Decentralized Privacy-Preserving Timed Execution in Blockchain-Based Smart Contract Platforms

The execution of smart contracts (SCs) relies on consensus algorithms that validate the miner who executes the contract and gets a fee to cover her expenditure. In this sense, miners are strategic agents who may focus on executing those contracts with the largest fee, to the detriment of other SCs’ execution times, which also harms the blockchain’s reputation. This paper analyzes the impact of miners’ competition on SCs’ execution times in a public blockchain. First, we explain that the Proof-of-Work mechanism casts similarities with a time auction, where the one who first adds blocks is the one who executes the contract and gets the fee. At equilibrium, costs negatively affect execution times, while the opposite holds concerning fees. However, this result does not capture the competition for other contracts; hence, we apply the Naïve Bayes method to classify SCs by considering a simulated database that comprises miners’ competition for several contracts. We observe that simultaneous competition generates patterns that differ from the ones expected by the auction solution. For example, miners’ valuation does not accelerate contracts’ execution, and high-cost smart contracts do not necessarily execute at last places.

Recently there has been a surge of interest in developing performance debugging tools to help programmers tune their applications for better memory performance [2, 4, 10]. These tools vary both in the detail of feedback provided to the user, and in the run-time overbead of using them. MemSpy [10] is a simulation-based tool which gives programmers detailed statistics on the memory system behavior of applications. It provides information on the frequency and causes of cache misses, and presents it in terms of source-level data and code objects with which the programmer is familiar. However, using MemSpy increases a program's execution time by roughly 10 to 40 fold. This overhead is generally acceptable for applications with execution times of several minutes or less, but it can be inconvenient when tuning applications with very long execution times.This paper examines the use of trace sampling techniques to reduce the execution time overhead of tools like MemSpy. When simulating one tenth of the references, we find that MemSpy's execution time overhead is improved by a factor of 4 to 6. That is, the execution time when using MemSpy is generally within a factor of 3 to 8 times the normal exwution time. With this improved performance, we observe only small errors in the performance statistics reported by MemSpy. On moderate sized caches of 16KB to 128KB, simulating as few as one tenth of the references (in samples of 0.5M references each) allows us to estimate the program's actual cache miss rate with an absolute error no greater than 0.3% on our five benchmarks. These errors are quite tolerable within the context of performance bugging. With larger caches we can also obtain good accuracy by using longer sample lengths. We conclude that, used with care, trace sampling is a powerful technique that makes possible performance debugging tools which provide both detailed memory statistics and low execution time overheads.

Blockchain-based Smart Contract allows reliable enforcement of the programmatically specified agreement between distributed agents. However, during the process of verifying the result of transaction execution with distributed consensus protocol, private information such as fund amount being transferred can be exposed to others. To hide such sensitive information while keeping the integrity of the Smart Contract instances, we employ a homomorphic encryption technique. With this encryption technique, the validity of the arithmetic operation in a transaction can be checked without decrypting the operands. For instance, a remaining balance after fund transfer can be validated while the exact amount of the transferred fund and the final balance are kept in a ciphertext. In this work, we discuss the novel system architecture for verifying Smart Contracts instances with homomorphic encryption and evaluate its efficiency.

Blockchain smart contracts are prevalent nowadays as numerous applications are developed based on this feature. Though smart contracts are important and widely used, they contain certain vulnerabilities. This paper discusses various security issues that arise in smart contract applications. They are categorized in the smart contract platform, the applications that integrate with the Blockchain, and the vulnerabilities in smart contract code. A detailed study of smart contract-specific vulnerabilities and the defense against those vulnerabilities are presented in this article. Because of certain limitations of platforms or programming language used to write smart contract, there are possibilities of attacks on smart contracts. Hence different security measures or precautions to be taken while writing the smart contract code is discussed in this article. This will prevent the potential attacks happening on Blockchain distributed applications.

