摘要:With the rapid development of cryptocurrency and its underlying blockchain technologies, platforms such as Ethereum and Hyperledger began to support various types of smart contracts. Smart contracts are computer protocols intended to digitally facilitate, verify, or enforce the negotiation or performance of a contract. Smart contracts have broad range of applications, such as financial services, prediction markets and Internet of Things (IoT), etc. However, there are still many challenges such as security issues and privacy disclosure that await future research. In this paper, we present a comprehensive overview on blockchain powered smart contracts. First, we give a systematic introduction for smart contracts, including the basic framework, operating mechanisms, platforms and programming languages. Second, application scenarios and existing challenges are discussed. Finally, we describe the recent advances of smart contract and present its future development trends, e.g., parallel blockchain. This paper is aimed at providing helpful guidance and reference for future research efforts.

摘要:Smart cities aim to provide smart governance with the emphasis on gaining high transparency and trust in public services and enabling citizen participation in decision making processes. This means on the one hand data generated from urban transactions need to be open and trustworthy. On the other hand, security and privacy of public data needs to be handled at different administrative and geographical levels. In this paper, we investigate the pivotal role of blockchain in providing privacy, self-verification, authentication, and authorization of participatory transactions in open governance. We also investigate up to what extent edge computing can contribute towardmanagement of permissioned sharing at specific administrative levels and enhance privacy and provide an economic approach for resource utilization in a distributed environment. We introduce a novel architecture that is based on distributed hybrid ledger and edge computing model. The architecture provides refined and secure management of data generated and processed in different geographical and administrative units of a city. We implemented a proof of concept of the architecture and applied it on a carefully designed use case, ie, citizen participation in administrative decisions through consensus. This use case highlights the need to keep and process citizen participation data at local level by deploying district chaincodes and only share consensus results through permissioned chaincodes. The results reveal that proposed architecture is scalable and provide secure and privacy protected environment for citizen participatory applications. Our performance test results are promising and show that under control conditions, the average registration time for a citizen transaction is about 42ms, whilst the validation and result compilation of 100 concurrent citizens' transactions took about 2.4 seconds.

摘要:Smart contract technology is reshaping conventional industry and business processes. Being embedded in blockchains, smart contracts enable the contractual terms of an agreement to be enforced automatically without the intervention of a trusted third party. As a result, smart contracts can cut down administration and save services costs, improve the efficiency of business processes and reduce the risks. Although smart contracts are promising to drive the new wave of innovation in business processes, there are a number of challenges to be tackled. This paper presents a survey on smart contracts. We first introduce blockchains and smart contracts. We then present the challenges in smart contracts as well as recent technical advances. We also compare typical smart contract platforms and give a categorization of smart contract applications along with some representative examples.

摘要:智 能合 约是 一种 无需 中 介 、 自 我验证 、 自 动执行合约条款 的计算机交易 协议 ， 近年来 随着 区块链技术 的 日 益普及而 备 受关 注 区 块链上 的智 能合 约具有去 中 心化 、 去信 任 、 可编程 、 不可篡 改等特 性 ， 可灵活嵌入各种数据 和 资产， 帮 助实现安全 高效 的信息交 换、 价值转移和 资产管理， 最 终 有望深入变革传统商业模 式和 社 会生产 关 系 ， 为构建可编程 资产 、 系 统和 社会奠 定基础 本文致力于 以 区块链智 能合约为研究对象 ， 对 已 有的 研究成果进行全面梳理和 系 统概述 ， 提 出 了 智 能合约 的基础架构 模 型并以 此为研究框架 阐 述了 智 能合约 的 运行 机制 与基 础架构， 总结 了 智 能 合约的 研究挑 战 与进展， 介绍 了 智 能合 约 的技术 优势与典型应用 领域 ， 讨 论了 智能 合约的 发展 趋势， 以期 为智能 合约 的后续研究提供参考

摘要:Smart Health is a real-time, intelligent, ubiquitous healthcare service based on the IoT aware network and sensing infrastructure. Thanks to the rapid development of related technologies such as cloud computing, fog computing and IoT, research on smart health is gradually on the right track. This paper analyzes research on smart health in recent years and then discusses the development of smart health from both cloud and edge, including cloud computing, fog computing, IoT sensors, blockchain, and privacy and security. At present, in the research of cloud and smart health, the focus is on how to use the cloud to complete the challenges of massive health data and improve service performance, including related issues such as storage, retrieval and calculation of health big data in the cloud. At the edge, research focuses on the collection, transmission, and computation of health data, including sensors and wearable devices for collecting health data, various sensor networks, and how to process health data and improve service performance at the edge. As an emerging technology, blockchain has a wide range of applications in smart health. We discuss typical smart health application, blockchain in smart health and privacy and security issues related to smart health. Finally, we present challenges and opportunities for smart health in the edge computing era.

