Elli Androulaki, Jan Camenisch, Angelo De, Maria Dubovitskaya · 6 authors
Token payment systems were the first application of blockchain technology and are still the most widely used one. Early implementations of such systems, like Bitcoin or Ethereum, provide virtually no privacy beyond basic pseudonymity: all transactions are written in plain to the blockchain, which makes them linkable and traceable.
Superlight clients enable the verification of proof-of-work-based blockchains by checking only a small representative number of block headers instead of all the block headers as done in simplified payment verification (SPV). Such clients can be embedded within other blockchains by implementing them as smart contracts, allowing for cross-chain verification. One such interesting instance is the consumption of Bitcoin data within Ethereum by implementing a Bitcoin superlight client in Solidity. While such theoretical constructions have demonstrated security and efficiency in theory, no practical implementation exists. In this work, we put forth the first practical Solidity implementation of a superlight client which implements the NIPoPoW superblocks protocol. Contrary to previous work, our Solidity smart contract achieves sufficient gas-efficiency to allow a proof and counter-proof to fit within the gas limit of a block, making it practical. We provide extensive experimental measurements for gas consumption. The optimizations that enable gas-efficiency heavily leverage a novel technique which we term hash-and-resubmit, which almost completely eliminates persistent storage requirements, the most expensive operation of smart contracts in terms of gas. Instead, the contract asks contesters to resubmit data and checks their veracity by hashing it. Other optimizations include off-chain manipulation of proofs in order to remove expensive look-up structures, and the usage of an optimistic schema. We show that such techniques can be used to bring down gas costs significantly and may be of independent interest. Lastly, our implementation allows us to calculate concrete cryptoeconomic parameters for the superblocks NIPoPoWs protocol and in particular to make recommendations about the monetary value of the collateral parameters. We provide such parameter recommendations over a variety of liveness settings.
Winkle protects any validator-based byzantine fault tolerant consensus mechanisms, such as those used in modern Proof-of-Stake blockchains, against long-range attacks where old validators' signature keys get compromised. Winkle is a decentralized secondary layer of client-based validation, where a client includes a single additional field into a transaction that they sign: a hash of the previously sequenced block. The block that gets a threshold of signatures (confirmations) weighted by clients' coins is called a "confirmed" checkpoint. We show that under plausible and flexible security assumptions about clients the confirmed checkpoints can not be equivocated. We discuss how client key rotation increases security, how to accommodate for coins' minting and how delegation allows for faster checkpoints. We evaluate checkpoint latency experimentally using Bitcoin and Ethereum transaction graphs, with and without delegation of stake.
Artificial intelligence (AI) has been witnessed to provide valuable solutions to all walks of life. However, data island and computing resources limitations in the centralized AI architectures have increased their technical barriers, and thus distributed AI collaboration in data, models, and resources has attracted intensive research interests. Since the existing trust-based collaboration models are no longer applicable for the large-scale distributed collaboration among trustless machines in open and dynamic environments, this article proposes a novel decentralized AI collaboration framework, i.e., learning markets (LM), in which blockchain provides a trustless environment for collaboration and transaction, while smart contracts serve as software-defined agents to encapsulate and process scalable collaboration relationships and market mechanisms. LM can not only help those participants without mutual trust realize collaborative mining with dynamic and quantitative rewards but also build an AI market with natural auditability and traceability for trading trusted and verified models. We implement and comprehensively analyze LM based on the Ethereum interplenary file system platform (IPFS), and the results prove that it has advantages in collaboration fairness, transparency, security, decentralization and universality. Based on our collaboration framework, distributed AI contributors are expected to cooperate and complete those learning tasks that cannot be done previously due to lack of complete data, sufficient computing resources and state-of-the-art models.
Dana Haj Hussein, Ragunath Anbarasu, Ashraf Matrawy, Mohamed Ibnkahla
The Internet of Things (IoT) technologies are transforming traditional businesses into digital-based platforms allowing for more service innovation, performance efficiency and customer satisfaction. Novel services enable users to utilize their personal devices (eg. mobile phones or laptops) to access the IoT platform, process data, and control the IoT infrastructure. However, these services impose critical user authentication and access control requirements. In this paper, we propose a decentralized user authentication and access control system for the IoT platforms via a permissioned blockchain network. We define an authorization sensitivity factor to provide clients with specific access control privileges and we consider an ehealth system as a use case example to demonstrate our solution. The proposed system is implemented using Ethereum platform. Besides, we investigate a threat model that considers an insider Distributed Denial of Service (DDoS) attack. The proposed defense mechanism utilizes a modifier function in the smart contract and keeps a real-time record of legitimate users to restrict function calls. The results illustrate the benefits of the defense mechanism in terms of the system response time.
