Preuves à divulgation nulle de connaissance pour le calcul sécurisé Dans cette thèse, nous étudions les preuves à divulgation nulle de connaissance, une primitive cryptographique permettant de prouver une assertion en ne révélant rien de plus que sa véracité, et leurs applications au calcul sécurisé. Nous introduisons tout d’abord un nouveau type de preuves à divulgation nulle, appelées arguments implicites à divulgation nulle, intermédiaire entre deux notions existantes, les preuves interactives et les preuves non interactives à divulgation nulle. Cette nouvelle notion permet d’obtenir les mêmes bénéfices en terme d’efficacité que les preuves non-interactives dans le contexte de la construction de protocoles de calcul sécurisé faiblement interactifs, mais peut être instanciée à partir des mêmes hypothèses cryptographiques que les preuves interactives, permettant d’obtenir de meilleures garanties d’efficacité et de sécurité. Dans un second temps, nous revisitons un système de preuves à divulgation nulle de connaissance qui est particulièrement utile dans le cadre de protocoles de calcul sécurisé manipulant des nombres entiers, et nous démontrons que son analyse de sécurité classique peut être améliorée pour faire reposer ce système de preuve sur une hypothèse plus standard et mieux connue. Enfin, nous introduisons une nouvelle méthode de construction de systèmes de preuves à divulgation nulle sur les entiers, qui représente une amélioration par rapport aux méthodes existantes, tout particulièrement dans un modèle de type client-serveur, où un client à faible puissance de calcul participe à un protocole de calcul sécurisé avec un serveur à forte puissance de calcul.
Bitcoin is a digital currency based on a peer-to-peer payment system managed by an open source software and characterized by lower transaction costs, greater security and scalability than fiat money and no need of a central bank. Despite criticisms about illegal uses and social consequences, it is attracting the interest of the scientific community. The purpose of this work is to define and evaluate the current trends of the literature concerned with the sustainability of bitcoin, considering the environmental impacts, social issues and economic aspects. From the analysis it emerges that the transition of the whole monetary system in the new cryptocurrency will result in an unacceptable amount of energy consumed to mine new bitcoins and to maintain the entire virtual monetary system, and probably bitcoin will remain a niche currency. Blockchain, which is the base for a distributed and democratically-sustained public ledger of the transactions, could foster new and challenging opportunities. Sharing the framework of medical data, energy generation and distribution in micro-grids at the citizen level, block-stack and new state-driven cryptocurrencies, may benefit from the wide spread of blockchain-based transactions. Under the perspective of its being a driver of social change, bitcoins and related blockchain technologies may overcome the issues highlighted by numerous detractors.
We compare two Demand Side Management (DSM) mechanisms, introduced\nrespectively by Mohsenian-Rad et al (2010) and Baharlouei et al (2012), in\nterms of efficiency and fairness. Each mechanism defines a game where the\nconsumers optimize their flexible consumption to reduce their electricity\nbills. Mohsenian-Rad et al propose a daily mechanism for which they prove the\nsocial optimality. Baharlouei et al propose a hourly billing mechanism for\nwhich we give theoretical results: we prove the uniqueness of an equilibrium in\nthe associated game and give an upper bound on its price of anarchy. We\nevaluate numerically the two mechanisms, using real consumption data from Pecan\nStreet Inc. The simulations show that the equilibrium reached with the hourly\nmechanism is socially optimal up to 0.1%, and that it achieves an important\nfairness property according to a quantitative indicator we define. We observe\nthat the two DSM mechanisms avoid the synchronization effect induced by non-\ngame theoretic mechanisms, e.g. Peak/OffPeak hours contracts.\n
This chapter describes a short-lived experiment in organizational governance that attempted to utilize algorithmic authority through cryptocurrency and block-chain technologies to create a social and political world quite unlike anything we have seen before. It details the governance structures that were promised by the developers and community members involved in the making of The decentralised autonomous organisation (DAO), and in contrast, those that were observed in its discourses before, during, and after the “exploit.” The DAO was a decentralized, crowdfunded, direct-management organization and investment platform. In the original vision of decentralized autonomous organizations, as proposed by Vitalik Buterin, founder and member of the Ethereum Foundation, a DAO is a pseudo-legal organization run by an assemblage of human and “robot” participants. From the earliest days of The DAO, many community members acknowledged that the enormous complexity of decentralized and algorithmic governance required a new kind of experimental “science” to map the “uncharted territory” The DAO was entering.
