Estruturas de dados tem sido um dos principais objetos de estudo da computação. Alguns cenários de aplicação dessas estruturas possuem requisitos relacionados à segurança e integridade dos dados nelas contidos. Deste modo, no decorrer da história da computação foram propostas estruturas de dados verificáveis, que apresentam características que visam atender a alguns requisitos de segurança como a garantia de imutabilidade e a verificação de um item de dado pertencente a estas estruturas. Este artigo analisa duas estruturas de dados verificáveis, a saber, a Mekle Tree e a Merkle PATRICIA Trie, descrevendo seus conceitos, características e cenários de aplicação no contexto das blockchains Ethereum e Neo.
Delegation of cryptographic signing rights has found many application in the literature and the real world. However, despite very advanced functionalities and specific use cases, existing solutions share the natural limitation that the number of usages of these signing rights cannot be efficiently limited, but users can at most be disincentivized to abuse their rights. In this paper, we suggest a solution to this problem based on blockchains. We let a user define a smart contract defining delegated signing rights, which needs to be triggered to successfully sign a message. By leveraging the immutability of the blockchain, our construction can now guarantee that a user-defined threshold of signature invocations cannot be exceeded, thereby circumventing the need for dedicated hardware or similar assistance in existing constructions for one-time programs. We discuss different constructions supporting different features, and provide concrete implementations in the Solidity language of the Ethereum blockchain, proving the real-world efficiency and feasibility of our construction.
Júlia Almeida Valadares, Vinícius Cunha Oliveira, José Eduardo de Azevedo Sousa, Heder S. Bernardino · 7 authors
Ethereum é uma das maiores plataformas de cripto ativos atualmente, e vem se tornando um ambiente de negócios digitais entre usuários. O Ethereum foi concebido para permitir transações descentralizadas entre usuários anônimos. Contudo, o desenvolvimento de métodos para identificar perfis de comportamentos de usuários, mantendo suas identidades anônimas, têm o potencial para alavancar negócios nessa plataforma. Nesse trabalho, investigamos o uso de aprendizado de máquina para classificar um perfil de usuário como profissional ou comum a partir de atributos de suas transações. Essa classificação é desafiadora devido à pequena fração de usuários publicamente rotulados no Ethereum e ainda a fração consideravelmente menor de usuários profissionais. Para conduzir essa investigação, treinamos modelos considerando conjuntos cuidadosamente balanceados de transações com usuários rotulados. Nossos resultados mostram modelos de alto desempenho para a classificação de perfis, alcançando desempenho superior a 90% para acurácia, precisão, revocação e demais medidas relacionadas. Adicionalmente, identificamos as características mais relevantes em transações para essa classificação.
Igor Gonçalves Silva, Pedro Henrique González, Diogo Mendonça
Blockchain technology is increasingly being used by several companies in the most varied sectors of the economy. The possibility of having decentralized applications (DApps) allows for the emergence of technological innovations such as cryptocurrencies and decentralized asset tracking applications. Many of these DApps are deployed in the cloud with Infrastructure as a Service (IaaS) payment model, in which the payment is made according to the use of the service. However, it is not simple to estimate the cloud infrastructure costs that a DApp will consume. Furthermore, correctly estimating infrastructure costs is essential to analyze the viability and develop business models for enterprise DApps. This work presents an experience report on estimating the cloud infrastructure cost for an enterprise DApp. To do that, we deployed a private Ethereum DApp, using Proof-of-Authority consensus algorithm, with several different configurations of Amazon Web Services (AWS) EC2 instances and blockchain parameters. We benchmark the transaction processing capacity, CPU and disk usage in each configuration, estimating their maximum capacity and costs. We shared our methodology to measure and estimate those costs and our insights on best configuration practices for reducing costs of deploying enterprise DApps in the cloud.
