A peer-to-peer network, enabling different parties to jointly store and run computations on data while keeping the data completely private. Enigma's computational model is based on a highly optimized version of secure multi-party computation, guaranteed by a verifiable secret-sharing scheme. For storage, we use a modified distributed hashtable for holding secret-shared data. An external blockchain is utilized as the controller of the network, manages access control, identities and serves as a tamper-proof log of events. Security deposits and fees incentivize operation, correctness and fairness of the system. Similar to Bitcoin, Enigma removes the need for a trusted third party, enabling autonomous control of personal data. For the first time, users are able to share their data with cryptographic guarantees regarding their privacy.
The availability of data on digital traces is growing to unprecedented sizes, but inferring actionable knowledge from large-scale data is far from being trivial. This is especially important for computational finance, where digital traces of human behavior offer a great potential to drive trading strategies. We contribute to this by providing a consistent approach that integrates various datasources in the design of algorithmic traders. This allows us to derive insights into the principles behind the profitability of our trading strategies. We illustrate our approach through the analysis of Bitcoin, a cryptocurrency known for its large price fluctuations. In our analysis, we include economic signals of volume and price of exchange for USD, adoption of the Bitcoin technology, and transaction volume of Bitcoin. We add social signals related to information search, word of mouth volume, emotional valence, and opinion polarization as expressed in tweets related to Bitcoin for more than 3 years. Our analysis reveals that increases in opinion polarization and exchange volume precede rising Bitcoin prices, and that emotional valence precedes opinion polarization and rising exchange volumes. We apply these insights to design algorithmic trading strategies for Bitcoin, reaching very high profits in less than a year. We verify this high profitability with robust statistical methods that take into account risk and trading costs, confirming the long-standing hypothesis that trading based social media sentiment has the potential to yield positive returns on investment.
Marlon Wanger Souza Silva, Alberto Ayres Benicio, Alessandro Rodrigues da Cruz
O conceito de “bitcoin” ou simplesmente a criptomoeda, e a primeira moeda digital descentralizada. Entender bitcoin nao e uma simples tarefa e nao ha uma forma simples de se explicar essa nova tecnologia que nao e mais tao nova assim porem de uma forma resumida bitcoins assim como o dolar real, e o euro e uma forma de dinheiro porem com algumas particularidades. Podemos citar algumas em especial, bitcoins e puramente digital e nao e emitida por nenhum governo, suas taxas de transicoes sao praticamente zero e nao possui nenhum tipo de restricao ao fazer transacoes com outros paises. Utilizando-se de conceito P2P a criptomoeda ‘“bitcoin” e uma realidade que muitos nao conhece. Neste artigo sera explicado o que sao e como funciona as criptomoedas os metodos de se obter bitcoins, vantagens, desvantagens e alguns exemplos de como os bitcoins pode ser utilizado
The power of linear and affine logic lies in their ability to model state change. However, in a trustless, peer-to-peer setting, it is difficult to force principals to commit to state changes. We show how to solve the peer-to-peer affine commitment problem using a generalization of Bitcoin in which transactions deal in types rather than numbers. This has applications to proof-carrying authorization and mechanically executable contracts. Importantly, our system can be---and is---implemented on top of the existing Bitcoin network, so there is no need to recruit computing power to a new protocol.
Abstract The article highlights major changes in systematic approach to family, establishment of institutions for child and family support, recognition of the priority of family-based care, decentralization of administration and financing of childcare institutions in Poland. The government tried to introduce a number of changes in legislation that would significantly improve the condition of the child. Childcare reforms in the 1990’s and at the beginning of the 21 st century aimed at modernizing local government and local organizations to provide appropriate childcare and social assistance to parents. The paradigm shift in social policy on child and family care determines the priority of family support aimed at creating comfortable conditions for the child. Nowadays the main objective of the family supportive policy of any country is to protect the child from the foster care model.
Despite being a unitary state overall, China is not unitary in its fiscal system, that’s why it is called decentralized structure of public finance and municipal fiscal, or tax federalism. This article describes the features of fiscal system of China which is formed as a fiscal federalism. The author reviews in details the process of forming and reforming fiscal federalism in China, and analyzes its current situation. In addition, the article gives some recommendations of usage of the Chinese experience in the Russia to improve local practice of fiscal federalism.