Adán Sánchez de Pedro, Daniele Levi, Luis Iván Cuende
Witnet is a decentralized oracle network (DON) that connects smart contracts to the outer world. Generally speaking, it allows any piece of software to retrieve the contents published at any web address at a certain point in time, with complete and verifiable proof of its integrity and without blindly trusting any third party. Witnet runs on a blockchain with a native protocol token (called Wit), which miners-called witnesses-earn by retrieving, attesting and delivering web contents for clients. On the other hand, clients spend Wit to pay witnesses for their Retrieve-Attest-Deliver (RAD) work. Witnesses also compete to mine blocks with considerable rewards, but Witnet mining power is proportional to their previous performance in terms of honesty and trustworthiness-this is, their reputation as witnesses. This creates a powerful incentive for witnesses to do their work honestly, protect their reputation and not to deceive the network. The Witnet protocol is designed to assign the RAD tasks to witnesses in a way that mitigates most attack vectors to the greatest extent. At the same time, it includes a novel 'sharding' feature that (1) guarantees the efficiency and scalability of the network, (2) keeps the price of RAD tasks within reasonable bounds and (3) gives clients the freedom to adjust certainty and price by letting them choose how many witnesses will work on their RAD tasks. When coupled with a Decentralized Storage Network (DSN), Witnet also gives us the possibility to build the Digital Knowledge Ark: a decentralized, immutable, censorship-resistant and eternal archive of humanity's most relevant digital data. A truth vault aimed to ensure that knowledge will remain democratic and verifiable forever and to prevent history from being written by the victors.
José Horta, Daniel Kofman, David Menga, Alonso Silva
Future electricity distribution grids will host a considerable share of variable renewable energy sources and local storage resources. Moreover, they will face new load structures due for example to the growth of the electric vehicle market. These trends raise the need for new paradigms for distribution grids operation, in which Distribution System Operators will increasingly rely on demand side flexibility and households will progressively become prosumers playing an active role on smart grid energy management. However, in present energy management architectures, the lack of coordination among actors limits the capability of the grid to enable the mentioned trends. In this paper we tackle this problem by proposing an architecture that enables households to autonomously exchange energy blocks and flexibility services with neighbors, operators and market actors. The solution is based on a blockchain transactive platform. We focus on a market application, where households can trade energy with their neighbors, aimed to locally balancing renewable energy production. We propose a market mechanism and dynamic transport prices that provide an incentive for households to locally manage energy resources in a way that responds to both pro-sumer and operator needs. We evaluate the impact of such markets through comprehensive simulations using power flow analysis and realistic load profiles, providing valuable insight for the design of appropriate mechanisms and incentives.
Aimable Mbituyumuremyi, Jennifer Ilo Van Nuil, Jeanne Umuhire, Jules Mugabo · 9 authors
With the introduction of direct-acting antiviral drugs, treatment of hepatitis C is both highly effective and tolerable. Access to treatment for patients, however, remains limited in low- and middle-income countries due to the lack of supportive health infrastructure and the high cost of treatment. Poorer countries are being encouraged by international bodies to organize public health responses that would facilitate the roll-out of care and treatment on a national scale. Yet few countries have documented formal plans and policies. Here, we outline the approach taken in Rwanda to a public health framework for hepatitis C control and care within the World Health Organization hepatitis health sector strategy. This includes the development and implementation of policies and programmes, prevention efforts, screening capacity, treatment services and strategic information systems. We highlight key successes by the national programme for the control and management of hepatitis C: establishment of national governance and planning; development of diagnostic capacity; approval and introduction of direct-acting antiviral treatments; training of key personnel; generation of political will and leadership; and fostering of key strategic partnerships. Existing challenges and next steps for the programme include developing a detailed monitoring and evaluation framework and tools for monitoring of viral hepatitis. The government needs to further decentralize care and integrate hepatitis C management into routine clinical services to provide better access to diagnosis and treatment for patients. Introducing rapid diagnostic tests to public health-care facilities would help to increase case-finding. Increased public and private financing is essential to support care and treatment services.
