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。

摘要:区块链应用有去中心化、可追溯、不可篡改等优点，但现有的区块链系统难以满足在大数据量下数据的查 询、访问需求。针对以上问题，结合ETL 流程与区块链自身特点，提出一种区块链应用查询优化流程模型ETLVQ （Extract-Transform-Load-Validation-Query）。模型分为三个阶段：在第一阶段将区块链应用中异构数据源的数据进 行抽取、转换并加载到查询优化数据仓库中；在验证阶段对加载后数据进行一致性校验；在查询阶段对外提供查询 访问服务。该模型在保证区块链数据安全性的前提下，显著提升了区块链应用的查询访问效率与并发能力。

摘要:Blockchain systems (more precisely Distributed Ledger Technologies (DLTs)) represent a different digital ecosystem compared with traditional computer systems. One major difference are the performance and scalability factors which will be discussed and analytically investigated in this paper. In doing so, we provide guidance for defining a research agenda focusing on the investigation of the crucial role of scalability for blockchain systems. System performance – measured in terms of (1) consensus response time (blockchain network latency or time to convergence/agreement); (2) number of transactions per second or throughput, and (3) computing (and power) resources consumed – can be understood by considering the design dimensions of a blockchain system, namely: (i) the type of blockchain system needed from a requirements perspective which in turn determines; (ii) the complexity of the consensus protocol used; (iii) the topography of the traffic flow on the network; (iv) the performance and complexity of the domain-specific language that implements smart contracts; and (v) by the anticipated growth in size and complexity of the distributed ledger itself.

摘要:区块链技术作为分布式账本的关键技术之一，其在不依赖于任何第三方可信机构的前提下， 解决开放网络中的信任问题，去中心化的特点使其有着广泛的应用前景，但面临着可扩展性不足的瓶 颈．目前，区块链可扩展性的瓶颈主要体现在２个方面：性能效率低下、功能难以扩展．以比特币为例，从 性能上讲，当前仅支持７笔?秒的交易吞吐量，显然无法满足现今数字支付的场景，也无法承载在数字支 付领域外的其他应用．从功能上讲，当前不同区块链系统之间的资产或数据难以交互．在现实情况中， 不同的区块链系统承载着不同的业务和需求．为此，需要实现链与链之间的交互，才能打通不同区块链 之间的信息或价值通道，避免每一区块链成为信息或价值孤岛，并在此基础上实现价值互联网．区块链 可扩展性的研究已经引起了学术界及产业界越来越多的关注，将从区块链性能提升及功能扩展２个角 度出发，分别介绍区块链可扩展性领域的相关技术和研究进展，其中包括３类当前主流的、提升区块链 交易吞吐量的方案：链下支付网络、Ｂｉｔｃｏｉｎ－ＮＧ和分片机制；以及４类代表性的、实现区块链功能扩展 的跨链互通技术．分析对比不同方案的特性、适合场景及可能存在的不足之处，并在此基础上给出进一 步研究方向

摘要:近年来，区块链作为一门新兴技术得到了广泛关注。但是，区块链技术离真正的投入使用 还有相当长的一段路程需要走。目前，区块链无法投入生产的一个重要因素，是现存的区块链系统 的低吞吐率无法满足现实生产的需要。例如，理论上，比特币是7 TPS，以太坊是15 TPS，而传统 的中心化系统如VISA，支持上千的TPS。因此，分析限制区块链扩展性的主要因素，抽离出提高 吞吐率的模型，并且针对每个方面进行具体分析，为以后的研究奠定基础。

摘要:Blockchain is a new technology for data sharing between untrusted peers. However, it does not work well with massive transactions. Besides, there are high barriers between heterogeneous blockchain systems. In this paper, we proposed an innovative component-based framework for exchanging information across arbitrary blockchain system called interactive multiple blockchain architecture. In our architecture, a dynamic network of multi-chain is created for inter-blockchain communication. We propose the inter-blockchain connection model for routing management and messages transferring. Additionally, our proposed protocols provide transactions with atomicity and consistency in crossing-chain scene. In the end, our experiment results based on a network of private multiple blockchain systems show that the throughput is increased by a number of chains parallel running.