In het Delta Lloyd magazine april 2015, p. 32, wordt aandacht besteed aan Martijn Wismeijer (43 jaar). Hij liet onlangs twee chips onder zijn huid implanteren, een voor bitcoins en een voor de honderden wachtwoorden die hij voor digitale toepassingen gebruikt. 1 Het is een feit dat we in het huidige ICT-tijdperk te maken krijgen met heel veel wachtwoorden die liefst zo weinig mogelijk identiek mogen zijn en het is duidelijk dat wie toegang krijgt tot die wachtwoorden ons leven behoorlijk kan ontwrichten. Maar is een chip voor bitcoins niet overbodig? Wat zijn bitcoins eigenlijk, wat is hun juridische status en zijn ze betaalmiddel?
The purpose of this study is to analyze the right of autonomy, to investigate the perception of local autonomy, and to propose the key factors which desirable the local decentralization has. The research methods of this study are literature investigations, and central and local public servants surveys and citizens survey. We made an analysis framework focused on the preceding researches, and drew revitalization strategies of the local decentralization. As a result of empirical study, we found that local finance autonomy and local organization autonomy are the most important factors to revitalize the local decentralization. And as a result of depths interview, we found that there are perception differences between central and local public servant about the detailed contents of local finance autonomy, but all interviewees agree that the local finance autonomy should be enhanced.
Open access
Diverse Approaches in Healthcare and Education Studies
The purpose of this study is to analyze the right of autonomy, to investigate the perception of local autonomy, and to propose the key factors which desirable the local decentralization has. The research methods of this study are literature investigations, and central and local public servants surveys and citizens survey. We made an analysis framework focused on the preceding researches, and drew revitalization strategies of the local decentralization. As a result of empirical study, we found that local finance autonomy and local organization autonomy are the most important factors to revitalize the local decentralization. And as a result of depths interview, we found that there are perception differences between central and local public servant about the detailed contents of local finance autonomy, but all interviewees agree that the local finance autonomy should be enhanced.
Open access
Diverse Approaches in Healthcare and Education Studies
The financial market is based on the currency and the volume of trade between different individuals, groups, or organizations. This trade is ruled or governed by several protocols, which limits the over flooding or inappropriations in the exchange markets. One such virtual currency that is becoming popular among users is Bitcoin. In this paper, we discussed the evolution of Bitcoin as a currency, situations preceding and aftermath, as well as its consequences and effects on the present economy. We also discussed its growth, transaction volumes, currency acceptability, and factors involved. In this paper, we have tried to ensemble related thoughts for seeking new ideas for developing an alternative financial system. The results attained thereof could give new hopes to both consumers and markets seeking more freedom in terms of volume, payment methods, anonymity, and so forth.
Jun 1, 2015·2015 IEEE/ACIS 16th International Conference on Software Engineering, Artificial Intelligence, Networking and Parallel/Distributed Computing (SNPD)
Bitcoin, a distributed, peer to peer crypto currency, has gained a significant popularity among different users around the world by promising users a fully decentralized network with an inherently independence from governments and without the influence of any central authorities and organizations. Mining is the fundamental concept in Bitcoin which must be done in checking all monetary transactions and verifying them which in return generates Bitcoin as a reward to encourage this work. While the qualitative nature of this unique system is clearly accepted and understood, there are some issues regarding to its decentralized network environment. Based on our analysis due to the high variance of solo mining, the number of users joining top most famous Bitcoin mining pools are increasing due to the fact that users together under a Bitcoin pool will have a higher chance of generating next block in the Bitcoin's blockchain by reducing the variance and earning the mining reward. Furthermore, emerging huge mining farms with strong mining resources and fast processing power is another trend toward centralization. Although some might argue that, the protocol itself is purely decentralized and these are marketbased centralization, this trend clearly illustrates that the pure, decentralized protocol of Bitcoin is going toward centralization in its distributed network, where any kind of centralization should be considered carefully due to the 51% attack. By analysing all the created blocks from 2009 to 2014 we proposed a centralization factor which shows how centralized is the state of Bitcoin's network in different years. Centralization, due its simplicity, is a phenomenon that happens to any disciplined and organized system automatically, which in case of Bitcoin is against the pure initial decentralized nature of it and might arise some concerns and threats to the Bitcoin's unforeseeable future.
