摘要:Developing smart contract decentralised application based systems typically involves writing code for various platforms, from the smart contract code residing on the underlying distributed ledger technology implementation to back end oracles and front end websites or mobile apps. In addition to the different technologies used for the different parts, the programmer is also burdened with implementing communication channels between the various parts. In this paper we propose a unified programming model allowing for developers to build such systems through a single code artifact, using a macroprogramming approach.

摘要:This research addresses the issue that in-depth programming knowhow is needed to read and write smart contracts. The goal was making the creation of smart contracts accessible to non-computer experts by the use of a graphical programming language (Blockly). We used modularization to capture the complexity of legal contracts and developed a mapping process to transform the graphical representation to the smart contract programming language Solidity. We applied our approach to legal purchase agreements and proved the practicality of our solution and explored its limitations. A prototype was built to show the feasibility of our approach. Our industry partner challenged the prototype by applying it to the contract creation process. We consider our work as the first step towards an application of smart contracts in the nonIT world and outside the today’s expert shaped ecosystem of blockchain specialists. Several continuative research questions have been derived from our finding and are listed at the end of this paper.

摘要:Emerging blockchain technology has introduced a new challenge to the distributed system research: Can Byzantine fault-tolerance protocols scale up to, for example, hundreds of nodes? In this work, we introduce HiBFT, a hierarchical Byzantine fault-tolerance protocol to address the problem. The core idea is to divide replicas into groups and exchange consensus messages among groups, thus avoiding the necessity of message broadcasting. The motivation for such approach bases on the hierarchical property of network architecture in permissioned block chains, our target deployments. HiBFT works very much in the same way as the classical Practical Byzantine Fault-Tolerance protocol. However, it replaces the concept of physical replica with a logical one that represents a replica group. As such, protocol message complexity can be reduced from O(N2) to O(s2) where N and s are the total number of replicas and the number of groups. Additionally, using threshold signature scheme for representing a logical group results in two important improvements: The cost of signature verification is significantly reduced at each replica; blocks can be secured more effectively in terms of signature size. Our protocol guarantees safety and liveness under partially synchronous assumption with a correctness proof. Our experiment results show that the protocol can scale up to hundred of nodes.

摘要:The block chain technology is changing rapidly. The block chain guarantees the integrity of the book through a specific consensus of the participants. In the past, the block chain technology had a limited range of applications. However, the use of block chain technology is gradually expanding as smart contracts that can formulate general business logic are mentioned. Already studied the components of smart contracts in other studies and proposed the possibility of extending them on the basis of ontology. And research on securing traceability of smart contract based on ontology has been carried out. However, research on various transactions constituting smart contracts is lacking. In this paper, the constituent elements of smart contract are analyzed and expressed by ontology. And the process of negotiating the components is represented by each transaction. Finally, we construct the component represented by the ontology as XML by including the state information in the transaction. In this way, the smart contract is represented in a formal language that contains state information. It also laid the foundation for a smart contract that can be reused and verified.

摘要:In this work, we acknowledge the need for software engineers to devise specialized tools and techniques for blockchain-oriented software development. Ensuring effective testing activities, enhancing collaboration in large teams, and facilitating the development of smart contracts all appear as key factors in the future of blockchain-oriented software development.

摘要:Smart contracts play an advent role in automated business participation by rendering collaboration processes more time efficient, cost-effective and establishing more transparency. Smart contracts facilitate trust-less systems, without the need for intervention from third-party intermediaries. Existing smartcontract languages mainly focus on technical utility and do not take into consideration social and legally relevant issues, e.g., lack of semantics, ontological completeness, and so on. In this research, we address the gap by developing with rigorous means a smart contract’s language that aims to be legally relevant, and that comprises socio-technical utility for crossorganizational business collaboration. The proposed language seeks to retain the strengths of the already existing languages of different generations while eluding their limitations. We aim to identify and implement abstract grammar patterns for a smart- contract language that has the expected application utility and verifiability. We evaluate the developed language based on automating industry-collaboration cases with our novel smartcontract language to test the suitability, utility and expressiveness.

