Today, the Blockchain Technology has been widely explored and continuously revolutionising many sectors around the world, including construction industry. Construction industry need blockchain technology to improve the current limitation of centralised technology in its various project life-cycle. In this paper, we presented literature review, aimed to identify the potentials of Blockchain applications in construction industry. This paper also reviewed the unique features behind the blockchain technology which trigger its capabilities in construction industry. Paper further discussed the implications of the blockchain application if it were adopted in construction industry. In short, Blockchain technology is still relatively new in construction industry and further deep research is needed to develop real life on-hand application for construction industry in near future.
Modern blockchain systems support creation of smart contracts -- stateful programs hosted and executed on a blockchain. Smart contracts hold and transfer significant amounts of digital currency which makes them an attractive target for security attacks. It has been shown that many contracts deployed to public ledgers contain security vulnerabilities. Moreover, the design of blockchain systems does not allow the code of the smart contract to be changed after it has been deployed to the system. Therefore, it is important to guarantee the correctness of smart contracts prior to their deployment. Formal verification is widely used to check smart contracts for correctness with respect to given specification. In this work we consider program synthesis techniques in which the specification is used to generate correct-by-construction programs. We focus on one of the special cases of program synthesis where programs are modeled with finite state machines (FSMs). We show how FSM synthesis can be applied to the problem of automatic smart contract generation. Several case studies of smart contracts are outlined: crowdfunding platform, blinded auction and a license contract. For each case study we specify the corresponding smart contract with a set of formulas in linear temporal logic (LTL) and use this specification together with test scenarios to synthesize a FSM model for that contract. These models are later used to generate executable Solidity code which can be directly used in a blockchain system.
Confirmation of Bitcoin transactions is executed in blocks, which are then stored in the Blockchain. As compared to the number of transactions in the mempool, the set of transactions which are verified but not yet confirmed, available space for inclusion in a block is typically limited. For this reason, successful miners can only process a subset of such transactions, and users compete with each other to enter the next block by offering confirmation fees. Assuming that successful miners pursue revenue maximization, they will include in the block those mempool transactions that maximize earnings from related fees. In the paper we model transaction fees as a Nash Equilibrium outcome of an auction game with complete information. In the game the successful miner acts as an auctioneer selling block space, and users bid for shares of such space to confirm their transactions. Moreover, based on expected fees we also discuss what the optimal, revenue maximizing, block size limit should be for the successful miner. Consistently with the intuition, the optimal block size limit resolves the trade-off between including additional transactions (which possibly lower the unit fees collected) and keeping the block capacity limited (with, however, higher unit fees).
We introduce Unity, a new consensus algorithm for public blockchain settings. Unity is an eventual consistency protocol merging the Proof-of-Work (PoW) and Proof-of-Stake (PoS) into a coherent stochastic process. It encompasses hardware and economic security without sacrificing availability, unpredictability and decentralization. Empirical results indicate that the proposed protocol is fair and scalable to an arbitrary number of miners and stakers.
In this paper, the authors propose to increase the efficiency of blockchain mining by using a population-based approach. Blockchain relies on solving difficult mathematical problems as proof-of-work within a network before blocks are added to the chain. Brute force approach, advocated by some as the fastest algorithm for solving partial hash collisions and implemented in Bitcoin blockchain, implies exhaustive, sequential search. It involves incrementing the nonce (number) of the header by one, then taking a double SHA-256 hash at each instance and comparing it with a target value to ascertain if lower than that target. It excessively consumes both time and power. In this paper, the authors, therefore, suggest using an inner for-loop for the population-based approach. Comparison shows that it's a slightly faster approach than brute force, with an average speed advantage of about 1.67% or 3,420 iterations per second and 73% of the time performing better. Also, we observed that the more the total particles deployed, the better the performance until a pivotal point. Furthermore, a recommendation on taming the excessive use of power by networks, like Bitcoin's, by using penalty by consensus is suggested.
Ever-growing incorporation of connected vehicle (CV) technologies into intelligent traffic signal control systems brings about significant data security issues in the connected vehicular networks. This paper presents a novel decentralized and secure by design architecture for connected vehicle data security, which is based on the emerging blockchain paradigm. In a simulation study, we applied this architecture to defend the Intelligent Traffic Signal System (I-SIG), a USDOT approved CV pilot program, against congestion attacks. The results show the performance of the proposed architecture for the traffic signal control system.
