Christopher Natoli, Jiangshan Yu, Vincent Gramoli, Paulo Verı́ssimo
It is no exaggeration to say that since the introduction of Bitcoin, blockchains have become a disruptive technology that has shaken the world. However, the rising popularity of the paradigm has led to a flurry of proposals addressing variations and/or trying to solve problems stemming from the initial specification. This added considerable complexity to the current blockchain ecosystems, amplified by the absence of detail in many accompanying blockchain whitepapers. Through this paper, we set out to explain blockchains in a simple way, taming that complexity through the deconstruction of the blockchain into three simple, critical components common to all known systems: membership selection, consensus mechanism and structure. We propose an evaluation framework with insight into system models, desired properties and analysis criteria, using the decoupled components as criteria. We use this framework to provide clear and intuitive overviews of the design principles behind the analyzed systems and the properties achieved. We hope our effort will help clarifying the current state of blockchain proposals and provide directions to the analysis of future proposals.
Mohamad Kassab, Joanna F. DeFranco, Tarek Malas, Phillip A. Laplante · 6 authors
Healthcare is a data-intensive domain, once a considerable volume of data is daily to monitoring patients, managing clinical research, producing medical records, and processing medical insurance claims. While the focus of applications of blockchain in practice has been to build distributed ledgers involving virtual tokens, the impetus of this emerging technology has now extended to the medical domain. With the increased popularity, it is crucial to study how this technology accompanied with a system for smart contracts can support and challenge the healthcare domain for all interrelated actors (patients, physicians, insurance companies, regulators) and involved assets (e.g., patients’ data, physician’s data, equipment’s and drug’s supply chain, etc.). The contributions of this paper are the following: (i) report the results of a systematic literature review conducted to identify, extract, evaluate and synthesize the studies on the symbiosis of blockchain in healthcare; (ii) summarize and categorize existing benefits/challenges on incorporating blockchain in healthcare domain; (iii) provide a framework that will facilitate new research activities; and (iv) establish the state of evidence with in-depth assessment.
Purathani Praitheeshan, Lei Pan, Jiangshan Yu, Joseph K. Liu · 5 authors
Smart contracts are software programs featuring both traditional applications\nand distributed data storage on blockchains. Ethereum is a prominent blockchain\nplatform with the support of smart contracts. The smart contracts act as\nautonomous agents in critical decentralized applications and hold a significant\namount of cryptocurrency to perform trusted transactions and agreements.\nMillions of dollars as part of the assets held by the smart contracts were\nstolen or frozen through the notorious attacks just between 2016 and 2018, such\nas the DAO attack, Parity Multi-Sig Wallet attack, and the integer\nunderflow/overflow attacks. These attacks were caused by a combination of\ntechnical flaws in designing and implementing software codes. However, many\nmore vulnerabilities of less severity are to be discovered because of the\nscripting natures of the Solidity language and the non-updateable feature of\nblockchains. Hence, we surveyed 16 security vulnerabilities in smart contract\nprograms, and some vulnerabilities do not have a proper solution. This survey\naims to identify the key vulnerabilities in smart contracts on Ethereum in the\nperspectives of their internal mechanisms and software security\nvulnerabilities. By correlating 16 Ethereum vulnerabilities and 19 software\nsecurity issues, we predict that many attacks are yet to be exploited. And we\nhave explored many software tools to detect the security vulnerabilities of\nsmart contracts in terms of static analysis, dynamic analysis, and formal\nverification. This survey presents the security problems in smart contracts\ntogether with the available analysis tools and the detection methods. We also\ninvestigated the limitations of the tools or analysis methods with respect to\nthe identified security vulnerabilities of the smart contracts.\n
Summary In this paper, we analyze the Ethereum blockchain using the complex networks modeling framework. Accounts acting on the blockchain are represented as nodes, while the interactions among these accounts, recorded on the blockchain, are treated as links in the network. Using this representation, it is possible to derive interesting mathematical characteristics that improve the understanding of the actual interactions happening in the blockchain. Not only, by looking at the history of the blockchain, it is possible to verify if radical changes in the blockchain evolution happened.
One of the most striking financial developments of the last five years involves the emergence and rapid adoption of digital currencies, with Bitcoin being the most prominent. This paper seeks to determine whether there is evidence of collusion between mining pools (coalitions of individuals that verify transactions for monetary returns). We first constructed a theoretical framework which modeled the mining activity as an infinitely repeated game between two competing pools. By devising payoffs in the form of value functions and applying the one shot deviation principle, we found that a collusive strategy was indeed an equilibrium–if certain conditions held. However, our empirical analysis offered more ambiguous results. Ultimately, our attempt to capture peer effects suggests the relationship between a mining pool and its competitors is negative and non-linear. While this could serve as evidence against collusive behavior, we also postulate alternate explanations that could account for the finding.
