We present eclipse attacks on Ethereum nodes that exploit the peer-to-peer network used for neighbor discovery. Our attacks can be launched using only two hosts, each with a single IP address. Our eclipse attacker monopolizes all of the victim’s incoming and outgoing connections, thus isolating the victim from the rest of its peers in the network. The attacker can then filter the victim’s view of the blockchain, or co-opt the victim’s computing power as part of more sophisticated attacks. We argue that these eclipse-attack vulnerabilities result from Ethereum’s adoption of the Kademlia peer-to-peer protocol, and present countermeasures that both harden the network against eclipse attacks and cause it to behave differently from the traditional Kademlia protocol. Several of our countermeasures have been incorporated in the Ethereum geth 1.8 client released on February 14, 2018.
Md. Selim Hossain, Sajjad Waheed, Ziaur Rahman, Sk. A. Shezan · 5 authors
Internet of Things (IoT) that has been developed owing toward the merging of various technologies such as instantaneous analytics, machine learning, artificial neural network, product sensors and implanted systems, etc. It also stages a significant part in multiple applications which are a smart city, smart home, agricultural, health monitoring, tourism, transportation, communication, business, education, etc. The security concern associating IoT has to be situated in the direction to attract the research community due to its immensely growing application in our daily life. Since it is light-weight nature, the security mechanism needs changes apart from comprehensive web security. PKI based certificate driven techniques, which in some instances seem not appropriate on the way toward encounter IoT challenges, e.g., as real-time effectiveness, costs, and performance from the security perspective. However, Blockchain has mind-blowing potentials to peer with the IoT aiming to build trust, transparency, and security. Its distinct properties, such as distributed behavior, immutability, and consensus mechanism, can stimulate and improve the rapidly growing IoT system through meaningful integration. We propose to address a practical smart home use case scenario using Ethereum Blockchain to improve IoT security. Public type and smart contract oriented Ethereum Blockchain are adaptable to enhance IoT security remains individual of the contributions that we claim throughout this research work.
The recent extreme volatility in cryptocurrency prices occurred in the setting of popular social media forums devoted to the discussion of cryptocurrencies. We develop a framework that discovers potential causes of phasic shifts in the price movement captured by social media discussions. This draws on principles developed in healthcare epidemiology where, similarly, only observational data are available. Such causes may have a major, one-off effect or recurring effects on the trend in the price series. We find a one-off effect of regulatory bans on bitcoin, the repeated effects of rival innovations on ether and the influence of technical traders, captured through discussion of market price, on both cryptocurrencies. The results for Bitcoin differ from Ethereum, which is consistent with the observed differences in the timing of the highest price and the price phases. This framework could be applied to a wide range of cryptocurrency price series where there exists a relevant social media text source. Identified causes with a recurring effect may have value in predictive modelling, whilst one-off causes may provide insight into unpredictable black swan events that can have a major impact on a system.
Christopher Klinkmüller, Ingo Weber, Alexander Ponomarev, An Binh Tran · 5 authors
Second generation blockchain platforms, like Ethereum, can store arbitrary data and execute user-defined smart contracts. Due to the shared nature of blockchains, understanding the usage of blockchain-based applications and the underlying network is crucial. Although log analysis is a well-established means, data extraction from blockchain platforms can be highly inconvenient and slow, not least due to the absence of logging libraries. To close the gap, we here introduce the Ethereum Logging Framework (ELF) which is highly configurable and available as open source. ELF supports users (i) in generating cost-efficient logging code readily embeddable into smart contracts and (ii) in extracting log analysis data into common formats regardless of whether the code generation has been used during development. We provide an overview of and rationale for the framework's features, outline implementation details, and demonstrate ELF's versatility based on three case studies from the public Ethereum blockchain.