O objetivo do estudo foi investigar o perfil e o comportamento da produção científica internacional do tema Bitcoin durante o período de 2008 a 2017. Utilizou-se das técnicas bibliométricas. Foram identificados 241 artigos sobre a temática em questão. Verificou-se uma evolução do tema Bitcoin a partir do ano de 2013. Predominância de artigos publicados individualmente, sendo que Zoe Thomas foi o autor mais profícuo; a instituição University of Birmingham é a mais produtiva. International Financial Law Review foi o periódico que mais publicou com 26 artigos. E as palavras que mais apareceram no título dos estudos divulgados foram: Bitcoin, Blockchain, Technology, Cryptocurrency e Currency. Conclui-se neste estudo uma visão macro, sob a ótica de estudos internacionais, sobre o tema ainda embrionário no âmbito nacional e internacional, Bitcoin. Os resultados, informações e conhecimentos vislumbrados nesta pesquisa, contribui para melhor compreender o referido tema, á luz de indicadores bibliométricos, colaborando assim para mitigar possíveis gaps, fornecer uma agenda de pesquisa, alargar e robustecer seu entendimento na literatura acadêmica das áreas de Administração, Contabilidade, Economia e Turismo, contribuindo assim para seu melhor discernimento, difusão e socialização no âmbito empresarial no Brasil.
Efficient information flow in an intelligent system is vital for effectively controlling the entire system. Currently, intelligent systems are used in many industries related to energy production, sustainable agriculture/transport, and intelligent building/cities. Information technology (IT) and information and communication technologies (ICT) play vital roles in introducing technical or technological innovation in these industries as well as establishing a collaborative network. Also, the digitization of existing systems has been quite effective at creating a sustainable global environment as it allows more efficient and well-balanced control of socio-economic factors. However, it has become clear that adopting an intelligent system to achieve innovation, sustainability, and safety may well depend on the quality of the algorithms to be used for that very system. Despite recent controversies, new and renewable energies are considered as a realistic alternative to fossil fuels, which have been integral to modern industries but are regarded as a cause of environmental or economic problems, not to mention their limited deposits. Therefore, since renewable energies will gradually replace existing energy sources but require more time to be fully available, it is essential to find a method of managing them in a fair and transparent way. The United States, Japan, and some European countries are attempting to achieve such a goal by utilizing a blockchain system, but the issues pertaining to its functionality, security, or efficiency have yet to be addressed. This study introduces a viable consensus algorithm (Hyper Delegation Proof of Randomness, or HDPoR algorithm) for blockchain and attempts to validate its parallel computing capability through simulations. This study also attempts to design an efficient but secure peer-to-peer (P2P) transaction service model for these energies for the future where blockchain-based systems will hold a key position in the digitalized world. As its main contribution, this study introduces an effective method of applying blockchain to a new and renewable energy transaction system by presenting a consensus algorithm that can improve its infrastructure and performance.
Sidra Malik, Volkan Dedeoglu, Salil S. Kanhere, Raja Jurdak
Traceability and integrity are major challenges for the increasingly complex supply chains of today's world. Although blockchain technology has the potential to address these challenges through providing a tamper-proof audit trail of supply chain events and data associated with a product life-cycle, it does not solve the trust problem associated with the data itself. Reputation systems are an effective approach to solve this trust problem. However, current reputation systems are not suited to the blockchain based supply chain applications as they are based on limited observations, they lack granularity and automation, and their overhead has not been explored. In this work, we propose TrustChain, as a three-layered trust management framework which uses a consortium blockchain to track interactions among supply chain participants and to dynamically assign trust and reputation scores based on these interactions. The novelty of TrustChain stems from: (a) the reputation model that evaluates the quality of commodities, and the trustworthiness of entities based on multiple observations of supply chain events, (b) its support for reputation scores that separate between a supply chain participant and products, enabling the assignment of product-specific reputations for the same participant, (c) the use of smart contracts for transparent, efficient, secure, and automated calculation of reputation scores, and (d) its minimal overhead in terms of latency and throughput when compared to a simple blockchain based supply chain model.
