China initiated a major decentralization reform in recent years to simultaneously improve tax autonomy and fiscal transfers toward county governments. We use an instrumental variables strategy and a county-level panel dataset for years 1995-2014 to examine the incentive effects of the reform. We find that the reform significantly reduced tax enforcement of the county governments, for which the result appears to be driven by the opposing incentive effects of the increased local tax autonomy and fiscal transfers. In particular, while the reform motivated county governments to improve tax enforcement by enhancing local tax autonomy, it dampened local tax enforcement because of the increased fiscal transfers. Our findings provide support to the argument in the decentralization literature that improving local tax autonomy, compared to increasing fiscal transfers, is a more effective way to finance local governments while strengthening local fiscal discipline.
In this article, we study ongoing blockchain and distributed ledger technologies (DLT) standardization. To this end, we list standards organizations and the efforts they devote to standardise blockchain and DLT. We then identify a lack of terminology that can hamper communication on this topic and propose clarifications to address these ambiguities. Finally, we propose a high-level description of blockchain and DLT by describing three elements of their functional architecture.
In the Bitcoin blockchain, rewarding methods for remunerating miners participating in a pool have to meet certain requirements in order to guarantee the proper functioning of the cryptocurrency ecosystem. In particular, these allocation rules reward pool participants in proportion to their contribution in the transaction validation process. Deployed rewarding methods met fairness concerns at the expense of vulnerability to miners exploiting pools' attractiveness for deciding when to mine for a pool and when to `hop' to another one resulting more attractive: a phenomenon called pool-hopping. The most used score-based methods are designed to prevent this practice, but are not completely hopping proof. In this work, we propose a methodology to analyze the pool-hopping phenomenon, focusing on the detection of pool-hoppers. Analyzing those Bitcoin transactions that pools create for rewarding its participants, it is possible to determine time epochs where miners worked. Thus, we analyze those miners that have worked intermittently for pools adopting a rewarding system which pays out for each validated block. This evaluation leads us qualifying the miners that have hopped along with their hopping behavior and financial performance.
Kristián Košťál, Tomáš Krupa, Martin Gembec, Igor Veres · 6 authors
This article is focused on the area of energy efficiency of cryptocurrencies. Nowadays, nearly two thirds of all cryptocurrencies use Proof of Work (PoW) consensus algorithm to add new blocks to blockchain network. The energy sustainability of whole networks using PoW algorithm is very doubtful. Furthermore, we can see that lots of cryptocurrencies are trying to implement and move to more efficient consensus algorithms like Proof of Stake (PoS). Therefore, in this article we present three potential scenarios to perform transition between PoW and PoS.
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
One of the ways in which a city can become smarter is to grow a local economy around the sharing of data from IoT devices and other open data that can be used in applications to improve the lives of its citizens. Prior work and ongoing projects have examined or are currently focused on the development of centralized data marketplaces for smart cities. Here we explore how a decentralized data marketplace could be created using blockchain and other distributed ledger technologies. We consider the possible benefits of such a decentralized architecture, identify different elements that such a decentralized marketplace should have, and show how they could be potentially integrated into a comprehensive solution. We also present a simple smart contract implementation of a decentralized registry where data products can be posted by data owners for retrieval by potential buyers.
Recently, the global outbreak of a blackmail virus WannaCry, makes the blockchain a hot topic. The security of blockchain is always the focus of people's attention, and it is also the main reason why the blockchain has not been widely used all over the world. Many researches use mathematical derivation method to analyse the 51%- Attacks influence of blockchain, which is very stiff and difficult to understand. In this paper, we propose a method to simulate blockchain's process and discover the rule between attacking method, attacking power and security of blockchain. We take 51%-Attacks as an example and use Java to simulate the running process. By adjusting the value of attacking power, we can get most states of blockchain and analyze the probability that honest state becomes attacking state. We use various forms to analyze and show the experimental result, which verify our method is correct and feasible. This method can also be implemented as a middleware software of blockchain to detect the security of blockchain.