Daniel Cabarcas, Denise Demirel, Florian Göpfert, Jean Lancrenon · 5 authors
Abstract. Commitment schemes are among cryptography’s most im-portant building blocks. Besides their basic properties, hidingness and bindingness, for many applications it is important that the schemes ap-plied support proofs of knowledge. However, all existing solutions which have been proven to provide these protocols are only computationally hiding or are not resistant against quantum adversaries. This is not suitable for long-lived systems, such as long-term archives, where com-mitments have to provide security also in the long run. Thus, in this work we present a new post-quantum unconditionally hiding commit-ment scheme that supports (statistical) zero-knowledge protocols and allows to refreshes the binding property over time. The bindingness of our construction relies on the approximate shortest vector problem, a lattice problem which is conjectured to be hard for polynomial approxi-mation factors, even for a quantum adversary. Furthermore, we provide a protocol that allows the committer to prolong the bindingness prop-erty of a given commitment while showing in zero-knowledge fashion that the value committed to did not change. In addition, our construc-tion yields two more interesting features: one is the ability to “convert” a Pedersen commitment into a lattice-based one, and the other one is the construction of a hybrid approach whose bindingness relies on the discrete logarithm and approximate shortest vector problems.
Unlink ability and accountability are conflicting yet critical requirements for on-line transactions that need to be addressed in order to preserve users' privacy as well as to protect service providers in today identity ecosystems. In this poster paper we introduce a pseudonymous identity management system in which users can carry out unlink able on-line transactions without having to disclose their actual identity to the service providers. At the same time, the service providers have strong assurance about the authenticity of the identity and credentials. In our approach, users' identity is cryptographically encoded in pseudonymous identity tokens issued by trusted identity providers. Our system includes a lightweight policy language which enables users and service providers to express their requirements pertaining to pseudonymous identity verification and a suite of protocols based on zero-knowledge-proofs which enables the fulfillment of these requirements.
This research related to the financial performance of local government districts/cities in the South Sumatra province, which need to be enhanced by the presence of regional autonomy (fiscal decentralization). Local government needs to build and manage public financial accounting system of their own. Many factors can affect the financial performance of local governments. This study aimed to know whether the level of local government wealth proxied by the ratio of the locally-generated revenue (PAD), the dependence of local governments on the central government to the ratio proxied by General Allocation Fund (DAU), and the level of capital expenditures of local governments may improve financial performance of local governments, as measured by the ratio of financial efficiency. By using multiple regression analysis in 15 local government districts/cities in the South Sumatra province from 2018 up to 2012 with 75 sample observations, this study proves that the level of dependency of local governments (DAU) gave positive significant effect on the efficiency (performance) of local government finance, while the level of regional wealth (PAD ratio of the total expenditure areas), and the level of capital expenditures of local government (the ratio of capital expenditure to total expenditure areas) do not significantly affect the efficiency (performance) of local government finance district/city in the province of South Sumatra, while simultaneously affect the efficiency (performance) of local government finance with adjusted R2 value 0.203135.
Como resultado de los avances tecnologicos propios del siglo XXI, en el ano 2009, el mundo presencio el nacimiento del bitcoin, una moneda de caracter estrictamente digital, que dado su avanzado desarrollo y aceptacion a nivel mundial entre los comerciantes, plantea cuestiones juridicas y economicas importantes que ya no pueden ser ignoradas por el Derecho.
En vista de que Colombia no ha sido ajena a este nuevo fenomeno social, esta investigacion se encarga de analizar, que pasaria a la luz del ordenamiento juridico colombiano, si dos particulares dentro del territorio nacional, de forma directa y en ejercicio de su voluntad libre y autonoma, acuerdan trasmitir la propiedad de una cosa a cambio de un pago en bitcoins, en lo que denominan contrato de compraventa comercial, y luego se demanda el incumplimiento contractual de la parte que se obligo a pagar con bitcoins.
