Markus Nissl, Emanuel Sallinger, Stefan Schulte, Michael Borkowski
In recent years, manifold blockchain protocols have been proposed by researchers and industrial companies alike. This has led to a very heterogeneous blockchain landscape. Accordingly, it would be desirable if blockchains could interact with each other. However, current blockchain technologies offer only limited support for interoperability, thus preventing tokens or smart contracts from leaving the scope of a particular blockchain. As a first step towards a solution for cross-chain smart contract interactions, we introduce a framework which allows to invoke a smart contract from another blockchain. We offer support for continuing a smart contract after receiving a result from a different blockchain, and for calling smart contracts recursively across blockchains. We provide a reference implementation for Ethereum-based blockchains using Solidity and evaluate the performance regarding time and cost overheads.
Lucas M. Palma, Martín Vigil, Jean Everson Martina
Blockchains oferecem propriedades como descentralização, transparência, pseudo-anonimização e integridade de dados. Combinadas com contratos inteligentes, elas permitem o desenvolvimento de aplicativos e acordos descentralizados sem a necessidade de terceiros confiáveis. Elas também podem funcionar como ferramentas para a melhoria de processos de governança. Destacam-se os trabalhos que utilizam blockchain na automação e aprimoramento da emissão de certificados de graduação. Esses trabalhos variam de uma simples prova de existência de certificados de graduação até propostas mais sofisticadas, que incluem o registro de créditos obtidos em um sistema de ensino superior. Neste trabalho, propõe-se um modelo automatizado, transparente, auditável e seguro para registrar créditos e emitir certificados de graduação utilizando blockchain. Os principais objetivos são minimizar a burocracia dos processos envolvidos, facilitar a auditoria e reduzir a falsificação de certificados de graduação. O modelo proposto considera a existência de uma agência reguladora pública de ensino superior e instituições educacionais independentes. Diferentemente de trabalhos relacionados, esta proposta abrange toda a trajetória dos estudantes de graduação, desde o registro até a emissão do seu certificado de graduação. Apresenta-se um protótipo e uma análise de custos considerando dados oficiais do sistema de ensino superior brasileiro e a plataforma de blockchain do Ethereum.
Ruby Benita K, Ganesh Kumar S, B Murugamantham, A. Murugan
<span>Tracking drugs became more difficult using the centralized architecture. Decentralized architecture using blockchain technology overcomes the difficulties faced by the centralized network like availability and recovery. Avoiding duplicate or fake drugs created by fake manufacturers is a big challenge in the centralized network. Authentic stock is managed and the supply chain is tracked efficiently using this blockchain technology. This is addressed by using the smart contract which helps to track the movement of drugs from manufacturer to supplier, supplier to the reseller, reseller to pharmacies and finally pharmacies to patient. By default, duplicate drugs or fake drugs are completely avoided by using the blockchain technology. Patients buy drugs without any prescription and it creates a lot of problems in real life. So, Patients cannot buy drugs without authenticated doctor’s prescriptions with the help of a QR Code scanner attached with the prescription which will be implemented using a mobile application and cannot buy excess drugs which might lose someone’s life. With the help of inventory management, the maximum limit of drugs to avoid overdose and pharmacies cannot sell those overdose drugs. Consulting a doctor before buying a drug for even a simple illness is important and it is tracked by using prescriptions provided by authentic doctors. In this project, these challenges are addressed using the smart contract which is written in solidity language and runs on a public ethereum network.</span>
[ES] En este TFG se va a exponer un sistema de notarización de documentos digitales aprovechando las cualidades de transparencia e inmutabilidad de Ethereum para almacenar los registros. \n \nSe van a presentar dos posibles arquitecturas para este sistema, siendo la gestión de las cuentas Ethereum la principal diferencia. \n \nEn el primer diseño, el usuario debe tener una cuenta de Ethereum con fondos para interactuar con el sistema. Los dos componentes fundamentales son: la interfaz web y el Smart Contract en Ethereum. El usuario se conecta al sistema en la página web, usando un Wallet específico de navegador (MetaMask). Desde la web podrá guardar, recuperar o validar cualquier registro en Ethereum. \n \nEn el segundo diseño, no será necesario que el cliente tenga su propia cuenta de Ethereum. En su lugar, habrá un servidor que identificará a los usuarios e interactuará con Ethereum en su nombre. \n \nPor último, se hablará de un sistema de gestión de identidades, basado en el estándar de W3C, el cual dará una capa extra de seguridad a nuestro sistema de notarización.
