Follow blockchain research across journals, conferences, and preprint repositories.
9,726 results · page 373 of 406
Emmanuelle Anceaume, Romaric Ludinard, Maria Potop-Butucaru, Frédéric Tronel
No abstract is available for this record.
Louise Axon, Michael Goldsmith
Conventional public-key infrastructure (PKI) designs using certificate authorities and web-of-trust are not optimal and have security flaws. The properties afforded by the Bitcoin blockchain are a natural solution to some of the problems with PKI - in particular, certificate transparency and elimination of single points-offailure. Proposed blockchain-based PKI designs are built as public ledgers linking identity with public key, providing no privacy. We consider cases requiring privacy-aware PKIs, which do not link identity with public key. We show that blockchain technology can be used to construct a privacy-aware PKI while eliminating some of the problems of conventional PKI, and present PB-PKI, a privacy-aware blockchain-based PKI.
Svein Ølnes, Arild Jansen
No abstract is available for this record.
L Er-Rajy, El Kiram My A, El Ghazouani M, Omar Achbarou
Bitcoin has experienced rapid growth in the transactions number and in their value since its appearance in 2008. Its success is mainly due to the innovative use of a peer-to-peer network to implement all aspects of the currency life cycle, from creation to transfer between users. Bitcoin offers cash transactions that are almost instant and non-refundable, while allowing truly global transactions processed at the same speed as local ones. It offers a public transactions history, which allows untrusted audibility, and introduces many new and innovative use cases such as smart property, micropayments, contracts and escrow transactions for disputes mediation. However, the same features that make Bitcoin attractive to its end users are also its main limitations. Its decentralized nature limits the number of transactions and the speed at which transactions can be carried out and confirmed. The problem with slow confirmations is combined with the semantics of the confirmations which are not definitive, requiring several confirmations and further delaying the transaction acceptance. In this paper, we described the operating principles of peer-to-peer cryptographic currencies and especially security of bitcoin system. Moreover, For Bitcoin enhancements and additional mitigations we provide ideas for node auditing users in the network in aim to keep clients from the trusted transaction branch database generated by the attackers.
Jona Derks, Jaap Gordijn, Arjen Siegmann
Bitcoin is a widely-spread payment instrument, but it is doubtful whether the proof-of-work (PoW) nature of the system is financially sustainable on the long term. To assess sustainability, we focus on the bitcoin miners as they play an important role in the proof-of-work consensus mechanism of bitcoin to create trust in the currency. Miners offer their services against a reward while recurring expenses. Our results show that bitcoin mining has become less profitable over time to the extent that profits seem to converge to zero. This is what economic theory predicts for a competitive market that has a single homogenous good. We analyze the actors involved in the bitcoin system as well as the value flows between these actors using the e3value methodology. The value flows are quantified using publicly available data about the bitcoin network. However, two important value flows for the miners, namely hardware investments and expenses for electricity power, are not available from public sources. Therefore, we contribute an approach to estimate the installed base of bitcoin hardware equipment over time. Using this estimate, we can calculate the expenses miner should have. At the end of our analysis period, the marginal profit of mining a bitcoin becomes negative, i.e., to a loss for the miners. This loss is caused by the consensus mechanism of the bitcoin protocol, which requires a substantial investment in hardware and significant recurring daily expenses for energy. Therefore, a sustainable crypto currency needs higher payments for miners or more energy efficient algorithms to achieve consensus in a network about the truth of the distributed ledger.
Jamal Bouoiyour, Refk Selmi
Much significant research has been done to investigate various facets of the link between Bitcoin price and its fundamental sources. This study goes beyond by looking into least to most influential factors-across the fundamental, macroeconomic, financial, speculative and technical determinants as well as the 2016 events-which drove the value of Bitcoin in times of economic and geopolitical chaos. We use a Bayesian quantile regression to inspect how the structure of dependence of Bitcoin price and its determinants varies across the entire conditional distribution of Bitcoin price movements. In doing so, three groups of determinants were derived. The use of Bitcoin in trade and the uncertainty surrounding China's deepening slowdown, Brexit and India's demonetization were found to be the most potential contributors of Bitcoin price when the market is improving. The intense anxiety over Donald Trump being the president of United States was shown to be a positive determinant pushing up the price of Bitcoin when the market is functioning around the normal mode. The velocity of bitcoins in circulation, the gold price, the Venezuelan currency demonetization and the hash rate were found to be the fundamentals influencing the Bitcoin price when the market is heading into decline.
