The pseudonymous nature of Bitcoin has sparked the twin rivaling researches in Bitcoin community, that is, either protecting or attacking anonymity. In spite of this intense battle, the answer to a primary question is absent – Do Bitcoin users themselves care about anonymity? This paper demystifies this doubt via analyzing the Bitcoin transaction graphs with the following three contributions: 1). We outline three representative metrics that can signify whether users concern about anonymity. 2). We examine the collective trend of anonymity concerns from a macroscope. 3). We pay particular attention on critical addresses in a microscope to unveil their anonymity concerns.This paper arrives at both expected conclusions and unexpected surprises. In particular, the expected ones are: rich addresses concern more about anonymity than poor ones. Miner addresses start caring about anonymity when exchange rate soars. Stock addresses never hide their intent of jump-and-dump. The surprises are: the majority of the users show weak concerns on anonymity. One can easily find both hot and cold wallet addresses owned by big organizations.
This paper presents a stochastic model for block arrival times based on the difficulty retargeting rule used in Bitcoin, as well as other proof-of-work blockchains. Unlike some previous work, this paper explicitly models the difficulty target as a random variable which is a function of the previous block arrival times and affecting the block times in the next retargeting period. An explicit marginal distribution is derived for the time between successive blocks (the blocktime), while allowing for randomly changing difficulty. This paper also aims to serve as an introduction to Bitcoin and proof-of-work blockchains for the controls community, focusing on the difficulty retargeting procedure used in Bitcoin.
Many blockchain consensus protocols have been proposed recently to scale the throughput of a blockchain with available bandwidth. However, these protocols are becoming increasingly complex, making it more and more difficult to produce proofs of their security guarantees. We propose a novel permissionless blockchain protocol OHIE which explicitly aims for simplicity. OHIE composes as many parallel instances of Bitcoin's original (and simple) backbone protocol as needed to achieve excellent throughput. We formally prove the safety and liveness properties of OHIE. We demonstrate its performance with a prototype implementation and large-scale experiments with up to 50,000 nodes. In our experiments, OHIE achieves linear scaling with available bandwidth, providing about 4-10 Mbps transaction throughput (under 8-20 Mbps per-node available bandwidth configurations) and at least about 20x better decentralization over prior works.
Blockchain is a decentralized transaction and data management solution, the technological weapon-of-choice behind the success of Bitcoin and other cryptocurrencies. As the number and variety of existing blockchain implementations continues to increase, adopters should focus on selecting the best one to support their decentralized applications (dApps), rather than developing new ones from scratch. In this paper we present a framework to aid software architects, developers, tool selectors and decision makers to adopt the right blockchain technology for their problem at hand. The framework exposes the correlation between technological decisions and architectural features, capturing the knowledge from existing industrial products, technical forums/blogs, experts' feedback and academic literature; plus our own experience using and developing blockchain-based applications. We validate our framework by applying it to dissect the most outstanding blockchain platforms, i.e., the ones behind the top 10 cryptocurrencies apart from Bitcoin. Then, we show how we applied it to a real-world case study in the insurtech domain.
Fatih Ceylan, Ramazan Eki̇nci̇, Osman Tüzün, Hakan Kahyaoğlu
Başta Bitcoin olmak üzere kripto paralar son dönemde çok sık kullanılmaya başlamıştır. “Para birimi” olarak ve “Değer birikim aracı” olarak kabul görmeye başlayan kripto paraların fiyat hareketlerinin analiz edilmesi ihtiyacı ortaya çıkmıştır. Bu piyasaların büyümesi ve küresel entegrasyonu ile birlikte fiyatlarda meydana gelen önemli değişimlerin temelinde spekülatif balonların olup olmadığı finansal istikrar konusunda açıklık ve güvence açısından önem arz etmektedir. Ayrıca kripto para piyasasında meydana gelen spekülatif hareketler piyasa katılımcılarının sürü psikolojisiyle hareket edip etmedikleri sorusunu ortaya çıkarmaktadır. Bu nedenle çalışmada Bitcoin ve Etherium para birimlerinde spekülatif balonların varlığı Philips vd. (2015) tarafından geliştirilen yöntem ile tespit edilmiş ve ne zaman oluştukları tahminlenmiştir. Piyasada balonların olması ve bu balonların süre olarak varlığı sürü psikolojisinin olduğu yönünde bilgi sağlarken, bu piyasada dengeleyici bir spekülasyonun olmadığı yönünde de bir bilgidir. Elde edilen bulgular doğrultusunda Bitcoin ve Etherium kripto para birimlerinde çok sayıda baloncuk olduğu tespit edilmiştir. Özellikle 2017-2018 yılları arasında büyük baloncukların ortaya çıkması bu para birimlerinin spekülatif hareketlere karşı eğilimli olduğunu gösterilmiştir.