摘要:智能合约是区块链核心技术之一，其安全可靠性至关重要。随着区块链技术的应用推广，智能合约的数量呈现爆 发式增长，但智能合约的漏洞将给用户带来巨大损失。在分析以太坊智能合约运行机制和常见漏洞原理的基础上，利用符号 执行技术检测智能合约漏洞。首先以太坊字节码构建智能合约执行控制流图，再根据智能合约漏洞特点设计相应的约束条件， 利用约束求解器生成软件测试用例，检测常见的整型溢出，权限控制，Call 注入，重入攻击等智能合约漏洞。实验结果表明， 检测方案具有良好的检测效果，智能合约漏洞检测正确率达 85%

摘要:A smart contract is hard to patch for bugs once it is deployed, irrespective of the money it holds. A recent bug caused losses worth around $50 million of cryptocurrency. We present ZEUS—a framework to verify the correctness and validate the fairness of smart contracts. We consider correctness as adherence to safe programming practices, while fairness is adherence to agreed upon higher-level business logic. ZEUS leverages both abstract interpretation and symbolic model checking, along with the power of constrained horn clauses to quickly verify contracts for safety. We have built a prototype of ZEUS for Ethereum and Fabric blockchain platforms, and evaluated it with over 22.4K smart contracts. Our evaluation indicates that about 94.6% of contracts (containing cryptocurrency worth more than $0.5 billion) are vulnerable. ZEUS is sound with zero false negatives and has a low false positive rate, with an order of magnitude improvement in analysis time as compared to prior art.

摘要:Smart contracts are full-fledged programs that run on blockchains (e.g., Ethereum, one of the most popular blockchains). In Ethereum, gas (in Ether, a cryptographic curren- cy like Bitcoin) is the execution fee compensating the computing resources of miners for running smart contracts. However, we find that under-optimized smart contracts cost more gas than necessary, and therefore the creators or users will be overcharged. In this work, we conduct the first investigation on Solidity, the recommended compiler, and reveal that it fails to optimize gas- costly programming patterns. In particular, we identify 7 gas- costly patterns and group them to 2 categories. Then, we propose and develop GASPER, a new tool for automatically locating gas- costly patterns by analyzing smart contracts’ bytecodes. The preliminary results on discovering 3 representative patterns from 4,240 real smart contracts show that 93.5%, 90.1% and 80% contracts suffer from these 3 patterns, respectively.

摘要:Finding and exploiting vulnerabilities in binary code is a challenging task. The lack of high-level, semantically rich information about data structures and control constructs makes the analysis of program properties harder to scale. However, the importance of binary analysis is on the rise. In many situations binary analysis is the only possible way to prove (or disprove) properties about the code that is actually executed. In this paper, we present a binary analysis framework that implements a number of analysis techniques that have been proposed in the past. We present a systematized implementation of these techniques, which allows other researchers to compose them and develop new approaches. In addition, the implementation of these techniques in a unifying framework allows for the direct comparison of these approaches and the identification of their advantages and disadvantages. The evaluation included in this paper is performed using a recent dataset created by DARPA for evaluating the effectiveness of binary vulnerability analysis techniques. Our framework has been open-sourced and is available to the security community.

摘要:Solidity is a language used for smart contracts on the Ethereum blockchain. Smart contracts are embedded procedures stored with the data they act upon. Debugging smart contracts is a really difficult task since once deployed, the code cannot be re- executed and inspecting a simple attribute is not easily possible because data is encoded. In this paper, we address the lack of inspectability of a deployed contract by analyzing contract state using decompilation techniques driven by the contract structure definition. Our solution, SmartInspect, also uses a mirror-based architecture to represent locally object responsible for the in- terpretation of the contract state. SmartInspect allows contract developers to better visualize and understand the contract stored state without needing to redeploy, nor develop any ad-hoc code.