Alex Groce, Josselin Feist, Gustavo Grieco, Michael D. Colburn
An important problem in smart contract security is understanding the\nlikelihood and criticality of discovered, or potential, weaknesses in\ncontracts. In this paper we provide a summary of Ethereum smart contract audits\nperformed for 23 professional stakeholders, avoiding the common problem of\nreporting issues mostly prevalent in low-quality contracts. These audits were\nperformed at a leading company in blockchain security, using both open-source\nand proprietary tools, as well as human code analysis performed by professional\nsecurity engineers. We categorize 246 individual defects, making it possible to\ncompare the severity and frequency of different vulnerability types, compare\nsmart contract and non-smart contract flaws, and to estimate the efficacy of\nautomated vulnerability detection approaches.\n
Due to the limitation of the capacity of each block, when the number of transactions increases at the same time, it will face congestion problems and reduce the efficiency of accounting. Collaborative computing and data slicing are effective methods to improve performance, and they have been widely used in various fields. This paper proposes a tree chain architecture that adds peer-to-peer blockchain to main chain of the Ethereum. When there is a task to be processed in the main chain, the architecture assigns the task to "branch" or "leaf". The "branch" first determines whether the task can be sliced. If the task can be sliced, divide the task into leaf nodes for processing, otherwise let the branch nodes handle. By assigning tasks in this way, it is possible to help the main chain reduce the computational pressure and increase the system throughput.
Ethereum blockchain is a revolutionary decentralized database technology on the Internet, with the characteristics of data tamperability, disintermediation, autonomy, traceability, point-to-point transaction, programmable and so on. Its emergence has an important impact on the development of many traditional industries. This paper analyzes the shortcomings of the traditional second-hand goods rental system and uses the blockchain technology to design the second-hand goods renting system based on ethereum smart contract. It introduces the background of blockchain and Ethereum smart contract, gives the overall framework of system design, and specifically describes the three parts of the system: blockchain module, smart contract module and the front end of DAPP, and the problems of combining blockchain and rental system are analyzed to provide a reference for better applications in the future.
Budankailu Kumar Subudhi, Faruk Catal, Nikolay Tcholtchev, Kin Tsun Chiu · 7 authors
VoIP-based emergency communication is a promising approach to improving the safety of citizens worldwide. The transition required in this scope includes substituting the legacy PSTN/SS7 based emergency call system by Next Generation IP based components for call establishment and control. Thereby, SIP is used as a session control protocol and RTP as the means to transfer emergency data between the caller and the corresponding Public Safety Access Point (PSAP). The emergency data is not only restricted to voice communication but can cover a rich variety of data, which can be acquired by different means (including the end-user devices) and transmitted over IP. This includes video, geopositioning data, voice, Real-Time Text, and sensor data in line with emerging IoT architectures and approaches. A vital aspect in this scope is given by the performance of the underlying network, including its capability to establish calls in emergencies and to transfer the data required for serving the situation. Therefore, in this paper, we evaluate the computational performance of the most recent VoIP emergency system implementation, which was developed by the H2020-EMYNOS project as a realisation of the EENA NG112 Long Term Definition (LTD) vision. We perform a series of trials and evaluate the performance of the EMYNOS system in a multi-party lab environment established during the project. We evaluate the time needed to perform basic emergency call operations over IP, whilst in parallel generating Internet type of background traffic. Correspondingly, we worked out a methodology and implemented it in our testbed, both of which are presented in the current paper. The obtained numerical results lead to the conclusion that SIP-based emergency services stand a good chance to replace legacy systems when it comes to their performance. Additionally, we also provide a perspective on how the blockchain technology could potentially be put to use to enhance the quality of the next-generation emergency services. We propose the utilisation of blockchain technology for tracking emergency calls and enabling efficient recognition of fraud calls, which is a critical aspect for PSAP providers concerning the potential denial of service attacks. In this context, we provide evaluations and numerical results based on a private Ethereum based blockchain playground running at the premises of Fraunhofer FOKUS.
