Alejandro Ranchal Pedrosa, Maria Potop-Butucaru, Sara Tucci-Piergiovanni
Bitcoin, the most popular blockchain system, does not scale even under very optimistic assumptions. Lightning networks, a layer on top of Bitcoin, composed of one-to-one lightning channels make it scale to up to 105 Million users. Recently, Duplex Micropayment Channel factories have been proposed based on opening multiple one-to-one payment channels at once. Duplex Micropayment Channel factories rely on time-locks to update and close their channels. This mechanism yields to situation where users funds time-locking for long periods increases with the lifetime of the factory and the number of users. This makes DMC factories not applicable in real-life scenarios.
Krishnendu Chatterjee, Amir Kafshdar Goharshady, Ehsan Kafshdar Goharshady
Smart contracts are programs that are stored and executed on the Blockchain and can receive, manage and transfer money (cryptocurrency units). Two important problems regarding smart contracts are formal analysis and compiler optimization. Formal analysis is extremely important, because smart contracts hold funds worth billions of dollars and their code is immutable after deployment. Hence, an undetected bug can cause significant financial losses. Compiler optimization is also crucial, because every action of a smart contract has to be executed by every node in the Blockchain network. Therefore, optimizations in compiling smart contracts can lead to significant savings in computation, time and energy.
In cloud computing, data is duplicated to prevent data loss. One way to achieve data consistency in such a distributed computing systems is to use a blockchain. Based on practical Byzantine fault tolerance (PBFT), a specific type of blockchain, this paper proposes a synchronous Byzantine fault tolerance (SBFT) algorithm that not only maintains data consistency, but also has much higher efficiency than other general blockchain algorithms. We provide experimental results that demonstrate the algorithm's data consistency, efficiency, and reliability.
The blockchain technology is more and more important in computer security. The core of the blockchain system is consensus. However, many consensus mechanisms reward those groups that own the majority of the resources. In addition, the performance of these consensus mechanisms is poor. In this paper we first present Proof of Value (POV), an incentive mechanism that rewards the value creators. With the help of POV, we reward the user who creates value and control the number of coins through the incentive coefficient adjustment algorithm. To improve the performance of POV in permissioned blockchain, we designed Hypernet, an off-chain transaction system. By designing the transaction system Hy-pernet, the transaction can be handled without blockchain. Finally, we evaluate our system by generating random parameters to invoke the contract. Then we record the real time for issuing the rewards. The test results show that the loss of the system is about 2% when the POV is added. The performance of the Hypernet is four times higher than the traditional permissioned blockchain transaction system.
Blockchain has gained much attention in recent academic and research works not only in crypto-currency but also in many other fields such as supply chain, health, storage etc. The application of blockchain in data management domain, however, is mostly geared towards the aspect of security and immutability. In this paper we propose integrating blockchain with distributed data management and study some open challenges and assumptions in doing so. We claim that, from data management perspective, blockchain's ability to handle unequal participants is more important than security and immutability. Finally, we propose possible ideas to integrate blockchain into distributed data transaction and management workflows to design a globally consistent data store ensuring availability guarantees along with support for unifying heterogeneous data backends.
The blockchain technology is complex and involves a wide range of fields, which leads to the lack of uniform specifications for the development of blockchain applications. Although blockchain used to be divided according to the decentralized degree by some organizations, which are difficult to give developers specific guidance and results. To this end, this paper proposed a feature-oriented classification method of blockchain applications based on the analysis and comparison of current typical blockchain applications and frameworks, including digital currency blockchain, development platform blockchain, decentralized application and extended blockchain, helping developer create blockchain applications of a targeted manner and clarifying the functional architecture of different types of above various blockchain applications. Finally, the above classification method has been verified by the analysis of an extended blockchain.
With the development of the Internet of Vehicles, more and more applications require collaboration between vehicles. Vehicles from different car manufacturers have their own private clouds, and the collaboration between them is poor, resulting in inefficient collaboration between heterogeneous vehicles. A single cloud lacks collaboration between vehicles and it's an inevitable trend for developing collaboration between clouds. JointCloud is a new computing model in which collaboration services provided between clouds are used to server users in a software-defined manner based on blockchain. This paper proposes the collaboration framework of multiple vehicle clouds, introduces the blockchain to establish the coordination mechanism, and describes standardization method and service combination method of the vehicular cloud service in detail. At the end of this paper, we designed a distributed cloud service evaluation method based on blockchain to provide users with an effective cloud service evaluation solution.
