Open Educational Resources (OER) play a pivotal role in the traditional teaching learning processes. So far, there are several problems in the conventional OER such as tracking and tracing of OER, proper attribution, sustainability, publishing time and single point of failure due to its centralized nature. This paper proposes a Ethereum blockchain based decentralized and distributed framework to alleviate the problems existing in present OER. In addition Interplanetary File System (IPFS) has been included in this proposed system for storing the hypermedia as distributed way. It reduces the storage time. In this paper, we design distributed and decentralized infrastructure for OER system that remedies all of these drawbacks through the use of the Ethereum blockchain platform.
PBFT is a consensus algorithm based on Byzantine fault tolerance that is widely used in current systems like blockchains. However, this algorithm has some problems that slow down its use on a large scale. In the interest of solving its problems, we have combined it with the Distributed Proof of Stake (DPoS) algorithm and smart contract technology to improve it and make it better. For this, Smart contracts were deployed in the network to improve the selection process of accounting nodes and participated in the operating process of the PBFT algorithm in order to make the selection process more transparent, incorruptible, and secure. Concerning the problem of the scalability of the nodes of the system, it will be possible to make a readjustment of the consensus algorithm to make it more flexible. The modification can be done by implementing readjustment counters, which will count the number of nodes in the network each time a consensus is reached or a node is ejected from the network, then automatically distributes the list of new nodes in the network. This new list of nodes will constitute the new network on which the new consensus will be based. To make it more secure and more sensitive to Byzantine faults, the sensitivity margin is improved.
The future of renewable energy transportation and distribution is dynamic and complex, with distributed renewable resources in required distributed control. It is suggested that Distributed Ledger Technology (DLT) is a timely innovation with the potential to facilitate this future. The transition to full renewable energy requires an infrastructure capable of handling intermittent production that has a low marginal cost. This requires a distributed control logic where devices with embedded intelligence coordinate local production, a decentralized energy market where prices are not primarily based on production, and an underlying digital infrastructure to enable both. Simulations and experiments have demonstrated great potential in such a digital infrastructure, but real-life tests have identified scalability as a remaining challenge. In this paper, we propose a DLT-based architecture for the energy grid with the development of existing solution concepts by implementing scalability solutions. To this end, we derive energy market components as a framework for building efficient microgrid. Then, we discuss the microgrid as a case study of such a market according to the required components within energy production, transmission, and distribution; distributed ledger platform operations, IoT device manufacturing,; software development; and research in IoT, edge and cloud computing, and energy systems.
The traditional method of blockchain retrieval is to search the “Block File” in sequence from the “tail” to the “head” of the blockchain, which always takes a lot of time. How to reduce the retrieval time has been a hot issue in blockchain research. This paper proposes a fast retrieval method for the Multi-Transaction Mode Consortium Blockchain (MTMCB). Firstly, we create a “User Set” and “Block Name Set” cached in Redis. Then, according to the transaction participants and “Block Name Set”, we can get the relevant “Block Name List”, and quickly obtain the corresponding block files. On this basis, in order to meet the needs of rapid retrieval in large-scale systems, an improved retrieval algorithm based on a B+-tree data structure is proposed. Firstly, the block file information is put into different ordered sets according to the transaction participants, and the B+-tree index is established to quickly get the information of relevant block files by participants. Experimental results show that the improved method of Redis cache retrieval in this paper can greatly increase the efficiency of blockchain retrieval, and can settle some crucial problem in the blockchain application and popularization.
John Kolb, Moustafa AbdelBaky, Randy H. Katz, David Culler
Blockchains are a topic of immense interest in academia and industry, but their true nature is often obscured by marketing and hype. In this tutorial, we explain the fundamental elements of blockchains. We discuss their ability to achieve availability, consistency, and data integrity as well as their inherent limitations. Using Ethereum as a case study, we describe the inner workings of blockchains in detail before comparing blockchains to traditional distributed systems. In the second part of our tutorial, we discuss the major challenges facing blockchains and summarize ongoing research and commercial offerings that seek to address these challenges.