Fatih Ceylan, Ramazan Eki̇nci̇, Osman Tüzün, Hakan Kahyaoğlu
Cryptocurrencies, especially Bitcoin, have been used very often recently. The need for analyzing the price movements of the cryptocurrencies, which are accepted as “a currency” and “a store of value”, has emerged. With the growth and global integration of these markets, whether there are speculative bubbles on the basis of significant changes in prices is important in terms of openness and security in respect of financial stability. In addition, speculative movements in the cryptocurrencies market raise the question of whether market participants act with herd mentality. For this reason, in the study, the presence of speculative bubbles in Bitcoin and Etherium is analyzed by using Philips et al. (2015) method and estimated when they were formed. While the presence of bubbles in the cryptocurrencies market and the existence of these bubbles as a duration of herd mentality, it is also known that there is no balancing speculation in this market. According to the findings, a large number of bubbles were found in the Bitcoin and Etherium cryptocurrencies. The emergence of large bubbles, especially between the years 2017-2018, has shown that these cryptocurrencies are prone to speculative movements.
Since the considerable ascent in the estimation of the digital money Bitcoin, which utilizes a blockchain for bookkeeping, there has been a huge enthusiasm for blockchain innovation. A blockchain is a transparent distributed ledger which is revolutionising the financial services industry by legimatizing millions across the globe to authenticate and transact immediately, without the involvement of expensive third-parties.Blockchain innovation is named as the 'Fifth Evolution' of processing. Till date, Bitcoin is the most generally utilized application utilizing blockchain innovation. But now days it is applied in almost every field, like finance, agriculture geospatial areas, gaming etc. The paper is emphasizing on different kinds of blockchains and the applications.
The obligatory features of the unit of account are formulated. Distinctive characteristic properties of a set of cryptocalculation units, in particular, subsets of x-type (coin) and y-type (token) calculation units, are revealed. It is proved that these sets do not intersect. It is proposed to allocate a subset of C 2 in the set of coins, which has an additional characteristic property — functioning on the basis of a smart contract. The thesis that any settlement unit carries the cost of a resource is proved. Even for units of account with the so-called “intrinsic value” (bitcoin), the presence of a resource in its functions was found. Four characteristic properties inherent in the set of “money” (M = {money}) are disclosed and a subset DM = {digital money} is allocated, containing a set of digital Fiat money secured by the state (sets F = {fat}) and a subset P = {private}, which is actually an addition to the set F). It is proved that cryptocurrencies have characteristic properties of the set M = {money} only within their own community. The paradox of the algorithmic guarantor, reflecting the absence of the need for formalization of algorithmic informal institutions, is formulated. Disclosed defnitions of such concepts as “cryptocurrency”, “token economy” and “tokenization economy”. Euler circles are used to visualize the relationship between different sets of calculation units. A coherent classifcation of calculation units based on the characteristic properties of the identifed sets is formed. The results of the study can be used to form the basis of legal regulation of the circulation of digital units of account.
We compute the revenue ratio of the Trail Stubborn mining strategy in the Bitcoin network and compare its profitability to other block-withholding strategies. We use for this martingale techniques and a classical analysis of the hiker problem. In this strategy the attacker could find himself mining in a shorter fork, but we prove that for some parameter values it is still profitable to not give up. This confirms previous numerical studies.
