The introduction of a review system in e-commerce platforms results in an effective business model. The effects of positive/negative reviews on the success of a product are well studied in the literature. Therefore, for the vendors, it is crucial to obtain positive reviews of their products. This fact opens fraudulent scenarios. Indeed, some vendors can pay an incentive to the buyers to obtain, in exchange, a fake positive review. This fake-review system (FRS) is so widespread that vendors rely on ad-hoc companies that, through intermediaries, find buyers available to release fake reviews. In this paper, we propose a game-theory-based strategy to discourage the above fraudulent business model, and an effective way to implement this strategy leveraging an Ethereum smart contract. Specifically, the contribution of the paper is two-fold. First, we formalize the current business model as a sequential game, and we identify sufficient conditions making FRS advantageous. Second, we propose to introduce in the review system a new mechanism, thanks to which, the corresponding sequential game requires conditions necessary to make advantageous FRS that are strictly less convenient than the previous ones. We implemented the solution and evaluate the cost of the smart contract execution.
This paper focuses on using blockchain technology to enhance efficiency and cost reduction in foreign transactions through the banking system. Blockchain provides crucial features such as immutability of records and decentralization, which is then used to carry out foreign transactions. This process could be a major change in the transactions carried out by removing middle banks during transactions thereby speeding up the process. This paper aims at designing an Ethereum decentralized Banking Application for foreign money transfer using blockchain technology. Smart Contract helps to eliminate middle banks in the process by acting on rules specified in the contract. Every participant needs to abide by these rules which make it trustworthy and maintain the authenticity of the process.
With the rapid development of society, all walks of life need the support of the Internet of Things, and the financial industry is no exception. This article integrates blockchain technology with supply chain finance and builds a supply chain financial alliance architecture based on blockchain technology and an underlying model of the Ethereum blockchain system suitable for supply chain finance. We innovated new supply chain finance models and operating mechanisms and proposed business scenarios for supply chain finance from the perspective of blockchain. Taking into account the actual operation of the blockchain supply chain financial platform, the principal‐agent model and the incentive theory are applied, and the supply chain financial accounts receivable model is taken as an example in the case of complete information and incomplete information. The incentive mechanism between the service provider of the chain supply chain financial platform and the core enterprise promotes the better implementation of blockchain technology and supply chain finance. Based on the existing theoretical research, this paper identifies the key influencing factors of the supply chain’s cross‐enterprise incentive mechanism. These influencing factors system includes two dimensions: transaction factors and relationship factors. Transaction factors include resource dependence, uncertainty, and cooperation experience; relationship factors include corporate reputation, trust level, and relationship commitment. Based on the nature of the incentive mechanism, information sharing and revenue sharing are extracted as the measurement dimensions of the supply chain’s cross‐enterprise incentive mechanism. On this basis, this article draws on the existing enterprise life cycle division method and constructs a hypothetical model of the influencing factors of the incentive mechanism in the incubation period, the growth period, and the maturity period. Relevant data was collected through questionnaires, and SPSS and AMOS software were used to perform statistical analysis, reliability analysis, exploratory factor analysis, confirmatory factor analysis, and structural equation hypothesis testing on the data. The performance of each influencing factor in different stages of the enterprise’s life cycle and the importance of each influencing factor in the same life cycle stage are obtained.
