Recent work has demonstrated significant anonymity vulnerabilities in Bitcoin's networking stack. In particular, the current mechanism for broadcasting Bitcoin transactions allows third-party observers to link transactions to the IP addresses that originated them. This lays the groundwork for low-cost, large-scale deanonymization attacks. In this work, we present Dandelion++, a first-principles defense against large-scale deanonymization attacks with near-optimal information-theoretic guarantees. Dandelion++ builds upon a recent proposal called Dandelion that exhibited similar goals. However, in this paper, we highlight simplifying assumptions made in Dandelion, and show how they can lead to serious deanonymization attacks when violated. In contrast, Dandelion++ defends against stronger adversaries that are allowed to disobey protocol. Dandelion++ is lightweight, scalable, and completely interoperable with the existing Bitcoin network. We evaluate it through experiments on Bitcoin's mainnet (i.e., the live Bitcoin network) to demonstrate its interoperability and low broadcast latency overhead.
Recent work has demonstrated significant anonymity vulnerabilities in\nBitcoin's networking stack. In particular, the current mechanism for\nbroadcasting Bitcoin transactions allows third-party observers to link\ntransactions to the IP addresses that originated them. This lays the groundwork\nfor low-cost, large-scale deanonymization attacks. In this work, we present\nDandelion++, a first-principles defense against large-scale deanonymization\nattacks with near-optimal information-theoretic guarantees. Dandelion++ builds\nupon a recent proposal called Dandelion that exhibited similar goals. However,\nin this paper, we highlight simplifying assumptions made in Dandelion, and show\nhow they can lead to serious deanonymization attacks when violated. In\ncontrast, Dandelion++ defends against stronger adversaries that are allowed to\ndisobey protocol. Dandelion++ is lightweight, scalable, and completely\ninteroperable with the existing Bitcoin network. We evaluate it through\nexperiments on Bitcoin's mainnet (i.e., the live Bitcoin network) to\ndemonstrate its interoperability and low broadcast latency overhead.\n
In the world finance and technological development in finance, along with innovative financial instruments, have attracted investors. The most popular of these developments is undoubtedly Bitcoin, which is an output of the blockchain infrastructure .Bitcoin that is not connected to a central authority and contains cryptographic features, is one of the crypto moneys. The fact that Bitcoin does not depend on Central Authority and disclose the factors affecting its price by supply and demand have resulted in high volatility. In this study, firstly blockchain technology will be explained briefly and time-dependent price estimates for Bitcoin which is one of the important outputs of this technology, will be made. Artificial Neural Networks (YSA), which has become increasingly popular among estimation methods in recent years, has been used in the study and compared with ARIMA in traditional estimation methods. The sample of the study was created using daily closing prices between 02.02.2012 - 09.01.2018 dates. As a result of this study, both directions and values of estimated prices by artificial neural networks MPL (6-3-1) model between 10.01.2018 - 18.01.2018 have been more successful than ARIMA (1.1.6) model.
The first high-profile decentralized autonomous organization formed in 2016. Called “TheDAO,” it used smart contracts on a bitcoin-style blockchain to allow strangers to come together online to vote on and invest in venture capital proposals. Newspapers raved about the $160 million it quickly raised, even though it purported to have no central human authority, including no managers, executives, or board of directors.
Technologists have grand plans for smart contracts and autonomous organizations. Rather than staying at traditional hotels with elaborate human staff, we may pay for hotel rooms using bitcoin (or another cryptocurrency) which will automatically unlock the room door. If the toilet breaks, the room itself will contract with a plumber to fix it. Similarly, a smart contract may allow us to hire a self-driving car. The car will not only drive passengers around but arrange for its own routine maintenance.
TheDAO itself, however, is now a cautionary tale. A bug in its smart contract code was exploited to drain more than $50 million in value. Some purists denounced efforts to mitigate the problem, arguing that the alleged hacker simply withdrew money in accordance with the organization’s agreed-upon contractual terms in the form of computer code. Since the “code is the contract” in their minds, the alleged hacker did nothing wrong.