Στην παρούσα διπλωματική εργασία σχεδιάστηκε και υλοποιήθηκε μία κατανεμημένη εφαρμογή ηλεκτρονικών δημοπρασιών αξιοποιώντας την τεχνολογία του blockchain. Παρέχονται στον χρήστη οι δυνατότητες δημιουργίας ανοιχτών ανοδικών δημοπρασιών, η εύρεση των ενεργών και των ολοκληρωμένων δημοπρασιών. καθώς και η δυνατότητα υποβολής προσφοράς. Η υλοποίηση έγινε χρησιμοποιώντας το δημόσιο blockchain του ethereum, υλοποιώντας smart contracts γραμμένα στην γλώσσα προγραμματισμού solidity. Παράλληλα, για την διεπαφή του χρήστη με το blockchain χρησιμοποιήθηκαν τεχνολογίες διαδικτύου όπως τα frameworks Laravel, Vue.js, web3.js.
This article analyzes the research on cryptocurrency and blockchain technology and the alternate banking system, led by giants like Bitcoin and Ethereum, and its potential utility for the millions of migrants living in working around the globe, who send nearly half a trillion dollars through various formal and informal channels to family and friends in their home countries. While research on migrant remittances is well established and has been examined from many different lenses, including economic, political, financial, sociological and entrepreneurial, there are few studies to date that examine how the growing crypto-blockchain channel can impact remittance flows, as a lower cost alternative to MoneyGram and Western Union, which have high transaction costs, and also considering that many migrants do not have formal bank accounts, eliminating formal bank transfers, and also that many migrants hold a vulnerable legal status, and may avoid formal money transfer channels. This article is exploratory in nature and identifies the work that has been done to date on this topic, and identifies potential future research in the area.
Hoy en dia la concurrencia y la distribucion se han convertido en una parte fundamental del proceso de desarrollo de software. Indiscutiblemente, Internet y el uso cada vez mas extendido de los procesadores multicore ha influido en el tipo de aplicaciones que se desarrollan. Esto ha dado lugar a la creacion de distintos modelos de concurrencia .En particular, uno de los modelos de concurrencia que esta ganando importancia es el modelo de objetos concurrentes basado en actores. En este modelo, los objetos (denominados actores) son las unidades de concurrencia. Cada objeto tiene su propio procesador y un estado local. La comunicacion entre los mismos se lleva a cabo mediante el paso de mensajes. Cuando un objeto recibe un mensaje puede: actualizar su estado, mandar mensajes o crear nuevos objetos. Es bien sabido que la creacion de programas concurrentes correctos es mas compleja que la de programas secuenciales ya que es necesario tener en cuenta distintos aspectos inherentes a la concurrencia como los errores asociados a las carreras de datos o a los interbloqueos. Con el n de asegurar el correcto comportamiento de estos programas concurrentes se han desarrollado distintas tecnicas de analisis estatico y verificacion para los diversos modelos de concurrencia existentes...
Wei Wang, J. J. Song, Guangquan Xu, Yidong Li · 6 authors
Smart contracts are decentralized applications running on Blockchain. A very large number of smart contracts has been deployed on Ethereum. Meanwhile, security flaws of contracts have led to huge pecuniary losses and destroyed the ecological stability of contract layer on Blockchain. It is thus an emerging yet crucial issue to effectively and efficiently detect vulnerabilities in contracts. Existing detection methods like Oyente and Securify are mainly based on symbolic execution or analysis. These methods are very time-consuming, as the symbolic execution requires the exploration of all executable paths or the analysis of dependency graphs in a contract. In this work, we propose ContractWard to detect vulnerabilities in smart contracts with machine learning techniques. First, we extract bigram features from simplified operation codes of smart contracts. Second, we employ five machine learning algorithms and two sampling algorithms to build the models. ContractWard is evaluated with 49502 real-world smart contracts running on Ethereum. The experimental results demonstrate the effectiveness and efficiency of ContractWard. The predictive Micro-F1 and Macro-F1 of ContractWard are over 96% and the average detection time is 4 seconds on each smart contract when we use XGBoost for training the models and SMOTETomek for balancing the training sets.
