Blockchain Papers

Benjamin Fabian, Tatiana Ermakova, Jonas Krah, Ephan Lando · 5 authors

No abstract is available for this record.

Ilaria Bertazzi, Sylvie Huet, Guillaume Deffuant, Floriana Gargiulo

Bitcoin-otc is a peer to peer (over-the-counter) marketplace for trading with bit- coin crypto-currency. To mitigate the risks of the p2p unsupervised exchanges, the establishment of a reliable reputation systems is needed: for this reason, a web of trust is implemented on the website. The availability of all the historic of the users interaction data makes this dataset a unique playground for studying reputation dynamics through others evaluations. We analyze the structure and the dynamics of this web of trust with a multilayer network approach distin- guishing the rewarding and the punitive behaviors. We show that the rewarding and the punitive behavior have similar emergent topological properties (apart from the clustering coefficient being higher for the rewarding layer) and that the resultant reputation originates from the complex interaction of the more regular behaviors on the layers. We show which are the behaviors that correlate (i.e. the rewarding activity) or not (i.e. the punitive activity) with reputation. We show that the network activity presents bursty behaviors on both the layers and that the inequality reaches a steady value (higher for the rewarding layer) with the network evolution. Finally, we characterize the reputation trajectories and we identify prototypical behaviors associated to three classes of users: trustworthy, untrusted and controversial.

JT Hamrick, Farhang Rouhi, Arghya Mukherjee, Amir Feder · 7 authors

The surge of interest in cryptocurrencies has been accompanied by a proliferation of fraud. This paper examines a pervasive tactic long known to financial markets: pump and dump schemes. While the fundamentals of the ruse have not changed in the last century, the recent explosion of nearly 2, 000 cryptocurrencies in a largely unregulated environment has greatly expanded the scope for abuse. The paper first quantifies the scope of cryptocurrency pump and dump on Discord and Telegram, two widely popular group messaging platforms with 130 million users and 200 million users respectively. Both platforms can handle large groups with thousands of users, and they are the most popular outlets for pump and dump schemes involving cryptocurrencies. We identified 3, 767 different pump signals advertised on Telegram and another 1, 051 different pump signals advertised on Discord during a six-month period in 2018. The schemes promoted more than 300 cryptocurrencies. These comprehensive data provide the first measure of the scope of pump and dump schemes across cryptocurrencies and suggest that this phenomenon is widespread and often quite profitable. This should raise concerns among regulators. We then examine which factors that affect the "success" of the pump, as measured by the percentage increase in price near the pump signal. We find that the coin's rank (market capitalization/volume) is the most important factor in determining the profitability of the pump: pumping obscure coins (with low volume) is much more profitable than pumping the dominant coins in the ecosystem.

Stephen Chan, Jeffrey Chu, Yuanyuan Zhang, Saralees Nadarajah

In financial trading, cryptocurrencies like bitcoin use decentralization, traceability, and anonymity features to perform transactional activities. These digital currencies, using the emerging blockchain technologies, are forming the basis of the largest unregulated markets in the world. This creates various regulatory challenges, including the illicit purchase of drugs and weapons, money laundering, and funding terrorist activities. This chapter analyzes various legal and ethical implications, their effects, and various solutions to overcome the inherent issues that are currently faced by the policymakers and regulators. The authors present the result of an analysis of 30 recently published peer-reviewed scientific publications and suggest various mechanisms that can help in the detection and prevention of illegal activities that currently account for a substantial proportion of cryptocurrency trading. They suggest methods and applications that can also be used to identify the dark marketplaces in the future.

Usman W. Chohan

This discussion paper examines the recent history of cryptocurrency thefts and exchanges shutdowns, focusing specifically on the largest cryptoinstrument: Bitcoin. The examination of thefts and shutdowns are intended to draw academic attention to the accountability deficits that pervade the cryptocurrency space, and the findings of the paper suggest that a much more robust accountability, transparency, and oversight architecture must be put in place vis-a-vis cryptocurrencies.