With the promotion of power energy market reform, it has been a trend to allow distributed energy agents and other multi-subject agents to participate in the market competition. However, due to the existing power market mechanism is designed according to the centralized power supply mode, the public services, power market transaction mechanism and government management system for distributed energy transaction is still more missing. The blockchain technology has the characteristics of decentralization, transparency, fairness, openness and so on. Under the background of the transactive energy system, a decentralized distributed energy transaction mechanism based on blockchain smart contract technology is proposed, which includes auditing, bidding, clearing and settlement. It realizes P2P energy trading among prosumers.
Bitcoin is a digital currency that has enticed considerable recognition as an alternative solution to the traditional payment system. Its success is mostly due to the use of Blockchain over a decentralised peer-to-peer network. Today's Bitcoin network has more than 10,000 online peers geographically scattered around the world. However, its topology is still unknown due to security concerns. In this paper, we design and implement a fast and efficient framework named BTCmap to discover and map the Bitcoin network topology. Our BTCmap framework includes two modules viz., a sniffer to collect the local addresses database of each peer, and a Bitcoin peer emulator to select neighbours and generate the topology. Our analyses show that to remain within 1% confidence interval, we have a window of 56 minutes 40 seconds for collecting the local address databases from all peers. Within this time duration, BTCmap requests more than 8200 reachable peers to map the real Bitcoin network topology. We present a Bitcoin topology snapshot captured on June 14, 2018, 15:53 CEST and show that this snapshot is connected.
Health-related data analysis plays an important role in self-knowledge, disease prevention, diagnosis, and quality of life assessment. With the advent of data-driven solutions, a myriad of apps and Internet of Things (IoT) devices (wearables, home-medical sensors, etc) facilitates data collection and provide cloud storage with a central administration. More recently, blockchain and other distributed ledgers became available as alternative storage options based on decentralised organisation systems. We bring attention to the human data bleeding problem and argue that neither centralised nor decentralised system organisations are a magic bullet for data-driven innovation if individual, community and societal values are ignored. The motivation for this position paper is to elaborate on strategies to protect privacy as well as to encourage data sharing and support open data without requiring a complex access protocol for researchers. Our main contribution is to outline the design of a self-regulated Open Health Archive (OHA) system with focus on quality of life (QoL) data.
Pilar Grau Carles, Diego Jaureguizar Arellano, Carlos Jaureguizar Francés
In this paper we examine the characteristics of the daily price series of 16 different cryptocurrencies between July 2017 and February 2018. The methodologies used for the analysis are the so-called Minimum Spanning Tree (MST) and hierarchical analysis by dendrogram, both obtained Pearson correlations between daily returns. This methodology visualizes the market relationships between the assets analyzed, identifying a high correlation between price movements for all the currencies. In addition, it has been possible to identify Ethereum’s position as a benchmark currency in the cryptocurrency market, rather than Bitcoin, as one might expect, due to its popularity and trading volume.
Alin Bogdan Popa, Ioan Mihail Stan, Răzvan Rughiniş
Blockchain is one of the most important technological trends today since it has a wide spectrum of use cases (financial industry applications, supply-chain tracking, MedTech EHR management, energy grid etc.) and it offers a wide range of implementations. However, the main goal of the Blockchain remains the transfer of value-bearing assets between an owner of a resource and a client. Due to CPU intensive consensus algorithms, transaction prioritization based on potential earnings, the validation process and so on, Blockchain implementations are not able to support real-time services and, also, to enable a varied cloud computing service catalog on top of the existing infrastructure. Our solution is addressing this drawback by developing a system supporting late payments through our innovative concept called latent-transactions. We also provide the instruments through which we make viable off-chain agreements, between the parties involved in a transaction. Therefore, one can benefit from a service, prior to actual payment. In addition, we offer a service enlargement mechanism by providing a catalog where any member of Blockchain can subscribe and from where one can sell services in a real-time manner with adaptive pricing, based on the context (demand, activity at runtime etc.).