The adoption of blockchain-based distributed computation platforms is growing fast. Some of these platforms, such as Ethereum, provide support for implementing smart contracts, which are envisioned to have novel applications in a broad range of areas, including finance and Internet-of-Things. However, a significant number of smart contracts deployed in practice suffer from security vulnerabilities, which enable malicious users to steal assets from a contract or to cause damage. Vulnerabilities present a serious issue since contracts may handle financial assets of considerable value, and contract bugs are non-fixable by design. To help developers create more secure smart contracts, we introduce FSolidM, a framework rooted in rigorous semantics for designing con- tracts as Finite State Machines (FSM). We present a tool for creating FSM on an easy-to-use graphical interface and for automatically generating Ethereum contracts. Further, we introduce a set of design patterns, which we implement as plugins that developers can easily add to their contracts to enhance security and functionality.
Jian Wang, Qianggang Wang, Niancheng Zhou, Yuan Chi
The installed capacity of distributed generation (DG) based on renewable energy sources has increased continuously in power systems, and its market-oriented transaction is imperative. However, traditional transaction management based on centralized organizations has many disadvantages, such as high operation cost, low transparency, and potential risk of transaction data modification. Therefore, a decentralized electricity transaction mode for microgrids is proposed in this study based on blockchain and continuous double auction (CDA) mechanism. A buyer and seller initially complete the transaction matching in the CDA market. In view of the frequent price fluctuation in the CDA market, an adaptive aggressiveness strategy is used to adjust the quotation timely according to market changes. DG and consumer exchange digital certificate of power and expenditure on the blockchain system and the interests of consumers are then guaranteed by multi-signature when DG cannot generate power due to failure or other reasons. The digital certification of electricity assets is replaced by the sequence number with specific tags in the transaction script, and the size of digital certification can be adjusted according to transaction energy quantity. Finally, the feasibility of market mechanism through specific microgrid case and settlement process is also provided.
The adoption of blockchain-based distributed computation platforms is growing\nfast. Some of these platforms, such as Ethereum, provide support for\nimplementing smart contracts, which are envisioned to have novel applications\nin a broad range of areas, including finance and Internet-of-Things. However, a\nsignificant number of smart contracts deployed in practice suffer from security\nvulnerabilities, which enable malicious users to steal assets from a contract\nor to cause damage. Vulnerabilities present a serious issue since contracts may\nhandle financial assets of considerable value, and contract bugs are\nnon-fixable by design. To help developers create more secure smart contracts,\nwe introduce FSolidM, a framework rooted in rigorous semantics for designing\ncon- tracts as Finite State Machines (FSM). We present a tool for creating FSM\non an easy-to-use graphical interface and for automatically generating Ethereum\ncontracts. Further, we introduce a set of design patterns, which we implement\nas plugins that developers can easily add to their contracts to enhance\nsecurity and functionality.\n
For countries looking to implement multisectoral nutrition plans, it is critical to understand what works and how programs should be delivered and scaled-up in each context. Programs can learn from each other on how to adapt to new information, evidence and events related to scaling-up and district stakeholders can play important roles in implementation of this multisectoral plan. As part of "Pathways-to-Better Nutrition" (PBN) case study conducted by USAID/SPRING Project, this research set out to explore district leaders' perceptions of the nutrition situation, programs and opportunities for integration. Qualitative data were collected through key-informant interviews and focus group discussions. Thirty-five district and local leaders belonging to district and sub-county multisectoral nutrition committees in Kisoro and Lira were interviewed. Grounded Theory Approach was used to identify themes for coding and key domains included: learning, adoption and evidence of scale-up; adoption of innovations/interventions to local context, financing of nutrition-sensitive activities and long-term planning. Additionally, quantitative data collected by Feed the Future Innovation Lab for Nutrition were