Table of Content

31 January 2021, Volume 39 Issue 1

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Blockchain

Verification of Smart Contracts with Time Constraints

ZHAO Yingqi, ZHU Xueyang, LI Guangyuan, GAO Ya, BAO Yulong

2021, 39(1):  1-16.  doi:10.3969/j.issn.0255-8297.2021.01.001

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In real life, a type of smart contract is closely related to time constraint, and whether the contract meets its time property will directly affect the correctness of its applications. In order to avoid serious problems after its deployment, this paper focuses on smart contracts of Ethereum, gives a timed automata semantics for smart contracts, after the smart contract is converted into a time automata model, and uses model checking tool UPPAAL to check whether the smart contract meets timed properties expressed by temporal logic formulas. Finally, we study two cases, an auction contract and a flight insurance contract. Experimental results indicate whether the real-time property is satisfied. If not, counter examples can be used to locate the problem points in the smart contract, showing the effectiveness of the work.

SGX-Based Approach for Blockchain Transactions Security and Privacy Protection

FAN Junsong, CHEN Jianhai, SHEN Rui, LIU Zhenguang, HE Qinming, HUANG Butian

2021, 39(1):  17-28.  doi:10.3969/j.issn.0255-8297.2021.01.002

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Compared to traditional payment, blockchain has the advantages of decentralization and privacy protection, while there are still issues with the privacy and security of transactions involving lightweight clients and with the user-friendliness of blockchain systems. This paper proposes SGXTrans, a system that can provide privacy protection for blockchain transaction. On the framework of lightweight clients, as SGXTrans creates a service, it uses Intel software guard extensions (SGX) to protect sensitive privacy information by putting them into the SGX enclave, including cryptographic data and operations such as the user key, the generation of user addresses, and the process of blockchain transactions. To hide the access patterns of local data storage processes, SGXTrans also introduces oblivious random access machine (ORAM) algorithm to prevent privacy information from being indirectly inferred by malicious attackers. Experiments based on the existing blockchain networks show that SGXTrans can provide better user-friendliness and higher security with a performance overhead less than 10%.

Auditable and Traceable Blockchain Anonymous Transaction Scheme

ZHAO Xiaoqi, LI Yong

2021, 39(1):  29-41.  doi:10.3969/j.issn.0255-8297.2021.01.003

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In recent years, with the strengthening of privacy protection for blockchain transactions, it has become more difficult to audit blockchain transactions and track the identity of illegal traders. For this reason, an auditable and traceable blockchain anonymous transaction scheme is proposed in this paper. Elgamal encryption, digital signature and improved hidden address technologies are used to realize the privacy protection of the transaction content and the identities of transaction senders and transaction receivers, and realize the distribution of power by introducing two roles of auditor and regulator. When an illegal transaction is audited, auditor sends a tracking identity request with signature to the regulator. After the signature is verified, the regulator can use the received tracking key and the personal key to trace the identities of both parties to the transaction. This scheme satisfies the anonymity, auditability and identity traceability of transactions. Simulation experiment results show the high audit efficiency of the scheme.

Trusted Query Method for Data Provenance Based on Blockchain

ZHANG Xuewang, FENG Jiaqi, YIN Zijie, LIN Jinzhao

2021, 39(1):  42-54.  doi:10.3969/j.issn.0255-8297.2021.01.004

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In order to reduce the storages needed in verifying provenance information of light clients in blockchain data provenance system, this paper firstly introduces a data structure titled by Merkle mountain range (MMR), which optimizes the dynamic append performance of Merkle trees and stores all block headers on blockchain in the MMR. Then we propose an efficient and reliable verification method for data provenance to reduce the size of the proof information required for the proof of the block contain. On this basis, a scheme of data provenance system based on block chain is designed, which encapsulates the common modules required for data provenance and opens them to the provenance application through interfaces. This scheme enables light clients to effectively verify whether the provenance information is contained in the block chain as long as they keep the information of the latest block in storage.

Blockchain and Capability Based Access Control Mechanism in Multi-domain IoT

WANG Siyuan, ZOU Shihong

2021, 39(1):  55-69.  doi:10.3969/j.issn.0255-8297.2021.01.005

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Data in Internet of things (IoT) usually contains a large amount of personal privacy information, In order to prevent privacy data leakage due to unauthorized access during device collaboration, this article proposes a set of access control mechanisms for multi-domain IoT device collaboration scenarios. By combining distributed capabilitybased access control (CapAC) with blockchain technology, this article designs a capability token stored in the blockchain and a token management contract based on smart contracts. According to CapACs access decision-making method, a blockchain-based token verification method is designed. The blockchain lightweight node is optimized for the characteristics of IoT. Finally, a blockchain system is built to implement the mechanism proposed in the article. Experimental test results show that compared to centralized access control mechanisms, this solution can safely and accurately execute access decisions in large-scale IoT scenarios and has more stable processing performance. Lightweight design can greatly reduce node storage burden.

