggregation involve what we consider to be Expenses directly related to teaching and Expenses indirectly related to education. From the specific categories, which are based on information on spending per school, we explore the relationship between spending per student and their performance in the Mathematics exam in Prova Brasil 2013, using a regression analysis. The estimates have shown that the relationship between spending and performance is not homogeneous among the different categories of expenditure, and that specification of models improves as costs are disaggregated. Among the obtained results, we highlight the indication of a positive and significant relation between spending on Pedagogical coordination and performance on the mathematics exam.

Made available in DSpace on 2016-04-26T20:48:39Z (GMT). No. of bitstreams: 1 Alessandro Elias Gumier.pdf: 858538 bytes, checksum: 548ca9bdd3a7fba9da9fcbf2880b0c89 (MD5) Previous issue date: 2013-06-04 / Public spending has gained increasing relevance in the economic analysis. However, few studies have dealt with the public expense of the legislative branch. The goal of this dissertation is to analyze legislative spending of São Paulo cities between 1997-2010, as well as estimate the socioeconomic points for the level of this expense. Thereby, we used the methodology of cluster analysis and linear regression in cross-section of socioeconomic factors of the 645 counties, based on 2010 data. The results suggest that the number of councilors is not clearly relevant factor to explain the legislative municipal spending, pointing out, however, the municipal income as the most significant variable for the occurrence of this sort of expense / O gasto público tem ganhado cada vez mais relevância nas análises econômicas. No entanto, poucos estudos têm tratado do gasto público do Poder Legislativo. O objetivo desta dissertação é analisar os gastos legislativos dos municípios do Estado de São Paulo no período 1997-2010, bem como estimar os fatores socioeconômicos determinantes para o nível deste gasto. Para tanto, utilizou-se a metodologia de análise de cluster e de regressão linear em corte transversal de fatores socioeconômicos dos 645 municípios paulistas, com base nos dados de 2010. Os resultados sugerem que o número de vereadores não constitui fator claramente relevante para explicar o gasto legislativo municipal, apontando, em contrapartida, a renda municipal como a variável mais significativa para a ocorrência deste tipo de dispêndio

Esta dissertação tem como objetivo explorar a relação entre gastos com educação e desempenho escolar, a partir de informações de gastos no nível das escolas. O debate em torno da relação entre gastos e desempenho, em geral, tem se baseado em estimativas que utilizam dados agregados de gastos municipais com educação. Dessa forma, como pouco se sabe a respeito do que é feito, na prática, com os recursos destinados às escolas, as pesquisas se restringem ao apontamento da existência ou não de uma relação entre gastos agregados com educação e desempenho. Neste trabalho, indicamos a relevância da informação de gastos no nível da escola, segundo categorias de agregação dos gastos que apontem para determinadas funções ou atividades escolares, para que se possa avançar no sentido de compreender não somente se gastos com educação estão ou não associados ao desempenho, mas como diferentes tipos de gastos, associados a diferentes atividades escolares, estão relacionados de diferentes formas ao desempenho dos alunos. Assim, com base na revisão da literatura pertinente, elaboramos uma proposta de categorias de gastos com pessoal, para as escolas da rede municipal de São Bernardo do Campo, que esteja alinhada às atividades desenvolvidas pelas escolas, sendo as categorias de maior agregação as que dizem respeito ao que consideramos Gastos diretamente relacionados ao ensino e Gastos indiretamente relacionados ao ensino. A partir das categorias delimitadas, baseadas nas informações de gastos por escola, exploramos a relação entre gasto por aluno e desempenho em matemática na prova Brasil de 2013, por meio de análise de regressão. As estimativas revelaram que a relação entre gastos e desempenho não é homogênea entre as diferentes categorias de gasto e que a especificação dos modelos melhora na medida em que os gastos são desagregados. Dentre os resultados obtidos, destacamos aquele que indica uma relação positiva e significante entre os gastos com Coordenação pedagógica e o desempenho em matemática. / This dissertation aims to explore the relationship between the money spent on education and school performance, based on the information about spending at the school-level. The debate on the relationship between expense and performance has been mostly based on estimates using the aggregated data of municipal spending on education. Thus, as little is known about what is actually done with the resources allocated to schools, researches on this subject are restricted to indicating the existence or the lack of a relationship between aggregate spending and performance. In this study, we show the relevance of the information on spending at the school level, according to categories of aggregate spending that point to certain functions or school activities. With this, we intend not only to understand if education expenses are or are not associated with performance, but also to observe how different types of costs associated with different school activities are related in different ways to the performance of students. Thus, based on literature review, we have proposed categories of personnel expenses for the municipal schools of São Bernardo do Campo, which are aligned to the activities developed by the schools. Categories of higher aggregation involve what we consider to be Expenses directly related to teaching and Expenses indirectly related to education. From the specific categories, which are based on information on spending per school, we explore the relationship between spending per student and their performance in the Mathematics exam in Prova Brasil 2013, using a regression analysis. The estimates have shown that the relationship between spending and performance is not homogeneous among the different categories of expenditure, and that specification of models improves as costs are disaggregated. Among the obtained results, we highlight the indication of a positive and significant relation between spending on Pedagogical coordination and performance on the mathematics exam.