Bitcoin is a crypto currency introduced by Satoshi Nakamoto in 2008. It has the features of decentralization cross-border and fixed total amount and has become one of the most widely used crypto-currencies. Bitcoin, as a new digital currency system, innovatively makes the use of cryptographic elements and consensus mechanisms and builds up a secure decentralized system. The Blockchain, as the core of Bitcoin, uses peer-to-peer network communications and backs up transaction data in every node of the system, thus creating a huge distributed public book. It is essentially a decentralized distributed ledger database, and the decentralization means that the transaction is broadcast to the entire network, where everyone is involved in book keeping. In order to make every participant in the Blockchain willing to participate in the bookkeeping, the reward mechanism of the Bitcoin system is mining. This article first introduces the concept of Blockchain technology, then expounds the principle and the operation mechanism of the Bitcoin and the Bitcoin mining principle, introduces an example of Bitcoin mining in-depth study and analysis, finally, summarize and prospect the development of the Bitcoin mining.
the blockchain is an emerging technology with a core of a distributed ledger of connected blocks consisting of immutable transactions with decentralized management. The importance of blockchain technology and its impact in different domains highlights the need for understanding and evaluation of this technology. Understanding and evaluating technology from different aspects requires identifying the characteristics and specific criteria of that technology. In this regard, in this paper, after discussing the subject literature, the concept of the blockchain platform is described and a number of selected blockchain platforms are examined. Besides, the high-level benchmarking of the platform is evaluated from two aspects of the expected features of the platforms and their architectural components. Finally, due to the importance and significance of the criteria and their frequency, a set of effective criteria is chosen and accordingly, selected platforms of the blockchain are analyzed.
Christian Banks, Samuel Kim, Neposchlan Michael, Nicholas Velez · 8 authors
Sharing information is an important part of regulating and maintaining efficient and safe power grids. This project's goal is to develop a way of using blockchain technology to share transaction information among different power grids in a secure, controlled, monitored, and efficient manner. The biggest concern regarding the data is integrity. By leveraging blockchain technology, the data will be reliable and resilient to attacks, such as man-in-the-middle and data spoofing attacks. The Hyperledger Fabric implementation provides a permissioned network in which power grids will act as nodes that maintain ledger information. By using a distributed ledger to validate transactions though the process of consensus, the system can share information in a manner that is more secure and transparent than traditional information sharing systems in which data is less secure and takes longer to validate. The additional layers of security and speed that Hyperledger technology provide help to prevent issues, such as power grid failures, that could stem from the latency or integrity issues involved with traditional methods of validating, processing, and reacting to shared data.
David Chen, Zhiyue Zhang, Ambrish Krishnan, Bhaskar Krishnamachari
We present PayFlow, a fine-granularity QoS micro-payment system that allows end devices in a software-defined network to make and pre-pay for guaranteed bandwidth reservations for their flows within the network for an arbitrary period of time. PayFlow combines payments using digital currency and storage of transaction records in a distributed ledger with queue-based QoS management using software-defined networks. While the PayFlow architecture is agnostic to the choice of digital currency, ledger technology and SDN platform used, we present a proof of concept implementation of PayFlow using OpenFlow and the IOTA cryptocurrency and distributed ledger, that we evaluate using the Mininet emulator.
Traditional cloud Service Level Agreement (SLA) suffers from lacking a trustworthy platform for automatic enforcement. The emerging blockchain technique brings in an immutable solution for tracking transactions among business partners. However, it is still very challenging to prove the credibility of possible violations in the SLA before recording them onto the blockchain. To tackle this challenge, we propose a witness model using game theory and the smart contract techniques. The proposed model extends the existing service model with a new role called “witness” for detecting and reporting service violations. Witnesses gain revenue as an incentive for performing these duties, and the payoff function is carefully designed in a way that trustworthiness is guaranteed: in order to get the maximum profit, the witness has to always tell the truth. This is analyzed and proved through game theory using the Nash equilibrium principle. In addition, an unbiased sortition algorithm is proposed to ensure the randomness of the independent witnesses selection from the decentralized witness pool, to avoid possible unfairness or collusion. An auditing mechanism is also introduced in the paper to detect potential irrational or malicious witnesses. We have prototyped the system leveraging the smart contracts of Ethereum blockchain. Experimental results demonstrate the feasibility of the proposed model and indicate good performance in accordance with the design expectations.