Authentication Method of Integrated Energy Management System Based on Blockchain

ZHOU Qi, SHEN Tao, ZHU Yan, LIU Yingli

2021, 39(1):  70-78.  doi:10.3969/j.issn.0255-8297.2021.01.006

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In order to improve the utilization of integrated energy management system, and simultaneously protect the identity information of accessing users in the process of energy trading account, this paper puts forward a integrated energy management system framework based on blockchain technology, and designed a special kind of zero-knowledge proof authentication method. First, this paper introduces applicability of blockchain technology in integrated energy management system, then analyzes privacy issues in data interaction between users and load aggregator's, and discusses the unique advantages of blockchain technology in integrated energy management system, such as traceability, openness, anonymity in solving trusting problems, and records all interactive information by using blocks. Finally, based on the proposed zero-knowledge proof method, the connection between user's biological information and user's stored information is established to realize an automatic, secured and trusted authentication mode.

Improved PBFT Scheme Based on Reputation Voting

TU Yuanchao, CHEN Yuling, LI Tao, REN Xiaojun, QING Xinyi

2021, 39(1):  79-89.  doi:10.3969/j.issn.0255-8297.2021.01.007

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As a decentralized, tamper-proof distributed ledger, the performance of blockchain is fundamentally affected by the efficiency of consensus mechanisms. Practical Byzantine fault tolerance (PBFT) algorithm randomly selects master nodes through view-switching, leading to problems of security vulnerabilities and low consensus efficiency in the case of large number of nodes. In response to the two problems, a PBFT improvement scheme based on reputation voting is proposed. The reliability of nodes is evaluated according to node division mechanism, where high reputation nodes are dynamically selected to participate in the consensus, and a malicious node is assigned with lower probability of becoming a consensus node, accordingly increasing the security of the system. By switching the role of nodes according to node state transfer mechanism, the scheme can maintain the correct operation of the system and improve the stability of the system. Experiments on the proposed and the traditional PBFT schemes show that the proposed one can reduce Byzantine nodes and communication overhead in long-term consensus processes, and improve the fault tolerance rate and the data throughput of transaction.

Roadside Parking Management System Based on Blockchain Technology

YANG Di, XU Han, LONG Chengnian, PENG Shaoliang

2021, 39(1):  90-98.  doi:10.3969/j.issn.0255-8297.2021.01.008

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Aiming at the shortcomings of low efficiency and opaque transaction in current roadside parking management, a roadside parking management system based on blockchain technology is proposed. Parking information is collected by license plate recognition algorithm of edge device terminal, and key parking transaction data is sent and stored in MySQL database cache of Web server, and then stored in Hyperledger Fabric blockchain platform through Fabric SDK middleware. Relying on the decentralization of the blockchain and the non-tamperable nature of the on-chain data, the system not only meets business needs but also improves the privacy of users and the reliability of transactions.

An Architecture Based on Lightweight Blockchain Suitable for Vehicular Cloud

FAN Jun, LI Ru, ZHANG Yihang

2021, 39(1):  99-108.  doi:10.3969/j.issn.0255-8297.2021.01.009

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The mobility of nodes in vehicular cloud, the dynamics of networks, the openness of communication methods, and the non-trustworthiness of vehicles bring more challenges to the security of task scheduling in vehicular cloud. Based on the full consideration of characteristics of vehicular cloud, this article introduces blockchain and proposes a lightweight blockchain architecture suitable for task scheduling in vehicular cloud. Road side units (RSU) are used to construct a blockchain network, and an improved practical Byzantine fault tolerance (PBFT) algorithm is used to complete the consensus. Based on the scheduling delay model of the architecture, the scheduling performance of the architecture is tested and analyzed through experiments. The comparison with Ethereum shows that the proposed architecture not only realizes the non-repudiation of the task scheduling process, avoids the single point failure of the task scheduling server, improves the availability, but also achieves lightweight, that is, no additional computing power or storage space is required, and can reach millisecond-level scheduling delay.

Research and Design of Legal Smart Contract Platform Model

XIANG Weijing, TSAI Weitek

2021, 39(1):  109-122.  doi:10.3969/j.issn.0255-8297.2021.01.010

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Blockchain is essentially a distributed database or a network database. A real smart contract should be legally effective chain code, namely, the digitization of legal contracts, and can realize the automatic execution of contract terms. This article firstly introduces important technologies relevant to this type of smart contract, including legal considerations, oracles, event models and others, then proposes five standard development steps for legal smart contracts and a method for designing smart contract templates. Moreover, we also design a secure multi-channel event model for data preprocessing. Consequently, contracts processed on the above smart contract platform are expected to have legal effect.