Abstract South Korea invests a budget of trillions in national R&D projects every year, and has achieved excellent performance doing so each year. However, since the projects are planned, evaluated, and managed by different departments and institutions, duplicate planning and submission leads to insufficient sharing of research results. Currently, the National Technology Information Service (NTIS) inspects project duplication based on keywords, which leads to duplicate planning among departments and closed management of research results. Since the NTIS builds in centralized systems, the inspection systems supports one-way management for duplication checking and information sharing. Therefore, we propose a new platform, called the Trusted Information Project Platform (TIP-Platform), for easily checking for project duplication, sharing research results, and updating research results. TIP-Platform adopts a new concept for user authority setting, the distributed ledger structure, transaction structure, and service. For the adaption, the TIP-Platform uses blockchain technology that performs recording and management via blocks by distributing the right to record and managing transactions. This platform makes it easy for anyone to view and use project-related information such as research results and duplication review. In this paper, we describe how the TIP-Platform can achieve excellent research results through information sharing of a project. This platform needs to be based on trust, because it shares information and continually updates information.
Although Bitcoin is mostly used as a decentralized application to transfer cryptocurrency, over the last ten years there have been several studies on how to exploit Bitcoin to execute smart contracts. These are computer protocols which allow users to exchange bitcoins according to complex pre-agreed rules. Some of these studies introduce formal models of Bitcoin contracts, which specify their behaviour in non-ambiguous terms, in some cases providing tools to automatically verify relevant contract properties. In this paper we survey the formal models proposed in the scientific literature, comparing their expressiveness and applicability in the wild.
Public Key Infrastructure (PKI) is used in Blockchain Technology to authenticate the entities and to ensure the integrity of the blockchain. Proper Protection of Bitcoin wallet is required for private keys, seeds and keys stored in external hardware in Blockchain infrastructure. In this paper, overview of Blockchain, analysis of existing PKI for Blockchain and key management for Blockchain wallet are discussed. To achieve the confidentiality of sensitive records over the Blockchain network, a Group Key Management scheme for secure group communication is also proposed.
The emerging parallel chain protocols represent a breakthrough to address the scalability of blockchain. By composing multiple parallel chain instances, the whole systems' throughput can approach the network capacity. How to coordinate different chains' blocks and to construct them into a global ordering is critical to the performance of parallel chain protocol. However, the existed solutions use either the global synchronization clock with the single-chain bottleneck or pre-defined ordering sequences with distortion of blocks' causality to order blocks. In addition, the prior ordering methods rely on that honest participants faithfully follow the ordering protocol, but remain silent for any denial of ordering (DoR) attack. On the other hand, the conflicting transactions included into the global block sequence will make Simple Payment Verification (SPV) difficult. Clients usually need to store a full record of transactions to distinguish the conflictions and tell whether transactions are confirmed. However, the requirement for a full record will greatly hinder blockchains' application, especially for mobile scenarios. In this technical report, we propose Eunomia, which leverages logical clock and fine-grained UTXO sharding to realize a simple, efficient, secure and permissionless parallel chain protocol. By observing the characteristics of the parallel chain, we find the blocks ordering issue in parallel chain has many similarities with the event ordering in the distributed system. Eunomia thus adopts "virtual" logical clock, which is optimized to have the minimum protocol overhead and runs in a distributed way. In addition, Eunomia combines the mining incentive with block ordering, providing incentive compatibility against DoR attack. What's more, the fine-grained UTXO sharding does well solve the conflicting transactions in parallel chain and is shown to be SPV-friendly.
A. Shamila Ebenezer, S. Jebapriya, Jefferson Raja Bose
The main objective of this paper is to analyze the characteristics and features that affects the fluctuations of cryptocurrency prices and to develop aninteractive cryptocurrencychatbot for providing the predictive analysis of cryptocurrency prices. The chatbot is developed using IBM Watson assistant service. The predictive analytics is performed by analyzing the datasets of various cryptocurrencies and applying appropriate time series models. Time Series Forecasting is used for predicting the future values of the prices. Predictive models like ARIMA model is used for calculating the mean squared error of the fitted model. Facebook’s package prophet () which implements a procedure for forecasting time series data based on an additive model where non-linear trends are fit with yearly and weekly seasonality are further used to predict cryptocurrency prices.