Mohamed Allouche, Mihai Mitrea, Alexandre Moreaux, Sang‐Kyun Kim
Formally known as ISO/IEC 23093, Internet of Media Things (IoMT) is an emerging paradigm ensuring interoperability among media-centric applications and services designed and deployed for the interpretation, representation or analysis of multimedia content collected by media devices such as cameras or microphones. Under this framework, the present paper establishes the proof of concept for the automation of IoMT specified Smart Contract generation. The advanced modus operandi enables media devices and their content to be seamlessly protected against payment counterfeiting, malicious control, access, interception and/or redirection. To this aim, a comprehensive architectural and experimental framework is conceived, designed, and demonstrated. While the methodological approach is blockchain agnostic, the experimental results are obtained on a 3-node, EEA (Enterprise Ethereum Alliance)-compliant private blockchain.
Open access
Blockchain Technology Applications and Security
FinTech, Crowdfunding, Digital Finance
Advanced Steganography and Watermarking Techniques
The passage of a yield from the producer to the buyer is traced by a farming supply chain. A clear stage that permits organization members to farm together is a blockchain-based farming supply chain. This method eliminates the requirement for a centralized trusted authority, mediators, and business histories, growing production and security whereas sustaining extreme integrity, liability, and safety. According to the planned resolution, smart contracts are used to switch and handle all communications and dealings amongst all shareholders in the supply chain network. AgriBlockIoT is a block chain-based traceability key that comprises facts since IoT devices in the supply chain. It comprises an example of watching harvest from farmhouse to branch, as well as assessments of Ethereum and Hyperledger implementations.
Varshinee Chukowry, Geeaneswari Nanuck, Roopesh Kevin Sungkur
Continuous Learning is seen as the key to remain competitive and effective at work. Very often, this also takes place outside the walls of a classroom. Nowadays Digital Badges and microcredentials are pathways to acknowledge and recognize achievements and specific skills of a learner. In this research, the different techniques used in existing blockchain-based educational systems have been reviewed and in the end, a novel web-based digital badge and microcredentials system which helps the learners to acquire the desired skills is proposed. For the Blockchain, Ethereum has been used and to develop the front end ReactJS has been used. A digital badging and micro-credential system consisting of quizzes and digital badges was built with Ethereum blockchain together with ipfs to store the badge image and firebase for examination, registration, and storing courses. The proposed system proved to be very much beneficial and addressed the inherent limitations of traditional learning content management systems (LCMS).
Ethereum platform operates with rich spectrum of data structures and hashing and coding functions. The main source describing them is the Yellow paper, complemented by a lot of informal blogs. These sources are somehow limited. In particular, the Yellow paper does not ideally balance brevity and detail, in some parts it is very detail, while too shallow elsewhere. The blogs on the other hand are often too vague and in certain cases contain incorrect information. As a solution, we provide this document, which summarises data structures used in Ethereum. The goal is to provide sufficient detail while keeping brevity. Sufficiently detailed formal view is enriched with examples to extend on clarity.
Haiqin Wu, Boris Düdder, Liangmin Wang, Shipu Sun · 5 authors
The ubiquity of crowdsourcing has reshaped the static sensor-enabled data sensing paradigm with cost efficiency and flexibility. Still, most existing triangular crowdsourcing systems only work under the centralized trust assumption and suffer from various attacks mounted by malicious users. Although incorporating the emerging blockchain technology into crowdsourcing provides a possibility to mitigate some of the issues, how to concretely implement the crucial components and their functionalities in a verifiable and privacy-aware manner remains unaddressed. In this article, we present BRPC, a blockchain-based decentralized system for general crowdsourcing. BRPC integrates the confident-aware truth discovery algorithm to provide task requesters with reliable task truths while evaluating each worker’s data quality. To mitigate the biased evaluation of malicious requesters, we propose a privacy-aware verification protocol leveraging the threshold Paillier cryptosystem, with which a certain number of workers can collaboratively verify the evaluation results without knowing any sensory data. Furthermore, we define the three roles of a user and elaborate a comprehensive reputation evaluation model enforced by smart contracts for its trustworthy running. Financial and social incentives are both offered to motivate users’ honest participation. Finally, we implement a prototype of BRPC and deploy it on the Ethereum blockchain. Theoretical analyses and experiment results show its security and practicality.