A Large-Scale Heterogeneous Network (LS-HetNet) integrates different networks into one uniform network system to provide seamless one-world network coverage. In LS-HetNet, various devices use different technologies to access heterogeneous networks and generate a large amount of data. For dealing with a large number of access requirements, these data are usually stored in the HetNet Domain Management Server (HDMS) of the current domain, and HDMS uses a centralized Authentication/Authorization/Auditing (AAA) scheme to protect the data. However, this centralized method easily causes the data to be modified or disclosed. To address this issue, we propose a blockchain-empowered AAA scheme for accessing data of LS-HetNet. Firstly, the account address of the blockchain is used as the identity authentication, and the access control permission of data is redesigned and stored on the blockchain, then processes of AAA are redefined. Finally, the experimental model on Ethereum private chain is built, and the results show that the scheme is not only secure but also decentral, without tampering and trustworthiness.
Using intraday data, this study employs the VAR-DCC-GARCH model to examine return and volatility transmission among Bitcoin, Ethereum, and Litecoin during the pre-COVID-19 and COVID-19 periods. We find that the return spillovers differ across both periods for the Bitcoin-Ethereum, Bitcoin-Litecoin, and Ethereum-Litecoin pairs. The volatility transmission is not significant between cryptocurrencies during the pre-COVID-19 period. We also find that the volatility spillover is unidirectional from Bitcoin to Ethereum and bidirectional between Ethereum and Litecoin during the COVID-19 period. Moreover, volatility transmission is not significant between Bitcoin and Litecoin during the COVID-19 period. The dynamic conditional correlations between all pairs of cryptocurrencies are higher during the COVID-19 period than during the pre-COVID-19 period. Lastly, we compute the optimal portfolio weights, time-varying hedge ratios, and hedging effectiveness for all pairs of cryptocurrencies during the pre-COVID-19 and COVID-19 periods. Overall, our findings provide new insights into channels of information transmission, which may improve the investment decisions and trading strategies of portfolio investors during crisis and non-crisis periods.
The emergence of cryptocurrency has introduced a transformative force in the global financial landscape, challenging the conventional structures of traditional financial markets. This paper explores the dynamic relationship between digital currencies and established financial systems, focusing on areas such as investment behavior, regulatory responses, market volatility, and the evolving role of financial institutions. It highlights how cryptocurrencies, particularly Bitcoin and Ethereum, have begun to influence asset allocation strategies, capital flows, and risk perceptions among investors. Furthermore, the paper examines the integration of blockchain technology in financial services and how its decentralized nature poses both opportunities and threats to conventional banking practices. While cryptocurrencies have opened up avenues for innovation and financial inclusion, their unregulated nature raises concerns regarding market stability and security. This study aims to provide a comprehensive understanding of the implications of cryptocurrency growth for traditional financial markets, suggesting the need for adaptive regulatory frameworks and strategic responses from financial institutions.