The process of reform and fiscal decentralization in the Republic of North Macedonia is already in the second decade of implementation, the legal deadline of which was 2007. However, local government units are still lagging behind in the realization of many of their functions and legal competencies, mainly as a result of lack of financial means, lack of knowledge or lack of capacities to access on alternative sources of funding. An important instrument of financing, especially for financing local and regional economic development are municipal bonds, which are considered the most used financial instruments for financing local and regional capital projects in almost all developed countries of the World, but still in Republic of North Macedonia, no municipality has used this funding source. It is reasonable and necessary that this practice to be developed also in North Macedonia that would result in the realization of strategic municipal projects and at the same time will have an impact on the development of the capital market.Therefore, the purpose of this paper is to analyze the factors, causes and barriers of non-application of municipal bonds in North Macedonia as a financing instrument by the municipalities. Also in this paper are analyzed and evaluated the opportunities and constraints, benefits and risks, criteria and budget constraints of municipal bonds as an additional or alternative source of financial resources for financing local and regional economic development.
Blockchain's properties in addressing trust in highly decentralized environments can make it an enabler for novel sharing economy services. In this paper, we demonstrate the practicality of blockchain-based Secure IoT as a Service (SIoTaaS), where an IoT device can be rented from a service provider, securely and in a privacy-preserving fashion. Our framework allows the simultaneous operations of distinct providers of IoT-based sharing economy services at a large scale. Multiple parties can securely share text and multimedia in the context of location and point-of-interest sharing, perform financial transactions by hiding true identity of parties involved in various online transactions, perform user and IoT registration, transfer value transactions via Ethereum tokens between providers and consumers, as well as raw IoT data payload. This can turn smart room IoT devices, such as smart locks, light bulbs, air conditioning and fans into rentable business entities within a secure sharing economy platform. We will demonstrate such a proof of concept IoT sharing economy framework, which is specifically designed to support the temporary IoT needs of very large numbers of users, such as Hajj pilgrims concentrating for a short period of time at a single area in Saudi Arabia.
We develop a model of stable assets, including non-custodial stablecoins backed by cryptocurrencies. Such stablecoins are popular methods for bootstrapping price stability within public blockchain settings. We derive fundamental results about dynamics and liquidity in stablecoin markets, demonstrate that these markets face deleveraging feedback effects that cause illiquidity during crises and exacerbate collateral drawdown, and characterize stable dynamics of the system under particular conditions. The possibility of such `deleveraging spirals' was first predicted in the initial release of our paper in 2019 and later directly observed during the `Black Thursday' crisis in Dai in 2020. From these insights, we suggest design improvements that aim to improve long-term stability. We also introduce new attacks that exploit arbitrage-like opportunities around stablecoin liquidations. Using our model, we demonstrate that these can be profitable. These attacks may induce volatility in the `stable' asset and cause perverse incentives for miners, posing risks to blockchain consensus. A variant of such attacks also later occurred during Black Thursday, taking the form of mempool manipulation to clear Dai liquidation auctions at near zero prices, costing $8m.
This paper proposes an architecture for dynamic decentralized marketplace for trading of Internet of Things data. To this end, we introduce a 3-tier framework which consists of provider, consumer and broker. The framework is realized using multiple trustless broker which matches and selects potential data provider based on the consumers requirements. Rather than using a centralized server to manage the contract between provider and consumer, the framework leverages smart contract-based agreement for automatically enforcing the terms of the contract to the involved parties.
Blockchain technology provides a tamper-proof mechanism to execute inter-organizational business processes involving mutually untrusted parties. Existing approaches to blockchain-based process execution are based on code generation. In these approaches, a process model is compiled into one or more smart contracts, which are then deployed on a blockchain platform. Given the immutability of the deployed smart contracts, these compiled approaches ensure that all process instances conform to the process model. However, this advantage comes at the price of inflexibility. Any changes to the process model require the redeployment of the smart contracts (a costly operation). In addition, changes cannot be applied to running process instances. To address this lack of flexibility, this paper presents an interpreter of BPMN process models based on dynamic data structures. The proposed interpreter is embedded in a business process execution system with a modular multi-layered architecture, supporting the creation, execution, monitoring and dynamic update of process instances. For efficiency purposes, the interpreter relies on compact bitmap-based encodings of process models. An experimental evaluation shows that the proposed interpreted approach achieves comparable or lower costs relative to existing compiled approaches.