Weili Chen, Zibin Zheng, Jiahui Cui, Edith C.‐H. Ngai · 6 authors

Blockchain technology becomes increasingly popular. It also attracts scams, for example, Ponzi scheme, a classic fraud, has been found making a notable amount of money on Blockchain, which has a very negative impact. To help dealing with this issue, this paper proposes an approach to detect Ponzi schemes on blockchain by using data mining and machine learning methods. By verifying smart contracts on Ethereum, we first extract features from user accounts and operation codes of the smart contracts and then build a classification model to detect latent Ponzi schemes implemented as smart contracts. The experimental results show that the proposed approach can achieve high accuracy for practical use. More importantly, the approach can be used to detect Ponzi schemes even at the moment of its creation. By using the proposed approach, we estimate that there are more than 400 Ponzi schemes running on Ethereum. Based on these results, we propose to build a uniform platform to evaluate and monitor every created smart contract for early warning of scams.

Mikkel Alexander Harlev, Haohua Sun Yin, Klaus Christian Langenheldt, Raghava Rao Mukkamala · 5 authors

Bitcoin is a cryptocurrency whose transactions are recorded on a distributed, openly accessible ledger. On the Bitcoin Blockchain, an entity’s real-world identity is hidden behind a pseudonym, a so-called address. Therefore, Bitcoin is widely assumed to provide a high degree of anonymity, which is a driver for its frequent use for illicit activities. This paper presents a novel approach for reducing the anonymity of the Bitcoin Blockchain by using Supervised Machine Learning to predict the type of yet-unidentified entities. We utilised a sample of 434 entities (with ~ 200 million transactions), whose identity and type had been revealed, as training set data and built classifiers differentiating among 10 categories. Our main finding is that we can indeed predict the type of a yet-unidentified entity. Using the Gradient Boosting algorithm, we achieve an accuracy of 77% and F1-score of ~ 0.75. We discuss our novel approach of Supervised Machine Learning for uncovering Bitcoin Blockchain anonymity and its potential applications to forensics and financial compliance and its societal implications, outline study limitations and propose future research directions.

Sean Foley, Jonathan R. Karlsen, Tālis J. Putniņš

Cryptocurrencies are among the largest unregulated markets in the world. We find that approximately one-quarter of bitcoin users are involved in illegal activity. We estimate that around $76 billion of illegal activity per year involve bitcoin (46% of bitcoin transactions), which is close to the scale of the U.S. and European markets for illegal drugs. The illegal share of bitcoin activity declines with mainstream interest in bitcoin and with the emergence of more opaque cryptocurrencies. The techniques developed in this paper have applications in cryptocurrency surveillance. Our findings suggest that cryptocurrencies are transforming the black markets by enabling “black e-commerce.” Received June 1, 2017; editorial decision December 8, 2018 by Editor Andrew Karolyi. Authors have furnished an Internet Appendix, which is available on the Oxford University Press Web site next to the link to the final published paper online.

Jeffrey Quesnelle

Zcash is a fork of Bitcoin with optional anonymity features. While transparent transactions are fully linkable, shielded transactions use zero-knowledge proofs to obscure the parties and amounts of the transactions. First, we observe various metrics regarding the usage of shielded addresses. Moreover, we show that most coins sent to shielded addresses are later sent back to transparent addresses. We then search for round-trip transactions, where the same, or nearly the same number of coins are sent from a transparent address, to a shielded address, and back again to a transparent address. We argue that such behavior exhibits high linkability, especially when they occur nearby temporally. Using this heuristic our analysis matched 31.5% of all coins sent to shielded addresses.