Financial services must monitor their transactions to prevent being used for money laundering and combat the financing of terrorism. Initially, organizations in charge of fraud regulation were only concerned about financial institutions such as banks. However, nowadays, the Fintech industry, online businesses, or platforms involving virtual assets can also be affected by similar criminal schemes. Regardless of the differences between the entities mentioned above, malicious activities affecting them share many common patterns. This dissertation's first goal is to compile and compare existing studies involving machine learning to detect and analyze suspicious transactions. The second goal is to synthesize methodologies from the last goal for tackling different use cases in an organized manner. Finally, the third goal is to assess the applicability of deep generative models for enhancing existing solutions. In the first part of the thesis, we propose an unsupervised methodology for detecting suspicious transactions applied to two case studies. One is related to transactions from a money remittance network, and the other is related to a novel payment network based on distributed ledger technologies. Anomaly detection algorithms are applied to rank user accounts based on recency, frequency, and monetary features. The results are manually validated by domain experts, confirming known scenarios and finding unexpected new cases. In the second part, we carry out an analogous analysis employing supervised methods, along with a case study where we classify Ethereum smart contracts into honeypots and non-honeypots. We take features from the source code, the transaction data, and the funds' flow characterization. The proposed classification models proved to generalize well to unseen honeypot instances and techniques and allowed us to characterize previously unknown techniques. In the third part, we analyze the challenges that tabular data brings into the domain of deep generative models, a particular type of data used to represent financial transactions in the previous two parts. We propose a new model architecture by adapting state-of-the-art methods to output multiple variables from mixed types distributions. Additionally, we extend the evaluation metrics used in the literature to the multi-output setting, and we show empirically that our approach outperforms the existing methods. Finally, in the last part, we extend the work from the third part by applying the presented models to enhance classification tasks from the second part, commonly containing a severe class imbalance. We introduce the multi-input architecture to expand models alongside our previously proposed multi-output architecture. We compare three techniques to sample from deep generative models defining a transparent and fair large-scale experimental protocol and interesting visual analysis tools. We showed that general machine learning detection and visualization techniques could help address the fraud detection domain's many challenges. In particular, deep generative models can add value to the classification task given the imbalanced nature of the fraudulent class, in exchange for implementation and time complexity. Future and promising applications for deep generative models include missing data imputation and sharing synthetic data or data generators preserving privacy constraints.
It is widely accepted that Ethereum mining is highly centralized.\nNonetheless, centralization has been mostly characterized by exclusively\nlooking at the influence that independent miners or mining pools can have over\nthe network. Moreover, models of mining behavior assume that miners are either\nunrelated or only relate via mining pools under highly structured and\ntransparent agreements. If these assumptions and the predictions they entail\nwere to be completely accurate, there would not be any evidence of on-chain\ntransactions between miners, other than the ones expected from mining pool\npayouts. By looking at on-chain transactions between miners in the Ethereum\nNetwork we find that aside from the payouts from mining pools to small miners,\nthere are also transactions that define relationships between mining pools,\nindependent miners and between independent miners and mining pools.\nFurthermore, by characterizing the topology of the network of miner\ntransactions, we find the emergence of highly connected clusters that control\nsignificant amounts of hashing power and exhibit relationships in the opposite\ndirection of what theoretical models predict. This more nuanced\ncharacterization of mining centralization can help identify network\nvulnerabilities and inform protocol redesigns.\n
In the medical system, the verification, preservation and synchronization of electronic medical records has always been a difficult problem, and the random dissemination of patient records will bring various risks to patient privacy. Therefore, how to achieve secure data sharing on the basis of ensuring users' personal privacy becomes the key. In recent years, blockchain has been proposed to be a promising solution to achieve data sharing with security and privacy preservation due to its advantages of immutability. So, a distributed electronic medical records searchable scheme was proposed by leveraging blockchain and smart contract technology. Firstly, we perform a hash calculation on the electronic medical data and store the corresponding value on the blockchain to ensure its integrity and authenticity. Then, we encrypt the electronic medical data and store it in the interplanetary file system which is a distributed storage protocol. These operations not only can solve centralized data store of servers of several medical institutions, but also be good at lowering stress from data store and high-frequency access to blockchain. Secondly, the encrypted keyword index information of electronic medical records was stored on the Ethereum blockchain, meanwhile a smart contract deployed in the Ethereum blockchain is used to realize keyword search instead of depending on a centralized third party. Furthermore, we use attribute-based encryption scheme to ensure that only the attributes meeting the access policy can decrypt the encrypted electronic medical records. Finally, our performance analysis and security analysis show that the scheme is secure and efficient.