analyzed in each of the districts to provide nutrition snapshots. Malnutrition in the study districts was worse than the national average for stunting, anemia and women's underweight. The majority (91%) of respondents were not familiar with these nutrition statistics. Both study areas have formed nutrition multisectoral working groups (District Nutrition Coordinating Committees) and have developed management structures to implement interventions. Government stakeholders from every nutrition-sensitive sector referred to the lack of clear government programs that support nutrition directly in local policy environment. Key agricultural-related programs are focusing on wealth creation, value-addition or increasing agricultural productivity without nutrition lens (not "nutrition sensitive"). Nutrition is not on the 'list' of key priorities of district health departments unlike HIV/AIDS, malaria or sexual reproductive health. About 69% respondents believe they lack operational capacities and soft-power skills to design, implement and manage nutrition interventions such as leveraging of resources and being able to convey evidence. The understanding of "Scaling-up Nutrition" also differed by respondent, and this has resulted in different goals and measurements. Challenges related to nutrition financing were also noted, including fiscal decentralization, use of Output-Based Financing mechanisms, limited flexibility to re-allocate funds for nutrition, and lack of standard reporting procedures or implementation strategy. Efforts to address malnutrition need to be multisectoral, coupled with increased coordination of different sectors and ministries for sustained impact on nutrition outcomes.
Abstract Drawing on economic transaction cost theory, this paper explores how blockchain and distributed ledger technology could shift the smart city agenda by altering transaction costs with implications for the coordination of infrastructures and resources. Like the smart city the crypto city utilizes data informatics, but can be coordinated through distributed rather than centralized systems. The data infrastructure of the crypto city can enable civil society to run local public goods and services, and facilitate economic and social entrepreneurship.
Temporary work is an employment situation useful and suitable in all occasions in which business needs to adjust more easily and quickly to workload fluctuations or maintain staffing flexibility. Temporary workers play therefore an important role in many companies, but this kind of activity is subject to a special form of legal protections and many aspects and risks must be taken into account both employers and employees. In this work we propose a blockchain-based system that aims to ensure respect for the rights for all actors involved in a temporary employment, in order to provide employees with the fair and legal remuneration (including taxes) of work performances and a protection in the case employer becomes insolvent. At the same time, our system wants to assist the employer in processing contracts with a fully automated and fast procedure. To resolve these problems we propose the D-ES (Decentralized Employment System). We first model the employment relationship as a state system. Then we describe the enabling technology that makes us able to realize the D-ES. In facts, we propose the implementation of a DLT (Decentralized Ledger Technology) based system, consisting in a blockchain system and of a web-based environment. Thanks the decentralized application platforms that makes us able to develop smart contracts, we define a discrete event control system that works inside the blockchain. In addition, we discuss the temporary work in agriculture as a interesting case of study.
Recent advancements in artificial intelligence systems can be justified by the success in the field of machine learning. This is due to increase in knowledge (data) which leads to increase in intelligence. Similarly, the blockchain has a power to transform the artificial intelligence systems. The blockchain can be defined as a peer-to-peer transaction database which maintains the integrity of information through the distributed open ledger. It is a decentralized way to store value transactions across the nodes in the network. Every node in the network has access to the ledger. The blockchain has a wide range of applications including digital currency or crypto-currencies, smart assets, contracts, voting, etc. When it comes to artificial intelligence, the smart contract can be used to create an artificial intelligence system or it can be helpful in reaching a consensus during a dilemma through voting. A peer-to-peer model training can also be implemented using a blockchain network. The blockchain database can be helpful in improving the quantity and quality of data.