The properties of a blockchain such as immutability, provenance, and peer-executed smart contracts could bring a new level of security, trust, and transparency to e-learning. In this paper, we introduce our proof-of-concept blockchain-based e-learning platform developed to increase transparency in assessments and facilitate curriculum personalisation in a higher education context. Most notably, our platform could automate assessments and issue credentials. We designed it to be pedagogically neutral and content-neutral in order to showcase the benefits of a blockchain back-end to end users such as students and teaching staff. Our evaluation suggests that our platform could increase trust in online education providers, assessment procedures, education history and credentials.
Kausthav Pratim Kalita, Debojit Boro, Dhruba K. Bhattacharyya
Due to the scalability factor associated with a blockchain, it is inevitable that it will grow with time. Therefore, one of the primary concerns associated with a blockchain is its growing size as more blocks are introduced into the chain. When a full node or a mining node joins a blockchain network, it requires downloading all the existing information available in the distributed chain before it can add new blocks. Thus, as time progresses and more blocks are appended to the chain, a large amount of information needs to be replicated in its local machine. We introduce an approach to keep a minimally shared blockchain in the network which keeps the size of the distributed ledger limited and, thus, new miners can participate in the mining process at a faster pace.
Blockchain as one of the most well-known examples of Distributed Ledger Technology, has been hailed across the industry as the key to future success within the financial services industry. Blockchain is a platform that supports multiple use cases within Financial Services, and it has the ability to transform a number of processes, including peer-to-peer payments, trade settlements and supply chain tracking. All these use cases depend on one thing that's the Identification and Verification of participant or users. That is called as Know Your Customer(KYC). Verification of User is one of the basic thing that establishes trust between the participants before making any of the transactions. Ever-increasing anti-money laundering (AML) regulations, coupled with other data protection regulations have led many financial institutions to implement lengthy, expensive processes in order to remain compliant. This paper provides solution to this problem using Hyperledger Fabric, which is framework under blockchain technology, provides some key features like permissioned network, confidentiality of Data, and Programmable. These features establish trust, transparency and accountability.
This paper presents a new blockchain network simulator that uses bitcoin's original reference implementation as its main application. The proposed simulator leverages the use of lightweight virtualization technology to build a fine tuned local testing network. To enable fast simulation of a large scale network without disabling mining service, the simulator can adjust the bitcoin mining difficulty level to below the default minimum value. In order to assess the performance of blockchain under different network conditions, the simulator allows to define different network topologies, and integrates Linux kernel traffic control (tc) tool to apply distinct delay or packet loss on the network nodes. Moreover, to validate the efficiency of our simulator we conduct a set of experiments and study the impact of the computation power and network delay on the network's consistency in terms of number of forks and mining revenues. The impact of applying different mining difficulty levels is also studied and the block time as well as fork occurrences are evaluated. Furthermore, a comprehensive survey and taxonomy of existing blockchain simulators are provided along with a discussion justifying the need of new simulator. As part of our contribution, we have made the simulator available on Github (https://github.com/noureddinel/core-bitcoin-net-simulator) for the community to use and improve it.
G. A. Pierro, Henrique Rocha, Roberto Tonelli, Sté́phane Ducasse
The Ethereum Blockchain is a distributed database that records all transactions and smart-contracts created on the platform. In Ethereum blockchain, the user needs to set a Gas price to get a transaction recorded. To have the transaction recorded, the Gas price has to be greater than or equal to the lowest Ethereum transaction fees. To help the users and smart contracts to set the right Gas price, the Gas Oracle categorizes the gas price into categories based on the interval of time the user might be willing to wait and for each of them suggests a gas price to set. The paper aims to verify the hypothesis that the predictions made by the EtherGasStation Oracle have a margin of error greater than the margin of error declared by it (2 %). We collected data in two-months time from the EthGasStation Oracle which predict the Gas Price every time that 100 blocks are added to the Ethereum Blockchain. In the same time frame, two-months, we also collected over 10 million transactions from a Transaction Pool. By cross-checking the data collected by the Transaction Pool and the Gas Oracle, the study revealed that the Gas Oracle fails more often than it advertises.
