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52,008 results · page 1877 of 2,167
Jiri Chod, Evgeny Lyandres
No abstract is available for this record.
Ha Xuan Son, Minh Ha Hoang, Nguyen Ngoc, Hai Trieu · 8 authors
In emerging economies, with the explosion of e-commerce, payment methods have increasingly enhanced security. However, Cash-on-Delivery (COD) payment method still prevails in cash-based economies. Although COD allows consumers to be more proactive in making payments, it still appears to be vulnerable by the appearance of a third party (shipping companies). In this paper, we proposed a payment system based on “smart contract” implemented on top of blockchain technology to minimize risks for parties. The platform consists of a set of rules that each party must follow including specific delivery time and place, cost of delivery, mortgage money; thereby, forcing parties to be responsible for their tasks in order to complete the contract. We also provided a detailed implementation to illustrate the efficiency of our model.
Adarsh Vijayakumaran
No abstract is available for this record.
Usman W. Chohan
This chapter seeks to contextualize the nature of cryptocurrencies as an alternate form of capital that, while being inspired by cryptoanarchist thought, has come to embody extreme forms of inequality among its owners. The concentration of wealth produces a “whale effect” that, as the chapter argues, in fact reflects the forms of inequalities that are found in the ownership of traditional forms of capital. The chapter thus alludes to the mismatch between the professed cryptoanarchist philosophical bent of cryptocurrency owners and the reality of capital ownership in the cryptocurrency domain; while cryptoanarchism postulates autonomy, decentralization, and the spread of ownership, the whale effect suggests that cryptocurrencies are insufficiently different from traditional forms of capital in this regard. This challenges the degree to which the praxis of cryptocurrencies coheres with the philosophy of cryptoanarchism.
Dominique Lammer, Tobin Hanspal, Andreas Hackethal
No abstract is available for this record.
Klaus Grobys
A total of 1.1 million bitcoins were stolen in the 2013–2017 period. Noting that the average price for a Bitcoin in 2018 was $7572 the corresponding monetary equivalent of losses is $8.9 billion highlighting the societal impact of this criminal activity. Investigating the response of the uncertainty of Bitcoin returns when hacking incidents occur, the results of this study point toward two different responses. After experiencing a contemporaneous effect at day t=0, the volatility increases significantly again at day t+5. Hacking incidents that occur in the Bitcoin market also affect the uncertainty in the Ethereum market with a time delay of five days. Notably, neither Bitcoin nor Ethereum appear to exhibit asymmetric responses to negative innovations.
Julián Andrada Félix, Adrián Fernández-Pérez, Simón Sosvilla‐Rivero
No abstract is available for this record.
Joshua R. Hendrickson, William J. Luther
No abstract is available for this record.
Michael Fröwis, Rainer Böhme
Efficient transfers to many recipients present a host of issues on Ethereum. First, accounts are identified by long and incompressible constants. Second, these constants have to be stored and communicated for each payment. Third, the standard interface for token transfers does not support lists of recipients, adding repeated communication to the overhead. Since Ethereum charges resource usage, even small optimizations translate to cost savings. Airdrops, a popular marketing tool used to boost coin uptake, present a relevant example for the value of optimizing bulk transfers. Therefore, we review technical solutions for airdrops of Ethereum-based tokens, discuss features and prerequisites, and compare the operational costs by simulating 35 scenarios. We find that cost savings of factor two are possible, but require specific provisions in the smart contract implementing the token system. Pull-based approaches, which use on-chain interaction with the recipients, promise moderate savings for the distributor while imposing a disproportional cost on each recipient. Total costs are broadly linear in the number of recipients independent of the technical approach. We publish the code of the simulation framework for reproducibility, to support future airdrop decisions, and to benchmark innovative bulk payment solutions.