The success of Bitcoin since 2009 stimulates the development of other blockchain-based applications, such as Ethereum, a second generation of cryptocurrency which supports the revolutionary idea of smart contracts. An Ethereum smart contract is a computer program written in some domain-specific high-level programming languages, such as Solidity, Vyper, Bamboo, Flint, etc., and stored on the blockchain to achieve certain functionality. Smart contracts benefit from the features of the blockchain in various aspects. For instance, it is not necessary to have an external trusted authority to achieve consensus, and transactions through smart contracts are always traceable and credible. Smart contracts must be verified for multiple reasons. Firstly, due to the decentralized nature of the blockchain, smart contracts are different from programs written in other programming languages (e.g., C/Java). For instance, the storage of each contract instance is located at a permanent address on the blockchain. In this way, each contract instance is a particular execution context and context switches are possible through external calls. Particularly, in Solidity, delegatecall is executed in the context of the caller rather than the recipient, making it possible to modify the state of the caller. Programmers must be aware of the execution context of each statement to guarantee the programming correctness. Therefore, programming smart contracts is error-prone without a proper understanding of the underlying semantic model. Secondly, a smart contract can be deployed on the blockchain by any user in the network. Vulnerabilities in deployed contracts can be exploited to launch attacks that lead to huge financial loss. Verifying smart contracts against such vulnerabilities is crucial for protecting digital assets. One famous attack on smart contracts is the DAO attack in which the attacker exploited the reentrancy vulnerability and managed to take 60 million dollars under his/her control. Finally, it is very difficult, if not impossible, to patch a smart contract once it is deployed due to the very nature of the blockchain. There is a surge of interest in analyzing and verifying smart contracts. To the best of our knowledge, most of the existing approaches either focus on EVM (Ethereum Virtual Machine) bytecode, or translate Solidity smart contracts into programs in intermediate languages that are suitable for verifying smart contracts or detecting potential issues in associated verifiers or checkers. Furthermore, none of the existing works can directly handle smart contracts written in different high-level programming languages without translating them into EVM bytecode or intermediate languages. None of the existing approaches defines security properties with the high-level semantics of smart contracts. A direct executable formal semantics of the high-level smart contract programming language concerned is a must for both understanding and verifying smart contracts. Firstly, programmers write and reason about smart contracts at the level of source code without the semantics of which they are required to understand how Solidity programs are compiled into EVM bytecode in order to understand these contracts, which is far from trivial. In addition, there may be semantic gaps between high-level smart contract programming languages and low-level bytecode which are introduced by compiler bugs. In other words, after compilation the semantics of bytecode may not be equivalent to that of the corresponding high-level programs due to the compiler bugs involved. Therefore, both high-level and low-level semantics definitions are necessary to conduct equivalence checking to guarantee that security properties are preserved at both levels and reason about compiler bugs. Secondly, even though smart contracts can be transformed into programs in intermediate languages to be analyzed and verified in existing model checkers and verifiers, the equivalence checking of the high-level smart contract programming language concerned and the intermediate language applied to interpret it is crucial to the validity of the verification. We develop an executable operational semantics for the Solidity programming language to formally reason about smart contracts written in Solidity. The contributions of this work lie in four aspects. Firstly, our work is the first approach, to the best of our knowledge, to a complete executable formal semantics of Solidity constructed directly on the language itself other than Solidity compilers. The proposed executable semantics completely covers the supported high-level core features specified by the official Solidity documentation and is validated with the official compiler Remix. In addition, a new and general way of semantics formalization is applied in the semantics design, making the proposed semantics robust in the language evolution of smart contracts. Secondly, the proposed semantics provides a formal specification of smart contracts which solves the specification issues in the existing verification and analysis tools. Thirdly, the proposed semantics allows us to formally define semantic-level security properties for verifying smart contracts to exclude the false positives and negatives introduced by the existing approaches. Finally, the proposed semantics defines correct and secure high-level execution behaviours of smart contracts to reason about compiler bugs and assist developers in writing secure smart contracts. Furthermore, we develop a generalized formal semantic framework for smart contracts. The contributions of this work lie in three aspects. Firstly, our work is the first approach, to the best of our knowledge, to a generalized formal semantic framework for smart contracts which can directly handle contracts written in different high-level programming languages. Secondly, a general semantic model of smart contracts is constructed with rewriting logic in the K-framework. With the general semantic model, a direct executable formal semantics of a particular high-level smart contract programming language can be constructed as long as its core features fall into the ones defined in this model. The general