Para tal proposito, se realizo un repaso historico del dinero y de la moneda, se estudio al bitcoin, su funcionamiento, sus principales caracteristicas, el papel que desempena en una economia, la forma en que ha sido regulado en un contexto internacional, los distintos pronunciamientos que sobre el bitcoin han sido emitidos en Colombia, y la legislacion aplicable en el ordenamiento juridico Colombiano que permita dar solucion al caso concreto.
Partiendo de que esta investigacion es pionera en Colombia en analizar este fenomeno desde el Derecho; se realizo una exhaustiva revision bibliografica, y un analisis comparado y juridico serio, que permitio clasificar al bitcoin como dinero mercancia digital, y de paso, plantear dos posibles posturas que pueden ser asumidas por el juez en Colombia para resolver el problema juridico: la postura del juez legalista y la postura del juez creador de Derecho.
Esta ultima postura, permite establecer cual deberia ser la mejor forma de entender e integrar al bitcoin dentro del ordenamiento juridico colombiano, y senala el camino para la configuracion de una comunidad juridica internacional alrededor del manejo uniforme del bitcoin, a traves de la ampliacion del principio de equivalencia funcional.
De forma complementaria a esta investigacion, se determino, que el contrato con bitcoins que se presenta dentro de las relaciones de consumo, tambien esta sujeto a la regulacion de proteccion al consumidor.
Abstract. Pedersen commitments are important cryptographic primi-tives. They allow a prover to commit to a certain value without revealing any information about it and without the prover being able to change its mind later on. Since the first property holds unconditionally this is an essential primitive for many schemes providing long-term confidential-ity. However, the second property only holds computationally. Hence, in the long run bindingness is lost, making the primitive improper for long-lived systems. Thus in this paper, we describe a protocol that, in a sense, prolongs the bindingness of a given Pedersen commitment. More precisely, we demonstrate how to prove in perfect zero-knowledge that a new Pedersen commitment- generated with a larger security param-eter- and a corresponding old commitment both commit to the same value. We stress that this is a non-trivial procedure. Up until now the only known perfect zero-knowledge proof techniques for proving mes-sage equivalence of two commitments work when both commitments use isomorphic message spaces. However, as we will show in this work, to prolong the security of Pedersen commitments we cannot tolerate this restriction. Our prolonging technique works for non-isomorphic message spaces, is efficient, can be repeated an arbitrary number of times, main-tains unconditional confidentiality, and allows to preserve the format of the Pedersen commitments. This makes the construction presented here an important contribution to long-lived systems. Finally, we illustrate this by discussing how commitments with prolongable bindingness can be used to allow for archiving solutions that provide not only integrity but also confidentiality in the long-term.
In this dissertation we show how to use cryptocurrencies (mostly Bitcoin) and techniques coming from the field of cryptocurrencies to construct new types of Multiparty Computation Protocols (MPC), which go beyond the standard definition of MPC. In the first part of the dissertation we study the MPC protocols, in which parties have access to a Bitcoin-like cryptocurrency. We show that in this setting it is possible to design a two-party MPC protocol for computing a value of an arbitrary function f that has two advantages over classical MPC protocols. First, classical two-party MPC protocols do not guarantee fairness, which means that a malicious party can interrupt the execution of a protocol in a state, in which he/she knows the output of the protocol, but the other party does not. In contrast, our MPC protocol do guarantee some kind of fairness. More precisely, a party who has not learnt the output due to the other party’s misbehaviour is given a financial compensation. Moreover, the value of the function f being computed can contain instructions like “The party A pays 1 bitcoin to the party B” and our protocol guarantees that such transfers will automatically take place. Therefore, it allows to create two-party protocols with financial consequences. We also discuss how to formally verify the correctness and the security of such protocols and show how to protect them against the so-called malleability of transactions, which is a problem concerning most cryptocurrencies. Then, we study cryptographic protocols in a fully peer-to-peer scenario under the assumption that the computing power of the adversary is limited and there is no trusted setup (like a PKI or an unpredictable beacon). We show that every primitive (e.g. Byzantine consensus) that can be realised under the classical assumption that the majority of the parties executing the protocol is honest and there is a PKI available can also be realised under the assumption that the majority of the computing power is controlled by honest parties and there is no PKI.