摘要:The smart contract on the blockchain allows credible transactions without a third party. These transactions are traceable and irreversible. The deployment and implementation of smart contracts in Ethernet will consume some gas, which will directly affect the cost of smart contracts. In order to reduce the consumption of gas during the execution of smart contracts, this article proposes an optimization algorithm for generating business process smart contracts. First, business process modeling notation (BPMN) models are extended to Petri nets. Second, Petri nets are simplified to find nodes in BPMN models that can be considered fusion tasks. Using new mapping rules from the BPMN model to solidity language, BPMN model is generated into Ethereum Smart contract model. In the BPMN models with multilayer fusion task, experimental results show that the proposed algorithm can save 15% gas on average for business processes with multiple fusion tasks.

摘要:Abstract—As the number of Web APls is rapidly increasing, itis an urgent issue to discover qualified Web APis and providevalue-added services by orchestrating them. How ever, most ofthe interface descriptions of Web APls are informal, and theWeb API SLA contracts, w hich are a key to quality of servicesorchestration，requirc manual operations at the consumers.Meanwhile，applying the blockchain，the distributed ledgertechnology， to various domains beyond Fintech is attractingattention because of its fault-tolerant and anti-4ampering.However,it isn't applied to Web API SLA contracts,yet.inthis article，the authors propose a formal specificationdescription of Web APls together with its associated SLAspecifications based on RDF,and an SLA contract mcthodbased on the common SLA contract platfor m built on theblockchain. We implementedtheprototype of the SLAcontract platform,and applied itto theexamples fordemonstrating itsfeasibility.Thosc experiences prove thcfe asibility of the proposed Web API SLA contract method andits supporting platform.

摘要:为解决区块链在查询方面存在的访问方法支持有限、查询功能单一、查询效率低等不足，提出一种区块链数据的 关系查询解决方案FabricSQL,将Hyperledged Fabric与MySQL结合,把实时存储的区块链有效交易数据同步存储到SQL数据库中。为防止数据库中的数据被篡改，提出一种交易数据存储验证机制，在SQL数据存储时使用Salt加密方法,在数据顺序追加时引入区块链前哈希的思想防止作恶,在用户访问时，进行数据的一致性校验，返回需求数据和校验结果，保证数据的安全性。在设计的实验模型和基于Fabric的区块链系统上进行多项查询性能的对比实验,实验结果表明,FabricSQL同时拥有区块链和关系型数据库的良好特性。

摘要:Due to limited computing and storage resources, light clients and full nodes coexist in a typical blockchain system. Any query from light clients must be forwarded to full nodes for execution, and light clients verify the integrity of query results returned. Since existing authenticated query based on Authenticated Data Structure (ADS) suffers from significant network, storage and computing overheads by virtue of Verification Objects (VO), an alternative way turns to Trust Execution Environment (TEE), with which light clients have no need to receive or verify any VO. However, state-of-the-art TEE cannot deal with largescale application conveniently due to limited secure memory space (i.e, the size of enclave in Intel SGX is only 128MB). Hence, we organize data hierarchically in both trusted (enclave) and untrusted memory and only buffer hot data in enclave to reduce page swapping overhead between two kinds of memory. Security analysis and empirical study validate the effectiveness of our proposed solutions.

摘要:Blockchain technology has gained immense popular- ity because many researchers believe that it could solve numerous problems and could be applied in various fields of study. Unfortunately, behind its potentials, blockchain also possessed many challenges and limitations. The highlighted problem is the usability aspect of blockchain technology examined from developer and user perspective. This paper tried to address this problem by proposing query functionalities, with the help of query layer system, to facilitate the developer and the user to access blockchain data easily. There are three main query functionalities that will be discussed in this paper: (1) finding blockchain data based on multiple search parameters (retrieval query), (2) providing simple statistical analysis from a collection of blockchain data (aggregate query) and (3) sorting blockchain data according to its blockchain component (ranking query). For the implementation stage, Ethereum is used as platform to provide blockchain network, MongoDB is used as cloud storage service and REST API is used as web services. For the testing stage, throughput and time response are used to evaluate the performance of the developed query functionalities in the query layer system. The results are: (1) the throughput of query layer system is lower than Ethereum service for blockchain data retrieval and (2) the time response of query layer system is affected by the number of thread and the amount of data stored in cloud storage.