I defend two related claims. First, contra the purists, I argue that the code does not reflect the entirety of the parties’ agreement, and so the “code is the contract” slogan does not resolve whether TheDAO exploitation should have been mitigated. I take no position on whether mitigation was appropriate except to say that the matter depends on many considerations aside from smart contract code itself.
Second, I point to a broader danger lurking in the code-is-the-contract view. TheDAO had tremendous “artificial responsibility” in that we gave it considerable control that couldn’t be easily revoked or reined in. Not-so-smart contracts in the future may prove even more dangerous: hotel guests might be locked out of their rooms, and self-driving cars might drive off bridges. I argue that unadulterated commitment to the code-is-the-contract slogan increases artificial responsibility and its associated risks.
Grigory O. Krylov, A. Yu. Lisitsyn, Leonid I. Polyakov
The article provides a comparative analysis of the volatility of the leading national fiat currencies and their transnational anonymous analogues, which received the slang name “cryptocurrency”.Volatility is the most important financial indicator in the management of financial flows, as a measure of the risk of using a financial instrument at a specified period of time. Cryptocurrency mining technology is available to the general public and has become an innovative phenomenon. The latest fi phenomena need to be investigated, so it is necessary to conduct a multilateral scientific analysis, identification and comparison of cryptocurrency with fi currency. The aim of this study is to obtain new estimates of cryptocurrency based on the use of tools such as GARCH-model, simple historical volatility (SHV) and developed by the author’s toolkit, which is based on the Chaikin method. The methodological basis of the research is logical, econometric, economic and statistical methods of analysis, technical and fundamental analysis, and method of scientific visualization. The calculated volatility estimates are based on the Central Bank’s data on currency rates and investigated using named three models. The article for the first time presents the results of comparison of volatility of the leading fiat currencies (uS dollar, euro, Chinese yuan and Japanese yen) and the most popular today so-called cryptocurrencies (bicoin, litecoin, ethereum, and monero). Estimation of volatility showed that the volatility of bitcoin is significantly higher than fiat money. In this regard, it is concluded that the recognition of cryptocurrency, in particular bitcoin, as a real money is premature, not only due to the lack of regulations of a certain cryptocurrency as a legal tender, but also on the grounds of violation of essential requirements for the properties of the currency, such as a low level of volatility.
The efficiency of decentralized book systems like Bitcoin and Ethereum has always been a challenge. It is usually measured by three major factors: scalability, throughput, and latency. Scalability refers to how the system capacity is increased by adding more physical resources. Throughput measures the volume of transactions for a given period of time, where most current solutions attempt to improve such as NEO, EOS, etc. Latency measures the processing time of any single transaction. In current blockchain based systems, the block generation rate is the main latency bottleneck. Off-chain processes such as state channels are the most recent work that can integrate partial inbound transactions, reducing latency. Unfortunately, the state channel introduces more issues at the same time, such as cross-channel synchronization, which makes the state channel unavailable for full adoption of current blockchain solutions. In order to solve the efficiency problem, we proposed an end-to-end solution called ALZA, which links the dedicated high-throughput blockchain with self-organizing payment fields. This mechanism allows arbitrary set of users to create payment fields that process extremely low latency transactions within each field. Therefore, users can make transactions almost immediately. Since all transactions are conducted within fields, transaction costs will be reduced by several orders of magnitude. In addition, ALZA distributes main ledger to each client through an innovative replication mechanism. Therefore, the system will be significantly more robust to blockchain system failures. In theory, ALZA can complete millions of transactions in one second, which naturally supports high-frequency trading.