Machine Learning is part of Artificial Intelligence that has the ability to make future forecastings based on the previous experience. Methods has been proposed to construct models including machine learning algorithms such as Neural Networks (NN), Support Vector Machines (SVM) and Deep Learning. This paper presents a comparative performance of Machine Learning algorithms for cryptocurrency forecasting. Specifically, this paper concentrates on forecasting of time series data. SVM has several advantages over the other models in forecasting, and previous research revealed that SVM provides a result that is almost or close to actual result yet also improve the accuracy of the result itself. However, recent research has showed that due to small range of samples and data manipulation by inadequate evidence and professional analyzers, overall status and accuracy rate of the forecasting needs to be improved in further studies. Thus, advanced research on the accuracy rate of the forecasted price has to be done.
Miguel Tavares, André Guerreiro, Carlos Coutinho, Filipe Veiga · 5 authors
Businesses and organizations have for long been trying to tackle the most prominent issues regarding identity management and systems. Traditionally, the proof of trust concerning the identification of a citizen, a customer or a participant in any business or transaction consisted always in a physical evidence (e.g., a signature, fingerprint, photo or other) whose value would rely on a trusted third-party such as a notary or attorney that confirmed the veracity of that physical evidence. More recent approaches include novel types of evidence such as digital certificates, but still these have no value unless they are issued and signed by a trusted centralized third-party that confirms the authenticity of the certificate. These are then often used by businesses to identify and trace their parties and stakeholders, in a process known as "Know Your Customer" (KYC). This process is often slow and requires costly human intervention. This paper presents WalliD, a decentralized approach of a secure protocol to handle customer identification using Blockchain. The paper then shows a proof of concept workflow implementation of this protocol developed using an Ethereum Wallet.
Cryptocurrency mining is an important process that ensures the reliability of cryptocurrency system. A significant computing power is used in cryptocurrency mining. One of the most important tasks in cryptocurrency mining is to ensure the maximum performance of used computing capacities. In this paper we review the existing Ethereum mining algorithm and search for possibilities for speeding up the mining by applying a new asynchronous mining algorithm.
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Xiaochen Zheng, Raghava Rao Mukkamala, Ravi Vatrapu, Joaqun Ordieres-Mere
With the advent of rapid development of wearable technology and mobile computing, huge amount of personal health-related data is being generated and accumulated on continuous basis at every moment. These personal datasets contain valuable information and they belong to and asset of the individual users, hence should be owned and controlled by themselves. Currently most of such datasets are stored and controlled by different service providers and this centralised data storage brings challenges of data security and hinders the data sharing. These personal health data are valuable resources for healthcare research and commercial projects. In this research work, we propose a conceptual design for sharing personal continuous-dynamic health data using blockchain technology supplemented by cloud storage to share the health-related information in a secure and transparent manner. Besides, we also introduce a data quality inspection module based on machine learning techniques to have control over data quality. The primary goal of the proposed system is to enable users to own, control and share their personal health data securely, in a General Data Protection Regulation (GDPR) compliant way to get benefit from their personal datasets. It also provides an efficient way for researchers and commercial data consumers to collect high quality personal health data for research and commercial purposes.
Blockchain is so far well-known for its potential applications in financial and banking sectors. However, blockchain as a decentralized and distributed technology can be utilized as a powerful tool for immense daily life applications. Healthcare is one of the prominent applications area among others where blockchain is supposed to make a strong impact. It is generating wide range of opportunities and possibilities in current healthcare systems. Therefore, this paper is all about exploring the potential applications of blockchain technology in current healthcare systems and highlights the most important requirements to fulfill the need of such systems such as trustless and transparent healthcare systems. In addition, this work also presents the challenges and obstacles needed to resolve before the successful adoption of blockchain technology in healthcare systems. Furthermore, we introduce the smart contract for blockchain based healthcare systems which is key for defining the pre-defined agreements among various involved stakeholders.