La tecnologa ha marcado un claro punto de inflexin en todos los mbitos del entorno actual, suscitando un cambio en el know how de las actividades empresariales, estableciendo nuevas pautas de actuacin en el mercado.Dentro de las tecnologas disruptivas que, de forma notable, estn incidiendo en estas ltimas podemos citar la cadena de bloques.Una de las obras de referencia en materia de Blockchain es, precisamente, la presente monografa.Como es conocido, el Blockchain es un anglicismo que se traduce como cadena de bloques.Representa un procedimiento informtico -protocolo-inicialmente creado con el objetivo de soportar las criptomonedas cuyo paradigma es Bitcoin.Esta ltima presenta dos caracteres diferenciadores bsicos, respecto a la moneda tradicional o decimonnica, a saber: la voluntariedad y su naturaleza descentralizada.La disrupcin que suscita en los medios de pago, en el espacio mercantil, estriba en que las criptomonedas, con carcter general, han operado al margen de las monedas fiduciarias.Podemos manifestar que los valores en los que las mismas oscilan se encuentran fuertemente condicionadas por la ley de la oferta y de la demanda.Blockchain es el soporte de Bitcoin, es decir es el protocolo informtico que sirve de base a la criptomoneda ms notable en la actualidad.La cadena de bloques constituye una combinacin de distintas tecnologas con un fin acreditativo.Es, en definitiva, una novedosa manifestacin de lo que se ha llamado economa colaborativa.Constituye, adems, una herramienta de carcter acreditativo que fomenta la aportacin/invocacin del procedimiento con el fin de sustentar las pretensiones de las partes frente a una posible controversia.Se ha dicho, con acierto, que la figura que analizamos es como un libro pblico de contabilidad.Ms bien, puede decirse que se erige en un instrumento registral o tabular que cuenta con una tabla indeleble o compartida como
There has been much debate about whether returns on financial assets, such as stock returns or commodity returns, are predictable; however, few studies have investigated cryptocurrency return predictability. In this article we examine whether bitcoin returns are predictable by a large set of bitcoin price-based technical indicators. Specifically, we construct a classification tree-based model for return prediction using 124 technical indicators. We provide evidence that the proposed model has strong out-of-sample predictive power for narrow ranges of daily returns on bitcoin. This finding indicates that using big data and technical analysis can help predict bitcoin returns that are hardly driven by fundamentals.
Although Bitcoin was intended to be a decentralized digital currency, in practice, mining power is quite concentrated. This fact is a persistent source of concern for the Bitcoin community. We provide an explanation using a simple model to capture miners' incentives to invest in equipment. In our model, $n$ miners compete for a prize of fixed size. Each miner chooses an investment $q_i$, incurring cost $c_i q_i$, and then receives reward $\frac{q_i^α}{\sum_j q_j^α}$, for some $α\geq 1$. When $c_i = c_j$ for all $i,j$, and $α= 1$, there is a unique equilibrium where all miners invest equally. However, we prove that under seemingly mild deviations from this model, equilibrium outcomes become drastically more centralized. In particular, (a) When costs are asymmetric, if miner $i$ chooses to invest, then miner $j$ has market share at least $1-\frac{c_j}{c_i}$. That is, if miner $j$ has costs that are (e.g.) $20\%$ lower than those of miner $i$, then miner $j$ must control at least $20\%$ of the \emph{total} mining power. (b) In the presence of economies of scale ($α> 1$), every market participant has a market share of at least $1-\frac{1}α$, implying that the market features at most $\fracα{α- 1}$ miners in total. We discuss the implications of our results for the future design of cryptocurrencies. In particular, our work further motivates the study of protocols that minimize "orphaned" blocks, proof-of-stake protocols, and incentive compatible protocols.
As a disruptive technology, blockchain, particularly its original form of bitcoin as a type of digital currency, has attracted great attentions. The innovative distributed decision making and security mechanism lay the technical foundation for its success, making us consider to penetrate the power of blockchain technology to distributed control and cooperative robotics, in which the distributed and secure mechanism is also highly demanded. Actually, security and distributed communication have long been unsolved problems in the field of distributed control and cooperative robotics. It has been reported on the network failure and intruder attacks of distributed control and multi-robotic systems. Blockchain technology provides promise to remedy this situation thoroughly. This work is intended to create a global picture of blockchain technology on its working principle and key elements in the language of control and robotics, to provide a shortcut for beginners to step into this research field.
This paper examines the day of the week effect in the cryptocurrency market using a variety of statistical techniques (average analysis, Student's t-test, ANOVA, the Kruskal–Wallis test, and regression analysis with dummy variables) as well as a trading simulation approach. Most crypto currencies (LiteCoin, Ripple, Dash) are found not to exhibit this anomaly. The only exception is BitCoin, for which returns on Mondays are significantly higher than those on the other days of the week. In this case the trading simulation analysis shows that there exist exploitable profit opportunities; however, most of these results are not significantly different from the random ones and therefore cannot be seen as conclusive evidence against market efficiency.