James Tapsell, Raja Naeem Akram, Konstantinos Markantonakis
Bitcoin is a decentralised digital currency that relies on cryptography rather than trusted third parties such as central banks for its security. Underpinning the operation of the currency is a peer-to-peer (P2P) network that facilitates the execution of transactions by end users, as well as the transaction confirmation process known as bitcoin mining. The security of this P2P network is vital for the currency to function and subversion of the underlying network can lead to attacks on bitcoin users including theft of bitcoins, manipulation of the mining process and denial of service (DoS). As part of this paper the network protocol and bitcoin core software are analysed, with three bitcoin message exchanges (the connection handshake, GETHEADERS/HEADERS and MEMPOOL/INV) found to be potentially vulnerable to spoofing and use in distributed denial of service (DDoS) attacks. Possible solutions to the identified weaknesses and vulnerabilities are evaluated, such as the introduction of random nonces into network messages exchanges.
We propose to use the terms Verfügungsmacht (power to dispose, analogous to possession) and Verfügungsrecht (right to dispose, analogous to ownership) to discern whom a Bitcoin belongs to in case of a bankruptcy. Using the example of Tezos, we demonstrate that the storage location of private keys alone does not suffice to meaningfully answer the question to whom the foundation's assets belong. Instead, the context and the contractual arrangement, from which the right to these assets can be derived, also need to be taken into account. This view provides a legal basis for the storage of Bitcoins on behalf of a client without taking them onto one's balance sheet, ensuring that the client's assets are not included in the bankruptcy estate. Furthermore, we classify the Internet currency Bitcoin as a rival, fictive, intangible asset sui generis and opine that there is a gap in the law regarding Aussonderung (removing an asset from the bankruptcy estate and returning it to the rightful owner) and Admassierung (adding an asset to the bankruptcy estate from a third party) of Bitcoins. Courts and bankruptcy administrators are encouraged to fill this gap in accordance with article 1 of the Swiss Civil Code when faced with Bitcoins in a bankruptcy case.
Starting with BitTorrent and then Bitcoin, decentralized technologies have been on the rise over the last 15+ years, gaining significant momentum in the last 2+ years with the advent of platform ecosystems such as the Blockchain platform Ethereum. New projects have evolved from decentralized games to marketplaces to open funding models to decentralized autonomous organizations. The hype around cryptocurrency and the valuation of innovative projects drove the market cap of cryptocurrencies to over a trillion dollars at one point in 2017. These high valued technologies are now enabling something new: globally scaled and decentralized business models. Despite their valuation and the hype, these new business ecosystems are frail. This is not only because the underlying technology is rapidly evolving, but also because competitive markets see a profit opportunity in exponential cryptocurrency returns. This extracts value from these ecosystems, which could lead to their collapse, if unchecked. In this paper, we explore novel ways for decentralized economies to protect themselves from, and coexist with, competitive markets at a global scale utilizing decentralized technologies such as Blockchain.
Yackolley Amoussou-Guenou, Antonella Del Pozzo, Maria Potop-Butucaru, Sara Tucci-Piergiovanni
Tendermint-core blockchains (e.g. Cosmos) are considered today one of the most viable alternatives for the highly energy consuming proof-of-work blockchains such as Bitcoin and Ethereum. Their particularity is that they aim at offering strong consistency (no forks) in an open system combining two ingredients (i) a set of validators that generate blocks via a variant of Practical Byzantine Fault Tolerant (PBFT) consensus protocol and (ii) a selection strategy that dynamically selects nodes to be validators for the next block via a proof-of-stake mechanism. However,the exact assumptions on the system model under which Tendermint underlying algorithms are correct and the exact properties Tendermint verifies have never been formally analyzed. The contribution of this paper is two-fold. First, while formalizing Tendermint algorithms we precisely characterize the system model and the exact problem solved by Tendermint. We prove that in eventual synchronous systems a modified version of Tendermint solves (i) under additional assumptions, a variant of one-shot consensus for the validation of one single block and (ii) a variant of the repeated consensus problem for multiple blocks. These results hold even if the set of validators is hit by Byzantine failures, provided that for each one-shot consensus instance less than one third of the validators is Byzantine. Our second contribution relates to the fairness of the rewarding mechanism. It is common knowledge that in permisionless blockchain systems the main threat is the tragedy of commons that may yield the system to collapse if the rewarding mechanism is not adequate. Ad minimum the rewarding mechanism must be fair, i.e.distributing the rewards in proportion to the merit of participants. We prove, for the first time in blockchain systems, that in repeated-consensus based blockchains there exists an (eventual) fair rewarding mechanism if and only if the system is (eventual) synchronous. We also show that the original Tendermint rewarding is not fair, however, a modification of the original protocol makes it eventually fair.