WebRTC (Web Real-Time Communication) is one of the most popular technologies that provide the infrastructure for real-time data communications. Many applications used in military and civilian life depend on WebRTC technology directly or indirectly in the background. Due to its wide area of applications, the security of WebRTC communications is of great importance. In this paper, we improve the existing security infrastructure of WebRTC. The proposed solution provides a real-time communication infrastructure between peers on the network by making use of quite new and popular blockchain and smart contract technologies. Within the scope of the paper, a web-based application with video calling feature demonstrating blockchain interactions and suggested security enhancements have been developed. In the application, operations such as adding, updating, and authorizing users can be performed on the smart contract deployed on the live Ethereum network. Based on the principle of immutability of blockchains, users on the smart contract are mapped to the peers (nodes) in the WebRTC communication to be established and used in the identity verification process. Consequently, this paper proposes a secure identity verification method that could be used by real-time WebRTC communication peers to verify each other on the blockchain. The proposed solution is shown to resilient against man-in-the-middle attacks.
The availability-finality dilemma says that blockchain protocols cannot be both available under dynamic participation and safe under network partition. Snap-and-chat protocols have recently been proposed as a resolution to this dilemma. A snap-and-chat protocol produces an always available ledger containing a finalized prefix ledger which is always safe and catches up with the available ledger whenever network conditions permit. In contrast to existing handcrafted finality gadget based designs like Ethereum 2.0's consensus protocol Gasper, snap-and-chat protocols are constructed as a black-box composition of off-the-shelf BFT and longest chain protocols. In this paper, we consider system aspects of snap-and-chat protocols and show how they can provide two important features: 1) accountability, 2) support of light clients. Through this investigation, a deeper understanding of the strengths and challenges of snap-and-chat protocols is gained.
The building workers sector is one of the most challenging for Human Resources (HR) management. In this work we propose a solution relying on the Blockchain technology and present the design of a Blockchain-Oriented Software system conceived for managing the building workers sector with a focus on workers' safety and guided by sustainable and Agile Methodologies in software design. The proposed approach takes advantage of different features of the Blockchain technology and provides transparency for labour inspectors, grants data integrity and immutability, relies in tamper proof time stamps for any recorded activity, allows the implementation of Smart Contracts where clauses are automatically respected without the need of a trusted control authority, acknowledges the legal requirements in the field, including the possibility of creating the Operational Safety Plans, which construction companies have to provide and finally implements the creation of vacant job positions which workers can find and apply to. In order to achieve these goals we adopt the Blockchain-Oriented Software Engineering (BOSE) methodology to design Blockchain software applications and apply an Agile methodology centered on Blockchain Software development, (called ABCDE) for the design and development of the decentralized application. Such methodology allows to center the software development around the actors of the system in the specific domain, such as Building Workers, Construction Companies, Labour Inspectors and so on. In addition we rely on the software sustainability analysis, based on the five dimensions of sustainability, to evaluate the approach and to avoid mistakes in the system development. We design system elements with specific diagrams and we divided our system in the on-chain and the out-of-chain components. The implementation of the system, done by using Ethereum and the ERC721 standard, allows us to improve some aspect of the design, to know the deployment and usage costs, and to evaluate the effect of the user interface. Finally, we discuss about the effects of our system and its sustainability, and provide a comparison of our system with a similar per aims but centralized system.
Current swarm robotics systems are not utilized as frequently in surveillance missions due to the limitations of the existing distributed systems' designs. The main limitation of swarm robotics is the absence of a framework for robots to be self-governing, secure, and scalable. As of today, a swarm of robots is not able to communicate and perform tasks in transparent and autonomous ways. Many believe blockchain is the imminent future of distributed autonomous systems. A blockchain is a system of computers that stores and distributes data among all participants. Every single participant is a validator and protector of the data in the blockchain system. The data cannot be modified since all participants are storing and watching the exact same records. In this study, we will focus on blockchain applications in swarm robotics using Ethereum smart contracts because blockchain can make a swarm globally connected and secure. A decentralized application (DApp) is used to deploy surveillance missions. After mission deployment, the swarm uses blockchain to communicate and make decisions on appropriate tasks within Ethereum private networks. We conclude that, although blockchain enables a swarm to be globally connected and secure, there are performance limitations that can become a critical issue.