semantic model is validated with its interpretation in Solidity using the Solidity compiler test set and evaluation results show that it is complete and correct. Lastly, the generated semantics facilitates the formal verification of smart contracts written in a particular high-level programming language as a formal specification of the corresponding language. Together with low-level specifications, it allows us to conduct equivalence checking on high-level contracts and low-level bytecode to reason about compiler bugs and guarantee that security properties are preserved at both levels. We define some security properties based on the formal semantics of the high-level smart contract programming languages. These security properties are defined from a general point of view and can be applied to detect a variety of vulnerabilities in smart contracts, such as the reentrancy vulnerability, exception disorders, integer underflows and overflows, etc. In addition, verification algorithms for these properties are constructed with the proposed semantic framework. We compare our approaches to the security analysis of smart contracts with the existing ones and highlight the importance of precise semantic foundations for the verification of smart contracts. Lastly, we systematize the existing approaches to the security analysis of smart contracts from the perspectives of domain-specific research and applications of general ideas to study the connection between the domain-specific issues in smart contracts and general analysis techniques. To conclude, this thesis studies the formal specification and verification of smart contracts, and combines domain-specific analysis and applications of general techniques. It also motivates other research directions related to the security analysis of smart contracts, such as the equivalence checking of high-level contracts and low-level bytecode, formal reasoning of high-level smart contract programming languages, the fairness analysis of smart contracts, etc.
Blockchain is an innovative technology that disrupts different industries and offers decentralized, secure, and immutable platforms. Its first appearance is connected with monetary cryptocurrency transactions, followed by adaptation in several domains. We believe that blockchain can provide a reliable environment by utilizing its unique characteristics to offer a more secure, costless, and robust mechanism suitable for a voting application. Although the technology has captured the interest of governments worldwide, blockchain as a service is still limited due to lack of application development experience, technology complexity, and absence of standardized design, architecture, and best practices. Therefore, this study aims to build an imperial example for a blockchain electronic voting (e-voting) application using digital identity management for fulfilling immutable, transparent, and secure distributed blockchain features. The paper reviews the current types of e-voting systems and discusses the standard processes. We propose a conceptual design for a blockchain providing a digital identity management service to secure the e-voting application results. The blockchain development process implemented in this study follows the Proof of Concept to verify the e-voting application’s function for illustrating the architecture and description of the application’s business process model. The development is based on the Ethereum platform, which allows the implementation of the Proof of Work consensus algorithm. The developed e-voting application saves time, requires fewer processes, and results in higher accuracy, more transparency, considerable voters’ privacy, and accountable system management. We expect that the e-voting blockchain application will impact governmental processes during the election, reduce spending, support digital transformation, and ensure fairness of results.
Though the world’s first cryptocurrency, Bitcoin, was introduced over a decade ago, it was not until recently that it became a mainstream subject. While cryptocurrencies offer many advantages, a potential downside for governments, is that no central bank controls the monetary policy and new coins can be mined by anyone anywhere in the world. Governments have always been deeply involved with how a their countries’ currency is ran and the policies they create are meant to keep a currencies’ value stable and make sure other factors like inflation is under control. Even though as of 2021, there were well over 4,000 different cryptocurrencies, the focus of this study will be Bitcoin since it is the most popular and at this point, the most valuable in terms of market capitalization. The United States government has become more involved with investigating how cryptocurrencies and Bitcoin are used, and have issued statements on the ways terrorism groups or other threats to our National Security could be effected by Bitcoin. One way countries could undermine the National Security Posture of the United States is by mining Bitcoin to replace revenue from exports that have been adversely effected by sanctions. Given the decentralized nature of Bitcoin, would it be possible for countries under sanctions from the United States to supplement their lost revenue by mining the cryptocurrency? There are a several necessary resources needed to mine Bitcoin, and countries hoping to mine Bitcoin would need an abundance of these resources. For this research, data from the World Bank Database was used to find if there was any positive or negative correlation between countries with sanctions and access to these Bitcoin mining resources. In addition to analyzing this data, different case studies were also analyzed to see if any countries are attempting to mine Bitcoins already and if so, what has been the implications so far. Furthermore, literature on sanctions, data iii analysis, recent mining activity, and white papers for Bitcoin and Ethereum where reviewed. Based on the data, it did not seem that countries with sanctions imposed were well equipped to mine Bitcoin and the case studies examined showed that there was not large mining activities taking place in sanctioned countries.