Blockchain has been adopted in many applications to construct trust among multiple participants, such as supply chain management, digital assets transfer, philanthropy, etc. Blockchain platforms are often used as decentralized databases. However, existing blockchain platforms are far less convenient to use than traditional databases. They are lack of the capability of modelling complex tasks conveniently and efficiently, especially when both on-chain and off-chain data are involved at the same time. In this paper, we propose and implement a novel blockchain database, called SEBDB, which leverages the existing databases' functionality which are optimized for decades. Comparing to existing works, SEBDB is the first platform which considers both useability and scalability. Specifically, first, weaddrelationaldata semantics into blockchain platform, where each transaction is a tuple with multiple attributes in a pre-defined table. Second, we use SQL-like language as the general interface, instead of code-level APIs, to support convenient application development, in which intrinsic operations are re-defined and re-implemented to suit for blockchain platform. Third, as RDBMS has achieved great success in the past decades, our system, though not relying on RDBMS, treats it as an important component. Finally, we define a mini-benchmark to evaluate the performance of the blockchain database. Extensive experiments demonstrate the effectiveness and efficiency of our proposed system.
The concerns held on the scalability of permissionless Blockchain platforms are a significant hindrance to their wider adoption. To address this issue rigorously, we consider it opportune to assess the current implementation and the associated improvement proposals, within a single coherent evaluation framework. This work addresses this specific question in the particular context of Ethereum, a prominent implementation of Blockchain, using a threefold approach. First, it maps the internal constituents of Ethereum onto a layered architecture inspired in the ISO/OSI model, so that its provisioning organization can be better understood. Second, it employs the AKF Scale Cube to analyze the pros and cons of the present specification of Ethereum, as well as of the current improvement proposals, so that the scalability challenges can be reasoned about in an orderly fashion. Finally, it uses an extensible test environment with synthetic benchmarks so that the transaction throughput of the current implementation of Ethereum can be evaluated in a private scenario, when no smart contract is to run. Our conclusions suggest that Ethereum respects the scalability trilemma being versed on security and decentralization renouncing scalability. These limits can be mitigated by adopting novel solutions such as Plasma and Sharding which enable a significant increment of performance by partitioning the data, and, ultimately, unlocking parallel execution of the transactions.
Today’s e-health system is centralized. This system obliges all users (patients and healthcare staff) to have a high level of trust in the intermediary who stores the data. Moreover, healthcare employees must trust that their patients are providing authentic medical records and are not altering th em in order to obtain drugs for illegal purposes. The solution proposed in this paper is a new blockchain-based architecture for the creation of an e-health system. In this architecture, wireless sensor networks (WSN) will be used in association with a WSN controller v.2 to supervise patients and their testing by healthcare staff. Transactions between blockchain and WSN are made through smart contracts, removing the need for intermediaries and preventing human error. This new model facilitates a distributed ledger, creating an e-health system that is much more optimized than the current one.
Summary Blockchains are increasingly studied in the context of new applications. Permissioned blockchains promise to deal with the issue of complete removal of trust, a notion that is currently the hallmark of the developed society. Before the idea is adopted in contexts where resource efficiency and fast operation is a requirement, one could legitimately ask the question: can permissioned blockchains match the performance of traditional large‐scale databases? This paper compares two popular frameworks, Hyperledger Fabric and Apache Cassandra, as representatives of permissioned blockchains and distributed databases, respectively. We compare their latency for varying workloads and network sizes. The results show that, for small systems, blockchains can start to compete with traditional databases, but also that the difference in consistency models and differences in setup can have a large impact on the resulting performance.
In a blockchain system, consensus protocol as an incentive and security mechanism, is to ensure the participants to build the block honestly and effectively. There are different consensus protocols for blockchain, like Proof of work (PoW), Proof of Stake (PoS), Proof of Space (PoSpace), Proof of Activities etc. But most of these consensus protocols are not designed for doing some useful jobs for society because of too much competition and scalability limitation. Massive electric power and computing resources, including CPU, RAM, storage and sensors have been wasted to run blockchain network based on these consensus protocols. Current frameworks and middleware for building decentralised applications (dApps) are largely limited to simple and less useful jobs. In this paper, we present Proofware which is designed for developers to build their dApps easily with existing public/crowd-based computing resources. Under Proofware, developers can develop and test their own Proof of Useful Work (PoUW) consensus protocols. Also, rather than depending on a centralised accounting system, each dApp has an embedded currency system to keep the whole incentive system decentralised, fair, transparent, stable and sustainable. Based on Proofware, we have built a crowd based video sharing application, called OurTube, as a case study. By the OurTube example, it has shown Proofware significantly improves the productivity to build crowd-based computing system with the features of cost-effectiveness, anti-censorship, elasticity and financial sustainability.