Permissionless blockchain systems, such as Bitcoin, rely on users using their computational power to solve a puzzle in order to achieve a consensus. To incentivise users in maintaining the system, newly minted coins are assigned to the user who solves this puzzle. A hardware race that has hence ensued among the users, has had a detrimental impact on the environment, with enormous energy consumption and increased global carbon footprint. On the other hand, proof of stake systems incentivise coin hoarding as players maximise their utility by holding their stakes. As a result, existing cryptocurrencies do not mimic the day-to-day usability of a fiat currency, but are rather regarded as cryptoassets or investment vectors. In this work we initiate the study of minting mechanisms in cryptocurrencies as a primitive on its own right, and as a solution to prevent coin hoarding we propose a novel minting mechanism based on waiting-time first-price auctions. Our main technical tool is a protocol to run an auction over any blockchain. Moreover, our protocol is the first to securely implement an auction without requiring a semi-trusted party, i.e., where every miner in the network is a potential bidder. Our approach is generically applicable and we show that it is incentive-compatible with the underlying blockchain, i.e., the best strategy for a player is to behave honestly. Our proof-of-concept implementation shows that our system is efficient and scales to tens of thousands of bidders.
In 2008, Satoshi Nakamoto proposed an electronic cash system (bitcoin) that is completely realized by peer-to-peer technology. The core value of this scheme is that it proposes a solution based on Proof-of Work, so that the cash system can run in a peer-to-peer environment and be able to prevent double-spend attacks. Bitcoin has been developed for ten years, and since then countless digital currencies have been created. But the discussion of double-spend attacks seems to still concentrate on 51% Attacks. In fact, our research has found that there are many other way to achieve double-spend attacks. In this paper, by introducing a number of double-spend attack vulnerabilities that we have found in EOS, NEO and other large blockchain platforms, we summarized various reasons for causing double-spend attacks, and propose an efficient mitigation measure against them.
Being in this digital era, technology continuously updates with new variants in providing security while performing the financial transactions. It is a mandated task for the user for conducting secure transactions in order to defend the intruders to restrict the interference. This paper deals with digital currency-Cryptocurrency, that provides a medium of secure exchange between the peers during financial management. Authors explored the internal scheme of bitcoin and the abstract view of cryptocurrency to know how the bitcoin is providing a shield during financial negotiation between peers with various application in security point of view.
Almost a decade on from the launch of Bitcoin, cryptocurrencies continue to generate headlines and intense debate. What started as an underground experiment by a rag tag group of programmers armed with a Libertarian manifesto has now resulted in a thriving $230 billion ecosystem, with constant on-going innovation. Scholars and researchers alike are realizing that cryptocurrencies are far more than mere technical innovation; they represent a distinct and revolutionary new economic paradigm tending towards decentralization. Unfortunately, this bold new universe is little explored from the perspective of Islamic economics and finance. Our work aims to address these deficiencies. Our paper makes the following distinct contributions We significantly expand the discussion on whether cryptocurrencies qualify as "money" from an Islamic perspective and we argue that this debate necessitates rethinking certain fundamental definitions. We conclude that the cryptocurrency phenomenon, with its radical new capabilities, may hold considerable opportunity which merits deeper investigation.
Boris Radovanov, Aleksandra Marcikić, Nebojša Gvozdenović
Because of increasing interest in cryptocurrency investments, there is a need to quantify their variation over time. Therefore, in this paper we try to answer a few important questions related to a time series of cryptocurrencies. According to our goals and due to market capitalization, here we discuss the daily market price data of four major cryptocurrencies: Bitcoin (BTC), Ethereum (ETH), Ripple (XRP) and Litecoin (LTC). In the first phase, we characterize the daily returns of exchange rates versus the U.S. Dollar by assessing the main statistical properties of them. In many ways, the interpretation of these results could be a crucial point in the investment decision making process. In the following phase, we apply an autocorrelation function in order to find repeating patterns or a random walk of daily returns. Also, the lack of literature on the comparison of cryptocurrency price movements refers to the correlation analysis between the aforementioned data series. These findings are an appropriate base for portfolio management. Finally, the paper conducts an analysis of volatility using dynamic volatility models such as GARCH, GJR and EGARCH. The results confirm that volatility is persistent over time and the asymmetry of volatility is small for daily returns.