In recent years there are lot of thrills spinning around BLOCKCHAIN technology. Blockchain initially released in 2008 by Satoshi Nakamoto as a fundamental technology for the first ever global decentralized cryptography based digital currency known as BITCOIN. Todays in tech world every person and industry discussing about blockchain, and they feel blockchain technology changed the world like open source software change. Every industry wants to use and explore blockchain technology in different application like trading, supply chain, healthcare etc. Blockchain is a revolutionary technology but the question is from where this technology invented. In this paper author will discuss about distributed ledger technology which is known as parental technology of blockchain. This paper will break the myth that distributed ledger and blockchain both are the same technology, and will tell that every DLT is not blockchain but blockchain is a DLT. This paper presents the comparison of different DLT's and blockchain. In this paper author discuss different type of potential application area where DLT is very helpful. In the end of paper author present future research direction for blockchain and DLT with some challenges.
In many typical application scenarios, it is necessary to revoke the incorrect account operations caused by user mis-operation, financial fraud, illegal hacking, etc. Unfortunately, users often blur the lines between the concept of "transaction state revocable" and "business status revocable", which result in revocable transaction not universally supported in blockchain systems at present. In this work, we propose GateChain , a blockchain that support revocable transaction model (RTM) on distributed ledger. Specifically, based on the state-of-the-art blockchain technologies, GateChain can safely withdraw the account status change operations by leveraging an improved account model and extra designed transaction types. On that basis, GateChain exploit the characteristics of functional completeness, easy to deployment and lower complexity.
Charla Griffy‐Brown, Howard Miller, Vincent Zhao, Demetrios Lazarikos · 5 authors
Emerging technologies such as artificial intelligence, the Internet of Things, and distributed ledger continue to transform businesses, enabling new value creation in transformative ways. Their potential social impacts create risks. These risks are not easily identified or evaluated making it difficult to address them. There are upside and downside risks. Business leaders from companies deploying these technologies are initially interviewed. Development and preliminary testing of three different risk optimization models using scenario analysis data are informed by this information. Using this analysis, we introduce the foundations for a risk model and potentially a dashboard that executives could use to consider these technologies.
Abstract Blockchain and cryptocurrency are a hot topic in today’s digital world. In this paper, we create a game theoretic model in continuous time. We consider a dynamic game model of the bitcoin market, where miners or players use mining systems to mine bitcoin by investing electricity into the mining system. Although this work is motivated by BTC, the work presented can be applicable to other mining systems similar to BTC. We propose three concepts of dynamic game theoretic solutions to the model: Social optimum , Nash equilibrium and myopic Nash equilibrium . Using the model that a player represents a single “miner” or a “mining pool”, we develop novel and interesting results for the cryptocurrency world.
Lin Chen, Lei Xu, Zhimin Gao, Sunny, Ahmed · 6 authors
Recent advances in the blockchain research have been made in two important directions. One is refined resilience analysis utilizing game theory to study the consequences of selfish behaviors of users (miners), and the other is the extension from a linear (chain) structure to a non-linear (graphical) structure for performance improvements, such as IOTA and Graphcoin. The first question that comes to people's minds is what improvements that a blockchain system would see by leveraging these new advances. In this paper, we consider three major metrics for a blockchain system: full verification, scalability, and finality-duration. We { establish a formal framework and} prove that no blockchain system can achieve full verification, high scalability, and low finality-duration simultaneously. We observe that classical blockchain systems like Bitcoin achieves full verification and low finality-duration, Harmony and Ethereum 2.0 achieve low finality-duration and high scalability. As a complementary, we design a non-linear blockchain system that achieves full verification and scalability. We also establish, for the first time, the trade-off between scalability and finality-duration.