This study back-tests a marginal cost of production model proposed to value the digital currency Bitcoin. Results from both conventional regression and vector autoregression (VAR) models show that the marginal cost of production plays an important role in explaining Bitcoin prices, challenging recent allegations that Bitcoins are essentially worthless. Even with markets pricing Bitcoin in the thousands of dollars each, the valuation model seems robust. The data show that a price bubble that began in the Fall of 2017 resolved itself in early 2018, converging with the marginal cost model. This suggests that while bubbles may appear in the Bitcoin market, prices will tend to this bound and not collapse to zero.
This study back-tests a marginal cost of production model proposed to value\nthe digital currency bitcoin. Results from both conventional regression and\nvector autoregression (VAR) models show that the marginal cost of production\nplays an important role in explaining bitcoin prices, challenging recent\nallegations that bitcoins are essentially worthless. Even with markets pricing\nbitcoin in the thousands of dollars each, the valuation model seems robust. The\ndata show that a price bubble that began in the Fall of 2017 resolved itself in\nearly 2018, converging with the marginal cost model. This suggests that while\nbubbles may appear in the bitcoin market, prices will tend to this bound and\nnot collapse to zero.\n
Revisiting analytically the notion of embeddedness and its connections with the concept of trust, this paper shows that contrary to Bitcoin’s premises and promises to be a trust-low or even trust-less currency, trust enters the system at many various levels and with different nuances. Applying a conceptual framework that conceives embeddedness as both the possible source and outcome of trust, it is pointed out that Bitcoin should better be regarded as doubly embedded: in technology and in its peculiar social structure. Due to the existence of computational and cognitive asymmetries within the system, in fact, trust is necessary for the very functioning of this new form of money, as well as for its future prospects.
Sanal para sistemi bitcoin ve altcoins olarak tanımlanan türevleri mevcut para politikasını ve para sistemlerini değişim ve dönüşüme zorlayacak bir trendin içinde oldukları gözlenmektedir. Genel olarak kripto para olarak tanımlanan bu sistem elektronik ortamda oluşturulabilen ve nakit benzeri bir ödeme aracı sisteminden ibarettir. Bu sistemin mevcut para ve ödeme araçlarına alternatif ve hatta geleneksel para teori ve uygulamalarının yerini alacağı yönünde bir gelişim süreci içinde olması bu sisteme odaklanmayı zorunlu hale getirmektedir. Bu makalede bitcoin ve benzeri kripto paraların yapıları, işlevleri ve mevcut para sistemi içerisindeki yeri ve önemi karşılaştırmalı ve analitik bir analizle değerlendirilmiştir.
A problem facing healthcare record systems throughout the world is how to share the medical data with more stakeholders for various purposes without sacrificing data privacy and integrity. Blockchain, operating in a state of consensus, is the underpinning technology that maintains the Bitcoin transaction ledger. Blockchain as a promising technology to manage the transactions has been gaining popularity in the domain of healthcare. Blockchain technology has the potential of securely, privately, and comprehensively manage patient health records. In this work, we discuss the latest status of blockchain technology and how it could solve the current issues in healthcare systems. We evaluate the blockchain technology from the multiple perspectives around healthcare data, including privacy, security, control, and storage. We review the current projects and researches of blockchain in the domain of healthcare records and provide the insight into the design and construction of next generations of blockchain-based healthcare systems.