The narrative of a Bitcoin is a bubble is very common. We employ statistical techniques to empirically evaluate such claim. A branch of literature links the existence of a bubble in some financial asset’s price to strict local martingales — a finitely lived asset has a bubble if, and only if, it is a strict local martingale under the equivalent risk-neutral measure. A diffusion process is a strict local martingale if its volatility increases faster than linearly as its level grows. We apply a nonparametric method to estimate the volatility function of Bitcoin daily and high frequency prices, as well as of more traditional financial assets. We then estimate the stochastic volatility model of Andersen and Piterbarg (2007), whose parameter space has a specific subset under which the asset’s price is a strict local martingale. Results suggest the existence of a bubble in Bitcoin prices from early 2013 to mid 2014, but, interestingly, not in late 2017.
Abstract It has been more than 10 years since Satoshi Nakamoto published his famous paper entitled ‘Bitcoin: a peer-to-peer electronic cash system’, which set the foundation of blockchain technology. Accompanied by the price volatility of bitcoins from 2017 to 2018, blockchain has been a hot word on the internet, and particularly hot in China. Blockchain offers a distributed and secure system for data storage and value transactions. Its applications are springing up in multiple fields. The Chinese government is considering these trends with great caution. Initial coin offering has been banned in China since September 2017. By contrast, an official white paper on China's blockchain technology, which was released in May 2018, said that blockchain technology will be widely applied in the real economy of China within 3 years. In a recent panel discussion held by National Science Review, experts talked about related topics. Their opinions may provide a quick view of the future development of blockchain in China and abroad. Jing Chen Assistant Professor of Computer Science Department, Stony Brook University and Chief Scientist at Algorand LLC, USA Xiaotie Deng Professor of School of Electronics Engineering and Computer Science, Peking University, China Guohua Gan Vice President of Beijing Tai Cloud Technology Corp., China Xiaoyun Wang Professor of Institute of Advanced Study, Tsinghua University, China Zhiming Zheng Professor of School of Mathematics and Systems Science, Beihang University, China Lei Guo (Chair) Professor of Academy of Mathematics and Systems Science, Chinese Academy of Sciences, China
Zijian Bao, Bin Wang, Yongxin Zhang, Qinghao Wang · 5 authors
We propose Lockcoin, a secure and privacy-preserving mix service for bitcoin anonymity. We introduce mix servers to provide mix service for user to prevent attackers linking the input address with output address by using blind signature shceme, multisignature scheme. Lockcoin provides anonymity, scalability, bitcoin compatibillity, theft impossibility and accountability. We have proposed a prototype of Lockcoin based on bitcoin test network, experimental results show that our solution is efficient. Lockcoin's source codes are released on github.com/Northeastern-University-Blockchain/Lockcoin.
One major shortcoming of permissionless blockchains such as Bitcoin and Ethereum is that they are unsuitable for running Computationally Intensive smart Contracts (CICs). This prevents such blockchains from running Machine Learning algorithms, Zero-Knowledge proofs, etc. which may need non-trivial computation. In this paper, we present YODA, which is to the best of our knowledge the first solution for efficient computation of CICs in permissionless blockchains with guarantees for a threat model with both Byzantine and selfish nodes. YODA selects one or more execution sets (ES) via Sortition to execute a particular CIC off-chain. One key innovation is the MultI-Round Adaptive Consensus using Likelihood Estimation (MIRACLE) algorithm based on sequential hypothesis testing. M I RACLE allows the execution sets to be small thus making YODA efficient while ensuring correct CIC execution with high probability. It adapts the number of ES sets automatically depending on the concentration of Byzantine nodes in the system and is optimal in terms of the expected number of ES sets used in certain scenarios. Through a suite of economic incentives and technical mechanisms such as the novel Randomness Inserted Contract Execution (RICE) algorithm, we force selfish nodes to behave honestly. We also prove that the honest behavior of selfish nodes is an approximate Nash Equilibrium. We present the system design and details of YODA and prove the security properties of MIRACLE and RICE. Our prototype implementation built on top of Ethereum demonstrates the ability of YODA to run CICs with orders of magnitude higher gas per unit time as well as total gas requirements than Ethereum currently supports. It also demonstrates the low overheads of RICE.