The blockchain is seen as a beneficial development for IoT (Internet of Things), as it offers vital answers for a package which can fix security and trust checks, major help expenses, etc. Blockchain's decentralization will be mainly due to the consensus mechanism which awards specific trade during a distributed path without the ties between others. It begins with the basic message of blockchain and explains why the accepted component recognizes a particular career during a blockchainIoT process. Two basic ideas of commended mechanisms such as Proof of Stake (PoS) and Proof of Work (PoW) are addressed and reports are demanded in IoT. The Direct Acyclic Graphs(DAG) is used to show why it is reactive than IoTPoS and PoW structure. Hashgraph and Tangle are mainly based on consensus mechanisms.
With the recent popularity of Blockchain and other Distributed Ledger Technologies (DLT), blockchain enabled smart contract applications has attracted increased research focus. However, the immutability of the blocks, where the smart contracts are stored, causes conflicts with the traditional Software Development Life Cycle (SDLC) models usually followed by software engineers. This clearly shows the unsuitability of the application of SDLC in designing blockchain enabled smart contract based applications. This research article addresses this current problem by first exploring the six traditional SDLC models, clearly identifying the conflicts in a table with the application of smart contracts and advocates that there is an urgent need to develop new standard model(s) to address the arising issues. The concept of both block immutability and contract is introduced. This is further set in a historical context from legacy smart contracts and blockchain enabled smart contracts extending to the difference between "shallow smart contracts" and "deep smart contracts". To conclude, the traditional SDLC models are unsuitable for blockchain enabled smart contract-based applications.
In recent years, blockchain technology has received unparalleled attention from academia, industry, and governments all around the world. It is considered a technological breakthrough anticipated to disrupt several application domains. This has resulted in a plethora of blockchain systems for various purposes. However, many of these blockchain systems suffer from serious shortcomings related to their performance and security, which need to be addressed before any wide-scale adoption can be achieved. A crucial component of any blockchain system is its underlying consensus algorithm, which in many ways, determines its performance and security. Therefore, to address the limitations of different blockchain systems, several existing as well novel consensus algorithms have been introduced. A systematic analysis of these algorithms will help to understand how and why any particular blockchain performs the way it functions. However, the existing studies of consensus algorithms are not comprehensive. Those studies have incomplete discussions on the properties of the algorithms and fail to analyse several major blockchain consensus algorithms in terms of their scopes. This article fills this gap by analysing a wide range of consensus algorithms using a comprehensive taxonomy of properties and by examining the implications of different issues still prevalent in consensus algorithms in detail. The result of the analysis is presented in tabular formats, which provides a visual illustration of these algorithms in a meaningful way. We have also analysed more than hundred top crypto-currencies belonging to different categories of consensus algorithms to understand their properties and to implicate different trends in these crypto-currencies. Finally, we have presented a decision tree of algorithms to be used as a tool to test the suitability of consensus algorithms under different criteria.
A decade long thrive of cryptocurrency has shown its potential as a source of alternative-finance and the security and the robustness of the underpinning blockchain technology. However, most cryptocurrencies fail to show inimitability and their meanings in the real world. As a result, they usually start off as favourites but quickly become the outcasts of the digital asset market. The blockchain society attempts to anchor the value of cryp-tocurrency with real values by employing smart contracts and link it with computation resources and the digital-productivity that have value and demands in the real world. But their attempts have some undesirable effects due to a limited number of practical applications. This limitation is caused by the dilemma between high performance and decentralisation (universal join-ability). The emerging of blockchain sharding models, however, has offered a possible solution to address this dilemma. In this paper, we explore a financial model for blockchain sharding that will build an active link between the value of cryptocurrency and computation resources as well as the market and labour behaviours. Our model can adjust the price of resources and the compensation for maintaining a system based on those behaviours. We anchor the value of cryptocurrency by the amount of computation resources participated in and give the cryptocurrency a meaning as the exchange between computation resources globally. Finally, we present a working example which, through financial regularities, regulates the behaviour of anonymous participants, also incents/discourages participation dynamically.