The peer-to-peer (P2P) network of blockchain used to transport its transactions and blocks has a high impact on the efficiency and security of the system. The P2P network topologies of popular blockchains such as Bitcoin and Ethereum, therefore, deserve our highest attention. The current Ethereum blockchain explorers (e.g., Etherscan) focus on the tracking of block and transaction records but omit the characterization of the underlying P2P network. This work presents the Ethereum Network Analyzer (Ethna), a tool that probes and analyzes the P2P network of the Ethereum blockchain. Unlike Bitcoin that adopts an unstructured P2P network, Ethereum relies on the Kademlia DHT to manage its P2P network. Therefore, the existing analytical methods for Bitcoin-like P2P networks are not applicable to Ethereum. Ethna implements a novel method that accurately measures the degrees of Ethereum nodes. Furthermore, it incorporates an algorithm that derives the latency metrics of message propagation in the Ethereum P2P network. We ran Ethna on the Ethereum Mainnet and conducted extensive experiments to analyze the topological features of its P2P network. Our analysis shows that the Ethereum P2P network possesses a certain effect of small-world networks, and the degrees of nodes follow a power-law distribution that characterizes scale-free networks.
Smart contracts are Turing-complete programs running on the blockchain. They cannot be modified, even when bugs are detected. The Selfdestruct function is the only way to destroy a contract on the blockchain system and transfer all the Ethers on the contract balance. Thus, many developers use this function to destroy a contract and redeploy a new one when bugs are detected. In this paper, we propose a deep learning-based method to find security issues of Ethereum smart contracts by finding the updated version of a destructed contract. After finding the updated versions, we use open card sorting to find security issues.
Santiago Morales Cardoso, Mario R. Morales, Vilmar Wladimir Chipuxi-Trujillo, Jhonathan Paucar
La presente investigación, tiene como objetivo proponer un modelo de cadena de suministro que sea soportado por la tecnología blockchain a través del desarrollo de contratos inteligentes. Se establecen especificaciones funcionales que cumplan con la propuesta a través de la selección de herramientas tecnológicas, para la construcción de un contrato inteligente, en donde se especifica su distribución como: estructuras, variables de estado y funciones, que brindan solución a los requerimientos del modelo en base a un ejemplo realizado en el sector farmacéutico. Simulando la interacción dentro de una red Ethereum de prueba con la finalidad de analizar el flujo de trazabilidad de un producto, a través de la intervención de participantes dentro de la cadena de suministro como pueden ser: fabricantes, proveedores o clientes.
Case law is the term that refers to reports of past court decisions. It is considered an essential source of law, vital for legal professionals. Existing case law services are currently centralized, with an entity having complete control over the data and often charging fees for its access and other adding value services. This paper attempts to leverage the potential of blockchain technology in order to develop a public and decentralized platform that allows the submission of court decisions in a decentralized database and employs a network of curators who offer their validation, classification, and evaluation. Specifically, we design, analyze and implement AnyCase, a proof-of-concept prototype system on the Ethereum platform. We focus on the establishment of a sybil-resistant voting protocol used for reaching agreement and the development of a tokenized economy that incentivizes participation. Our preliminary analysis indicates that, besides being decentralized, AnyCase has the potential to compete with existing centralized systems in several other aspects.
The article concerns selected issues regarding smart contracts from the perspective of private law, in particular the concept of a contract, determination of its content, principles of performance and breach of an obligation. The legal analysis jest supplemented with technological aspects that show the essence and mechanism of operation of Blockchain, smart contracts, Ethereum. The legal doctrine generally referred to the technological aspects of smart contracts, attempting to include them in the traditional contract law system. The article contends that this is the wrong approach. The authors argue that a smart contract as such is not a contract, but a computer program (code) that can be a manner of concluding a contract and at the same time self-executing it. The qualification of a smart contract as a method of conclusion a contract, and not the contract itself, determines the conclusions on other aspects of concluding the contract, its interpretation, etc. Considerations concerning the model of a self-executing contract are formulated around this thesis. This model determines the proposals for regulation of the principles of performance of the contract, the consequences of the breach of contract and others areas of concern.