Smart contracts on a blockchain network can be implemented to control digital value. A key question that arises is the extent to which smart contracts can, or should, operate as “smart legal contracts”. Simply put, can smart contracts meet requirements of validity at law and practical efficacy. In order to achieve the goal of value maximization, the efforts of policy-makers, standards organisations and regulators should be informed by first principles. Standards, and other regulatory activities, must be driven by consideration of the techno-legal functions of contracting. Blockchain-based smart contracts offer the potential to reduce transaction costs through new methods of stateful computation. When applied to commercial transactions, smart contracts can represent enforcement of an executed state. This paper argues that distributed ledger and smart contracts standards should seek to provide sufficient flexibility to facilitate contracting parties to coordinate in an optimal manner.

In this paper, we propose a patient-centric care system based on a smart contract mechanism which is an enhancement to Blockchain technologies. The health records are controlled by the patients, it means the patients could choose and share what kind of information related to their health history to the clinics even the sensitive information. The secure information mechanism and e.ective technical infrastructures to enhance care coordination of individuals and communities are achieved by using Smart Contract which is implemented on Hyperledger Fabric and Ethereum Blockchain. Six algorithms were utilized for interacting data between the components of a Patient-centered healthcare system: createData(), query-Data(), get.eryHistory(), createPatientInformation() / createMedicalRecord() / createDrugInformation() / createHospitalFees() and modifyPatientInformation() / modifyMedicalRecord() / modifyDrug-Information() / modifyHospitalFees(). The simulation results show that the healthcare system and record resources consumption by the aforementioned six algorithms, in terms of execution speed and memory capacity that are allocated for each function at the execution time ranges from 1s.

With the widespread application of smart contracts, there is a growing concern over the quality assurance of smart contracts. The data flow testing is an important technology to ensure the correctness of smart contracts. We propose an approach named IABC‐TCG (Improved Artificial Bee Colony‐Test Case Generation) to generate test cases for the data flow testing of smart contracts. With a dominance relations‐based fitness function, an improved artificial bee colony algorithm is used to generate test cases, in which the bee colony search coefficient is adaptively adjusted to improve the effectiveness and efficiency of the search. In addition, an improved test case selection and updation strategy is used to avoid unnecessary test cases. The experimental results show that IABC‐TCG achieves 100% coverage for all the test requirements on a dataset of 30 smart contracts and outperforms the baseline approaches in terms of the number of test cases and the execution time. Performing tests with the generated test cases, IABC‐TCG can find more errors with less test cost.

Blockchain-based smart contract platforms have traditionally employed the transaction-driven execution model. This paper presents an alternate framework for blockchain-based smart contract execution called EDSC. Our platform design presents a novel approach to tackle the scalability and performance challenges facing the smart contract ecosystem. We base EDSC's design on the Ethereum template, and it can be readily implemented for other existing smart contract platforms. To evaluate our design, we perform an experimental implementation using the Ethereum client. Our experiments with performance modeling show, on average, a 2.2 to 4.6 times reduced total latency of event-triggered smart contracts, demonstrating the effectiveness of the design in supporting time-sensitive applications. Additionally, we comment on the design's potential security aspects and demonstrate its utility by discussing potential use cases.

PurposeCross border trade, involving different business environments between the sellers’ and buyers’ countries, may result in conflicts because of asymmetry in the information structure across the borders. The International Chambers of Commerce (ICC) has laid down ground rules on terms of shipment and payment, enabling harmonization and standardization of business process, and fixing of responsibilities for international trade. The international commercial (INCO) terms by ICC define the duties, obligations and cost borne by the exporter and the importer. An exporter’s uncertainty looms once the goods cross his/her border. Therefore, there is a need for a smart contract that is secured, transparent, legitimate and trustworthy. The authors propose a blockchain technology-based smart global contract (BTGC) framework for international trade.Design/methodology/approachIn this paper, the authors develop the framework based on value chain analysis (VCA) of international trade and an ontology-driven-blockchain-design approach. The paper analyzes the sequence of activities in the value chain of global trade, the terms of the contract, the data structure templates, the validation rules and the points-of-failure, and proposes the smart contract blockchain structure.FindingsThis paper proposes the BTGC framework considering the INCO terms 2020; it provides the validation rules and the probability of failures; and identifies the elements that cause the halting of contracts and conditions of creation of side blockchains. The framework also includes the governance of the BTGC system.Research limitations/implicationsThe proposed framework not only has implications at the firm level as it automates and secures a global sale contract but also is expected to harmonize the global-trade process as well. The developers may use the attributes, data structure templates and the rules identified in this paper for developing the GC software. Future research may consider using case analysis, class diagrams and the related steps for developing the blockchain software.Originality/valueThis paper proposes a complete value chain of global contract (GC) concerning exports, an ontology of GC and a blockchain-based smart-contract framework based on global standards. Besides, it specifies the elements of fraud (such as the non-integration of side chains) and uncertainty, i.e. the probability of failures. Such a framework will harmonize the global-trade process and build an international standards for smart GC based on blockchain technology (ISSGCBT), which is not yet done.

