Blockchain Papers

Thomas Bocek, Sina Rafati, Bruno Rodrigues, Burkhard Stiller

No abstract is available for this record.

George Cornel Dumitrescu

Along the history, people organised in communities needed payment means in order to exchange goods or deliver services. From beads and feathers to metal and paper money they have always improved the way transactions were made. The invention of the Internet opened new doors in the field of payments, through the quick access to information and the emergence of significant international online communities. The members of these communities became aware of the importance of decentralising the way they acquire goods or services, thus eliminating the middlemen. Cryptocurrencies represent the response of these communities to the old centralised means of payment, controlled by the bankers, politicians and interest groups. Our paper aims to analyse the cryptocurrency phenomenon revealing some of its advantages and disadvantages, to increase the awareness on the topic. We based our research on the existing literature, the relevant international databases, the official positions of the financial and regulatory institutions on the analysed matter.

A. Pinar Ozisik, George Bissias, Brian Neil Levine

We make several contributions that quantify the real-time hash rate and therefore the consensus of a blockchain. We show that by using only the hash value of blocks, we can estimate and measure the hash rate of all miners or individual miners, with quanti able accuracy. We apply our techniques to the Ethereum and Bitcoin blockchains; our solution applies to any proof-of-work-based blockchain that relies on a numeric target for the validation of blocks. We also show that if miners regularly broadcast status reports of their partial proof-of- work, the hash rate estimates are signi cantly more accurate at a cost of slightly higher bandwidth. Whether using only the blockchain, or the additional information in status reports, merchants can use our techniques to quantify in real-time the threat of double-spend attacks.

Jan Lánský

Cryptocurrency systems are purely digital and decentralized systems that use cryptographic principles to confirm transactions. Bitcoin is the first and also the most widespread cryptocurrency. The aim of this article is to introduce Bitcoin system using a language understandable also to readers without computer science education. This article captures the Bitcoin system from three perspectives: internal structure, network and users. Emphasis is placed on brief and clear definitions (system components) and their mutual relationships. A new system view of the stated terms constitutes author's own contribution.

Luqman Nurhisam

<p>Di Indonesia, bitcoin merupakan bentuk mata uang digital (e-money) dan alat transaksi pembayaran yang sudah digunakan oleh sebagian masyarakat. Hal tersebut perlu mendapatkan perhatian, khususnya dari Bank Indonesia. Lain dari pada itu, pengawasan yang dulu sepenuhnya dilakukan oleh bank sentral yaitu Bank Indonesia, sekarang diambil alih oleh OJK (Otoritas Jasa Keuangan). Sehingga Bank Indonesia pun hanya memiliki wewenang untuk mengatur dan mengontrol peredaran mata uang saja. Sejak sebagian tugas dan wewenang Bank Indonesia diambil alih oleh OJK (Otoritas Jasa Keuangan), banyak hal yang belum tercover seperti adanya fenomena baru dalam bidang keuangan dalam hal permodalan, investasi, peredaran mata uang, dan lain-lain. Selain belum ada payung hukum terhadap bitcoin, yaitu semakin merebaknya transaksi yang menggunakan bitcoin yang dilakukan dalam transaksi e-commerce. Sehingga dari segi keamananannya juga perlu dipertanyakan, maka dari itu perlu ada regulasi dan pengawasan secara khusus terhadap bitcoin, dan masyarakat tidak akan merasa dirugikan. Jika dilihat dalam perspektif hukum Islam, bahwa yang berkaitan dengan penerbitan uang sebagai alat transaksi di suatu negara, merupakan masalah yang dilindungi oleh kaidah-kaidah umum dalam syari’at Islam. Oleh sebab itu, penerbitan uang dan penentuan jumlahnya merupakan hal-hal yang berkaitan dengan kemaslahatan umat. Aspek lain yang menjadi pertimbangan dalam penggunaan bitcoin yaitu apakah dari sisi kemadharatannya yang lebih besar ataukah manfaatnya yang diambil jika digunakan sebagai mata uang dan alat transaksi, bahkan sebagai komoditas sekalipun. Sehingga yang menjadi fokus dalam penelitian ini adalah penggunaan bitcoin sebagai mata uang (currency) dan alat transaksi dengan menggunakan pendekatan dan pengkajian hukum Islam.</p>