Vicenta Inmaculada Aveiga Macay, José Ponce Figueroa Ponce Figueroa
El acoso sexual laboral es una forma de violencia que provoca discriminación y desigualdad sin enfoque de género en las organizaciones laborales, provocando un ambiente intimidatorio, discrepante, degradante e humillante para los servidores de una institución. El objetivo de este artículo fue sistematizar los fundamentos teóricos que sustentan la Intervención del Trabajador Social en la problemática de acoso sexual laboral, el método utilizado fue la investigación documental permitiendo indagar fuentes secundarias accesibles. Además se exponen los principales resultados de un estudio cualitativo y cuantitativo que evidenció la existencia de esta problemática en el Gobierno Autónomo Descentralizado Municipal del Cantón Jipijapa. PALABRAS CLAVE: acoso sexual laboral; violencia de género; intervención; trabajo social. A PROBLEM OF INTERVENTION OF THE SOCIAL WORKER: LABOR SEXUAL HARASSMENT ABSTRACT Workplace sexual harassment is a form of violence that causes discrimination and inequality without a gender focus in labor organizations, causing an intimidating, discrepant, degrading and humiliating environment for the servants of an institution. The objective of this article was to systematize the theoretical foundations that underpin the Social Worker Intervention in the problem of labor sexual harassment; the method used was documentary research allowing investigating accessible secondary sources. In addition, the main results of a qualitative and quantitative study that evidenced the existence of this problem in the Municipal Decentralized Autonomous Government of the Jipijapa Canton are presented. KEYWORDS: labor sexual harassment; gender violence; intervention; social work.
This paper investigates the level of liquidity of digital currencies during the very intense bearish phase in their markets. The data employed span the period from April 2018 until January 2019, which is the second phase of bearish times with almost constant decreases. The Amihud’s illiquidity ratio is employed in order to measure the liquidity of these digital assets. Findings indicate that the most popular cryptocurrencies exhibit higher levels of liquidity during stressed periods. Thereby, it is revealed that investors’ preferences for trading during highly risky times are favorable for well-known virtual currencies in the detriment of less-known ones. This enhances findings of relevant literature about strong and persistent positive or negative herding behavior of investors based on Bitcoin, Ethereum and highly-capitalized cryptocurrencies in general. Notably though, a tendency towards investing in the TrueUSD stablecoin has also emerged.
Sofia Belikovetsky, Oded Leiba, Asaf Shabtai, Yuval Elovici
Additive manufacturing (AM), or 3D printing, is an emerging manufacturing technology that is expected to have far-reaching socioeconomic, environmental, and geopolitical implications. As the use of this technology increases, the need for validation of 3D designs grows. In order to create a marketplace in which 3D designs are traded, it is necessary to develop a platform that enables the attestation of the 3D designs and promotes truthfulness. In this paper, we introduce a novel concept of a distributed marketplace that will support the attestation of 3D printing designs. We build a mathematical trust model that ensures truthfulness among rational, selfish, and independent agents, which is based on a reward/penalty system. The payment for participating in the evaluation is calculated by factoring in agents' reputation and peer feedback. Moreover, we describe the architecture and the implementation of the trust model on blockchain using smart contracts for the creation of a distributed marketplace. Our model relies both on theoretical and practical best practices to create an unique platform that elicit effort and truthfulness from the participants.
Blockchain technology can be used to solve many educational problems and can help educators as well as learners to monitor the learning outcomes. The data can be stored securely and tamper proof format when it's stored onto the blockchain network. The Blockchain for Education platform helps us to make the tamper-proof certificates and their correct and the overall permanent allocation of these certificates to learners, as well as verification of certificates. It can reduce the overall frauds and tampering of the degrees and certificates. Here smart contracts can be designed and deployed on to the Ethereum blockchain that can be designed using the solidity programming language. Blockchain can be applied to private, public and consortium sectors depending upon the usage and the scope of the blockchain. Education system can take benefit of this scalability of the blockchain and can be effectively useful in the
In the highly connected age of information and data, the push for the development of ‘clean data’ has necessitated sustainability strategies for data centers. Green innovations are increasingly implemented to reduce the formidable power consumption of inefficient computing processes while heat reuse solutions repurpose the large volumes of server waste heat, decreasing facility footprint. This project examined the efficiency optimization potential of co-located power generation and greenhouse waste heat reuse for cryptocurrency data center platforms in Alberta. The proposed 45 MW data center capitalized on favorable climatic conditions to reduce energy requirements, improving facility efficiency and decreasing theoretical PUE values from 2.13 to 1.51. Resultant waste heat sufficiently supplied year-round heating to an 8.34-acre greenhouse suitable for commercial cannabis growth. The total annual avoided emissions for this proposed system were calculated at 70,000 tonnes of CO2, illustrating the potential of integrated economizer cyles and waste heat reuse in Alberta.