In recent years, a lot of vulnerabilities of smart contracts have been found. Hackers used these vulnerabilities to attack the corresponding contracts developed in the blockchain system such as Ethereum, and it has caused lots of economic losses. Therefore, it is very important to find out the potential problems of the smart contracts and develop more secure smart contracts. As blockchain security events have raised more important issues, more and more smart contract security analysis methods have been developed. Most of these methods are based on traditional static analysis or dynamic analysis methods. There are only a few methods that use emerging technologies, such as machine learning. Some models that use machine learning to detect smart contract vulnerabilities cost much time in extracting features manually. In this paper, we introduce a novel machine learning-based analysis model by introducing the shared child nodes for smart contract vulnerabilities. We build the Abstract-Syntax-Tree (AST) for smart contracts with some vulnerabilities from two data sets including SmartBugs and SolidiFI-benchmark. Then, we build the Abstract-Syntax-Tree (AST) of the labeled smart contract for data sets named Smartbugs-wilds. Next, we get the shared child nodes from both of the ASTs to obtain the structural similarity, and then, we construct a feature vector composed of the values that measure structural similarity automatically to build our machine learning model. Finally, we get a KNN model that can predict eight types of vulnerabilities including Re-entrancy, Arithmetic, Access Control, Denial of Service, Unchecked Low Level Calls, Bad Randomness, Front Running, and Denial of Service. The accuracy, recall, and precision of our KNN model are all higher than 90%. In addition, compared with some other analysis tools including Oyente and SmartCheck, our model has higher accuracy. In addition, we spent less time for training .
Ángel Alberto Varón Quimbayo, Yenny Marcela Mina Hinestroza
Esta investigación pretende presentar la forma como blockchain asocia el desarrollo de Contrato Inteligentes (Smart Contracts), a través de una nueva plataforma que relaciona aspectos éticos, legales, sociológicos y filosóficos que se consideran latentes. Los contratos inteligentes plantean un nuevo protocolo informático el cual garantiza el cumplimiento de cláusulas de un contrato automáticamente, generando una serie de derechos y obligaciones entre las partes intervinientes, actualmente existen varias plataformas para crear y gestionar este tipo de contratos, sin embargo la más recomendada es Ethereum que fue creada específicamente para Smart Contracts. Su objetivo enfoca en que se pueda utilizar en un gran número de servicios en sectores como servicios judiciales, salud, banca, inmobiliario, bolsa de valores entre otros, con la posibilidad de que surjan investigaciones para mejorar la forma cómo se ejecutan los contratos actualmente. en este artículo se describe qué es un contrato inteligente y como se realiza, Qué hace que un contrato sea inteligente, entre otros conceptos que nos ayudaran a entender a mayor profundidad teniendo encueta que el objetivo principal de los Smart Contracts, es mejorar el proceso y la ejecución de los contratos tradicionales, haciéndolos más seguros y económicos, para entender el funcionamiento de los contratos inteligentes es de suma importancia Identificar y analizar el funcionamiento y uso del blockchain ya que es una parte fundamental se basa en la infraestructura Ethereum para hacer posible la ejecución de contratos inteligentes, y como está a aportado y beneficiado la tecnología actualmente. En esta investigación se realizó una búsqueda de artículos científicos, donde se hizo una lectura crítica y analítica para poder emitir juicios de valor y poder construir el artículo, donde se obtuvo como resultado el análisis y la implementación del Smart Contract y cómo estos contribuyen a la promoción de los contratos en general y por último concluimos que los contratos inteligentes se expresan en códigos y que se ejecutan de forma automática, eliminando la necesidad de que existan intermediarios, ofreciendo seguridad y reducción de costes.