Medical Data Security Sharing Scheme Based on Consortium Blockchain

ZHOU Zhengqiang, CHEN Yuling, LI Tao, REN Xiaojun, QING Xinyi

2021, 39(1):  123-134.  doi:10.3969/j.issn.0255-8297.2021.01.011

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The existing blockchain-based medical data sharing schemes perform access control without the consideration of time dimension. To solve this problem, this paper proposes a medical data security sharing scheme, based on consortium blockchain in consideration of time dimension to perform access control. Firstly, medical data ciphertext is stored in cloud storage, and the metadata is stored in the consortium blockchain, such that the medical data can be stored and shared safely. Secondly, by combining smart contract with ciphertext-policy attribute-based encryption (CP-ABE), a data security sharing protocol is designed to realize fine-grained access control with time dimension. The security analysis and experimental results show that this scheme could realize fine-grained access control with time dimension, besides ensuring the security of the stored medical data.

Data Protection Scheme for Targeted Poverty Alleviation Based on Blockchain

ZHANG Lihua, HUANG Yang, WANG Xinyi, BAI Jiayi, CAO Yu, ZHANG Ganzhe

2021, 39(1):  135-150.  doi:10.3969/j.issn.0255-8297.2021.01.012

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Aiming at the problems of centralized storage, weak tamper proofing, poor traceability and lack of safe and effective sharing channels, etc., a data protection scheme for targeted poverty alleviation based on blockchain is studied. By taking the advantages of blockchain technology, such as decentralization and unforgeability, poverty reduction data are recorded in the form of personal files. Through smart contract and inter-planetary file system (IPFS) technology, the data can be added, updated, verified and shared in the form of digital files. The combination of public chain and consortium ensures data security by anchoring data snapshot information. In the construction of smart contract, combined with secure multi-party computing (SMPC) technology, the security of contract execution is enhanced, and sensitive issues such as fund transfer are solved. With an improved Raft consensus algorithm, the performance, reliability and regional influence of each node are taken as comprehensive performance, based on which, a Raft consensus algorithm is designed to solve the problems of data storage and data processing efficiency. We use postman and JMeter tools to test the storage certificate and the throughput of the system, and obtain satisfying experimental results.

Analysis of Security Strategies for Smart Contracts Based on Ethereum

ZHANG Dengji, ZHAO Xiangfu, CHEN Zhongyu, TONG Xiangrong

2021, 39(1):  151-163.  doi:10.3969/j.issn.0255-8297.2021.01.013

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A smart contract is a collection of code and data. Once a smart contract is deployed, it cannot be changed. Smart contracts have financial properties, thus, it would cause huge losses if there were vulnerabilities in smart contracts. Therefore, it is essential to write safe and reliable smart contracts. Based on the Ethereum platform, related security of smart contracts is analyzed, and several common vulnerabilities are summarized, including reentrancy vulnerabilities, integer overflow vulnerabilities, deny of service (DoS) vulnerabilities, timestamp dependence vulnerabilities, and transaction-ordering dependence vulnerabilities. We made theoretical analysis in detail and scenario recurrence on these vulnerabilities, proposed corresponding preventive security strategies, and verified the effectiveness of these strategies. Finally, we analyzed and compared several popular tools for detecting smart contract vulnerabilities.

Cloud Storage Data Integrity Verification Scheme Based on Blockchain

LIU Feng, ZHAO Junfeng

2021, 39(1):  164-173.  doi:10.3969/j.issn.0255-8297.2021.01.014

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Aiming at the problems existing in data integrity of cloud storage services, a blockchain-based cloud storage data integrity verification scheme is proposed by referring to the current remote data integrity verification scheme. Firstly, an integrity certificate is stored in a tamper-proof blockchain, thus an accountable data integrity certificate is constructed. At the same time, the third-party auditor is replaced by the smart contract in the blockchain to verify the integrity of the data. In the verification stage, the integrity verification of data copies is added, and the cloud storage service is forced to store at least one data copy. In addition, a third-party arbitration organization is introduced for the first time, which uses the accountable data integrity certificate to arbitrate the integrity of illegal requests from malicious cloud storage providers and users. Finally, the proposed scheme is proved to be safe and feasible by analysis and experiment.

Convergence of Blockchain and IoT: Research Status and Prospect

YAO Zhongyuan, PAN Heng, ZHU Weihua, SI Xueming

2021, 39(1):  174-184.  doi:10.3969/j.issn.0255-8297.2021.01.015

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With the rapid development of blockchain and Internet of things (IoT) technology, the research of integrating two technologies and the development of collaborating applications have become prominent. In order to help researchers in the field of blockchainIoT convergence to analyze and grasp the research hot-spots and trends conveniently, this paper extensively investigates current relevant research literature and summarizes a large number of relevant achievements according to the specific research content. This paper also makes a detailed comparison between the research works in our country and those of foreign counterparts, with an objective clarification of the advantages and disadvantages of these research works. Finally, based on the literature research results, this paper forecasts the development trend of the research on the convergence of blockchain and IoT.