El blockchain i el smart contract són dos tecnologies emergents, independents entre elles, que estan adoptant cada volta més protagonisme i rellevància social. Aquest article fa una aproximació a ambdues tecnologies des d’una òptica fiscal i tributària. En particular, s’explora la relació de les dos tecnologies amb l’Impost sobre les Transmissions Patrimonials i els Actes Jurídics Documentats, regulat al Text Refós de la Llei de l’Impost sobre Transmissions Patrimonials i Actes Jurídics Documentats i el seu corresponent reglament.
The global Electronic Health Record (EHR) market is growing dramatically and expected to reach $39.7 billions by 2022. To safe-guard security and privacy of EHR, access control is an essential mechanism for managing EHR data. This paper proposes a hybrid architecture to facilitate access control of EHR data by using both blockchain and edge node. Within the architecture, a blockchain-based controller manages identity and access control policies and serves as a tamper-proof log of access events. In addition, off-chain edge nodes store the EHR data and apply policies specified in Abbreviated Language For Authorization (ALFA) to enforce attribute-based access control on EHR data in collaboration with the blockchain-based access control logs. We evaluate the proposed hybrid architecture by utilizing Hyperledger Composer Fabric blockchain to measure the performance of executing smart contracts and ACL policies in terms of transaction processing time and response time against unauthorized data retrieval.
<ns4:p> <ns4:bold>Background:</ns4:bold> Health sector decentralization, defined as the transfer of decision making over health sector resources from a central to a peripheral entity; has been and continues to be a widely adopted health system reforms in many low and middle-income countries (LMICs). However, its reported effects have been varied. Nevertheless, decentralization reforms aimed at providing public hospital management autonomy are increasing in prevalence in many LMICs. The range and form of this autonomy because of these reforms has often produced mixed effects. We set out to understand the range of financial management autonomy that has been granted to public hospitals in decentralized health systems in LMICs, and what forms of accountability arrangements have been used to facilitate this autonomy. </ns4:p> <ns4:p> <ns4:bold>Methods:</ns4:bold> We systematically searched PubMed, Google Scholar, Web of Science and CINAHL databases for published articles on this subject. We only included articles that reported empirical findings on hospital level financing and financial management in the context of decentralization in LMICs and/or those that included findings on hospital level finance management accountability arrangements. After a systematic search we found four articles that met our inclusion criteria. We undertook a thematic synthesis of the data and narrative reporting of our findings. </ns4:p> <ns4:p> <ns4:bold>Results:</ns4:bold> From the review – we find that decentralization reforms did not result in improved funding flows, finance management autonomy or accountability mechanisms and for public hospitals. These outcomes were irrespective of the mode and form of decentralization reform adopted. </ns4:p> <ns4:p> <ns4:bold>Conclusion:</ns4:bold> From our review, it is evident that though health sector decentralization reforms have been widely promoted and adopted in the past few decades across LMICs, there is minimal evidence that these reforms have improved funding flows to public hospitals, improved financial management autonomy or accountability mechanisms; so as to enhance the performance of these hospitals at sub-national level. </ns4:p>
Niclas Kannengießer, Sebastian Lins, Tobias Dehling, Ali Sunyaev
When developing peer-to-peer applications on distributed ledger technology (DLT), a crucial decision is the selection of a suitable DLT design (e.g., Ethereum), because it is hard to change the underlying DLT design post hoc. To facilitate the selection of suitable DLT designs, we review DLT characteristics and identify trade-offs between them. Furthermore, we assess how DLT designs account for these trade-offs and we develop archetypes for DLT designs that cater to specific requirements of applications on DLT. The main purpose of our article is to introduce scientific and practical audiences to the intricacies of DLT designs and to support development of viable applications on DLT.
Blockchains have attracted a great deal of attention as a technology for the distributed management of register information at multiple nodes without a centralized system. However, they possess the drawbacks of low transaction throughput and long approval time. These problems can be addressed by shortening the block generation interval; however, shortening this interval alone has the effect of increasing the frequency of forks. In this study, we aim to shorten the block generation interval without increasing the fork generation rate by improving the network topology of the nodes and shortening the propagation time. We propose a neighbor node selection method forming a network topology with a short block propagation time. A blockchain simulator is used to demonstrate the effect of the proposed neighbor node selection method on the propagation delay of the network. This result indicates that the proposed method improves block propagation time.