Antonio Welligton S. Abreu, Emanuel Ferreira Coutinho, Carla Bezerra
Blockchain is an emerging technology that has piqued the interest of researchers and industry today. Following the success of this technology in the financial market with virtual currencies, blockchain begins to be used by different domains such as government and education as it provides a reliable, scalable and unchanging distributed environment for conducting and storing transactions on a network. Higher education is a system with many challenges that could be solved by adopting this technology. Protecting data transactions that involve student degrees is one of the challenges considered by educational institutions. Thus, this paper presents a reference architecture proposal based on blockchain technology and a proof of concept to register and consult student certificates issued by higher education institutions. With this architecture, we intend to evaluate a new business model in this technology applied to the educational domain. As a proof of concept, we presented a prototype implementation using smart contracts based on the Ethereum platform and an evaluation made by experts in high education.
Sarad Venugopalan, Ivan Homoliak, Zengpeng Li, Pawel Szalachowski
Voting is a means to agree on a collective decision based on available choices (e.g., candidates), where participants agree to abide by their outcome. To improve some features of e-voting, decentralized blockchain-based solutions can be employed, where the blockchain represents a public bulletin board that in contrast to a centralized bulletin board provides extremely high availability, censorship resistance, and correct code execution. A blockchain ensures that all entities in the voting system have the same view of the actions made by others due to its immutability and append-only features. The existing remote blockchain-based boardroom voting solution called Open Voting Network (OVN) provides the privacy of votes, universal & End-to-End verifiability, and perfect ballot secrecy; however, it supports only two choices and lacks robustness enabling recovery from stalling participants. We present BBB-Voting, an equivalent blockchain-based approach for decentralized voting such as OVN, but in contrast to it, BBB-Voting supports 1-out-of-$k$ choices and provides robustness that enables recovery from stalling participants. We make a cost-optimized implementation using an Ethereum-based environment respecting Ethereum Enterprise Alliance standards, which we compare with OVN and show that our work decreases the costs for voters by 13.5% in normalized gas consumption. Finally, we show how BBB-Voting can be extended to support the number of participants limited only by the expenses paid by the authority and the computing power to obtain the tally.
Mohammad Hamdaqa, Lucas Alberto Pineda Metz, Ilham Qasse
Smart contracts are immutable digital programs deployed onto blockchain platforms to codify agreements. They enable blockchain technology to play a vital role in many fields, such as finance, health care, and energy. An important aspect of modeling and deploying smart contracts is to define the business process and rules that govern the agreements under which the corresponding actions are executed. Unfortunately, these models use a mix of technical and business-centric terminologies that are different based on the underlying blockchain platform that the smart contract is targeting. To address this issue, in this paper, we followed a feature-oriented domain analysis approach to identify the commonalities and variations between three of the common blockchain platforms that are used to deploy smart contracts; namely IBM Hyperledger Composer, Azure Blockchain Workbench, and Ethereum. Accordingly, we propose a reference model for smart contracts. The reference model is then realized as a modeling framework that enables developers to model and generate the structural code required to deploy a smart contract onto multiple blockchain platforms. The coverage of the proposed reference model was shown through mapping the concepts of the reference models to its corresponding constructs within each blockchain platform. Moreover, we provide three use cases to show how the proposed framework can empower developers to generate the structural code of smart contracts for the target platform through model transformation.
Large-scale power systems are composed of regional utilities with assets that stream sensor readings in real time. In order to detect cyberattacks, the globally acquired, real-time sensor data needs to be analyzed in a centralized fashion. However, owing to operational constraints, such a centralized sharing mechanism turns out to be a major obstacle. In this article, we propose a blockchain-based decentralized framework for detecting coordinated replay attacks with full privacy of sensor data. We develop a Bayesian inference mechanism employing locally reported attack probabilities that is tailor made for a blockchain framework. We compare our framework to a traditional decentralized algorithm based on the broadcast gossip framework both theoretically as well as empirically. With the help of experiments on a private Ethereum blockchain, we show that our approach achieves good detection quality and significantly outperforms gossip-driven approaches in terms of accuracy, timeliness, and scalability.
I Gusti Made Teddy Pradana, Taufik Djatna, Irman Hermadi
The traceability system is increasingly becoming a concern in the current food supply chain. In line with shifting consumer trends, the issue of food security is becoming more important. One of the problems that occur in the supply chain is the risk of counterfeiting, such as bean-adulteration, along with the supply chain product. This risk cannot be anticipated effectively due to a lack of transparency in the flow of product information in the supply chain. This study aims to propose a task analysis of each stakeholder to achieve and construct a design of a traceability system for agroindustry-consumers information access from the field until the coffee shop. The methodology designs consisted of the use case diagram, actor relational analysis, features selection, and cosine similarity algorithm. As an ethereum based architecture, the model equipped with the design process initiated with the BPMN where BCT workflow modeling set. The data attributes construction was based on relational ERD, resulting in database table relation schemes. The construction of a smart contract was based on decision trees mechanism. The traceability of the final result has successfully demonstrated the prototype to fulfill the requirements.