Audi Ramadhan, Chandra Indira Septiarani, Faisal Dias, Deden Yoga Pratama
Aplikasi trading cryptocurrency merupakan sebuah aplikasi yang relatif baru yang ditandai dengan munculnya banyak cryptocurrency seperti Bitcoin, Ethereum dan lain sebagainya. Oleh sebab itu, analisis penerimaan teknologi pada aplikasi tersebut sangat penting untuk dikaji lebih dalam. Penelitian ini bertujuan untuk menganalisis dan mengukur penerimaan aplikasi trading cryptocurrency yaitu Indodax Trading Platform dengan menggunakan Technology Acceptance Model (TAM) yang diintegrasikan dengan faktor resiko dan kepercayaan. Penelitian ini merupakan penelitian kuantitatif asosiatif dengan menggunakan kuesioner untuk mendapatkan data primer. Sampel yang digunakan pada penelitian ini sebesar 134 dengan menggunakan teknil analisis Semi Equation Model – Partial Least Square (SEM-PLS). Hasil dari penelitian ini yaitu adanya pengaruh dari perceived usefulness dan trust terhadap penggunaan aplikasi trading cryptocurrency. Sedangkan resiko dan perceived ease of use tidak berpengaruh terhadap penggunaan aplikasi trading cryptocurrency.
Asmali Badarudin, Thien Wan Au, Somnuk Phon-Amnuaisuk
This paper proposes the adoption of consortium blockchain technologies as a more efficient and effective means of transferring funds from corporate donors as part of corporate social responsibility to victims of natural disaster. The main benefit envisaged is that post-disaster disruptions to normal lives can be minimized or normal lives can resume better than the current situation as donation mechanism relies largely on manual and centralized processes. Using blockchain, corporations can donate fund anytime and this is especially useful for small and medium enterprises (SMEs) where they can donate in small amounts in a consistent manner to a fund setup for a disaster relief and recovery that disaster victim can use whenever required. The use case for this blockchain is corporate donors donating funds to victims of strong wind disaster in Brunei Darussalam. Through smart contracts of Ethereum, corporations incorporate details of donations and set out other requirements. A Brunei Government’s agency use of set of criteria can be used as part of the smart contract terms and conditions. These smart contracts can be part of decentralized applications that can be deployed to the blockchain network using cryptographic mechanisms to ensure security and integrity of the transactions. By this way, more companies are motivated to participate in donations while ensuring that victims can receive much needed assistance in the shortest time possible without solely relying on centralized bureaucratic processes.
Jae-Yun Kim, Jun-Mo Lee, Yeon-Jae Koo, Sang-Hyeon Park · 5 authors
As ethereum blockchain has become popular, the number of users and transactions has skyrocketed, causing an explosive increase of its data size. As a result, ordinary clients using PCs or smartphones cannot easily bootstrap as a full node, but rely on other full nodes such as the miners to run or verify transactions. This may affect the security of ethereum, so light bootstrapping techniques such as fast sync has been proposed to download only parts of full data, yet the space overhead is still too high. One of the biggest space overhead that cannot easily be reduced is caused by saving the state of all accounts in the block's state trie. Fortunately, we found that more than 90% of accounts are inactive and old transactions are hard to be manipulated. Based on these observations, this paper propose a novel optimization technique called ethanos that can reduce bootstrapping cost by sweeping inactive accounts periodically and by not downloading old transactions. If an inactive account becomes active, ethanos restore its state by running a restoration transaction. Also, ethanos gives incentives for archive nodes to maintain the old transactions for possible re-verification. We implemented ethanos by instrumenting the go-ethereum (geth) client and evaluated with the real 113 million transactions from 14 million accounts between 7M-th and 8M-th blocks in ethereum. Our experimental result shows that ethanos can reduce the size of the account state by half, which, if combined with removing old transactions, may reduce the storage size for bootstrapping to around 1GB. This would be reasonable enough for ordinary clients to bootstrap on their personal devices.
Agriculture is indispensable for every country. Farmers use pesticides in large quantities to increase productivity, thus causing serious damage to the agro-ecological environment. If consumers consume a large number of such vegetables, there can be an adverse effect on their health. Therefore, consumers shift from consuming general vegetables to organic vegetables. However, the price of organic vegetables is higher than that of general vegetables, and there are doubts about the authenticity of the production and marketing process. Unfortunately, production and sales records are often falsified. The blockchain may be able to guarantee the authenticity of organic vegetables because the blockchain is tamperproof and transparent. Therefore, we proposed an exercise environment for the production and marketing of organic vegetables by using Ethereum. This proposed system can ensure the authenticity of the production and sales record, it may increase the sales of organic vegetables and solve the problem of agricultural ecological environment pollution in the real world.