William J. Luther
Abstract By declaring an item legal tender or making it publicly receivable, governments might generate sufficient demand to determine the medium of exchange. How do private actors launch a new money? There are two views in the literature. The first requires offering an item with a use value to some agents that is distinct from its role as a medium of exchange. The second suggests that agents might coordinate on an intrinsically useless item. With these views in mind, I survey the logs from the original bitcoin forum, bitcoin-list. I find that early participants in the bitcoin community understood the importance of coordination and took steps to coordinate users.
Alessandra Cretarola, Gianna Figà‐Talamanca, Marco Patacca
In recent literature it is claimed that BitCoin price behaves more likely to a volatile stock asset than a currency and that changes in its price are influenced by sentiment about the BitCoin system itself; in Kristoufek [10] the author analyses transaction based as well as popularity based potential drivers of the BitCoin price finding positive evidence. Here, we endorse this finding and consider a bivariate model in continuous time to describe the price dynamics of one BitCoin as well as a second factor, affecting the price itself, which represents a sentiment indicator. We prove that the suggested model is arbitrage-free under a mild condition and, based on risk-neutral evaluation, we obtain a closed formula to approximate the price of European style derivatives on the BitCoin. By applying the same approximation technique to the joint likelihood of a discrete sample of the bivariate process, we are also able to fit the model to market data. This is done by using both the Volume and the number of Google searches as possible proxies for the sentiment factor. Further, the performance of the pricing formula is assessed on a sample of market option prices obtained by the website deribit.com.
Zura Kakushadze, Jim Kyung-Soo Liew
We discuss Russia's underlying motives for issuing its government-backed cryptocurrency, CryptoRuble, and the implications thereof and of other likely-soon-forthcoming government-issued cryptocurrencies to some stakeholders (populace, governments, economy, finance, etc.), existing decentralized cryptocurrencies (such as Bitcoin and Ethereum), as well as the future of the world monetary system (the role of the U.S. therein and a necessity for the U.S. to issue CryptoDollar), including a future algorithmic universal world currency that may also emerge. We further provide a comprehensive list of references on cryptocurrencies.
Stavros Stavroyiannis
Digital currencies and cryptocurrencies have hesitantly started to penetrate the investors, and the next step will be the regulatory risk management framework. We examine the Value-at-Risk and Expected Shortfall properties for the major digital currencies, Bitcoin, Ethereum, Litecoin, and Ripple. The methodology used is GARCH modelling followed by Filtered Historical Simulation. We find that digital currencies are subject to a higher risk, therefore, to higher sufficient buffer and risk capital to cover potential losses.
Iddo Bentov, Ranjit Kumaresan, Andrew Miller
We present efficient protocols for amortized secure multiparty computation with penalties and secure cash distribution, of which poker is a prime example. Our protocols have an initial phase where the parties interact with a cryptocurrency network, that then enables them to interact only among themselves over the course of playing many poker games in which money changes hands. The high efficiency of our protocols is achieved by harnessing the power of stateful contracts. Compared to the limited expressive power of Bitcoin scripts, stateful contracts enable richer forms of interaction between standard secure computation and a cryptocurrency. We formalize the stateful contract model and the security notions that our protocols accomplish, and provide proofs using the simulation paradigm. Moreover, we provide a reference implementation in Ethereum/Solidity for the stateful contracts that our protocols are based on. We also adopt our off-chain cash distribution protocols to the special case of stateful duplex micropayment channels, which are of independent interest. In comparison to Bitcoin based payment channels, our duplex channel implementation is more efficient and has additional features.