Abdullah Omar Abdul Kareem Alassaf, Fakhrul Hazman Yusoff
Trust and transparency are significant facets that are much esteemed by charitable organizations in achieving their mission and encouraging donations from the public. However, after many high-profile scandals, the faith in charities is questionable, heralding the need for an increased level of transparency among such organizations. Fortunately, leveraging Blockchain technology in charities’ systems could help to rebuild the integrity of these organizations. This study aims to raise the level of integrity showcased by charities by creating a multi-point fundraising approach using smart contracts. The proposed system offers a transparent fundraising platform through its integration of charity organization evaluators. Various steps were deployed to satisfy the intended target. Firstly, the study investigated the potentials of Blockchain in improving the level of transparency. Secondly, a probing process was undertaken to choose a suitable platform as a server-side in the system. This process involved garnering salient features in Blockchain platforms based on the proposed system requirements. After the probing process, a Decision Support System (DSS) was utilized to investigate the most suitable Blockchain platform. Results garnered proved that the Ethereum platform is best for the proposed system.
The notion of smart contracts was introduced in 1997 by Nick Szabo, to describe agreements among mutually distrusting parties that can be automatically enforced without resorting to a trusted intermediary. \nThen, the idea was mostly forgotten due to the technical impossibility to implement it. The advent of distributed ledger technologies, pioneered by Bitcoin, provided a technical foundation to reshape and develop smart contracts. \nSince smart contracts handle the ownership of valuable assets, attackers may be tempted to exploit vulnerabilities in their implementation to steal or tamper with these assets. For instance, a series of vulnerabilities in Ethereum contracts have been exploited, causing money losses in the order of hundreds of millions of dollars. \nOver the last years, a variety of smart contracts for Bitcoin have been proposed, both by the academic community and by that of developers. However, the heterogeneity in their treatment, the informal (often incomplete or imprecise) descriptions, and the use of poorly documented Bitcoin features, poses obstacles to the development of secure smart contracts. \nUsing formal models and domain-specific languages to describe the behaviour of the underlying platform, and to model contracts, could help to overcome these security issues, by reducing the distance between the intended behaviour of a contract and the implementation. \nIn this thesis, we propose a formal model of Bitcoin transactions, which is the foundation for a new process algebra for defining Bitcoin smart contracts. Furthermore, we present a toolchain for developing smart contracts in BitML, a domain-specific language based on the contributions of this thesis. Moreover, we propose a new extension to Bitcoin, called neighbourhood covenants, which extends its expressiveness as a smart contract platform. We then exploit neighbourhood covenants to implement fungible tokens on Bitcoin.
Internet of things (IoT) devices generate a massive amount of data every second in our lives. While cloud storage brings convenience to the users, it has the disadvantages of low scalability and weak reliability. Blockchain-based distributed storage eliminates data loss due to the tamper-resistant characteristic. Nonetheless, blockchain storage raises some confidentiality and retrieval efficiency issues of data. Searchable Symmetric Encryption (SSE) is an effective search scheme based on ciphertexts, which ensures data security. However, with the increase of data on the blockchain, the data retrieval on the blockchain will be difficult. In this paper, a Complete Binary Tree Searchable Symmetric Encryption using Blockchain (KCB-BC-SSE) scheme is proposed. According to the number of searchers, the scheme is divided into single searcher and multiple searchers where the search efficiency is improved in theory. And the simulation on ethereum shows the feasibility of our scheme. The security analysis illustrates our scheme achieves security under the chosen keyword attack.