Lin Chen, Lei Xu, Zhimin Gao, Sunny, Ahmed · 6 authors
Recent advances in the blockchain research have been made in two important directions. One is refined resilience analysis utilizing game theory to study the consequences of selfish behaviors of users (miners), and the other is the extension from a linear (chain) structure to a non-linear (graphical) structure for performance improvements, such as IOTA and Graphcoin. The first question that comes to people's minds is what improvements that a blockchain system would see by leveraging these new advances. In this paper, we consider three major metrics for a blockchain system: full verification, scalability, and finality-duration. We { establish a formal framework and} prove that no blockchain system can achieve full verification, high scalability, and low finality-duration simultaneously. We observe that classical blockchain systems like Bitcoin achieves full verification and low finality-duration, Harmony and Ethereum 2.0 achieve low finality-duration and high scalability. As a complementary, we design a non-linear blockchain system that achieves full verification and scalability. We also establish, for the first time, the trade-off between scalability and finality-duration.
As the largest public blockchain-based platform supporting smart contracts, Ethereum has accumulated a large number of user transaction records since its debut in 2014. Analysis of Ethereum transaction records, however, is still relatively unexplored till now. Modeling the transaction records as a static simple graph, existing methods are unable to accurately characterize the temporal and multiplex features of the edges. In this brief, we first model the Ethereum transaction records as a complex network by incorporating time and amount features of the transactions, and then design several flexible temporal walk strategies for random-walk based graph representation of this large-scale network. Experiments of temporal link prediction on real Ethereum data demonstrate that temporal information and multiplicity characteristic of edges are indispensable for accurate modeling and understanding of Ethereum transaction networks.
Zhipeng Gao, Lingxiao Jiang, Xin Xia, David Lo · 5 authors
Smart contracts have been increasingly used together with blockchains to automate financial and business transactions. However, many bugs and vulnerabilities have been identified in many contracts which raises serious concerns about smart contract security, not to mention that the blockchain systems on which the smart contracts are built can be buggy. Thus, there is a significant need to better maintain smart contract code and ensure its high reliability. In this paper, we propose an automated approach to learn characteristics of smart contracts in Solidity, which is useful for clone detection, bug detection and contract validation on smart contracts. Our new approach is based on word embeddings and vector space comparison. We parse smart contract code into word streams with code structural information, convert code elements (e.g., statements, functions) into numerical vectors that are supposed to encode the code syntax and semantics, and compare the similarities among the vectors encoding code and known bugs, to identify potential issues. We have implemented the approach in a prototype, named SmartEmbed,11.The anonymous replication packages can be accessed at:https://drive.google.com/file/d/1kauLT3y2IiHPkUlVx4FSTda-dVAyL4za/view?usp=sharing.and evaluated it with more than 22,000 smart contracts collected from the Ethereum blockchain. Results show that our tool can effectively identify many repetitive instances of Solidity code, where the clone ratio is around 90 percent. Code clones such as type-III or even type-IV semantic clones can also be detected accurately. Our tool can identify more than 1000 clone related bugs based on our bug databases efficiently and accurately. Our tool can also help to efficiently validate any given smart contract against a known set of bugs, which can help to improve the users’ confidence in the reliability of the contract.
The state-of-the-art approach to manage blockchains is to process blocks of transactions in a shared-nothing environment. Although blockchains have the potential to provide various services for high-performance computing (HPC) systems, HPC will not be able to embrace blockchains before the following two missing pieces become available: (i) new consensus protocols being aware of the shared-storage architecture in HPC, and (ii) new fault-tolerant mechanisms compensating for HPC's programming model---the message passing interface (MPI)---that is vulnerable for blockchain-like workloads. To this end, we design a new set of consensus protocols crafted for the HPC platforms and a new fault-tolerance subsystem compensating for the failures caused by faulty MPI processes. Built on top of the new protocols and fault-tolerance mechanism, a prototype system is implemented and evaluated with two million transactions on a 500-core HPC cluster, showing $6\times$, $12\times$, and $75\times$ higher throughput than Hyperldeger, Ethereum, and Parity, respectively.