The need to protect sensitive data is growing, and environmental data are now considered sensitive. The application of last-generation procedures such as blockchains coupled with the implementation of new air quality monitoring technology allows the data protection and validation. In this work, the use of a blockchain applied to air pollution data is proposed. A blockchain procedure has been designed and tested. An Internet of Things (IoT)-based sensor network provides air quality data in terms of particulate matter of two different diameters, particulate matter (PM)10 and PM2.5, volatile organic compounds (VOC), and nitrogen dioxide (NO2) concentrations. The dataset also includes meteorological parameters and vehicular traffic information. This work foresees that the data, recovered from traditional Not Structured Query Language (NoSQL) database, and organized according to some specifications, are sent to the Ethereum blockchain daily automatically and with the possibility to choose the period of interest manually. There was also the development of a transaction management and recovery system aimed at retrieving data, formatting it according to the specifications and organizing it into files of various formats. The blockchain procedure has therefore been used to track data provided by air quality monitoring networks unequivocally.
Iniciada em julho de 2015, Ethereum e a segunda maior criptomoeda em volume de transacoes nesse momento, atras apenas do Bitcoin, que e a criptomoeda pioneira. A popularidade de Ethereum esta em franca ascensao, atraindo a comunidade cientifica. Uma importante questao em discussao pelo comportamento da plataforma diz respeito a cobranca obrigatoria da taxa por transacao no Ethereum e a sua possivel relacao com o tempo de espera para confirmacao da transacao. Ao enviarem suas transacoes a outros utilizadores da rede, os usuarios sao obrigados a fornecer uma especie de gorjeta, a taxa de mineracao, para que sua transacao seja incluida na rede. A crenca comum na rede Ethereum e que quanto maior a taxa, menor o tempo de confirmacao. No presente trabalho, foi realizada uma investigacao e analise detalhada dessa questao. Para conduzir esse trabalho, foram coletadas 7.2 milhoes de transacoes no Ethereum. A seguir, foram realizadas diversas analises acerca das taxas fornecidas pelos usuarios e o tempo de espera para uma transacao ser minerada. Primeiramente foi verificado se existe alguma correlacao entre o tempo de espera de uma transacao para adentrar a rede e diversos recursos relacionados as taxas pagas aos operadores da rede Ethereum para execucao de transacoes, por meio de correlacoes de Pearson e Spearman. Posteriormente, analises agrupando as transacoes por caracteristicas sao conduzidas de duas formas: (i) por valores absolutos e (ii) por grupos definidos a partir de algoritmos de clusterizacao. Esses agrupamentos buscam encontrar usuarios com comportamentos parecidos, tentando encontrar correlacao entre o tempo de espera das transacoes nesses casos. As analises empiricas mostraram fortes evidencias de que nao ha uma correlacao clara entre as taxas pagas pelos usuarios e o tempo de espera da transacao, concluindo que tais taxas, assim como as caracteristicas do sistema delas derivadas, inerentes a plataforma Ethereum, nao determinam o tempo de espera. Alem da avaliacao da relacao existente entre tempo de confirmacao e taxa, nesse trabalho, foi avaliado ataque de negacao de servico, um problema que tambem pode afetar o tempo de confirmacao de transacoes na rede Ethereum. Inicialmente, foi definido um ataque semelhante ao de negacao de servico distribuido (DDoS), em que usuarios maliciosos inserem transacoes especificas, as quais possuem valores muito baixos de gas price, com intuito de provocar lentidao na rede sao inseridas na rede, aumentando o tempo de espera das transacoes. Para estudar este ataque, aqui denominado de Penny Attack, foi definida uma arquitetura capaz de replicar a rede ETH do Ethereum em uma estrutura local. Em seguida foram executadas simulacoes para verificar a resposta do sistema em situacoes normais da rede, em periodo sobre ataque, e tambem em periodos de alta demanda da rede. Por fim, foram propostas sete tecnicas de aprendizado de maquina buscando melhores metricas de classificadores capazes de identificar o ataque aqui proposto, onde foram obtidos metodos com acuracia maior que 0,95 e AUC de 0,89, fornecendo uma modelo confiavel para deteccao deste ataque.