摘要:智能合约是区块链系统的核心组件,在现实中广泛应用.然而,目前没有关于智能合约的统一定义,在不同 的区块链平台上,智能合约的实现也相差甚远.这样将影响公众对智能合约的认知,也对产业的发展造成障碍.回顾 了智能合约的发展历史,梳理其概念的变化过程.归纳智能合约的本质,对现有智能合约的实现进行了分析和对比. 给出了面向合同的智能合约的形式化定义,为智能合约的标准化奠定基础.提出了独立于区块链平台的、通用的智 能合约实现方法.在目前广泛应用的联盟链区块链平台 Hyperledger Fabric 上面进行了具体实现.最后对未来工作进 行了展望.

摘要:随着以比特币为代表的区块链技术的蓬勃发展，区块链技术已经开始逐步超越可编程货币时代 而进入智能合约时代．智能合约（ｓｍａｒｔｃｏｎｔｒａｃｔ）是一种由事件驱动的、具有状态的代码合约和算法合 同，随着区块链技术的深入发展而受到广泛关注和研究．智能合约利用协议和用户接口完成合约过程的 所有步骤，允许用户在区块链上实现个性化的代码逻辑．基于区块链的智能合约技术具有去中心化、自治化、可观察、可验证、可信息共享等特点，可以有效构建可编程金融和可编程社会，广泛应用于数字 支付、金融资产处置、多重签名合约、云计算、物联网、共享经济等多个领域．首先阐述了智能合约技术的 基本概念、全生命周期、基本分类、基本架构、关键技术、发展现状以及智能合约的主要技术平台；然后探 讨了智能合约技术的应用场景以及发展中所存在的问题；最后，基于智能合约的理论知识，搭建了以太 坊实验环境并开发了一个众筹智能合约系统，旨在为基于区块链的智能合约技术的研究与发展提供参 考与借鉴．

摘要:In recent years, Blockchain has attracted tremendous attention due to its salient features including auditability, immutability, security, and anonymity. Resulting from these salient features, blockchain has been applied in multiple non-monetary applications including the Internet of Things (IoT). However, blockchain is computationally expensive, has limited scalability and incurs significant bandwidth overheads and delays which are not suited for most IoT applications. In this paper, we propose a Lightweight Scalable blockchain (LSB) that is optimized for IoT requirements while also providing end-to-end security. Our blockchain instantiation achieves decentralization by forming an overlay network where high resource devices jointly manage the blockchain. The overlay is organized as distinct clusters to reduce overheads and the cluster heads are responsible for managing the public blockchain. We propose a Distributed Time-based Consensus algorithm (DTC) which reduces the mining processing overhead and delay. Distributed trust approach is employed by the cluster heads to progressively reduce the processing overhead for verifying new blocks. LSB incorporates a Distributed Throughput Management (DTM) algorithm which ensures that the blockchain throughput does not significantly deviate from the cumulative transaction load in the network. We explore our approach in a smart home setting as a representative example for broader IoT applications. Qualitative arguments demonstrate that our approach is resilient to several security attacks. Extensive simulations show that packet overhead and delay are decreased and blockchain scalability is increased compared to relevant baselines.

摘要:In recent years, the rapid development of cryptocurrencies and their underlying blockchain technology has revived Szabo’s original idea of smart contracts, i.e., computer protocols that are designed to automatically facilitate, verify, and enforce the negotiation and implementation of digital contracts without central authorities. Smart contracts can find a wide spectrum of potential application scenarios in the digital economy and intelligent industries, including financial services, management, healthcare, and Internet of Things, among others, and also have been integrated into the mainstream blockchain-based development platforms, such as Ethereum and Hyperledger. However, smart contracts are still far from mature, and major technical challenges such as security and privacy issues are still awaiting further research efforts. For instance, the most notorious case might be “The DAO Attack” in June 2016, which led to more than $50 million Ether transferred into an adversary’s account. In this paper, we strive to present a systematic and comprehensive overview of blockchain-enabled smart contracts, aiming at stimulating further research toward this emerging research area. We first introduced the operating mechanism and mainstream platforms of blockchain-enabled smart contracts, and proposed a research framework for smart contracts based on a novel six-layer architecture. Second, both the technical and legal challenges, as well as the recent research progresses, are listed. Third, we presented several typical application scenarios. Toward the end, we discussed the future development trends of smart contracts. This paper is aimed at providing helpful guidance and reference for future research efforts.