Data security is a major issue for smart home networks. Yet, different existing tools and techniques have not been proven highly effective for home networks’ data security. Blockchain is a promising technology because of the distributed computing infrastructure network that makes it difficult for hackers to intrude into the systems through the use of cryptographic signatures and smart contracts. In this paper, an architecture for smart home networks that could guarantee data integrity, robust security, and the ability to protect the validity of the blockchain transactions has been investigated. The system model is tested using various sizes of realistic datasets (30, 3 k, and 30 k to represent a small, medium, and large number of transactions, respectively). Four different consensus algorithms were considered, the conventional schemes concatenated hash transactions (CHT) and Merkle hash tree (MHT), as well as the newly proposed odd and even modified MHT (O&E MHT) and modified MHT (MMHT). Moreover, 15 hash functions were also examined and compared to understand the effects of each consensus algorithms on the data integrity verification check execution time and the time optimization provided by the proposed MMHT algorithm. The results show that even though the CHT algorithm gives the lowest execution time, it is impractical for a blockchain implementation due to the requirement to copy the entire blockchain ledger in real time. Meanwhile, the O&E MHT does not give any tangible benefit in the execution time. However, the proposed MMHT offers a minimum of 30% gain in time optimization than the conventional MHT algorithm typically used in blockchains. This work shows that the proposed MMHT consensus algorithm not only can identify malicious codes but has an improved data integrity check performance in smart homes, all while ensuring network stability.

The world today has realized the vast technological evolution that has greatly shaped the production and management functions of business enterprises. Traditional contracts can take weeks or even months to initiate, and there have been numerous instances of breaches and lack of trust for contracts in both the private and public sector. A smart contract can be defined as a self-executing contract that utilizes blockchain technology to digitally enforce, verify, or facilitate the performance or negotiation of a contract. Owing to the security and decentralized system exhibited by blockchain technology, smart contracts can foster transaction credibility between contracting parties without the necessity of third parties as exhibited in traditional contracts. Any business organization that aims at achieving greater heights in management and production dimensions must consider utilizing robust technologies that are aimed at bolstering its competitive edge. Owing to the newness of smart contracts, characterized by very few studies on the same, this research reviews how smart contracts through blockchain technology can be implemented in an organization to enhance performance and outlines the applications, benefits, and limitations associated with such contracts. Keywords: Blockchain technology; smart contracts; smart contract applications; smart contract benefits; smart contract implementation; cryptography; cryptocurrency DOI : 10.7176/JIEA/9-5-07 Publication date :September 30 th 2019