For any industry or company, to be a competent in market needs increase in performance in all possible ways. Quick response to market and sufficient production as per requirement is the only way to increase the returns, which require critical planning and production systems. For this co-ordination between business units or workstations is essential. Many of the executive managers in industries has to instruct only the task flows to its subordinates, that is a single straightforward production planning process is followed as executed from top level of organization; their capacity as per their education level is not utilized more than 10%. The use of multi-agent system allows physical distribution of the decisional system and procures a hierarchical organization structure with decentralized control that guarantees the autonomy of each entity and flexibility of network. Our study focuses on managers/partners that adapt together their local planning process to face different requirements of supply chain environment using different planning strategies, when decisions are supported by distributed planning systems. The agent based system has the advantage of making collaborative management of disturbances in supply chain as the agents has the advantage of making autonomous decisions in a distributed network. Because each partner can choose different behavior and all behavior has an impact on the overall performance, it is difficult to know which is preferable for each partner to increase their performance. Thus, in this paper study of Multi-behavior planning agent model is done using different planning strategies when decisions are supported by distributed planning system.
Blockchain uses the idea of storing transaction data in the form of a distributed ledger wherein each node in the network stores a current copy of the sequence of transactions in the form of a hash chain. This requirement of storing the entire ledger incurs a high storage cost that grows undesirably large for high transaction rates and large networks. In this work we use the ideas of secret key sharing, private key encryption, and distributed storage to design a coding scheme such that each node stores only a part of the entire transaction thereby reducing the storage cost to a fraction of its original cost. When further using dynamic zone allocation, we show the coding scheme can also improve the integrity of the transaction data in the network over current schemes. Further, block validation (bitcoin mining) consumes a significant amount of energy as it is necessary to determine a hash value satisfying a specific set of constraints; we show that using dynamic distributed storage reduces these energy costs.
Most user authentication methods and identity proving systems rely on a centralized database. Such information storage presents a single point of compromise from a security perspective. If this system is compromised it poses a direct threat to users' digital identities. This paper proposes a decentralized authentication method, called the Horcrux protocol, in which there is no such single point of compromise. The protocol relies on decentralized identifiers (DIDs) under development by the W3C Verifiable Claims Community Group and the concept of self-sovereign identity. To accomplish this, we propose specification and implementation of a decentralized biometric credential storage option via blockchains using DIDs and DID documents within the IEEE 2410-2017 Biometric Open Protocol Standard (BOPS).
In this study, we consider a decentralized agricultural supply chain consisting of a capital-constrained smallholder farmer and an intermediary platform. The smallholder farmer sells the agricultural products through the intermediary platform but lacks the financial resources for production. In addition to the traditional solution of bank financing (provided by a bank) as a source of finance for the capital-constrained farmer to ensure the sustainable production of the agricultural goods, the intermediary platform can also provide loans directly to the smallholder farmer (known as direct financing) or serve as a guarantor if the capital-constrained farmer has insufficient creditworthiness to obtain bank loans (known as guarantor financing). The farmer can thus obtain a loan through three methods: bank financing, guarantor financing, and direct financing. We find that the smallholder farmer produces the most under direct financing and the least under bank financing, and that the intermediary platform prefers direct financing over guarantor financing in a weak sense. Specifically, when the farmer’s production cost is low, the intermediary platform prefers financing the farmer directly; when the cost is in an intermediate range, the platform prefers either direct or guarantor financing; and when the cost is high, it is in the best interest of the intermediary platform to encourage the farmer to raise funds from the banking market. We also assess the best financing format for profitability of the smallholder farmer and the sustainability of the whole supply chain, and find that the farmer prefers bank financing while the preference of the supply chain as a whole depends on the cost. Interestingly, under both guarantor financing and direct financing, the smallholder farmer’s level of production can be higher than that under a centralized chain (where the farmer and the intermediary platform belong to the same entity) regardless of whether the chain encounters financial constraints. Moreover, the decentralized supply chain can be coordinated under direct financing when the farmer’s production cost is relatively low.