Abstract. At present all business activities are bound to contracts or agreements. A written contract has several weaknesses, the contract can be lost and damaged, it is not cost effective and one party can commit fraud. The solution for that is to use the smart contract Ethereum. Smart contract Ethereum is a computer protocol that functions to facilitate, verify, or enforce digital negotiations written through the program code. Smart contract works without going through a third party and has a credible transaction process so that it cannot be tracked or changed. But Blockchain technology is not suitable for storing large amounts of data and expensive costs, the authors combine IPFS technology on Ethereum Blockchain. So the Ethereum Blockchain only stores the hash of the file, then the hash of this file can be connected to the file on IPFS to access it. In this study a web-based DApp (Decentralized applications) system was built that implemented IPFS on the smart contract Ethereum. The final result of this study is a discussion of data integrity and Quality of Service (QoS) communication between IPFS nodes on the smart contract Ethereum as a reference for implementation of the company. With the results of the implementation it was found that the data integrity possessed by IPFS was very good by fulfilling aspects of information security and having Quality of Service with average throughput values of 56.41 Kbps, 65.81 Kbps and 79.68 Kbps, for average packet loss values of 1.92%, 1.58% and 1.06%, while the average value of delay is 24.79 ms, 25.87 ms and 17.30 ms with the average value of the Quality of Service index which is 3 which meets the Satisfying category based on THIPON standards. Keywords: Blockchain, Smart Contract Ethereum, IPFS, Data Integrity, Quality of Service (QoS)
Abstract. Smart contract is an agreement between two entities established in the program code. All Smart contract transactions are stored on the Blockchain. But storing large data on the Blockchain is expensive, so many developers are currently creating a DApp (Decentralized Application) that integrates IPFS on smart contract Ethereum. Files will be stored on IPFS while the Blockchain only stores hash files from IPFS to access them again. Blockchain & IPFS are distributed peer-to-peer technologies for storing and distributing digital data supported by the confidentiality, integrity and authenticity of the data. The study was conducted to measure memory usage to run the DApp web that integrates IPFS on smart contract Ethereum and find out the effect of the file size uploaded via the web DApp and the number of nodes connected in the network. The memory usage test results will be used as a standard for the memory capacity planning to implement a DApp web system that integrates IPFS on smart contract Ethereum in an organization. Based on the research result, to run a web DApp that integrates IPFS on a smart contract requires 774MB of memory. The result proves that IPFS is suitable for handling large files. The efficiency of DApp's web performance that integrates IPFS on the smart contract Ethereum are obtained by a small file size and a large number of nodes connected in a network. The smaller the file size, the less memory usage. The more nodes that are connected in the network, the less memory usage. Keywords: Decentralized Application, IPFS, Smart Contract Ethereum, Blockchain, Memory Usage.
Katarina Preikschat, Moritz Böhmecke‐Schwafert, Jan‐Paul Buchwald, Carolin Stickel
Summary Blockchain technology has the potential to bring transparency and trust to a multitude of use cases. Our research demonstrates that the technology can reduce asymmetric information in markets by bridging trust gaps. The combination of blockchain and Internet of Things technology that automatically collects sensor data, provides a feasible, decentralized technological solution for such an inefficient “Market of Lemons” coined by nobel laureate Georg Akerlof. In this paper, we develop a system prototype to reduce mileage fraud on the used car markets. Our work demonstrates the feasibility of a trusted system of records for (vehicle) data such as mileage data using a distributed database based on the public Ethereum network and smart contracts. We have identified eight requirements that are fulfilled by the prototype and the functional logic and design of thesolution can be reproduced to any other application area characterized by a lack of trust between actors or by the absence of a trusted central authority. However, the developed prototype suffers from similar limitations and challenges as the technology itself. Low throughput causes limitations in scalability and transaction costs are unpredictable. Further development of the blockchain technology and considering more cost‐efficient consensus mechanisms will address these issues.