S. P. Novikov, Олег Казаков, Н. А. Кулагина, Natalya Y. Azarenko
The blockchain typically described as a decentralized system in which transactional or ancient statistics are recorded, stored, and maintained throughout a peer-to-peer community of personal computers referred to as nodes. Counterfeit drugs are one consequence of such limitations within existing supply chains, which not only has serious adverse impact on human health but also causes severe economic loss to the healthcare industry. Blockchain technology has gained tremendous attention, with an escalating hobby in a plethora of several applications like safe and relaxed healthcare records management. Similarly, blockchain is reforming the traditional healthcare practices to an extra reliable means, in phrases of powerful progno- sis and treatment through safe and cosy facts sharing using SHA Hash Generation Algorithm. Within the future, blockchain will be an era that can probably assist in personalized, authentic, and at ease healthcare by means of merging the entire actual-time scientific information of a patient’s fitness and offering it in an up to date cosy healthcare setup. In this paper, we evaluation each the present and modern day trends inside the subject of healthcare with the aid of imposing blockchain as a model. We also talk the packages of blockchain, at the side of the demanding situations confronted and destiny views. The proposed system executed blockchain implementation in distributed computing surroundings and it gives the automated restoration of invalid chain by using Consensus and Mining Algorithm. In this system, we present a Custom blockchain- based approach leveraging smart contracts and decentralized off-chain storage for efficient product traceability in the healthcare supply chain. The smart contract guarantees data provenance, eliminates the need for intermediaries and provides a secure, immutable history of transactions to all stakeholders. We present the system architecture and detailed algorithms that govern the working principles of our proposed solution. We perform testing and validation, and present cost and security analysis of the system to evaluate its effectiveness to enhance trace- ability within pharmaceutical supply chains. Keywords— Blockchain Technology, Decentralization / Decentralized System, Distributed Com- puting, Peer-to- Peer Network, Healthcare, Supply chains, etc.
Smart contracts enable autonomous decentralized organizations (DADs) in large, trustless and open trading networks by specifying conditions for automated transactions of cryptographically secured data. This data could represent cryptocurrencies but also sensor data or commands to Cyber-Physical Systems (CPS) connected to the Internet. To provide reliability, the contract code is enforced by consensus and the transactions it triggers are nonrevertible, even if they were not intended by the programmer, which could lead to dangerous system behavior. In this paper, we conduct a survey over existing smart contract platforms and languages to determine requirements for the design of a safer contract language. Subsequently we propose concepts that enhance the understanding of code by limiting confusing language constructs, such as nesting, arbitrary naming of operations, and unreadable hash identifiers. This enables human reasoning about the contract semantics on a much higher abstraction layer, because a common understanding can be derived from the language specification itself. We implement these concepts in a new domain specific language called SmaCoNat to illustrate the feasibility and show that our concepts are barely covered by existing languages but significantly enhance readability and safety without violating deterministic parsability.
In the world of technology, change is the only constant. As soon as people start adapting to a new invention, another innovation starts paving its way into people's lives. Each change in technology brings in new and improved devices. Old devices are replaced and abandoned. Such Electronic and Electrical Equipments (EEEs) that are discarded by users are termed as e-waste. Management of e-waste includes proper collection, segregation and recycling of discarded devices in an environment friendly manner. The volume of EEEs that is produced throughout the world, has led governments in various countries to create strict policies, to ensure efficient disposal of the generated e-waste. The Indian government also upgraded its E-Waste Management (EWM) laws in 2016 and 2018. These laws are a step towards environment friendly disposal of e-waste but their compliance is still at a nascent stage. Even today, e-waste collection and recycling in India is largely dominated by the unorganized sector, which makes the enforcement of such laws very difficult. In this paper, we propose a novel approach for EWM using blockchain based smart contracts. Blockchain is the technology that enables us to write smart contracts. Smart contracts are self-executing computer codes that take specified actions when certain conditions are met in the real world. EWM using smart contracts will bring more coordination among producers, importers, retailers and recyclers of EEEs. It will enable the government to regulate e-waste collection and recycling. It will also reduce the imbalance between the organized and unorganized sectors which will lead to increased transparency throughout the process.