Introduction: Although blockchain technology and smart contracts are garnering attention in various sectors, their applications and familiarity within the realm of radiology remain largely unexplored. Blockchain, a decentralized digital ledger technology, offers secure, transparent, and resilient data management by distributing the verification process across a network of independent entities. This decentralized technology presents a possible solution for a range of healthcare challenges, from secure data transfer to automated verification processes. To address such challenges in the context of medical imaging, blockchain could provide different approaches, including smart contracts, machine learning algorithms, and the secure dissemination of large files among key stakeholders such as patients, healthcare providers, and institutions. This manuscript aims to explore the current attitudes and perspectives of trainees and radiologists to the utilization of blockchain technology and smart contracts in clinical radiology. Additionally, the study provides an in-depth analysis of the potential applications for incorporating blockchain into radiology.Methods: After obtaining The George Washington University Committee on Human Research Institutional Review Board (IRB) approval, we conducted a 10-question survey among radiologists and trainees at several institutions and private practices. Surveys were created via the Google Forms application and were emailed to potential participants. Participants were asked about their current academic level (medical student, resident/fellow, academic radiologist, private practice radiologist, others), their knowledge level about the field of imaging informatics and blockchain and smart contract technologies, their level of interest in learning more about blockchain and smart contracts, and their opinion about possible applications of blockchain and smart contract in the future of medical imaging.Results: A total of 118 survey requests were distributed; 83 were returned, reflecting a 70.3% overall response rate. Of these, 19 were sent to private practices with a 15.8% response rate (3/19), and 99 to academic centers, yielding an 80.8% response rate (80/99). The survey respondents demonstrated a strong interest and need to further understand these technologies among radiologists and trainees. This study focuses on key components of this technology as it relates to healthcare and the practice of radiology, including data storage, patient care, secure communication, and automation, as well as strengths, weaknesses, opportunities, and threats (SWOT) analysis.Discussion: To our knowledge, this is the first study to investigate and establish a baseline for the current perspectives on the application of blockchain technology and smart contracts in clinical radiology amongst trainees and radiologists across academic and private settings. Incorporating blockchain and smart contracts technologies into the field of radiology has the potential to achieve greater efficiency, security, and patient empowerment. However, the adoption of this technology comes with challenges, such as infrastructure, interoperability, scalability, and regulatory compliance. Collaboration between radiologists, hospital administration, policymakers, technology developers, and patient advocacy organizations will help guide and advance our understanding of the potential applications of blockchain and smart contracts in radiology and healthcare.

Smart contracts are set of instructions which are stored on a blockchain. These instructions will be executed automatically without middle-man interaction. Smart contracts in the blockchain allows the transactions and contracts to be executed across undesignated nodes without an interaction of central system or external enforcement. The transactions are transparent, traceable and irreversible. In blockchain all the data stored are secure and immutable. So blockchain would be the suitable environment for smart contracts. Smart contract data is encrypted and placed in a distributed ledger, which means the information stored in the blocks cannot be deleted or modified. There are many blockchain platforms supporting smart contracts. This paper explores the information about various smart contract platforms and its features.

Smart contract technology plays a significant role in various fields for achieving secure and automated transactions without the interference of third parties. There arise certain issues of security and privacy issue during the transaction with the assistance of a smart contract. In this present work, a comparative analysis is carried out between various existing techniques in blockchain-based smart contract techniques. First, analysis is done on the security issue. Second, on the basis of smart contract design. Finally, on privacy issue in smart contract platform. To analyse the performance, metrics such as consumption cost, transaction cost, time overhead and processing time are validated. The cost consumption and time overhead attained for the Auditable Access Control System (AACS) technique is 30,125,894 gas and 3,285 sec. The processing time attained for Online Auto Update Smart Contract (OAUSC) is 2,653 sec. This analysis suggested AACS technique functions better in comparison to other existing techniques.

Smart contract technology plays a significant role in various fields for achieving secure and automated transactions without the interference of third parties. There arise certain issues of security and privacy issue during the transaction with the assistance of a smart contract. In this present work, a comparative analysis is carried out between various existing techniques in blockchain-based smart contract techniques. First, analysis is done on the security issue. Second, on the basis of smart contract design. Finally, on privacy issue in smart contract platform. To analyse the performance, metrics such as consumption cost, transaction cost, time overhead and processing time are validated. The cost consumption and time overhead attained for the Auditable Access Control System (AACS) technique is 30,125,894 gas and 3,285 sec. The processing time attained for Online Auto Update Smart Contract (OAUSC) is 2,653 sec. This analysis suggested AACS technique functions better in comparison to other existing techniques.