Cryptocurrencies are one of the greatest technological innovations. Cryptocurrencies are decentralized payment systems in which ownership is demonstrated cryptographically. An overview of ownership of payment units is stored in a data structure called blockchain. Of the thousands of cryptocurrencies, the best known are Bitcoin, Ethereum, Ripple, Litecoin, EOS, Cardano, NEO, Dash, and Monero. In the past, new cryptocurrencies were most often created by modifying the parameters of another cryptocurrency and by launching a new blockchain. Nowadays, new cryptocurrencies are most commonly created as applications on another existing cryptocurrency. Such cryptocurrencies are called tokens. Creating a new cryptocurrency is easy, but its value depends on users’ willingness to pay for its units. If a cryptocurrency loses its users, it becomes worthless. In this article, we analyze over 2,500 cryptocurrencies that are or were previously traded on cryptocurrency exchanges. We have explored the probability that a cryptocurrency will not survive and will be delisted from exchanges. For the different categories of cryptocurrencies according to their previous trading time on exchanges, we have determined the conditional probability of delisting within 1 to 5 years. We found out that the new cryptocurrencies are the riskiest. With the increasing age of the cryptocurrency, the probability of its delisting decreases. <b>TOPICS:</b>Currency, statistical methods, risk management, exchanges/markets/clearinghouses <b>Key Findings</b> • Cryptocurrencies constitute an expanding area for potential participation and investment. Since the first cryptocurrency was created in 2009 (Bitcoin) more than 2,500 cryptocurrencies have been listed on exchanges. • Consider waiting at least a year before buying a new cryptocurrency. More than 70% of cryptocurrencies that become delisted do so in the first year. • Consider waiting five years before buying a new cryptocurrency. Cryptocurrencies that have been trading for five years have a 9% chance of being delisted within one year..
We present a model/executable specification of smart contract execution in Coq. Our formalization allows for inter-contract communication and generalizes existing work by allowing modelling of both depth-first execution blockchains (like Ethereum) and breadth-first execution blockchains (like Tezos). We represent smart contracts programs in Coq's functional language Gallina, enabling easier reasoning about functional correctness of concrete contracts than other approaches. In particular we develop a Congress contract in this style. This contract -- a simplified version of the infamous DAO -- is interesting because of its very dynamic communication pattern with other contracts. We give a high-level partial specification of the Congress's behavior, related to reentrancy, and prove that the Congress satisfies it for all possible smart contract execution orders.
Automated tasks play an important role in both consumer and industrial IoT environments. In many scenarios, the IoT tasks are performed given certain conditions. To facilitate the tasks, it is necessary to delegate a third party to listen to events that trigger the conditions and issue commands to the IoT resources accordingly. However, without restriction, the third party may be over-privileged and able to control the resources unconditionally. We define the third party's permission to act under some conditions as a conditional action. We propose PPCA, a privacy-preserving service that allows users to create conditional actions in a decentralized platform using smart contracts. PPCA can guarantee strict privilege at the third party that holds conditional actions. By generalizing a variety of conditions into simple forms of conditional logic, the conditions can be verified in a privacy-preserving manner. We build a prototype of PPCA on Ethereum. The performance shows the feasibility of PPCA in IoT environments.
Roben Castagna Lunardi, Regio A. Michelin, Charles V. Neu, Henry C. Nunes · 6 authors
The Internet of Things (IoT) is transforming our physical world into a complex and dynamic system of connected devices on an unprecedented scale. Connecting everyday physical objects is creating new business models, improving processes and reducing costs and risks. Recently, blockchain technology has received a lot of attention from the community as a possible solution to overcome security issues in IoT. However, traditional blockchains (such as the ones used in Bitcoin and Ethereum) are not well suited to the resource-constrained nature of IoT devices and also with the large volume of information that is expected to be generated from typical IoT deployments. To overcome these issues, several researchers have presented lightweight instances of blockchains tailored for IoT. For example, proposing novel data structures based on blocks with decoupled and appendable data. However, these researchers did not discuss how the consensus algorithm would impact their solutions, i.e., the decision of which consensus algorithm would be better suited was left as an open issue. In this paper, we improved an appendable-block blockchain framework to support different consensus algorithms through a modular design. We evaluated the performance of this improved version in different emulated scenarios and studied the impact of varying the number of devices and transactions and employing different consensus algorithms. Even adopting different consensus algorithms, results indicate that the latency to append a new block is less than 161ms (in the more demanding scenario) and the delay for processing a new transaction is less than 7ms, suggesting that our improved version of the appendable-block blockchain is efficient and scalable, and thus well suited for IoT scenarios.