Saketh Aleti, Bruce Mizrach
Abstract We study Bitcoin (BTC) trading at the Chicago Mercantile Exchange (CME) and four settlement spot exchanges that transact $146 million per day in the BTC/USD pair. Spot market median trade sizes are under $1,300 but exceed $18,000 on the CME. Bid‐ask spreads average 0.0298%. Trade sizes of over $1 million move markets by less than 1%. 2.5% of trades and 15.5% of cancellations on Coinbase take place within 50 ms. Bid‐ask spreads exceed 0.8% for only 226 s. Most executions trade‐through better quotes, with estimated losses of $36 million. The CME leads price discovery. BTC leads Ethereum price adjustment.
Sana Guizani, Ines Kahloul Nafti
The emergence of Bitcoin (BTC) has triggered intense discussions. Despite the particular interest of the public, the theoretical understanding of the value of this crypto currency is limited. This is why current research is trying to find better leads to evaluate a complex phenomenon: the BTC price. The volatility of its price presents a certain specificity compared to the traditional currencies. In order to understand the reasons for this volatility, we try to identify and to analyze the main determinants of the BTC price and to estimate their influence. We apply time series to daily data for the period from 19/12/2011 to 06/02/2018. We used several approaches, including the Auto Regressive Distributed Lag ARDL model, the cointegration test at Pesaran et al. (2001) and the Granger causality test in the sense of Toda and Yamamoto (1995). Our estimated results suggest that the number of addresses, the attractiveness indicator and the mining difficulty have a significant impact on the BTC price with variations over time. On the other hand, the transaction volume, the stock, the EUR/USD exchange rate and the macroeconomic and financial development do not determine the price of the BTC in the short term as well as in the long term.
Silvia Bartolucci, Fabio Caccioli, Pierpaolo Vivo
The Lightning Network is a so-called second-layer technology built on top of the Bitcoin blockchain to provide "off-chain" fast payment channels between users, which means that not all transactions are settled and stored on the main blockchain. In this paper, we model the emergence of the Lightning Network as a (bond) percolation process and we explore how the distributional properties of the volume and size of transactions per user may impact its feasibility. The agents are all able to reciprocally transfer Bitcoins using the main blockchain and also - if economically convenient - to open a channel on the Lightning Network and transact "off chain". We base our approach on fitness-dependent network models: as in real life, a Lightning channel is opened with a probability that depends on the "fitness" of the concurring nodes, which in turn depends on wealth and volume of transactions. The emergence of a connected component is studied numerically and analytically as a function of the parameters, and the phase transition separating regions in the phase space where the Lightning Network is sustainable or not is elucidated. We characterize the phase diagram determining the minimal volume of transactions that would make the Lightning Network sustainable for a given level of fees or, alternatively, the maximal cost the Lightning ecosystem may impose for a given average volume of transactions. The model includes parameters that could be in principle estimated from publicly available data once the evolution of the Lighting Network will have reached a stationary operable state, and is fairly robust against different choices of the distributions of parameters and fitness kernels.
Leopoldo Catania, Mads Sandholdt
This paper studies the behaviour of Bitcoin returns at different sample frequencies. We consider high frequency returns starting from tick-by-tick price changes traded at the Bitstamp and Coinbase exchanges. We find evidence of a smooth intra-daily seasonality pattern, and an abnormal trade- and volatility intensity at Thursdays and Fridays. We find no predictability for Bitcoin returns at or above one day, though, we find predictability for sample frequencies up to 6 h. Predictability of Bitcoin returns is also found to be time–varying. We also study the behaviour of the realized volatility of Bitcoin. We document a remarkable high percentage of jumps above 80 % . We also find that realized volatility exhibits: (i) long memory; (ii) leverage effect; and (iii) no impact from lagged jumps. A forecast study shows that: (i) Bitcoin volatility has become more easy to predict after 2017; (ii) including a leverage component helps in volatility prediction; and (iii) prediction accuracy depends on the length of the forecast horizon.
Till Neudecker, Hannes Hartenstein
No abstract is available for this record.