Andrew Cullen, Pietro Ferraro, Christopher King, Robert Shorten
Distributed ledgers have been proposed for a number of applications in the Internet-of-Things domain where it is essential to have an immutable and irreversible record of transactions. Directed acyclic graph (DAG)-based architectures, in particular, seem to provide a vast array of advantages over the more traditional Blockchain; however, it can be challenging to conduct a thorough analysis of DAG-based ledgers and derive reliable performance guarantees. In this article, we analyze one commonly discussed attack scenario known as the parasite chain attack, which aims at disrupting the immutability and irreversibility of the ledger, in the context of the IOTA Foundation's DAG-based system. Using a Markov chain model, we study the vulnerabilities of IOTA's core tip selection method against this attack and we present an extension of the algorithm to improve the resilience of the ledger in this scenario.
Bruno W. França, Sophie Radermacher, Reto Trinkler
Katal is a new blockchain that provides a standard way to build and deploy decentralized financial applications. It brings together all the components necessary for the backend of a financial application, namely: a high-performance consensus, an authenticated data feed system, a standard for financial contracts and connectivity to the rest of the blockchain ecosystem. Katal enables and simplifies the creation of financial services that are non-custodial, trustless, fast, convenient and interoperable.
Ramesh Viswanathan, Dipankar Dasgupta, S. R. Govindaswamy
Enterprise Blockchain network solutions facilitate the extension and optimization of processes across organizational boundaries. This increased level of sharing provides greater visibility, provenance of transactions to all parties involved, and reduces friction that arises due to organizational boundaries. Blockchain Solution Reference Architecture (BSRA) provides comprehensive guidance to architect and build end-to-end solutions based on Blockchain technologies. BSRA was primarily developed based on client engagements across industries such as retail, financial, supply chain, and telco, and addresses two major parts of a Blockchain solution: 1) building a Blockchain business network that receives, builds, and shares blocks in a secure manner; and 2) onboarding members on to the business network with the appropriate level of access and collaboration privileges. BSRA provides a foundational set of architectural artifacts that can help accelerate development of solutions based on Blockchain technologies. It also provides a starter list of architectural decisions that every project will have to set during development.
ABSTRACT This case promotes discussions about blockchain technology. It shows a transaction execution scenario and its tax implications. The case provides (1) an overview of the steps required to install a Digital Wallet; (2) an explanation of the need to add cryptocurrencies to the wallet in order to transact on the blockchain; (3) an overview of executing a transaction, in which an accounting consulting service is provided in the exchange of a cryptocurrency; (4) methods to review the existing transaction, from the service provider side, the service receiver side, and from the blockchain side, with a highlight of the role of both internal and external auditors; (5) clarifies the importance of dealing with cryptocurrencies, given that the IRS identifies cryptocurrencies as properties; and (6) a reflection on the link between a company ERP system and the transaction information on the blockchain.
Florian Wessling, Christopher Ehmke, Ole Meyer, Volker Gruhn
Blockchain-based applications usually consist of centralized elements (e.g., web servers and back-end logic) connected to decentralized elements such as smart contracts. The engineering of such hybrid software architectures poses a challenge as it is unclear which elements should be centralized or decentralized. Furthermore the impact of this decision (or the balance between those two areas) on software quality attributes such as security, maintainability, performance or costs is currently unknown. The goal is to build a software architecture using the benefits and handling the challenges of blockchain technology while fulfilling the relevant quality attributes. While there are several approaches examining the relation between architectural decisions and quality attributes in centralized systems, research is at an early stage for decentralized elements in software architectures. This paper presents a first step towards architectural blockchain tactics. With a simplified experiment comparing two implementation variants of an Ethereum smart contract we show that software design patterns are not always beneficial and that the expected usage scenarios have a strong impact on the operational costs. We argue that further research and validation is necessary for gaining more qualitative and quantitative insights to make informed architectural design decisions when using blockchain technology and give a first outline on how to achieve this.
Prior to blockchain technology coming into much usage, the earlier cryptographic digital cash schemes relied merely on trusted authorities. Bitcoin revolutionized this conventional view of a cryptocurrency, trading decentralized, distributed ledger, completely secured by the majority rule without predetermined authority or owner. Only standard cryptographic primitives such as signatures and hash functions were used to achieve security. Though other cryptocurrencies such as Bit-gold and B-money which are among the authority-free cryptocurrencies, Bitcoin is the first one to experience public acceptance on a large scale. There are various factors which contribute to Bitcoins success, though there is still a little question of doubt that the decentralized design of blockchain technology and perceived resilience to government or third-party intervention played an extremely crucial role in its uptake. Distributed crypto cash, more specifically in Blockchain technology has hailed as one key and most eminent and widely accepted innovation of Bitcoin. In this paper we have worked on the use of blockchain technology to implement cryptocurrency for IOT.