Cryptocurrency is a recent and popular topic that attracts the interest of investors and fund managers. Beyond the market discipline, researchers question the interaction between cryptocurrecies and macroeconomic variables. This study we focus on how the changes in gold and oil prices effect the daily price movements of different cryptocurrencies. The daily database includes prices of the cryptocurrencies of Bitcoin, Tether, Ethereum Litecon and EOS for the period between August 1, 2017 and April 3, 2019. Initially the stationarity of the series is tested by The existence of the cointegration relationship between the series is tested by The presence of causality relationships between the series is investigated with the Dolado and Ltkepohl (1996) causality test. The paper explains the details of the empirical findings.
This paper provides a systematic survey on return and volatility spillovers of cryptocurrencies based on the empirical results of relevant academic literature. Evidence reveals that Bitcoin is the most influential among digital coins mainly as a transmitter toward digital currencies but also as a receiver of spillovers from virtual currencies and alternative assets. Ethereum, Litecoin, and Ripple present the most significant interlinkages with Bitcoin. Return spillovers are more pronounced but volatility spillovers often present a bi-directional character. Volatility shock transmission is detected among Bitcoin and national currencies, while economic policy uncertainty is not influential. This survey provides useful guidance in the hotly-debated issue of reform and decentralization of financial systems.
Modern Blockchains support the execution of user programs, called smart contracts. As a trusted computing platform, smart contracts bring decentralization, computation integrity, open access and information transparency to average users on the Internet. However, running smart-contract programs leads to high costs, known as Gas. Such costs prevent the use of smart contracts in data-intensive application scenarios, such as high-frequency trading and transparency logging. This paper addresses the Gas-based cost effectiveness in the most consuming layer of a smart contract, namely data storage. We present GRuB, a dynamic data-replication framework that monitors the smart-contract workload and makes online replication decisions. A new online algorithm is proposed that provides constant-bounded 'competitiveness' in Gas. To further save Gas, the workload monitor and decision maker are run off the Blockchain and with security against the forging of workload trace being monitored. A GRuB prototype is built, including a smart-contract component on Ethereum and an off-chain middleware on top of Google LevelDB. The cost evaluation under the YCSB workloads shows that GRuB can converge quickly to changing workloads and save Gas significantly compared with static replication schemes. Two case studies are conducted for data-intensive applications, including high-frequency trading and transparency logging, in which running GRuB leads to affordable Gas.
Feeding external data to a blockchain, a.k.a. data feed, is an essential task to enable blockchain interoperability and support emerging cross-domain applications, notably stablecoins. Given the data-intensive feeds in real life (e.g., high-frequency price updates) and the high cost in using blockchain, namely Gas, it is imperative to reduce the Gas cost of data feeds. Motivated by the constant-changing workloads in finance and other applications, this work focuses on designing a dynamic, workload-aware approach for cost effectiveness in Gas. This design space is understudied in the existing blockchain research which has so far focused on static data placement. This work presents GRuB, a cost-effective data feed that dynamically replicates data between the blockchain and an off-chain cloud storage. GRuB's data replication is workload-adaptive by monitoring the current workload and making online decisions w.r.t. data replication. A series of online algorithms are proposed that achieve the bounded worst-case cost in blockchain's Gas. GRuB runs the decision-making components on the untrusted cloud off-chain for lower Gas costs, and employs a security protocol to authenticate the data transferred between the blockchain and cloud. The overall GRuB system can autonomously achieve low Gas costs with changing workloads. We built a GRuB prototype functional with Ethereum and Google LevelDB, and supported real applications in stablecoins. Under real workloads collected from the Ethereum contract-call history and mixed workloads of YCSB, we systematically evaluate GRuB's cost which shows a saving of Gas by 10% ~ 74%, with comparison to the baselines of static data-placement.