Fridtjof Nystrøm
A blockchain is a distributed ledger comprised of practically unchange- able, digital recorded data in packages called blocks. Each block in the chain contains data and is cryptographically hashed. The blocks of hashed data draw upon the previous block in the chain, ensuring all data in the overall blockchain is untampered. Blockchain and Distributed Ledger ad- vantages are related to enhanced transparency in business applications and between the involved parties compared to using ordinary databases. Since the blockchain is cryptographically protected, it can be shared, al- lowing anyone to check the correctness of a transaction. Previously, this technology was mostly used for enabling public, decent- ralized digital currencies, known as cryptocurrencies, such as BitCoin and LiteCoin. In the latest years, however, additional use-cases have been de- signed, including non-money asset tokenization, digital identity and sup- ply chain management. Together with the rise of new use-cases, distrib- uted ledger technology frameworks emerged to assist and simplify the development process of such use-cases. These frameworks accelerate the development process at the cost of resource overhead. In this thesis, we use Hyperledger Fabric, a distributed ledger technology framework maintained by the Linux Foundation, to design, develop and analyze the performance of a use-case granted by DNV-GL. We explore the network resource cost of a transaction and model the network traffic flow. In addition, we measure and present the performance of this system and demonstrate why such a performance display alone is misleading.
Daniel Burkhardt, Patrick Frey, Heiner Lasi
The Internet of Things (IoT) describes the fusion of the physical and digital world which enables assets on the edge to send data to a platform where it gets analyzed. Defined actions are then triggered to influence cross-functional edge activities. Furthermore, on the platform tier functionalities and relations need to be identified and implemented to realize assets operating autonomously and ubiquitously. The exploration of this paper results in the identification of autonomous characteristics and shows functional components to implement autonomous assets on the edge. Distributed Ledger Technology (DLT) and its fusion with Machine Learning (ML) as an area of Artificial Intelligence (AI) provides an integral part to realize the described outline. Thus, the recognition of DLT’s and ML’s usage in the IoT and the evaluation of the relevance as well as the synergies build the main focus of this paper.
Yibin Xu, Yangyu Huang
Distributed Ledger Technology (DLT) is promising to become the foundation of many decentralised systems. However, the unbalanced and unregulated network layout contributes to the inefficiency of DLT especially in the Internet of Things (IoT) environments, where nodes connect to only a limited number of peers. The data communication speed globally is unbalanced and does not live up to the constraints of efficient real-time distributed systems. In this paper, we introduce a new communication protocol, which enables nodes to calculate the tradeoff between connecting/disconnecting a peer in a completely decentralised manner. The network layout globally is continuously re-balancing and optimising along with nodes adjusting their peers. This communication protocol weakened the inequality of the communication network. The experiment suggests this communication protocol is stable and efficient.
Authors unavailable
No abstract is available for this record.
Mieszko Mazur
No abstract is available for this record.
Benjamin Agbo, Yongrui Qin, Richard Hill
The significant growth and adoption of Internet of Things (IoT) solutions has led to tremendous increase in the generation of data. The need for high speed data processing has become very important to meet with the ever increasing volume and velocity of IoT data, due to the large scale and distributed nature of IoT infrastructure and networks. Present cloud based technologies are struggling to meet up with these needs for real time data processing in the midst of enormous amounts of data. The success of bitcoin has inspired more research in the application of Distributed ledger technologies in various domains. The decentralized nature of these platforms have enabled security and privacy of data in previous research and their architecture has a potential for enabling large scale decentralized data processing. In this paper, we identify some open areas of research in the use of distributed ledger technology and propose a framework for storing, analyzing and ensuring the security of large volumes of IoT data.