Nazmiye Ceren Abay, Cüneyt Gürcan Akçora, Yulia R. Gel, Murat Kantarcıoğlu · 7 authors
With emergence of blockchain technologies and the associated cryptocurrencies, such as Bitcoin, understanding network dynamics behind Blockchain graphs has become a rapidly evolving research direction. Unlike other financial networks, such as stock and currency trading, blockchain based cryptocurrencies have the entire transaction graph accessible to the public (i.e., all transactions can be downloaded and analyzed). A natural question is then to ask whether the dynamics of the transaction graph impacts the price of the underlying cryptocurrency. We show that standard graph features such as degree distribution of the transaction graph may not be sufficient to capture network dynamics and its potential impact on fluctuations of Bitcoin price. In contrast, the new graph associated topological features computed using the tools of persistent homology, are found to exhibit a high utility for predicting Bitcoin price dynamics. %explain higher order interactions among the nodes in Blockchain graphs and can be used to build much more accurate price prediction models. Using the proposed persistent homology-based techniques, we offer a new elegant, easily extendable and computationally light approach for graph representation learning on Blockchain.
Fatemeh MohammadZadeh, Seyed Ali Mirghasemi, Ali Dorri, HamidReza Ahmadifar
Smart cities are growing significantly due to the growth of smart connected vehicles and Internet of Things (IoT) where a wide range of devices are connected to share data. Online mapping is one of the fundamental services offered in smart cities which enables the vehicle owners to find shortest or fastest direction toward a destination thus reduces travel cost and air pollution. However, existing online mapping services rely on centralized servers, e.g., Google, which collect data from users to offer service. This method is unlikely to scale with growth in the smart city participants and introduces privacy concerns and data wall where data of the users is managed by big companies. To address these challenges, in this paper we introduce DMap, a blockchain-based platform where the users can share data in an anonymous distributed manner with service providers. To the best of our knowledge, DMap is the first distributed blockchain-based solution for online mapping. To improve the scalability of the blockchain, we propose to use edge-computing along with blockchain. To protect against malicious vehicles that may inject false data, we define a reputation system where the collected data of the vehicles is verified by monitoring the neighbor data. We introduce data marketplace where users can trade their data to address data wall challenge.
Zhaoming Yin, Anbang Ruan, Ming Wei, Huafeng Li · 9 authors
To achieve high throughput in the POW based blockchain systems, researchers proposed a series of methods, and DAG is one of the most active and promising fields. We designed and implemented the StreamNet, aiming to engineer a scalable and endurable DAG system. When attaching a new block in the DAG, only two tips are selected. One is the parent tip whose definition is the same as in Conflux[1]; another is using Markov Chain Monte Carlo (MCMC) technique by which the definition is the same as IOTA [2]. We infer a pivotal chain along the path of each epoch in the graph, and a total order of the graph could be calculated without a centralized authority. To scale up, we leveraged the graph streaming property; high transaction validation speed will be achieved even if the DAG is growing. To scale out, we designed the direct signal gossip protocol to help disseminate block updates in the network, such that messages can be passed in the network more efficiently. We implemented our system based on IOTA's reference code (IRI) and ran comprehensive experiments over the different sizes of clusters of multiple network topologies.
The concept of a blockchain has given way to the development of cryptocurrencies, enabled smart contracts, and unlocked a plethora of other disruptive technologies. But, beyond its use case in cryptocurrencies, and in network coordination and automation, blockchain technology may have serious sociotechnical implications in the future co-existence of robots and humans. Motivated by the recent explosion of interest around blockchains, and our extensive work on open-source blockchain technology and its integration into robotics - this paper provides insights in ways in which blockchains and other decentralized technologies can impact our interactions with robot agents and the social integration of robots into human society.
This paper presents a new consensus protocol based on verifiable delay function. First, we introduce the concept of verifiable delay puzzle (VDP), which resembles the hashing puzzle used in the PoW mechanism but can only be solved sequentially. We then present a VDP implementation based on the continuous verifiable delay function. Further, we show that VDP can be combined with the Nakamoto consensus in a proof-of-stake/proof-of-delay hybrid protocol. We analyze the persistence and liveness of the protocol, and show that compared to PoW, our proposal consumes much less energy; compared to BFT leader-election based consensus algorithms, our proposal achieves better resistance to long-range attacks and DoS attacks targeting the block proposers.