Reginald D. Smith
Attempts to accurately measure the monetary velocity or related properties of Bitcoin have often attempted to either directly apply definitions from traditional macroeconomic theory or to use specialized metrics relative to the properties of the Blockchain such as bitcoin-days destroyed. In this paper, it is demonstrated that beyond being a useful metric, bitcoin-days destroyed has mathematical properties that allow one to calculate the average dormancy (time since last use in a transaction) of the bitcoins used in transactions over a given time period. In addition, transaction volume and average dormancy are shown to have unexpected significance in helping estimate the average size of the pool of traded bitcoins by virtue of the expression Little's Law, though only under limited conditions.
Benedikt Bünz, Jonathan Bootle, Dan Boneh, Andrew Poelstra · 6 authors
We propose Bulletproofs, a new non-interactive zero-knowledge proof protocol with very short proofs and without a trusted setup; the proof size is only logarithmic in the witness size. Bulletproofs are especially well suited for efficient range proofs on committed values: they enable proving that a committed value is in a range using only 2 log_2(n)+9 group and field elements, where n is the bit length of the range. Proof generation and verification times are linear in n. Bulletproofs greatly improve on the linear (in n) sized range proofs in existing proposals for confidential transactions in Bitcoin and other cryptocurrencies. Moreover, Bulletproofs supports aggregation of range proofs, so that a party can prove that m commitments lie in a given range by providing only an additive O(log(m)) group elements over the length of a single proof. To aggregate proofs from multiple parties, we enable the parties to generate a single proof without revealing their inputs to each other via a simple multi-party computation (MPC) protocol for constructing Bulletproofs. This MPC protocol uses either a constant number of rounds and linear communication, or a logarithmic number of rounds and logarithmic communication. We show that verification time, while asymptotically linear, is very efficient in practice. The marginal cost of batch verifying 32 aggregated range proofs is less than the cost of verifying 32 ECDSA signatures. Bulletproofs build on the techniques of Bootle et al. (EUROCRYPT 2016). Beyond range proofs, Bulletproofs provide short zero-knowledge proofs for general arithmetic circuits while only relying on the discrete logarithm assumption and without requiring a trusted setup. We discuss many applications that would benefit from Bulletproofs, primarily in the area of cryptocurrencies. The efficiency of Bulletproofs is particularly well suited for the distributed and trustless nature of blockchains. The full version of this article is available on ePrint.
Nadim Mahomed
Cryptocurrency, most notably Bitcoin, has continued to attract attention and consequently substantial investment from businesses, consumers, and the media. Understanding what drives consumer adoption of the technology, however, is not understood. This study uses the UTAUT2 technology adoption theory in order to fill this research gap. A conceptual model is built through a review of the technical aspects of cryptocurrency, an analysis of the technology as currency, and finally a review of technology adoption theory to date. UTAUT2 is found to be the most appropriate adoption theory directly dealing with consumer context. The model conceptualised is tested using multiple linear regression analyses on primary survey data. The findings indicate that facilitating conditions have the highest explanatory effect on actual usage ahead of behavioural intention to use cryptocurrency. Behavioural intention was predicted most strongly by hedonic motivation, followed by perceived trust, and social influence. Interestingly, effort expectancy and performance expectancy were found to be non-significant, contrary to much of the studies in related fields. The study also aimed to identify the primary use-case finding that investment was the primary consumer use. Due to characteristics of the sample collected, the studyÕs findings are limited to the South African context.
Marit Rudlang
Since Bitcoin was launched in 2009, several new cryptocurrencies have been initiated with variations to Bitcoin's original design. Although Bitcoin still remains the most prominent actor in the market, some technical problems have been raised to the design of the protocol. The objective of this thesis is to determine whether the newer cryptocurrencies handle the technical problems of Bitcoin, or if they also suffer from the same issues. Instead of evaluating several cryptocurrencies for this comparison, the cryptocurrency Ethereum has been chosen as a proxy for the others. Ethereum was started in 2014, is widely backed in the community and is second in line to Bitcoin when it comes to market capitalization. \n\nAs a basis for the comparative analysis a rigorous study of the Bitcoin and Ethereum protocols have been performed, and parallel descriptions of the systems have been devised. Three technical problem have shaped the focus of the analysis: computational waste, concentration of power and ambiguity of transactions. Real world statistical data has been gathered and synthesized to enlighten the findings in the comparison. The main result of the comparison is that both systems suffer from the same problems to a certain degree, due to the fact that they utilize the same consensus mechanism. However, Ethereum utilizes several newer techniques to try and reduce the severity of these problems compared to Bitcoin, with varying degrees of success.