Bitcoin-NG is among the first blockchain protocols to approach the \emph{near-optimal} throughput by decoupling blockchain operation into two planes: leader election and transaction serialization. Its decoupling idea has inspired a new generation of high-performance blockchain protocols. However, the existing incentive analysis of Bitcoin-NG has several limitations. First, the impact of network capacity is ignored. Second, an integrated incentive analysis that jointly considers both key blocks and microblocks is still missing. In this paper, we aim to address these two limitations. First, we propose a new incentive analysis that takes the network capacity into account, showing that Bitcoin-NG can still maintain incentive compatibility against the microblock mining attack even under limited network capacity. Second, we leverage a Markov decision process (MDP) to jointly analyze the incentive of both key blocks and microblocks, showing that the selfish mining revenue of Bitcoin-NG is a little higher than that in Bitcoin only when the selfish miner controls more than 35\% of the mining power. We hope that our in-depth incentive analysis for Bitcoin-NG can shed some light on the mechanism design and incentive analysis of next-generation blockchain protocols.
An educational institute demands significant computational resources for which it mostly relies on centralized servers, networks and storage facilities. Currently these systems are built around the centralized model which exposes it to risks of data breach, low fault tolerance and the numerous pitfalls of a centralized system. Furthermore, the maintenance of these systems incur significant costs for the institute. The purpose of this research is to introduce a decentralized model of computational system built on blockchain for educational institutions which can mitigate the several drawbacks of a centralized system and further explore the possibilities of introducing a cryptocurrency within the network of the institute. This model proposes to utilize the computational power of devices of the members of the institute by allowing them to be participant nodes in the network. Using the Ethereum blockchain, this study proposes a Smart Contract based system and introduces a cryptocurrency to incentivize the participants of the network.
Blockchain as a novel technology has shown the capacity to transform multiple sectors. Due to opportunities such as data security, transparency, privacy and interoperability presented by decentralized applications on blockchain networks, organizations are now moving their inter-organizational functions to blockchain-based systems. Traditional system-design methods are not suitable for developing blockchain systems since they are not capable of capturing new functions that are associated with decentralized applications. This paper seeks to address this gap by exploring existing design methods and frameworks that support the development of decentralized application on a blockchain. To achieve this, case-study based research is used in identifying current software-development techniques used in designing decentralized applications (DApp). Experts in this field are interviewed to identify their chosen techniques for designing and developing block-chain applications. Furthermore, related literature is selected to identify current techniques for DApp-designs based on the state of the art. A systematic analysis of the identified techniques is conducted using the current limitations of blockchain technology as criteria for the analyses. Finally, based on the findings of this study, we propose a new model-driven framework for designing blockchain applications.
The interoperability across multiple blockchains would play a critical role in future blockchain-based data management paradigm. Existing techniques either work only for two blockchains or requires a centralized component to govern the cross-blockchain transaction execution, neither of which would meet the scalability requirement. This paper proposes a new distributed commit protocol, namely \textit{cross-blockchain transaction} (CBT), for conducting transactions across an arbitrary number of blockchains without any centralized component. The key idea of CBT is to extend the two-phase commit protocol with a heartbeat mechanism to ensure the liveness of CBT without introducing additional nodes or blockchains. We have implemented CBT and compared it to the state-of-the-art protocols, demonstrating CBT's low overhead (3.6\% between two blockchains, less than $1\%$ among 32 or more blockchains) and high scalability (linear scalability on up to 64-blockchain transactions). In addition, we developed a graphic user interface for users to virtually monitor the status of the cross-blockchain transactions.
In the blockchain, the consensus mechanism plays a key role in maintaining the security and legitimation of contents recorded in the blocks. Various blockchain consensus mechanisms have been proposed. However, there is no technical analysis and comparison as a guideline to determine which type of consensus mechanism should be adopted in a specific scenario/application. To this end, this work investigates three mainstream consensus mechanisms in the blockchain, namely, Proof of Work (PoW), Proof of Stake (PoS), and Direct Acyclic Graph (DAG), and identifies their performances in terms of the average time to generate a new block, the confirmation delay, the Transaction Per Second (TPS) and the confirmation failure probability. The results show that the consensus process is affected by both network resource (computation power/coin age, buffer size) and network load conditions. In addition, it shows that PoW and PoS are more sensitive to the change of network resource while DAG is more sensitive to network load conditions.