Cryptocurrencies are often thought to operate out of the reach of national regulation, but in fact their valuations, transaction volumes and user bases react substantially to news about regulatory actions. The impact depends on the specific regulatory category to which the news relates: events related to general bans on cryptocurrencies or to their treatment under securities law have the greatest adverse effect, followed by news on combating money laundering and the financing of terrorism, and on restricting the interoperability of cryptocurrencies with regulated markets. News pointing to the establishment of specific legal frameworks tailored to cryptocurrencies and initial coin offerings coincides with strong market gains. These results suggest that cryptocurrency markets rely on regulated financial institutions to operate and that these markets are segmented across jurisdictions, bringing cryptocurrencies within reach of national regulation.
This paper tackles the shortcomings of the traditional centralized stock exchange systems, such as high transaction fees, centralized governance susceptible to attacks and lack of openness regarding the market actions and algorithms, by proposing an innovative architecture using blockchain to develop a decentralized stock exchange and an open continuous market. The proposed blockchain based solution solves the drawbacks of the centralized stock exchange architecture by ensuring the integrity and security of the owner's assets and orders, self-enforcing smart agreements between parties as well as achieving democratic and reliable decisions regarding the execution and settlement of the orders through consensus algorithms. The proposed architecture uses smart contracts to enforce the validation of the owner's rights and the correct execution and settlement of the orders, thus eliminating the need of a central authority that ensures the correctness of the stock exchange process. The solution was validated by implementing a prototype in Ethereum for a subset of rules for the Bucharest Stock Exchange. The experimental results show that the decentralized solution can offer lower transaction fees by replacing the commissions owed to brokers and central authorities with mining fees that are used to compensate the miners for their honest work in keeping the integrity of the system.
Amjad Aldweesh, Maher Alharby, Ellis Solaiman, Aad van Moorsel
A defining feature of the Ethereum blockchain is its ability to execute smart contracts, providing a Turing complete programming model for distributed applications in non-trusted environments. The successful operation of the Ethereum blockchain depends on whether the miners' incentives (in the form of fees) to execute contracts is proportional to the miners' cost (in terms of energy usage, and thus CPU usage). In general, if the received fee is not proportional to the computational cost, miners would prefer some tasks over others, thus potentially adversely affecting the continuing dependable operation of the blockchain. In this paper we design a benchmark to compare smart contract execution time with the award a miner would receive, to determine if incentives align. We present the design of the benchmarking approach and provide initial results for the Python Ethereum client running on a Mac. The results indicate that for functions in Ethereum's most popular contracts the difference of reward per CPU second can be up to a factor of almost 50. In addition, contract creation, which is done once for each new contract, can be up to 6 times more lucrative than the regular execution of contract functions. Potentially, these discrepancies result in misaligned incentives that impact the dependable operation of the blockchain.
Shalini Shukla, A.N. Thasmiya, Donthi Shashank, H. R. Mamatha
Voting is an important part of the administration of a country. Votes are still being carried out by physically going to voting booths. This process doesn't guarantee security and cases of tampering has been observed. This paper aims at removing these issues in the voting process by making it online and using the technology, Blockchain. Blockchain uses encryption and hashing to make every vote secure. In this case, one vote is considered as a transaction. A peer to peer network is created to create a private blockchain that share this distributed ledger having voting transaction. The application is designed in such a way so that the intricacies of the underlying architecture is hidden from the user. Each voter is uniquely identified by Government approved Aadhar number. The application makes use of this number to make sure that each voter gets only one chance to vote. When the vote gets submitted as a transaction then all the peers get synch up. Since each peer is associated with a public and private key the votes are encrypted and hashed and added to the blockchain to increase security and form a chain of blocks. Votes cannot be tracked back to the voter. In this paper, a peer to peer network is created having minimum three peers. Since voting is made online, it is expected that this paper will increase the voter turnouts. The scalability of the blockchain application depends on the secondary memory limit of the peer.