Kazi Masudul Alam, J.M. Ashfiqur Rahman, Anisha Tasnim, Aysha Akther
Bangladesh is a small country with a large population. Its increasingly developing economy further makes land a lucrative source of fixed capital. On the other hand, land titling is a cumbersome and lengthy process, where different government bodies process different sets of documents, and bureaucratic loopholes encourage fraudulent activities by organized people. As a result, the current model suffers from good governance. In this paper, we propose a Blockchain-based solution that offers data synchronization and transparency, ease of access, immutable records management, a faster and cheaper solution. Considering the technological knowledge and capacity of the people and the government, we introduced a phase by phase Blockchain adoption model that starts with a public Blockchain ledger and later gradually incorporates two levels of Hybrid Blockchain. We provide detailed smart contracts design of the public Blockchain and implement a prototype system using Ethereum. Our experimental setup uses local and live Ethereum test networks to demonstrate the efficacy of the proposed system. Our analysis shows that the proposed model reduces the number of required travels, the overall cost of information processing as well as provide easy access to vital information. As a result, Blockchain adoption can improve the land title digitization effort of Bangladesh.
In recent years, with the popularity of Bitcoin and other cryptocurrencies, the blockchain technology behind it has gradually become a research focus. After the official launch of Facebook's cryptocurrency project Libra and the publication of the Libra white paper, Libra triggered extensive discussions around the world. Libra has aroused the public's awareness of open finance and is deeply impacting the traditional financial system. In this paper, we systematically review and discuss the blockchain technology and summarize Libra's innovations in consensus algorithm, performance, and application scenario through a comparative analysis of Libra, Bitcoin, and Ethereum. Finally, we put forward the challenges that Libra will face in the future.
To mitigate the scalability problem of decentralized cryptocurrencies such as Bitcoin and Ethereum, the payment channel, which allows two parties to perform secure coin transfers without involving the blockchain, has been proposed. The payment channel increases the transaction throughput of two parties to a level that is only limited by their network bandwidth. Recent proposals focus on extending the two-party payment channel to the N-party payment hub. Unfortunately, none of them can achieve efficiency, flexibility in the absence of a trusted third-party. In this paper, we propose Garou, a secure N-party payment hub that allows multiple parties to perform secure off-chain coin transfers. Except in the case of disputes, participants within the payment hub can make concurrent and direct coin transfers with each other without the involvement of the blockchain or any third-party intermediaries. This allows Garou to achieve both high-performance and flexibility. If all participants keep online, Garou guarantees all honest users’ balance security against strong adversarial capabilities. To demonstrate the feasibility of the Garou protocol, we develop a proof of concept prototype for the Ethereum network. Experimental evaluations show that, with 300 participants and without disputes, that the maximum transaction throughput of Garou is$20{ \times }$higher than that of state-of-the-art payment hubs.
Increased adoption of the Internet of Things (IoT) in multiple domain areas continuously increases the volume of data and transactions from the IoT devices. The IoT systems are vulnerable to more attacks because of increased adoptions and technology adoptions. Protecting the data and providing security to the data and transactions is one of the critical issues for the effective quality of service (QoS) in the IoT environments. An adaptable IoT framework is proposed based on the research approach of 'ADOPT' that leverages the blockchain technology and features considering security as one of the QoS parameters. In the proposed model of a three-layer IoT architecture with an application layer, network layer, and perception layer, the blockchain features are adopted for the resource-constrained IoT environment. In the perception layer, the model uses a local and temporary memory to maintain the local chain, which is managed based on the memory size and time constraints. The application layer nodes manage the synchronization of the data from the corresponding local chain at the edge node. The implementation of the proposed model uses Ethereum, an open-source public blockchain, and using mobile devices as an edge node. The results are verified for security factors like access, authorizations, confidentiality, and computing resources.
The purpose of this paper is to discuss the determinants of G7, and Chinese stock market returns during the COVID-19 outbreak. We find that Bitcoin and Ethereum can generate benefits from portfolio diversification and hedging strategies for G7 financial investors in early 2020. Our result reveals that Gold is neither hedge nor haven during the COVID-19 pandemic. In addition, the results indicated that the expected volatility of the US stock market has no effect on the Japanese and Chinese financial markets. Finally, our results suggest that the growth rate of confirmed COVID-19 cases and deaths has an impact only on the US stock market.
A product of the 21st century, crypto-currency is a digital representation of a value that can be digitally traded and functions as a medium of exchange, a unit of account or store of value. Safety, simplicity, affordability, reachability, and transparency are advantages however, challenges such as fraud, complexity, money laundering plague Bitcoin, Lite coin, Dodge coin, Amazon coin,ethereum coin, Nemcoin, Libra, DC/EP coin.