Renato P. dos Santos
Abstract The philosophy of blockchain technology is concerned, among other things, with blockchain ontology, how it might be characterised, how it is being created, implemented, and adopted, how it operates in the world, and how it evolves over time. This paper concentrates on whether Bitcoin/blockchain can be considered a complex system and, if so, whether it is a chaotic one. Beyond mere academic curiosity, a positive response would raise concerns about the likelihood of Bitcoin/blockchain entering a 2010‐Flash‐Crash‐type of chaotic regime, with catastrophic consequences for financial systems based on it. The paper starts by highlighting the relevant details of the Bitcoin/blockchain ecosystem formed by the blockchain itself, bitcoin end users (payers and payees), capital gains seekers, miners, full nodes maintainers, and developers, and their interactions. Then the Information Theory of Complex Systems is briefly discussed for later use. Finally, the blockchain is investigated with the help of Crutchfield's Statistical Complexity measure. The low non‐null statistical complexity value obtained suggests that the blockchain may be considered algorithmically complicated but hardly a complex system and unlikely to enter a chaotic regime.
Thomas Dimpfl
Bitcoin is traded on exchanges which use an open limit order book. This paper investigates the microstructure of various bitcoin markets with respect to liquidity and private information processing. The markets are found to be fairly liquid, providing liquidity at a stable rate throughout the 24 hours trading period. The spread itself as well as the proportion attributed to adverse selection costs are high suggesting that private information is an important aspect in the bid-ask spread.
Daniel Augot, Hervé Chabanne, Thomas Chenevier, William R. George · 5 authors
We present an identity management scheme built into the Bitcoin blockchain, allowing for identities that are as indelible as the blockchain itself. Moreover, we take advantage of Bitcoin's decentralized nature to facilitate a shared control between users and identity providers, allowing users to directly manage their own identities, fluidly coordinating identities from different providers, even as identity providers can revoke identities and impose controls.
V. Čermák
No abstract is available for this record.
William J. Luther
Monies are typically categorized as commodity or fiat, depending on whether the item in question is intrinsically worthless. In the case of bitcoin, it is not so clear. I consider the superficial subjective value argument often put forward by non-monetary economists and a more sophisticated payments technology argument. After dismissing both, I argue that there are two reasonable views on the value of bitcoin. One might claim bitcoin lacks intrinsic worth, in which case its value depends on foresight and coordination. Alternatively, one might claim that bitcoin has intrinsic worth, even if no one else accepts it, because some users have peculiar preferences. In either case, the existence of bitcoin calls into question the practical relevance of the regression theorem.
Tatiana Ermakova, Benjamin Fabian, Annika Baumann, Mykyta Izmailov · 5 authors
No abstract is available for this record.
Stavros Stavroyiannis, Vassilios Babalos
No abstract is available for this record.
Massimo Bartoletti, Stefano Lande, Livio Pompianu, Andrea Bracciali
Modern cryptocurrencies exploit decentralised blockchains to record a public and unalterable history of transactions. Besides transactions, further information is stored for different, and often undisclosed, purposes, making the blockchains a rich and increasingly growing source of valuable information, in part of difficult interpretation. Many data analytics have been developed, mostly based on specifically designed and ad-hoc engineered approaches. We propose a general-purpose framework, seamlessly supporting data analytics on both Bitcoin and Ethereum --- currently the two most prominent cryptocurrencies. Such a framework allows us to integrate relevant blockchain data with data from other sources, and to organise them in a database, either SQL or NoSQL. Our framework is released as an open-source Scala library. We illustrate the distinguishing features of our approach on a set of significant use cases, which allow us to empirically compare ours to other competing proposals, and evaluate the impact of the database choice on scalability.
Jeffrey Chu, Stephen Chan, Saralees Nadarajah, Joerg Osterrieder
No abstract is available for this record.