Zhengyao Jiang, Dixing Xu, Jinjun Liang

Financial portfolio management is the process of constant redistribution of a\nfund into different financial products. This paper presents a\nfinancial-model-free Reinforcement Learning framework to provide a deep machine\nlearning solution to the portfolio management problem. The framework consists\nof the Ensemble of Identical Independent Evaluators (EIIE) topology, a\nPortfolio-Vector Memory (PVM), an Online Stochastic Batch Learning (OSBL)\nscheme, and a fully exploiting and explicit reward function. This framework is\nrealized in three instants in this work with a Convolutional Neural Network\n(CNN), a basic Recurrent Neural Network (RNN), and a Long Short-Term Memory\n(LSTM). They are, along with a number of recently reviewed or published\nportfolio-selection strategies, examined in three back-test experiments with a\ntrading period of 30 minutes in a cryptocurrency market. Cryptocurrencies are\nelectronic and decentralized alternatives to government-issued money, with\nBitcoin as the best-known example of a cryptocurrency. All three instances of\nthe framework monopolize the top three positions in all experiments,\noutdistancing other compared trading algorithms. Although with a high\ncommission rate of 0.25% in the backtests, the framework is able to achieve at\nleast 4-fold returns in 50 days.\n

Olugbemi T. Olaniyan, Mayowa J. Adeniyi, Charles Oluwaseun Adetunji, Omosigho Omoruyi Pius · 7 authors

Abstract Objectives To introduce blockchain technologies, including their benefits, pitfalls, and the latest applications, to the biomedical and health care domains. Target Audience Biomedical and health care informatics researchers who would like to learn about blockchain technologies and their applications in the biomedical/health care domains. Scope The covered topics include: (1) introduction to the famous Bitcoin crypto-currency and the underlying blockchain technology; (2) features of blockchain; (3) review of alternative blockchain technologies; (4) emerging nonfinancial distributed ledger technologies and applications; (5) benefits of blockchain for biomedical/health care applications when compared to traditional distributed databases; (6) overview of the latest biomedical/health care applications of blockchain technologies; and (7) discussion of the potential challenges and proposed solutions of adopting blockchain technologies in biomedical/health care domains.

Zhiyong Li

Blockchain technology is the underlying technology of bitcoin. The bitcoin can be used to consume and exchange real currencies, because the blockchain can provide credit certificate of online transaction, and all transaction related information is encrypted and stored in the blockchain. So, it is safe and decentralized, and it will reduce the transaction cost and be widely used. Another important feature of blockchain is non-modifiable. Since all transaction related information is recorded in blockchain and not changeable, this feature facilitates the audit work.

Luisanna Cocco, Andrea Pinna, Michele Marchesi

This paper looks at the challenges and opportunities of implementing blockchain technology across banking, providing food for thought about the potentialities of this disruptive technology. The blockchain technology can optimize the global financial infrastructure, achieving sustainable development, using more efficient systems than at present. In fact, many banks are currently focusing on blockchain technology to promote economic growth and accelerate the development of green technologies. In order to understand the potential of blockchain technology to support the financial system, we studied the actual performance of the Bitcoin system, also highlighting its major limitations, such as the significant energy consumption due to the high computing power required, and the high cost of hardware. We estimated the electrical power and the hash rate of the Bitcoin network, over time, and, in order to evaluate the efficiency of the Bitcoin system in its actual operation, we defined three quantities: “economic efficiency”, “operational efficiency”, and “efficient service”. The obtained results show that by overcoming the disadvantages of the Bitcoin system, and therefore of blockchain technology, we could be able to handle financial processes in a more efficient way than under the current system.

Davor Maček, Dino Alagić

This paper describes proposed methodology for evaluation of critical systems and prioritization of critical risks and assets identified in highly secured information systems. For different types of information assets or security environments it is necessary to apply different techniques and methods for their prioritization and evaluation. In this article, VECTOR matrix method for prioritization of critical assets and critical risks is explained and integrated into AHP (Analytic Hierarchy Process) technique as a set of fixed criteria for evaluation of defined alternatives. Bitcoin cryptocurrency was compared and evaluated along with other common Internet transaction systems by information security professionals according to defined VECTOR criteria. Also, the newly proposed hybrid AHP model is presented with potential case studies for future research. This article tries to discover security posture of Bitcoin cryptocurrency in the context of information security risks related to the existing most common online payment systems like e-banking, m-banking, and e-commerce