The IRS recently dealt a blow to Bitcoin enthusiasts by ruling that Bitcoin and other similar currencies should be treated as property–and not foreign currency–for income tax purposes. As a result, those who use bitcoins to purchase goods or services must report gain or loss on each transactionn if the bitcoins have changed value between the time they were acquired and spent. Treating Bitcoin as a foreign currency would have permitted individuals to take advantage of the $200 personal-use exemption and required taxpayers to adopt a formulaic system for tracking the basis of commingled bitcoins.The IRS's decision seems correct as a matter of positive law, but laws can always be changed. In this Article I consid4r whether Bitcoin should be treated as a foreign currency for income tax purposes. I conclude that tax authorities should adopt a foreign currency definition that excludes bitcoin and similar currencies because (1) a broad definition ciould create significant administrative and line-drawing problems, and (2) the government has little interest in promoting alternate currencies . Nor should authorities extend the personal-use exemption to virtual currencies. In contrast, authorities should extend the basis rules applicable to foreign currency to virtual currencies to prevent taxpayers from using the basis rules to improperly reduce their tax obligations.
We review the so called selfish mining strategy in the Bitcoin network and compare its profitability to honest mining.We build a rigorous profitability model for repetition games. The time analysis of the attack has been ignored in the previous literature based on a Markov model,but is critical. Using martingale's techniques and Doob Stopping Time Theorem we compute the expected duration of attack cycles. We discover a remarkable property of the bitcoin network: no strategy is more profitable than the honest strategy before a difficulty adjustment. So selfish mining can only become profitable afterwards, thus it is an attack on the difficulty adjustment algorithm. We propose an improvement of Bitcoin protocol making it immune to selfish mining attacks. We also study miner's attraction to selfish mining pools. We calculate the expected duration time before profit for the selfish miner, a computation that is out of reach by the previous Markov models.
Blockchain-based consensus protocols present the opportunity to develop new protocols, due to their novel requirements of open participation and explicit incentivization of participants. To address the first requirement, it is necessary to consider the leader election inherent in consensus protocols, which can be difficult to scale to a large and untrusted set of participants. To address the second, it is important to consider ways to provide incentivization without relying on the resource-intensive proofs-of-work used in Bitcoin. In this paper, we propose a secure leader election protocol, Caucus; we next fit this protocol into a broader blockchain-based consensus protocol, Fantomette, that provides game-theoretic guarantees in addition to traditional blockchain security properties. Fantomette is the first proof-of-stake protocol to give formal game-theoretic proofs of security in the presence of non-rational players.
Freya Sheer Hardwick, Raja Naeem Akram, Konstantinos Markantonakis
At a time when society is in constant transition to keep up with technological advancement, we are seeing traditional paradigms being increasingly challenged. The fundamentals of governance are one such paradigm. As society's values have shifted, so have expectations of government shifted from the traditional model to something commonly referred to as `open governance'. Though a disputed term, we take open governance to mean a concept, which encourages and facilitates openness, accountability, and responsiveness to citizens. For the success of open governance initiatives, there are some technologies, such as the internet, that are crucial. These technologies enable access to both the data and to engagement activities between citizens and government. There are also other technologies, like blockchain and smart contacts, which could be utilised to assist open governance. A sound starting point would be moving from a system where information is tediously released by a government, on an `as they please' basis, to an infrastructure where critical actions are captured with strong integrity, non-repudiation and evidential guarantees. With an added dimension that facilitates these actions record be accessible to public scrutiny in near real-time. One candidate technology for capturing such actions is blockchain. Initially, blockchains were mainly used to facilitate cryptocurrencies as a record of transactions. The notable example being bitcoin. However, in recent years, blockchains utility is being recognised through smart contracts - potentially a vital building block to realising open and transparent government activities. In this paper, we employ the concept of smart contracts to government tendering activities. The proposed scheme is based on smart contracts, enabling a fair, transparent and independently verifiable (auditable) government tendering scheme. The scheme is then implemented on the Ethereum platform to evaluate the performance and financial cost implications, along with an evaluation of the potential security and auditability challenges.