Matteo Loporchio, Anna Bernasconi, Damiano Di Francesco Maesa, Laura Ricci
In many blockchain networks, light nodes (e.g. mobile clients) with few computational resources must rely on more powerful full nodes to retrieve transactions from the chain. However, in this untrusted environment a malicious full node could deliver altered or incomplete information, requiring query authentication techniques to ensure the integrity of the results. To this aim, we study an authentication mechanism for spatial information (i.e. data representing the location, size, and shape of objects in a geographical coordinate system). We assume that light nodes issue range queries to obtain data from a single block. To enable authentication, we propose to construct a Merkle R-tree for each block and embed its root into the corresponding header, so that full nodes can exploit it to fetch information and construct a proof of integrity for lightweight clients. We also develop a new algorithm based on sorting and partitioning for constructing Merkle R-trees from a set of spatial transactions and employ space-filling curves to preserve the locality of elements. We examine its theoretical complexity, evaluate it experimentally on a real data set and compare it against other popular construction strategies. Results show that, as queries become more selective, trees generated with our solution improve query performance and reduce verification times with respect to other approaches. Moreover, we observe that the overhead induced by the tree construction is negligible if compared to the average inter-block time of popular blockchain protocols such as Bitcoin and Ethereum.
El concepto de Smart Contract (SC) o contrato inteligente fue introducido a finales del siglo pasado por el criptógrafo informático Nick Szabo, quien lo propuso para automatizar el cumplimiento de las promesas computarizadas. Szabo indicó que estos son un conjunto de promesas especificadas en forma digital, que incluyen protocolos dentro de los cuales se asegura que las partes cumplan lo prometido (Sanz, 2019). Se entiende también como un protocolo de transacción electrónica que tiene el objetivo de facilitar, verificar y/o hacer cumplir digitalmente la negociación y ejecución de los términos de un contrato legal diseñado por las partes involcuradas. Los contratos inteligentes se caracterizan por reducir el costo de transacción, es decir, el arbitraje y el costo de ejecución al realizar transacciones rastreables e irreversibles todo ello mediante el uso de la tecnología blockchain (Prause, 2019).
Alex Hoffman, Phillipe Austria, Chol Hyun Park, Yoohwan Kim
A C TBug Bounty Programs (BBPs) play an important role in providing and maintaining security in software applications.These programs allow testers to discover and resolve bugs before the general public is aware of them, preventing incidents of widespread abuse.However, they have shown problems such as organizations providing accountability of reporting bugs and nonrecognition of testers.In this paper, we discuss Bountychain, a decentralized application using Ethereum-based Smart Contracts (SCs) and the Interplanetary File System (IPFS), a distributed file storage system.Blockchain and SCs provide a safe, secure and transparent platform for a BBP.Testers can submit bug reports and organizations can accept or reject the defect via the SCs.Transactions on the blockchain serve as a persistent and transparent record of software bugs, while IPFS serves as a long-term storage system for bug details.Thus, Bountychain ensures organization accountability and allows testers to gain irrefutable recognition.
Cryptocurrency works on a system that admits people to make payments all over the world without the requirement for any intermediary. Most digital currencies experience frequent periods of intense volatility. This paper examines the day of the week effects in return and volatility on Bitcoin, Ethereum, Ripple, Litecoin, and Tether currencies. To estimate volatile variance, this research uses five ARCH family models: ARCH, GARCH, EGARCH, TARCH and PARCH Models. The best models are derived based on Akaike Info Criterion and Schwarz Criterion. The sample periods vary based on the date of the initial release of each currency up to 31 December 2019. Results indicate the Power ARCH (PARCH) is the best model for Bitcoin and Litecoin, Threshold ARCH (TARCH) model is the best for Ethereum, Ripple, and Litecoin, and the EGARCH model is for Tether. Each model shows a different day of the week effects on each currency.