Pavel Ciaian, Miroslava Rajčániová, d’Artis Kancs

This paper empirically examines interdependencies between BitCoin and altcoin markets in the short- and long-run. We apply time-series analytical mechanisms to daily data of 17 virtual currencies (BitCoin + 16 alternative virtual currencies) and two altcoin price indices for the period 2013–2016. Our empirical findings confirm that indeed BitCoin and altcoin markets are interdependent. The BitCoin-altcoin price relationship is significantly stronger in the short-run than in the long-run. We cannot fully confirm the hypothesis that the BitCoin price relationship is stronger with those altcoins that are more similar in their price formation mechanism to BitCoin. In the long-run, macro-financial indicators determine the altcoin price formation to a slightly greater degree than BitCoin does. The virtual currency supply is exogenous and therefore plays only a limited role in the price formation.

Paraskevi Katsiampa

No abstract is available for this record.

Aljosha Judmayer, Nicholas Stifter, Katharina Krombholz, Edgar Weippl

No abstract is available for this record.

Pierre Schweitzer

The author makes a summary and commentary of Nigel Dodd's article « The Social Life of Bitcoin », (Theory, Culture & Society, 2017). For the proponents of this alternative currency that is Bitcoin, technological power should be able to replace trust. This idea may be challenged by the real world test.

Arvind Narayanan, Malte Möser

In the cryptographic currency Bitcoin, all transactions are recorded in the blockchain - a public, global, and immutable ledger. Because transactions are public, Bitcoin and its users employ obfuscation to maintain a degree of financial privacy. Critically, and in contrast to typical uses of obfuscation, in Bitcoin obfuscation is not aimed against the system designer but is instead enabled by design. We map sixteen proposed privacy-preserving techniques for Bitcoin on an obfuscation-vs.-cryptography axis, and find that those that are used in practice tend toward obfuscation. We argue that this has led to a balance between privacy and regulatory acceptance.

Christoph Prybila, Stefan Schulte, Christoph Hochreiner, Ingo Weber

The usage of process choreographies and decentralized Business Process Management Systems has been named as an alternative to centralized business process orchestration. In choreographies, control over a process instance is shared between independent parties, and no party has full control or knowledge during process runtime. Nevertheless, it is necessary to monitor and verify process instances during runtime for purposes of documentation, accounting, or compensation. To achieve business process runtime verification, this work explores the suitability of the Bitcoin blockchain to create a novel solution for choreographies. The resulting approach is realized in a fully-functional software prototype. This software solution is evaluated in a qualitative comparison. Findings show that our blockchain-based approach enables a seamless execution monitoring and verification of choreographies, while at the same time preserving anonymity and independence of the process participants. Furthermore, the prototype is evaluated in a performance analysis.

Бухонова, Sofiya Buhonova, Дорошенко, Yuriy Doroshenko · 6 authors

No abstract is available for this record.

Fahad Almudhaf

This article examines the pricing efficiency of Bitcoin Investment Trust. We investigate the deviation between prices and net asset values and find that there is a significant and persistent premium with an average of 44%. Such evidence points to pricing inefficiency of the currently available trust and encourages practitioners to introduce better instruments such as Exchange Traded Funds as alternatives to investors interested in having exposure to bitcoins and the digital currencies market.

Tri A Sundara, Ideva Gaputra, Siska Aulia

Blockchain as a distributed ledger system which provide underlying technology behind Bitcoin. Blockchain paradigm can be extended to provide a generalized framework for implementing decentralized compute resources. Some attempts has been made to visualize Blockchain transaction flow. This research aims to assess those attempts through systematic review.

Axel Moinet, Benoît Darties, Jean-Luc Baril

Sensor networks and Wireless Sensor Networks (WSN) are key components for the development of the Internet of Things. These networks are subject of two kinds of constraints. Adaptability by the mean of mutability and evolutivity, and constrained node resources such as energy consumption, computational complexity or memory usage. In this context, none of the existing protocols and models allows reliable peer authentication and trust level management. In the field of virtual economic transactions, Bitcoin has proposed a new decentralized and evolutive way to model and acknowledge trust and data validity in a peer network by the mean of the blockchain. We propose a new security model and its protocol based on the blockchain technology to ensure validity and integrity of cryptographic authentication data and associate peer trust level, from the beginning to the end of the sensor network lifetime.