Muitos pesquisadores sao confrontados com problemas nos quais existem nao linearidades entre as variaveis independentes e a variavel dependente. Em tais circunstancias, busca-se a aplicacao de modelos nao lineares. Recentemente, modelos de redes neurais tem sido aplicados com sucesso em mercados financeiros, os quais usualmente sao compostos por nao linearidades. O mercado de troca entre criptomoedas e razoavelmente atual e, em relacao ao volume, um par de moedas com forte expressao sao o Bitcoin e o Ethereum. Nesse sentido, o objetivo do presente trabalho e desenvolver um sistema de predicao de tendencia para identificar oportunidades de investimento no par de criptomoedas. Para isso, utilizou-se uma rede neural fomentada com indicadores usuais empregados na analise tecnica de mercados financeiros. A rede foi construida no modelo de Perceptron de multiplas camadas, com uma estrutura de quatro camadas compostas por 17, 8, 3 e 1 neuronios, respectivamente. Os dados utilizados foram obtidos da plataforma Binance, para o periodo de 11 de janeiro ate 6 de setembro de 2019. Em um teste simulado no periodo, com 107 pares de operacoes, a rede obteve 78,5% de acoes positivas, agregando um rendimento de 123,876%, ao atuar com reinvestimento de ganhos e sem custos operacionais. Com base nos resultados obtidos, a implementacao demonstrou um potencial emprego de redes neurais para a previsao de tendencia no mercado do par Bitcoin e Ethereum. Implementacoes futuras viabilizarao validar outros indicadores, bem como aplicar heuristicas para garantir uma boa generalizacao do modelo
Smart contract brings more versatile functions in blockchain technology. However, its adoption rate is not as high as expected. Currently, there is no thorough study addressing such problem. To fill such gap, we propose to use peer influence to explain smart contract adoption in blockchain user network. We explore whether and how multiple types of peer influence including direct pee influence and indirect peer influence, simultaneously affect individual adoption decisions of smart contracts. Our hypotheses are examined in the context of CryptoKitties adoption in the Ethereum network using the public dataset of Ethereum including 350 million transactions from over 20 million distinct accounts. Our results suggest that the adoption of the software is positively affected by direct peer influence and indirect peer influence. Moreover, we find that users who have higher social status in the blockchain network are less susceptible to peer influence. The results provide strong evidence of peer influence on smart contract adoption through various mechanisms.
Shantanu Pal, Tahiry Rabehaja, Ambrose Hill, Michael Hitchens · 5 authors
With the advancement of the Internet of Things (IoT) in recent years, there is a bigger potential to use online services than ever before. The use of the IoT brings numerous opportunities for both service providers and end users, however, it faces critical questions of security and privacy. Toward this, access control is one of the significant security challenges for the IoT, in particular, considering the characteristics of such IoT systems. To develop a secure access control architecture for the IoT, the propagation of access right delegation is a major issue. Many proposals present access control issues for the IoT but given the specific context of access right delegation, it is still in its infancy. This article presents an approach to address such a delegation issue for the IoT using the blockchain technology. We propose a delegation model that employv the critical issues, e.g., the use of nonunique identities, asynchronous and flexible delegation nature of communication for the IoT without the need of a centralized system. The goal of our primitive is to use attributes for validating the identity of an entity instead of relying on a concrete unique identity of an entity. To provide privacy for the attributes, we propose a dual blockchain architecture that moves the attribute storage and access of the public blockchain and onto a secure private blockchain. To demonstrate the feasibility of our proposed approach, we evaluate the system performances using the Ethereum blockchain network.
We present a new primitive supporting file replication in distributed storage networks (DSNs) called a Public Incompressible Encoding (PIE). PIEs operate in the challenging public DSN setting where files must be encoded and decoded with public randomness-i.e., without encryption-and retention of redundant data must be publicly verifiable. They prevent undetectable data compression, allowing DSNs to use monetary rewards or penalties in incentivizing economically rational servers to properly replicate data. Their definition also precludes critical, demonstrated attacks involving parallelism via ASICs and other custom hardware. Our PIE construction is the first to achieve experimentally validated near-optimal performance-within a factor of 4 of optimal by one metric. It also allows decoding orders of magnitude faster than encoding, unlike other comparable constructions. We achieve this high security and performance using a graph construction called a Dagwood Sandwich Graph (DSaG), built from a novel interleaving of depth-robust graphs and superconcentrators. PIEs' performance makes them appealing for DSNs, such as the proposed Filecoin system and Ethereum data sharding. Conversely, their near-optimality establishes concerning bounds on the practical financial and energy costs of DSNs allowing arbitrary data.