Willi Brammertz, Allan I. Mendelowitz
Nick Szabo defined smart contracts as, “….a set of promises, specified in digital form, including protocols within which the parties perform on the other promises.” The essence of a smart contract is that it is self-executing and has a protocol to effect this, i.e. the mechanism for communicating with the smart contract. In addition, Szabo distilled four basic objectives of any contract that should be fulfilled by smart contracts. Two of these, verifiability and enforceability, are given more attention in this paper. Szabo, however, did not address what types of contracts would be most suited to be executed as smart contracts. This paper describes first the unique aspects of financial contracts that make them the most promising candidates for implementation as smart contracts. Secondly, we analyze the conditions under which the use of distributed ledgers and smart financial contracts are most likely to prove successful. This analysis concludes that unless a distributed ledger is combined with an algorithmic financial contract standard and a standard protocol, the potential benefits of smart contracts will not be realized. The corollary to this conclusion is that it is essential for FinTech to adopt such a standard in order to be able to realize its promise of a paradigm shift in finance. The combination of distributed ledger technology and an open, well documented and well tested algorithmic financial contract standard is the next logical step in the development of FinTech.
Wei She, Qi Liu, Tian Zhao, Jian-Sen Chen · 6 authors
The Internet of Things (IoT) has been widely used because of its high efficiency and real-time collaboration. A wireless sensor network is the core technology to support the operation of the IoT, and the security problem is becoming more and more serious. Aiming at the problem that the existing malicious node detection methods in wireless sensor networks cannot be guaranteed by fairness and traceability of detection process, we present a blockchain trust model (BTM) for malicious node detection in wireless sensor networks. First, it gives the whole framework of the trust model. Then, it constructs the blockchain data structure which is used to detect malicious nodes. Finally, it realizes the detection of malicious nodes in 3D space by using the blockchain smart contract and the WSNs' quadrilateral measurement localization method, and the voting consensus results are recorded in the blockchain distributed. The simulation results show that the model can effectively detect malicious nodes in WSNs, and it can also ensure the traceability of the detection process.
Shangping Wang, Xu Wang, Yaling Zhang
Now more and more data are being outsourced to cloud services. In order to ensure data security and privacy, data are usually stored on the cloud server in the form of ciphertext. When a user requests access to the encrypted data, an access key distributed by a third party is needed. However, if the third party is dishonest, the security of the system will be threatened. Faced with this problem, in this paper, we propose a new secure cloud storage framework with access control by using the Ethereum blockchain technology. Our new scheme is a combination of Ethereum blockchain and ciphertext-policy attribute-based encryption (CP-ABE). The proposed cloud storage framework is decentralized, that is, there is no trusted third party in the system. Our scheme has three main features. First, as the Ethereum blockchain technology is used, the data owner can store ciphertext of data through smart contracts in a blockchain network. Second, the data owner can set valid access periods for data usage so that the ciphertext can only be decrypted during valid access periods. Finally, as the creation and invocation of each smart contract can be stored in the blockchain, thus, the function of the trace is achieved. The analysis of the security and experiment shows that our scheme is feasible.
Yong Wang, Aiqing Zhang, Peiyun Zhang, Huaqun Wang
The sharing of electronic health records (EHRs) has great positive significance for research of disease and doctors' diagnosis. In recent years, cloud-based electronic medical record sharing scheme has brought a lot of conveniences, but the centralization of cloud exposes threats inevitably to data security and privacy preservation. Blockchain technology can be seen as a promising solution to address these problems on account of its unique propertis of decentration, anonymity, unforgeability and verifiability. In this paper, we propose a blockchain based secure and privacy-preserving EHR sharing protocol. Data requester can search desired keyword from data provider to find relevant EHRs on the EHR consortium blockchain and get the re-encryption ciphertext from cloud server after getting the data owner's authorization. The scheme mainly uses searchable encryption and conditional proxy re-encryption to realize data security, privacy preservation, and access control. Furthermore, proof of authorization is designed as the consensus mechanism for consortium blockchain to guarantee system's availability. Security analysis demonstrates that the proposed protocol can achieve security goals. Besides, we emulate the cryptographic primitives and implement the proposed scheme on Ethereum platform. Performance evaluation shows that the proposed scheme has high computational efficiency.