After granting permission to the Internal Revenue Service to serve a digital exchange company a summons for user information, the Federal District Court for the Northern District of California created some uncertainty regarding the privacy of cryptocurrencies. The IRS views this information gathering as necessary for monitoring compliance with Notice 2014-21, which classifies cryptocurrencies as property for tax purposes. Cryptocurrency users, however, view the attempt for information as an infringement on their privacy rights and are seeking legal protection. This Issue Brief investigates the future tax implications of Notice 2014-21 and considers possible routes the cryptocurrency market can take to avoid the burden of capital gains taxes. Further, this Issue Brief attempts to uncover the validity of the privacy claims made against the customer information summons and will recommend alternative actions for the IRS to take regardless of whether it succeeds in obtaining the information.
Zhen Hong, Zehua Wang, Wei Cai, Victor C. M. Leung
Device-to-device (D2D) communication is becoming an increasingly important technology in future networks with the climbing demand for local services. For instance, resource sharing in the D2D network features ubiquitous availability, flexibility, low latency and low cost. However, these features also bring along challenges when building a satisfactory resource sharing system in the D2D network. Specifically, user mobility is one of the top concerns for designing a cooperative D2D computational resource sharing system since mutual communication may not be stably available due to user mobility. A previous endeavour has demonstrated and proven how connectivity can be incorporated into cooperative task scheduling among users in the D2D network to effectively lower average task execution time. There are doubts about whether this type of task scheduling scheme, though effective, presents fairness among users. In other words, it can be unfair for users who contribute many computational resources while receiving little when in need. In this paper, we propose a novel blockchain-based credit system that can be incorporated into the connectivity-aware task scheduling scheme to enforce fairness among users in the D2D network. Users’ computational task cooperation will be recorded on the public blockchain ledger in the system as transactions, and each user’s credit balance can be easily accessible from the ledger. A supernode at the base station is responsible for scheduling cooperative computational tasks based on user mobility and user credit balance. We investigated the performance of the credit system, and simulation results showed that with a minor sacrifice of average task execution time, the level of fairness can obtain a major enhancement.
<strong>Abstract</strong><br> Many reforms have been undertaken in local governance after the collapse of the<br> totalitarian, centrist and bureaucratic regimes in Central and Eastern Europe. Albania<br> has demonstrated that decentralization is a major development tool. More than two<br> decades of decentralization activities have revealed that the decentralization process has<br> brought about changes in the operation of institutions and delivery of services, even<br> though this change has taken place gradually. Fiscal decentralization is one of the three<br> dimensions that characterize the decentralization process. Local finance issues are an<br> everyday topic in countries in transition and should be addressed by means of an approach<br> that favors consolidation of local autonomy. Local governments in Albania have lacked,<br> and continue to lack, the fiscal capacity to deliver on the promise of decentralization<br> to improve public services and to promote and nurture local economic development.<br> Decentralization can promote economic development and improve citizens’ welfare<br> and living standards when service delivery and the quality of the decisions over how<br> public resources are deployed are improved, but local governments remain hampered<br> by inadequate transfers from the central government and from restraints imposed on<br> various revenue-generating options. However, inadequate financial instruments,<br> especially those of intergovernmental transfers, have affected regional disparities. In this<br> paper, through comparative analysis, analyzing a part of the Region (Qark) of Lezha’s<br> LGUs, economic development indicators, will approve the need for reform of these LGUs’<br> financial instruments in order to narrow the gap of regional disparities in Albania.
This article considers Bitcoin as a system of exchange, and the block chain technology it is built on, in the context of supporting developing nations. If integrated correctly Bitcoin could have far reaching applications, from tackling corruption to empowering women. This article found Bitcoin to be a feasible option, with support from real world applications and global endorsement from users. The discussion is then applied in the context of corruption as it puts forward this emerging technology as an alternative to traditional centralised fiscal systems. The article posits that public libraries could be potential facilitators and a crucial component of this integration.