The aim of this paper is to find out if the COVID-19 outbreak in the USA has a robust impact on the prices of cryptocurrencies. Inspired by the literature related to the determinants of cryptocurrency prices and based on data availability, six potential determinants of cryptocurrency prices and five proxies for the COVID-19 outbreak were selected. The impact of the COVID-19 outbreak was tested using two approaches of extreme bounds analysis and the robustness of our findings was further checked with different cryptocurrencies (Bitcoin, Ethereum, Litecoin and Bitcoin Cash). Our results show that new deaths from the COVID-19 have a robust positive impact on the price of cryptocurrencies while the impact of new confirmed cases, total cases, and total deaths is not robust. In line with previous studies, it is also found that economic uncertainty, stock, gold, and oil prices are robust determinants of the value of cryptocurrencies.
Tarik Hidar, Anas Abou El Kalam, Siham Benhadou, Oussama Mounnan
Since the Tactile Internet has been considered as a new era of Internet, delivering real-time interactive systems as well as ultra-reliable and ultra-responsive network connectivity, tremendous efforts have been made to ensure authentication between communication’s parties to secure remote surgery. Since this human to machine interaction like remote surgery is critical and the communication between the surgeon and the tactile actor i.e. robot arms should be fully protected during the surgical procedure, a fully secure mutual user authentication scheme should be used in order to establish a secure session among the communicating parties. The existing methods usually require a server to ensure the authentication among the communicating parties, which makes the system vulnerable to single of point failure and not fit the design of such critical distributed environment i.e. tactile internet. To address these issues, we propose a new decentralized blockchain based authentication solution for tactile internet. In our proposed solution, there is no need for a trusted party; moreover, the decentralized nature of our proposed solution makes the authentication immutable, efficient, secure, and low latency requirement. The implementation of our proposed solution is deployed on Ethereum official test network Ropsten. The experimental results show that our solution is efficient, highly secured, and flexible.
Shiva Jairam, Jaap Gordijn, Isaac da Silva Torres, Fadime Kaya · 5 authors
Blockchain systems are a new way to reduce or even eliminate the role of the middlemen in an eco-system. For example, the Bitcoin, as one of the most well-known blockchain platforms, shows that it is possible to transfer money without the need of any (intermediate) bank at all. More generally, it allows for the decentralization of roles. In this paper, we focus on permissionless blockchains, which are systems that allow participation without upfront approval on other parties, as opposed to permissioned blockchains. Permissionless blockchain systems support direct business transactions between peers, so without any intermediate and centralized entity very well. However, the organization of the governance of such systems is less obvious. We argue that, in order to arrive at a really decentralized eco-system where power is fairly distributed, the governance should be decentralized; in other words, it should not be in the hand of one controlling entity. In this paper, we analyse, in a model-based way, for three well-known blockchain systems (Bitcoin, Ethereum, Tezos) the governance processes. Based on this analysis, we draft an improved governance process for permissionless blockchains.
Cryptocurrency, powered by blockchain technology, is transforming retail finance by introducing decentralized payment systems and alternative financial instruments. This study examines the technological, economic, behavioral, and regulatory factors influencing cryptocurrency adoption among consumers and businesses. Cryptocurrencies such as Bitcoin, Ethereum, and stablecoins offer benefits including faster transactions, cross-border payments, greater transparency, and reduced reliance on centralized intermediaries. However, challenges such as price volatility, regulatory uncertainty, cybersecurity risks, limited merchant acceptance, and low consumer awareness continue to hinder widespread adoption. Using a conceptual research framework, the study analyzes factors such as perceived usefulness, security, trust, ease of use, financial benefits, and regulatory support. The findings indicate that cryptocurrency adoption is gradually shifting from speculative investment toward practical applications, including digital payments, cross-border settlements, loyalty programs, and decentralized financial services. Stablecoins and blockchain-based payment solutions show greater potential for retail finance due to their stability and usability. The study concludes that successful cryptocurrency integration requires a balance between innovation, security, regulatory compliance, and consumer trust, while improved regulations and financial education are essential for sustainable adoption.