Francesco Bruschi, Vincenzo Rana, Alessio Pagani, Donatella Sciuto
The idea of Smart contracts foresees the possibility of automating contractual clauses using hardware and software tools and devices. One of the main perspectives of their implementation is the automation of interactions such as bets, collaterals, prediction markets, insurances. As blockchain platforms, such as Ethereum, offer very strong guarantees of untampered, deterministic execution, that can be exploited as smart contracts substrate, the problem of how to provide reliable information from the “outside world” into the contracts becomes central. In this article, we propose a system based on a Merkle tree representation of structured documents (such as all XML), with which it is possible to generate compact proofs on the content of web documents. The proofs can then be efficiently checked on-chain by a smart contract, to trigger contract action. We provide an end-to-end proof of concept, applying it to real use case scenarios, which allows us to give an estimate of the costs.
It is well known that users on open blockchains are tracked by an industry providing services to governments, law enforcement, secret services, and alike. While most blockchains do not protect their users' privacy and allow external observers to link transactions and addresses, a growing research interest attempts to design add-on privacy solutions to help users regain their privacy on non-private blockchains. In this work, we propose to our knowledge the first censorship resilient mixer, which can reward its users in a privacy-preserving manner for participating in the system. Increasing the anonymity set size, and diversity of users, is, as we believe, an important endeavor to raise a mixer's contributed privacy in practice. The paid-out rewards can take the form of governance tokens to decentralize the voting on system parameters, similar to how popular "DeFi farming" protocols operate. Moreover, by leveraging existing "Defi" lending platforms, AMR is the first mixer design that allows participating clients to earn financial interests on their deposited funds. Our system AMR is autonomous as it does not rely on any external server or third party. The evaluation of our AMR implementation shows that the system supports today on Ethereum anonymity set sizes beyond thousands of users, and a capacity of over $66,000$ deposits per day, at constant system costs. We provide a formal specification of our zksnark-based AMR system, a privacy and security analysis, implementation, and evaluation with both the MiMC and Poseidon hash functions.
Open access
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cs.CR
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Abstract The popularity of blockchain, Bitcoin and Ethereum in 2017 can be described as an empty alley. However, the reason why such a popular technology has strong vitality must be to find the most suitable application. In view of the security and privacy, lack of resources, network transmission delay and other issues in the current Internet of Things system, analyze the advantages brought by the introduction of blockchain technology, and compare the architecture of the blockchain Internet of Things with the traditional Internet of Things system. Aiming at the problems existing in the application of blockchain IoT, a blockchain IoT architecture based on edge computing is proposed. In this architecture, the data collected by the edge device is filtered and transmitted to the fog node of the fog layer through the multi-interface base station, and the fog node reports the data processing result to the distributed cloud layer based on the blockchain. The fog layer provides positioning, and the cloud layer provides wide-area monitoring. It provides large-scale event detection, behavior analysis and long-term pattern recognition through distributed computing and storage, and combines blockchain technology to provide scalable, reliable and highly available Internet of Things services. Therefore, the proposed architecture has important reference significance for subsequent computer technology application research based on blockchain IoT technology.
Blockchain is a kind of technology which comprehensively uses cryptography, distributed databases, P2P communication, smart contracts and other technologies. In a decentralized and trustless network, it uses encryption algorithms to verify and store data in a chained data structure. Blockchain technology is a universal low-level technical architecture that generates and synchronizes data on distributed nodes through a consensus mechanism, and implements automatic execution of contract terms and data operations with the help of programmable scripts. This paper systematically sorts out the blockchain and deconstructs its key technical elements. Under this premise, the basic architecture of the blockchain system is analyzed starting from the architecture and the implementation protocol. Taking the application development of blockchain technology as the context and combining with the application scenarios of Bitcoin, Ethereum and Super Ledger, the technical principles, implementation paths, app-lication status and existing challenges are expounded. This paper seeks to provide readers with help and reference in the systematic learning and in-depth research of blockchain technology.