In the area of blockchains, a wallet is anything that manages the access to cryptocurrencies and tokens. Off-chain wallets appear in different forms, from paper wallets to hardware wallets to dedicated wallet apps, while on-chain wallets are realized as smart contracts. Wallet contracts are supposed to increase trust and security by being transparent and by offering features like daily limits, approvals, multiple signatures, and recovery mechanisms. The most prominent platform for smart contracts in general and the token ecosystem im particular, and thus also for wallet contracts is Ethereum. Our work aims at a better understanding of wallet contracts on Ethereum, since they are one of the most frequently deployed smart contracts. By analyzing source code, bytecode, and execution traces, we derive usage scenarios and patterns. We discuss methods for identifying wallet contracts in a semi-automatic manner by looking at the deployed bytecodes and the on-chain interaction patterns. We extract blueprints for wallets and compile a ground truth. Furthermore, we differentiate characteristics of wallets in use, and group them into six types. We provide numbers and temporal perspectives regarding the creation and use of wallets. For the 40 identified blueprints, we compile detailed profiles. We analyze the data of the Ethereum main chain up to block 11,500,000, mined on December 22, 2020.
Electronic Health Records (EHRs) have improved many aspects of healthcare and allowed for easier patient management for medical providers. Blockchains have been proposed as a promising solution for supporting Electronic Health Records (EHRs), but have also been linked to scalability concerns about supporting real-world healthcare systems. This paper quantifies the scalability issues and bottlenecks related to current blockchains and puts into perspective the limitations blockchains have with supporting healthcare systems. Particularly we show that well known blockchains such as Bitcoin, Ethereum, and IOTA cannot support transactions of a large scale hospital system such as the University of Kentucky HealthCare system and leave over 7.5M unsealed transactions per day. We then discuss how bottlenecks of blockchains can be relieved with sidechains, enabling well-known blockchains to support even larger hospital systems of over 30M transactions per day. We then introduce the Patient-Healthchain architecture to provide future direction on how scaling blockchains for EHR systems with sidechains can be achieved.
Ethereum is one of the most popular blockchain systems that supports more than half a million transactions every day and fosters miscellaneous decentralized applications with its Turing-complete smart contract machine. Whereas it remains mysterious what the transaction pattern of Ethereum is and how it evolves over time. In this paper, we study the evolutionary behavior of Ethereum transactions from a temporal graph point of view. We first develop a data analytics platform to collect external transactions associated with users as well as internal transactions initiated by smart contracts. Three types of temporal graphs, user-to-user, contract-to-contract and user-contract graphs, are constructed according to trading relationship and are segmented with an appropriate time window. We observe a strong correlation between the size of user-to-user transaction graph and the average Ether price in a time window, while no evidence of such linkage is shown at the average degree, average edge weights and average triplet closure duration. The macroscopic and microscopic burstiness of Ethereum transactions is validated. We analyze the Gini indexes of the transaction graphs and the user wealth in which Ethereum is found to be very unfair since the very beginning, in a sense, "the rich is already very rich".
The information systems of decentralized organizations are now networked as components of a global information system. Organizations, individuals and software act autonomously and are at the same time cooperatively involved in the creation of services. The planning and execution of the necessary interactions in the form of processes are not under the control of individuals. For the development and execution of processes under decentralized coordination, this work proposes an approach based on blockchain technologies. This addresses, on the one hand, the design of decentralized organizations and, on the other hand, the coordination of development that is distributed within such systems and is not centrally controlled. The thesis describes the decentralization and the model-based development of process-oriented systems from an organizational theory perspective. The focus is then on decentralized blockchain systems as development and execution platforms, with which the binding nature and integrity of transactions between a priori unknown nodes of a network can be guaranteed. The development and execution of processes are implemented on this basis using a model-based approach. This is established by an architectural framework for conceptual modeling, for cooperative modeling and for the tracking of instances. The conceptual modeling of networks, processes and instances makes use of the semantic object model (SOM) in order to map the task level of decentralized organizations to a decentralized task management level. The cooperative modeling and the tracking of instances use technologies for distributed version management in connection with smart contracts of the blockchain system Ethereum. The demonstration of the applicability of the approach based on a case study and a software implementation concludes the work.