Conventional crop insurance systems are complex and often not economically feasible. Farmers are often reluctant to be covered for their crops due to lack of trust in insurance firms and the fear of delayed or non-payment of claims. In this paper, a blockchain based crop insurance solution is suggested. The solution suggested in this paper is an affordable, efficient, low cost crop insurance solution which will ensure many farmers are insured and benefiting from timely crop insurance. Currently the cost of administering insurance is an essential barrier to accessing this facility. With the proper use of blockchain based on ethereum this expense can be reduced dramatically. We have conducted various tests on platforms such as Google Cloud and found that the least throughput is 165 transactions. Upon analysis we have found that the time taken by the block formation is directly proportional to the timing of processing. The end-to-end average latency of the system was achieved as 31.2 s, which was quite effective for the infrastructure what we are using. Upon conducting acceptance testing, we found that the system suggested in the paper is effective and we are planning to release the application on open source platforms for future improvements.
Abstract The number of users approaching the world of cryptocurrencies exploded in the last years, and consequently the daily interactions on their underlying distributed ledgers have intensified. In this paper, we analyze the flow of these digital transactions in a certain period of time, trying to discover important insights on the typical use of these technologies by studying, through complex network theory, the patterns of interactions in four prominent and different Distributed Ledger Technologies (DLTs), namely Bitcoin, DogeCoin, Ethereum, Ripple. In particular, we describe the Distributed Ledger Network Analyzer (DiLeNA), a software tool for the investigation of the transactions network recorded in DLTs. We show that studying the network characteristics and peculiarities is of paramount importance, in order to understand how users interact in the DLT. For instance, our analyses reveal that all transaction graphs exhibit small world properties.
In this paper, we examine the presence of herding in cryptocurrency market for four distinct sub-periods (Pre and During COVID-19 period, bear and bull markets) using daily closing prices of 5 largest cryptocurrencies by market capitalization (Bitcoin, Ethereum, XRP, Stellar and Tether) from April 20, 2019 to January 31, 2021. The study employs cross-sectional absolute deviations (CSAD) model to test herd behavior and the results of the study provide evidence of herd behavior in the whole market for the selected period under study. The study also proofs the presence of herding during COVID-19 period and in positive market returns. These indicate that, investors in the cryptocurrency market, during COVID-19 periods, and in bullish market are inclined to the investment behavior of other peer investors in the market. The study is significant to investors, regulators and players in the cryptocurrency market so as to deepen their understanding of herding behavior since herding is thought to increase the volatility of the market. The study is significant to investors, regulators and players in the cryptocurrency market so as to deepen their understanding of herding behavior since herding is thought to increase the volatility of the market.
Aug 7, 2021·In: Awan, I., Benbernou, S., Younas, M., Aleksy, M. (eds) The International Conference on Deep Learning, Big Data and Blockchain (Deep-BDB 2021). Deep-BDB 2021. Lecture Notes in Networks and Systems, vol 309. Springer, Cham
On the Ethereum network, it is challenging to determine a gas price that ensures a transaction will be included in a block within a user's required timeline without overpaying. One way of addressing this problem is through the use of gas price oracles that utilize historical block data to recommend gas prices. However, when transaction volumes increase rapidly, these oracles often underestimate or overestimate the price. In this paper, we demonstrate how Gaussian process models can predict the distribution of the minimum price in an upcoming block when transaction volumes are increasing. This is effective because these processes account for time correlations between blocks. We performed an empirical analysis using the Gaussian process model on historical block data and compared the performance with GasStation-Express and Geth gas price oracles. The results suggest that when transactions volumes fluctuate greatly, the Gaussian process model offers a better estimation. Further, we demonstrated that GasStation-Express and Geth can be improved upon by using a smaller training sample size which is properly pre-processed. Based on the results of empirical analysis, we recommended a gas price oracle made up of a hybrid model consisting of both the Gaussian process and GasStation-Express. This oracle provides efficiency, accuracy, and better cost.