In a previous paper, it was discussed whether Bitcoin and/or its blockchain could be considered a complex system and, if so, whether a chaotic one, a positive response raising concerns about the likelihood of Bitcoin/blockchain entering a chaotic regime, with catastrophic consequences for financial systems based on it. This paper intends to simplify and extend that analysis to other PoW, PoS, and hybrid protocol-based cryptocurrencies. As before, this study was carried out with the help of Information Theory of Complex Systems, in general, and Crutchfield's Statistical Complexity measure, in particular. This paper is a work-in-progress. We intend to uncover some other measures that capture the qualitative notion of complexity of systems that can be applied to these cryptocurrencies to compare with the results here obtained.
In recent years bitcoin has been attracted eminent attraction all around world in the area of cryptocurrency and its unique peer to peer transaction system. Analyzing and forecasting is most common task for data scientists that helps organizations to improve there business strategies. \n \nThis report is built around the fact that in bitcoin trading and analysis, the factors underlying are basically the traditional price predictions using the data mining technique.The project aim to gather data on bitcoin, analyse and forecast in order to see the fall or rise in bitcoin price.The bitcoin Dataset used is bitcoinmarketcap. This report intend to help the reader and understand what approach and methodology used to complete different milestones.This report summarizing all the aspect used throughout this project. \n \nThis is done using different techniques and algorithm to predict and forecast the rise or fall of bitcoin with the use of Crisp-DM methodology.The techniques used in the projects are Time Series ARIMA ,Time Series( Facebook prophet API), Linear Regression and and Multiple Regression.
Both “big data” and “analytics” have become popular keywords in many organizations. The power data analytics has on harnessing the increasing volumes, velocity and complexity of data in a world of constant change and disruptive technologies has been recognized. Many companies are making significant investments to better understand the impact of these capabilities on their businesses. One area with significant potential is the transformation of the audit. This project explores ways in which analytics can change and shape the work of accountants. \n \nAnomaly detection plays a pivotal role in data mining since most outlying points contain crucial information for further investigation. In the financial world which the Bitcoin network is a part of, anomaly detection can indicate fraud. Using data mining tools such as Regression, we simultaneously examine the relationship among variables whilst visually inspecting the data for possible outliers. By doing so, I have chosen the world’s leading cryptocurrency, Bitcoin. This project will conclude with an in-depth analysis on whether or not data analytics can shape how effectively, and secure accountants can audit transactions by implementing analytics tools into their daily protocols.
The purpose of this project is to perform an analysis on the comments by users on cryptocurrency discussion platforms and the prices of the mentioned cryptocurrencies. Although the blockchain has been around close to 10 years, cryptocurrencies are still a relatively young market. Bitcoin which has the first mover advantage has always been a dominating force within the sphere, but within the last year the market has seen a huge increase in interest. One year ago, the entire market capitalization of all cryptocurrencies was $13 billion and bitcoin held a dominance of 88% with a market cap of $11.5 billion. Compare that to today and all cryptocurrencies have a market cap of $310 billion with bitcoin only having a 54% dominance. The entire sphere has seen growth of more than 2284% in less than a year and bitcoin is beginning to lose a lot of its market share to newer more promising currencies. Unlike traditional stocks, cryptocurrencies have no tangible value attached and prices fluctuate with perceived value. Cryptocurrency trading relies on speculation more so than fundamental analysis and as a result most of the price speculation takes place online. Due to the abundance of data regarding speculation around prices on various cryptocurrency discussion platforms, I hope to find a correlation between the sentiment of the posts and the prices of the mentioned cryptocurrencies. This project will follow the KDD methodology.
We propose a bitcoin generalization as a solution to the problem of scalability. The block is redefined as a sequence of sub-blocks of increasing sizes that coexist as different levels of compromise between decentralization and transactions throughput. Miners and users can decide individually the sizes they use without affecting others in the network.