摘要:随着物联网技术的进步，物联网结构变得日益复杂，采集的数据量呈现爆发式增长，如何在不同的参与方间安全地共 享数据成为了一个巨大的挑战． 传统的数据共享模型往往依赖于可信的第三方中心化机构，但这种方案易发生单点故障，对参 与方不透明，数据可能遭到篡改． 本文利用区块链能够去中心解决信任问题这一特点，提出一种基于区块链的物联网数据共享 模型． 本文首先分析了现有的物联网数据共享模型以及Hyperledger Fabric 区块链平台的关键组件，然后介绍了本文所述模型的 网关组成方式和数据存储到区块链账本的内容，并对安全性和数据隐私性提出了增强改进设计方法，最后分析了模型的安全和 可用性，通过测试简化模型的性能证明了模型实施的可行性．

摘要:区块链是一个全球性的去中心化分布式数据库账本。智能合约作为一段由事件驱动的、具有状态的、运行于 区块链系统之上的程序，能够保管、处理区块链账本上的数字资产；运行在通用平台上的智能合约还能够实现传统应 用系统的部分功能。区块链技术的发展为智能合约提供了很好的运行基础，智能合约在区块链上能够发挥重要作用。 随着比特币和以太坊等区块链平台的迅速发展，智能合约具备了良好的发展契机。然而，智能合约应用还处于早期发 展阶段，相关研究相对较少，实际应用中智能合约的适用场景不够丰富。文中从智能合约编程语言、实现技术、发展现 状和存在的挑战、未来前景等几个方面进行研究和探讨，重点描述了不同智能合约开发语言的特性，以及相互 之 间 的 对比；以智能合约运行环境为标准进行分类，研究了各种区块链系统中智能合约的开发、部署和运行机制，并探讨了不 同类型智能合约平台的应用范围，对不同区块链系统在智能合约开发、社区支持以及相应的生态系统等方面进行了全 面的比较；然后，介绍智能合约的研究现状和面临的挑战，从安全性、可扩展性、可维护性等方面进行深入分析；最 后， 分析了区块链和智能合约技术的发展趋势，探讨了未来的应用场景。

摘要:Blockchain technology has received extensive attention recently, but still a large of technical challenges such as scalability and security. This paper helps to find where recent studies have been focused on and offers a broad perspective relating blockchain applications and smart contracts, their main problems and corresponding solutions and will help to specify gaps and future research. The study extracted 292 articles from top Digital Libraries such as IEEE, ACM, Science Direct and Springer. After a detailed review process only 28 publications were considered based on defined inclusion and exclusion criteria.

摘要:IoT devices are quickly becoming a critical source of information about the physical world considered in business processes. Blockchains are a promising platform for such processes if they involve multiple parties with no shared, commonly trusted IT infrastructure. Transacting with a blockchain, however, requires software whose footprint overwhelms many lightweight IoT devices. In this paper we introduce the concept of a blockchain proxy to which an IoT device can offload a large part of this software footprint. The proxy only requires a slim proxy SDK on the device that holds a regular blockchain identity with its own private key, retaining full control of the transactions in the device. We discuss security implications and present cold-chain monitoring as a use case. Preliminary results show significant savings in CPU time and communication bandwidth for the IoT device.

摘要:With the advent of blockchain, smart contracts have become one of the most sought-after technologies because of the high customisability they add to transactions. This has given rise to many smart contract applications in areas ranging from financial services, life sciences and healthcare to energy resources and voting. However, due to their infancy, smart contracts still pose many challenges that encumber the stakeholders who interact with them: users, developers and the organisations that are built on top of smart contracts. This study aims to contribute to the body of knowledge of smart contracts within blockchain technology. Based on a systematic mapping study, we offer a broad perspective on their problems and corresponding solutions, present the research trends within the area and compile the 64 papers identified, grouped by top publication sources, channels, methods and approaches. We conclude that, since 2016, there has been an increasing trend towards the publication of blockchain-based smart contract articles at conferences and journals, mainly reflecting experiments and presenting methods, tools and models. According to the results, the most commonly discussed problems and solutions in the literature are related to the security, privacy and scalability of blockchain and the programmability of smart contracts.

摘要:针对传统电力调度过程中难以调控能源、易产生网络损耗等缺陷，提出基于区块链的能源电力 供需网调度优化模型。结合区块链的去中心化、可信任、交易透明化的特性，建立能源电力供需网模型；利用 区块链激励机制，实现能源电力供需网协调控制分布式能源独立并网的行为；在此基础上，根据运营成本最 低、有功损耗最小等目标函数建立调度优化模型，运用协作型协同进化算法（CCEA）对模型进行求解，并通 过区块链的ＰＯＷ 共识机制，安排能源电力供需网各节点进行分布式计算，实现调度方案的二次验证与优 化。算例结果表明，与传统的电力能源调度模型相比，本文所提出的方法可使总运营成本降低９．９％，有功 网络损耗降低３．５％，日负荷方差等因素也有所改善，提高了电力系统的稳定性，为优化能源电力调度问题 提供决策支持和理论支撑。