During the Coincheck incident, which recorded the largest damages in cryptocurrency history in 2018, it was demonstrated that using Mosaic token can have a certain effect. Although it seems attractive to employ tokens as countermeasures for cryptocurrency leakage, Mosaic is a specific token for the New Economy Movement (NEM) cryptocurrency and is not employed for other blockchain systems or cryptocurrencies. Moreover, although some volunteers tracked leaked NEM using Mosaic in the CoinCheck incident, it would be better to verify that the volunteers can be trusted. Simultaneously, if someone (e.g., who stole cryptocurrencies) can identify the volunteers, then that person or organization may be targets of them. In this paper, we propose an anonymous trust-marking scheme on blockchain systems that is universally applicable to any cryptocurrency. In our scheme, entities called token admitters are allowed to generate tokens adding trustworthiness or untrustworthiness to addresses. Anyone can anonymously verify whether these tokens were issued by a token admitter. Simultaneously, only the designated auditor and no one else, including nondesignated auditors, can identify the token admitters. Our scheme is based on accountable ring signatures and commitment, and is implemented on an elliptic curve called Curve25519, and we confirm that both cryptographic tools are efficient. Moreover, we also confirm that our scheme is applicable to Bitcoin, Ethereum, and NEM.
The statistical concept of gambler’s ruin suggests that gambling has a large amount of risk. Nevertheless, gambling at casinos and gambling on the Internet are both hugely popular activities. In recent years, both prospect theory and laboratory-controlled experiments have been used to improve our understanding of risk attitudes associated with gambling. Despite theoretical progress, collecting real-life gambling data, which is essential to validate predictions and experimental findings, remains a challenge. To address this issue, we collect publicly available betting data from a DApp (decentralized application) on the Ethereum blockchain, which instantly publishes the outcome of every single bet (consisting of each bet’s timestamp, wager, probability of winning, userID and profit). This online casino is a simple dice game that allows gamblers to tune their own winning probabilities. Thus the dataset is well suited for studying gambling strategies and the complex dynamic of risk attitudes involved in betting decisions. We analyse the dataset through the lens of current probability-theoretic models and discover empirical examples of gambling systems. Our results shed light on understanding the role of risk preferences in human financial behaviour and decision-makings beyond gambling.
Previous studies have shown that cryptocurrencies could hedge equities. However, most of those studies did not take into account the recent cryptocurrencies bubbles in 2018 and domestic currencies. Therefore, this research aimed to study whether the hedge effectiveness of cryptocurrencies still exists. This research used five cryptocurrencies (bitcoin, ethereum, monero, ripple, and litecoin), equity indices (Indonesia, Malaysia, Vietnam, Thailand, and the Philippines), and iShares ETF MSCI World (developed world). Commodities-based hedging using iShares S&P GSCI Commodity-Indexed Trust was also analyzed as a comparison. The asymmetric generalized dynamic conditional correlation (AG-DCC) GARCH showed that one cryptocurrency could not significantly and consistently hedge equities while five equally weighted cryptocurrencies could marginally hedge equities. Meanwhile, the classical minimum variance model also showed that the hedge effectiveness of cryptocurrencies was insignificantly positive. Equity traders could add cryptocurrencies into portfolios when the purpose was to maximize the Sharpe ratio instead of hedging. Overall, commodities were the better hedge for Southeast Asia emerging markets.
Michael Rodler, Wenting Li, Ghassan Karame, Lucas Davi
Recent attacks exploiting errors in smart contract code had devastating consequences thereby questioning the benefits of this technology. It is currently highly challenging to fix errors and deploy a patched contract in time. Instant patching is especially important since smart contracts are always online due to the distributed nature of blockchain systems. They also manage considerable amounts of assets, which are at risk and often beyond recovery after an attack. Existing solutions to upgrade smart contracts depend on manual and error-prone processes. This paper presents a framework, called EVMPatch, to instantly and automatically patch faulty smart contracts. EVMPatch features a bytecode rewriting engine for the popular Ethereum blockchain, and transparently/automatically rewrites common off-the-shelf contracts to upgradable contracts. The proof-of-concept implementation of EVMPatch automatically hardens smart contracts that are vulnerable to integer over/underflows and access control errors, but can be easily extended to cover more bug classes. Our extensive evaluation on 14,000 real-world (vulnerable) contracts demonstrate that our approach successfully blocks attack transactions launched on these contracts, while keeping the intended functionality of the contract intact. We perform a study with experienced software developers, showing that EVMPatch is practical, and reduces the time for converting a given Solidity smart contract to an upgradable contract by 97.6 %, while ensuring functional equivalence to the original contract.