Mizanur Rahman, Ruben Recabarren, Bogdan Carbunar, Dongwon Lee

The profitability of fraud in online systems such as app markets and social networks marks the failure of existing defense mechanisms. In this paper, we propose FraudSys, a real-time fraud preemption approach that imposes Bitcoin-inspired computational puzzles on the devices that post online system activities, such as reviews and likes. We introduce and leverage several novel concepts that include (i) stateless, verifiable computational puzzles, that impose minimal performance overhead, but enable the efficient verification of their authenticity, (ii) a real-time, graph-based solution to assign fraud scores to user activities, and (iii) mechanisms to dynamically adjust puzzle difficulty levels based on fraud scores and the computational capabilities of devices. FraudSys does not alter the experience of users in online systems, but delays fraudulent actions and consumes significant computational resources of the fraudsters. Using real datasets from Google Play and Facebook, we demonstrate the feasibility of FraudSys by showing that the devices of honest users are minimally impacted, while fraudster controlled devices receive daily computational penalties of up to 3,079 hours. In addition, we show that with FraudSys, fraud does not pay off, as a user equipped with mining hardware (e.g., AntMiner S7) will earn less than half through fraud than from honest Bitcoin mining.

Obryan Poyser

Currently, there is no consensus on the real properties of Bitcoin. The discussion comprises its use as a speculative or safe haven assets, while other authors argue that the augmented attractiveness could end accomplishing money's functions that economic theory demands. This paper explores the association between Bitcoin's market price and a set of internal and external factors using Bayesian Structural Time Series Approach. I aim to contribute to the discussion by differentiating among several attractiveness sources and employing a method that provides a more flexible analytic framework that decompose each of the components of the time series, apply variable selection, include information on previous studies, and dynamically examine the behavior of the explanatory variables, all in a transparent and tractable setting. The results show that the Bitcoin price is negatively associated with a neutral investor's sentiment, gold's price and Yuan to USD exchange rate, while positively related to stock market index, USD to Euro exchange rate and variated signs among the different countries' search trends. Hence, I find that Bitcoin has mixed properties since still seems to act as a speculative, safe haven and a potential a capital flights instrument.

Obryan Poyser

Currently, there is no consensus on the real properties of Bitcoin. The\ndiscussion comprises its use as a speculative or safe haven assets, while other\nauthors argue that the augmented attractiveness could end accomplishing money's\nfunctions that economic theory demands. This paper explores the association\nbetween Bitcoin's market price and a set of internal and external factors using\nBayesian Structural Time Series Approach. I aim to contribute to the discussion\nby differentiating among several attractiveness sources and employing a method\nthat provides a more flexible analytic framework that decompose each of the\ncomponents of the time series, apply variable selection, include information on\nprevious studies, and dynamically examine the behavior of the explanatory\nvariables, all in a transparent and tractable setting. The results show that\nthe Bitcoin price is negatively associated with a neutral investor's sentiment,\ngold's price and Yuan to USD exchange rate, while positively related to stock\nmarket index, USD to Euro exchange rate and variated signs among the different\ncountries' search trends. Hence, I find that Bitcoin has mixed properties since\nstill seems to act as a speculative, safe haven and a potential a capital\nflights instrument.\n

Giulia Fanti, Shaileshh Bojja Venkatakrishnan, Surya Bakshi, Bradley Denby · 7 authors

Bitcoin and other cryptocurrencies have surged in popularity over the last decade. Although Bitcoin does not claim to provide anonymity for its users, it enjoys a public perception of being a privacy preserving financial system. In reality, cryptocurrencies publish users' entire transaction histories in plaintext, albeit under a pseudonym; this is required for transaction validation. Therefore, if a user's pseudonym can be linked to their human identity, the privacy fallout can be significant. Recently, researchers have demonstrated deanonymization attacks that exploit weaknesses in the Bitcoin network's peer-to-peer (P2P) networking protocols. In particular, the P2P network currently forwards content in a structured way that allows observers to deanonymize users. In this work, we redesign the P2P network from first principles with the goal of providing strong, provable anonymity guarantees. We propose a simple networking policy called Dandelion which provides quasi-optimal, network-wide anonymity, with minimal cost to the network's utility. We also discuss practical implementation challenges and propose heuristic solutions.