Haohua Sun Yin, Ravi Vatrapu

Bitcoin, a peer-to-peer payment system and digital currency, is often involved in illicit activities such as scamming, ransomware attacks, illegal goods trading, and thievery. At the time of writing, the Bitcoin ecosystem has not yet been mapped and as such there is no estimate of the share of illicit activities. This paper provides the first estimation of the portion of cyber-criminal entities in the Bitcoin ecosystem. Our dataset consists of 854 observations categorised into 12 classes (out of which 5 are cybercrime-related) and a total of 100,000 uncategorised observations. The dataset was obtained from the data provider who applied three types of clustering of Bitcoin transactions to categorise entities: co-spend, intelligence-based, and behaviour-based. Thirteen supervised learning classifiers were then tested, of which four prevailed with a cross-validation accuracy of 77.38%, 76.47%, 78.46%, 80.76% respectively. From the top four classifiers, Bagging and Gradient Boosting classifiers were selected based on their weighted average and per class precision on the cybercrime-related categories. Both models were used to classify 100,000 uncategorised entities, showing that the share of cybercrime-related is 29.81% according to Bagging, and 10.95% according to Gradient Boosting with number of entities as the metric. With regard to the number of addresses and current coins held by this type of entities, the results are: 5.79% and 10.02% according to Bagging; and 3.16% and 1.45% according to Gradient Boosting.

Thomas F Heston

Blockchain technology can be utilized to improve gun control without changing existing laws. Firearm related mortality is at epidemic levels in the United States and not only has a significant impact upon public health, it also creates a large financial burden. Suicide is the most common way guns kill. Through better gun tracking and improved screening of high risk individuals, this technological advance in distributed ledger technology will improve background checks on individuals and tracing of guns used in crimes.

Qing Zhou, Qingqing Zhang, Qi Zhang

In recent years, with the development of the Internet, network currency has gradually emerged. Bitcoin which is produced on the basis of complex algorithms has developed rapidly and attracted wide attention in academia. This paper explores the influence factors of bitcoin market transaction by analyzing the interaction between agents in bitcoin market transaction. Applying complex adaptive system modeling method based on multi-agent, this paper establishes an agent-based bitcoin market transaction model, and designs behavioral rules as well as transaction mechanism in detail for each agent in the process of market transaction. Then, we carry out a simulation on the Starlogo simulation platform and analyze the impact of the change in trader’s number on market transaction.

Greg Wolfond

IntroductionIdentity verification and authentication has long been a critical component in service delivery for both the private and public sectors, but changing citizen demands in the digital age have stressed the need for new approaches to verify that an individual is who they say they are – with surety.

Natalija Kostrikova

Decentralization, on one hand, brings more transparency and trust to the parties involved in transactions,but on the other hand, it narrows possibilities for central control. Distributed Ledger Technology(DLT) is a recent decentralized innovation in the field of information and communication technology(ICT) that acts as self-sustainable ledger for documenting transactions self-protected against counterfeitingand hacker attacks. The aim of the current research paper is to reveal opportunities and barriersfor utilization of distributed ledgers in the context of EU digital single market strategy. The main tasksare (1) to analyze functionality dynamics of existing distributed ledgers, (2) to analyze utilization areasof distributed ledgers, (3) to analyze digital trends related to utilization of distributed ledgers within theEU. The current research paper utilizes methods of content analysis, grounded theory, descriptive statistics,correlation analysis and regression analysis. The research has revealed that half of EU DigitalSingle Market priorities can be facilitated through distributed ledgers.DOI: http://dx.doi.org/10.5755/j01.eis.0.11.18134

Amir Feder, Neil Gandal, JT Hamrick, Tyler Moore

We investigate how distributed denial-of-service (DDoS) attacks and other disruptions affect the Bitcoin ecosystem. In particular, we investigate the impact of shocks on trading activity at the leading Mt. Gox exchange between April 2011 and November 2013. We find that following DDoS attacks on Mt. Gox, the number of large trades on the exchange fell sharply. In particular, the distribution of the daily trading volume becomes less skewed (fewer big trades) and had smaller kurtosis on days following DDoS attacks. The results are robust to alternative specifications, as well as to restricting the data to activity prior to March 2013, i.e., the period before the first large appreciation in the price of and attention paid to Bitcoin.