Ricardo Borges dos Santos, Nunzio Marco Torrisi, Rodrigo Palucci Pantoni
Every consumer's buying decision at the supermarket influences food brands to make first party claims of sustainability and socially responsible farming methods on their agro-product labels. Fine wines are often subject to counterfeit along the supply chain to the consumer. This paper presents a method for efficient unrestricted publicity to third party certification (TPC) of plant agricultural products, starting at harvest, using smart contracts and blockchain tokens. The method is capable of providing economic incentives to the actors along the supply chain. A proof-of-concept using a modified Ethereum IGR token set of smart contracts using the ERC-1155 standard NFTs was deployed on the Rinkeby test net and evaluated. The main findings include (a) allowing immediate access to TPC by the public for any desired authority by using token smart contracts. (b) Food safety can be enhanced through TPC visible to consumers through mobile application and blockchain technology, thus reducing counterfeiting and green washing. (c) The framework is structured and maintained because participants obtain economic incentives thus leveraging it´s practical usage. In summary, this implementation of TPC broadcasting through tokens can improve transparency and sustainable conscientious consumer behaviour, thus enabling a more trustworthy supply chain transparency.
Smart cities use the Internet of Things (IoT) devices such as connected sensors, lights, and meters to collect and analyze data to improve infrastructure, public utilities, and services. However, the true potential of smart cities cannot be leveraged without addressing many security concerns. In particular, there is a significant challenge for provisioning a reliable access control solution to share IoT data among various users across organizations. We present a novel entitlement-based blockchain-enabled access control architecture that can be used for smart cities (and for any ap-plication domains that require large-scale IoT deployments). Our proposed entitlement-based access control model is flexible as it facilitates a resource owner to safely delegate access rights to any entities beyond the trust boundary of an organization. The detailed design and implementation on Ethereum blockchain along with a qualitative evaluation of the security and access control aspects of the proposed scheme are presented in the paper. The experimental results from private Ethereum test networks demonstrate that our proposal can be easily implemented with low latency. This validates that our proposal is applicable to use in the real world IoT environments.
Public blockchain records are widely studied in various aspects such as cryptocurrency abuse, anti-money-laundering, and monetary flow of businesses. However, the final blockchain records, usually available from block explorer services or querying locally stored data of blockchain nodes, do not provide abundant and dynamic event logs that are only visible from a live large-scale measurement. In this paper, we collect the network logs of three popular permissionless blockchains, that is, Bitcoin, Ethereum, and EOS. The discrepancy between observed events and the public block data is studied via a noble analysis model provided with the soundness of measurement. We share our key findings including a false universal assumption of previous mining-related studies and the block/transaction arrival characteristics.
Technology has evolved over the years, making our lives easier. It has impacted the healthcare sector, increasing the average life expectancy of human beings. Still, there are gaps that remain unaddressed. There is a lack of transparency in the healthcare system, which results in inherent trust problems between patients and hospitals. In the present day, a patient does not know whether he or she will get the proper treatment from the hospital for the fee charged. A patient can claim reimbursement of the medical bill from any insurance company. However, today there is minimal scope for the Insurance Company to verify the validity of such bills or medical records. A patient can provide fake details to get financial benefits from the insurance company. Again, there are trust issues between the patient (i.e., the insurance claimer) and the insurance company. Blockchain integrated with the smart contract is a well-known disruptive technology that builds trust by providing transparency to the system. In this paper, we propose a blockchain-enabled Secure and Smart HealthCare System. Fairness of all the entities: patient, hospital, or insurance company involved in the system is guaranteed with no one trusting each other. Privacy and security of patients' medical data are ensured as well. We also propose a method for privacy-preserving sharing of aggregated data with the research community for their own purpose. Shared data must not be personally identifiable, i.e, no one can link the acquired data to the identity of any patient or their medical history. We have implemented the prototype in the Ethereum platform and Ropsten test network, and have included the analysis as well.
With the release of the electricity sales side, large-scale small-capacity distributed power generation units are connected to the distribution side, forming multi-type market entities such as microgrids, integrated energy systems, and virtual power plants. With the large-scale integration of distributed energy, the energy market under the energy internet is different from a traditional transmission grid. It is currently developing in the direction of diversified entities and commodities, a flat structure, and a flexible and competitive multi-agent market mechanism. In this context, this study analyzes the value of combining blockchain and the electricity market presents the design of a blockchain trading framework for multi-agent cooperation and sharing of the energy internet. The nodes in market transactions are modeled through power system modeling in the physical layer and the transaction consensus strategy in the cyber layer; moreover, the nodes are verified in a modified IEEE 13 testing feeder of a distribution network. A transaction example is demonstrated using the multi-agent cooperation and sharing transaction platform based on the Ethereum private blockchain.