摘要:We discuss the problem of constructing efficient temporal indexes on Hyperledger Fabric, a popular Blockchain platform. The temporal nature of the data inserted by Fabric transactions can be leveraged to support various use-cases. This requires that temporal queries be processed efficiently on this data. Currently this presents significant challenges as this data is organized on file-system, is exposed via limited API and does not support temporal indexes. In a prior work [1], we presented two models for creating temporal indexes on Fabric which overcome these limitations and improve the performance of temporal queries on Fabric. The first model creates a copy of each event inserted and stores temporally close events together on Fabric. The second model keeps the event count intact but tags metadata to each event s.t. temporally close events share the same metadata. In this paper, we present variants on these two models which are better able to handle the skew present in Fabric data. We discuss the details and show that these variants significantly outperform the approaches presented in [1] when Fabric data contains skew. We also discuss the performance tradeoffs among these variants across various dimensions - data storage, query performance, event insertion time etc.

摘要:区块链是在数字加密货币的应用基础之上发展起来的一种分布式数据库技术。区块链系统具有去中心化、不可篡 改、分布共识、可溯源和最终一致性等特点，这使其可以用于解决不可信环境下数据管理问题。区块链独特的数据管理功能 已经成为各领域应用中发挥其价值的关键。本文基于对比特币、以太坊、超级账本等代表性区块链系统的研究分析，阐述区 块链系统中分布式数据管理技术。首先，深入讨论区块链系统与传统分布式数据库系统之间的异同点，从分布式部署模式、 节点角色、链拓扑结构等多个方面给出区块链的分类。然后，详细分析各类区块链系统所使用的数据存储结构、分布式查询 处理与优化技术及其优缺点。最后，总结区块链系统的分布式数据管理技术在各专门领域应用中所面临的挑战和发展趋势。

摘要:作为支撑比特币实现无中心高可信的账本管理的技术 ， 区块链在金融领域得到了广泛关注． 区块链实现 了不完全可信环境中的可信数据管理，具有去中心化、防篡改、不可抵赖、强一致和完整性等特性 ，但同时也存在 高延迟和低呑吐率的性能问题． 在互联网技术发展、新型应用层出不穷的大背景下，借鉴区块链在数字加密货币应 用中的成功经验，探索可信数据管理的理论、技术 ， 并设计、实现系统 ， 是学术界所面临的重要问题． 从可信数据管 理角度，介绍了区块链相关的技术和研究进展， 包括分布式共识、智能合约、数据溯源等，并分析了应用对可信数据 管理所提出的需求和研究战。

摘要:区块链是一项具有颠覆许多传统行业的潜力的新兴技术。自以比特币为代表的区块链1.0诞生以来，区块链技术获得了广泛的关注，积累了大量的用户交易数据，而以以太坊为代表的区块链2.0的 诞生,更加丰富了区块链的数据类型。区块链技术的火热，催生了大量基于区块链的技术创新的同时也带来许多新的问题，如用户隐私泄露，非法金融活动等.而区块链数据公开的特性,为研究人员通过分析区块链数据了解和解决相关问题提供了前所未有的机会。因此，总结目前区块链数据存在的研究问题、取得的分析成果、可能的研究趋势以及面临的挑战具有重要意义。为此，全面回顾和总结了当前的区块链数据分析的成果，在介绍区块链技术架构和关键技术的基础上，分析了目前区块链系统中主要的数据类型，总结了目前区块链数据的分析方法,并就实体识别、隐私泄露风险分析、网络画像、网络可视化、市场效应分析、交易模式识别、非法行为检测与分析等7个问题总结了当前区块链数据分析的研究进展.最后针对目前区块链数据分析研究中存在的不足分析和展望了未来的研究方向以及面临的挑战。