Blockchain technology is a disruptive innovation with the potential to replace existing business models that rely on centralized systems and third parties for trust. Even if there are a lot of application areas, blockchain used primarily for cryptocurrencies. Satoshi Nakamoto implemented the first blockchain application and invented the world’s first digital currency which is named as Bitcoin in 2008. Fundementally Bitcoin relies on cryptographic “proof of work” mechanism, digital signatures, and peer to peer distributed networking layer in order to provide a distributed ledger holding transactions. In 2014, a second generation of blockchains allow to program and execute them over distributed networks such as Ethereum project. The code to program any asset stored in blockchain’s peer-to-peer network is called as "smart contract" and smart contracts gives a powerful tool to developers for decentralized applications. There are various types of tokens that anyone can built on top of Ethereum and by combining smart contracts and new tokens, this paved the way of possibility to build a wide range of decentralized projects. One of the disruptive blockchain based innovation impacting intellectual property is called non-fungible-tokens or NFTs firstly introcuced in late 2017 on Ethereum network. This research contends that blockchain and non-fungible tokens (NFTs) which are cryptographically unique, scarce, non-replicable digital assets created through smart contracts and provably digital collectible assets. Our objective is to give NFT taxonomy, review NFT platforms and discuss technical challenges as well as recent advances in tackling the challenges. Moreover, this paper also aims to point out the future directions for NFT technology.
Smart Contracts, die auf der Ethereum Blockchain eingesetzt werden, halten Vermögenswerte im Wert von Milliarden von USD. Ethereum ist derzeit die am meisten genutzte Plattform für Smart Contracts. Gemessen an der Marktkapitalisierung ist Ethereum nach Bitcoin die zweitgrößte Blockchain mit einem stetig wachsenden Marktanteil. Da Smart Contracts nach der Bereitstellung nicht mehr geändert werden können, ist es von entscheidender Bedeutung, dass der Code auf potenzielle Schwachstellen überprüft wird, die erhebliche finanzielle Verluste verursachen und das Vertrauen beschädigen können. Zu diesem Zweck wurden zahlreiche Tools entwickelt, und es wird immer mehr Literatur über Schwachstellen und Erkennungsmethoden zu diesem Thema veröffentlicht. Regelmäßige Literaturanalysen sind unerlässlich, um mit der raschen Entwicklung auf diesem Gebiet Schritt halten zu können. Diese Arbeit präsentiert eine systematische Literatur- und Toolanalyse, die einen strukturierten, umfassenden Überblick über den aktuellen Stand der Technik von Tools, Smart Contract Schwachstellen und Erkennungsmethoden bietet. Die Einhaltung und Protokollierung einer präzisen Evaluierungsstrategie, Such- und Relevanzprüfungen gewährleisten umfassende und reproduzierbare Ergebnisse. Nach Bereinigung der Referenzen, Entfernung von Duplikaten sowie Anwendung von definierten Ein- und Ausschlusskriterien, führte die initiale Literatursuche zu einer ersten Identifikation von 303 Publikationen. Auf Basis einer Qualitätsbewertung auf Grundlage intrinsischer und kontextbezogener Datenqualitätsmetriken wurden schließlich 149 Primärstudien, 38 Surveys und 8 systematische Literaturanalysen für die Datenextraktion ausgewählt. Die Synthese beinhaltet eine umfassende Klassifizierung von Smart Contract Schwachstellen, eine neue Taxonomie der Eigenschaften und verwendeten Methoden von Analysetools sowie einen Überblick über Tools, einschließlich eines strukturierten Vergleichs auf Grundlage der Taxonomie. Schließlich wird eine konsolidierte Sammlung veröffentlichter und verfügbarer Benchmark-Datensätze bereitgestellt.