Daniel Broby, Greig Paul

Blockchain is the technology at the core of what could become the "Fintech" transformation of capital markets. It can potentially facilitate cheaper, more efficient and secure operations. The mechanism behind it is introduced in this paper, as are its uses and suggested areas for future academic research. The paper critically reviews the promise that blockchain and distributed ledgers will speed up financial settlements and transactions. In it we recommend financial institutions evaluate the adoption of blockchain and/or adapt their existing legacy systems to allow for digital clearing over the internet.

Malte Möser, Kyle Soska, Ethan Heilman, Kevin Lee · 11 authors

Abstract Monero is a privacy-centric cryptocurrency that allows users to obscure their transactions by including chaff coins, called “mixins,” along with the actual coins they spend. In this paper, we empirically evaluate two weaknesses in Monero’s mixin sampling strategy. First, about 62% of transaction inputs with one or more mixins are vulnerable to “chain-reaction” analysis - that is, the real input can be deduced by elimination. Second, Monero mixins are sampled in such a way that they can be easily distinguished from the real coins by their age distribution; in short, the real input is usually the “newest” input. We estimate that this heuristic can be used to guess the real input with 80% accuracy over all transactions with 1 or more mixins. Next, we turn to the Monero ecosystem and study the importance of mining pools and the former anonymous marketplace AlphaBay on the transaction volume. We find that after removing mining pool activity, there remains a large amount of potentially privacy-sensitive transactions that are affected by these weaknesses. We propose and evaluate two countermeasures that can improve the privacy of future transactions.

Ruben Recabarren, Bogdan Cărbunar

Abstract Stratum, the de-facto mining communication protocol used by blockchain based cryptocurrency systems, enables miners to reliably and efficiently fetch jobs from mining pool servers. In this paper we exploit Stratum’s lack of encryption to develop passive and active attacks on Bitcoin’s mining protocol, with important implications on the privacy, security and even safety of mining equipment owners. We introduce StraTap and ISP Log attacks, that infer miner earnings if given access to miner communications, or even their logs. We develop BiteCoin, an active attack that hijacks shares submitted by miners, and their associated payouts. We build BiteCoin on WireGhost, a tool we developed to hijack and surreptitiously maintain Stratum connections. Our attacks reveal that securing Stratum through pervasive encryption is not only undesirable (due to large overheads), but also ineffective: an adversary can predict miner earnings even when given access to only packet timestamps. Instead, we devise Bedrock, a minimalistic Stratum extension that protects the privacy and security of mining participants. We introduce and leverage the mining cookie concept, a secret that each miner shares with the pool and includes in its puzzle computations, and that prevents attackers from reconstructing or hijacking the puzzles. We have implemented our attacks and collected 138MB of Stratum protocol traffic from mining equipment in the US and Venezuela. We show that Bedrock is resilient to active attacks even when an adversary breaks the crypto constructs it uses. Bedrock imposes a daily overhead of 12.03s on a single pool server that handles mining traffic from 16,000 miners.

Massimo Bartoletti, Salvatore Carta, Tiziana Cimoli, Roberto Saia

Ponzi schemes are financial frauds which lure users under the promise of high profits. Actually, users are repaid only with the investments of new users joining the scheme: consequently, a Ponzi scheme implodes soon after users stop joining it. Originated in the offline world 150 years ago, Ponzi schemes have since then migrated to the digital world, approaching first the Web, and more recently hanging over cryptocurrencies like Bitcoin. Smart contract platforms like Ethereum have provided a new opportunity for scammers, who have now the possibility of creating "trustworthy" frauds that still make users lose money, but at least are guaranteed to execute "correctly". We present a comprehensive survey of Ponzi schemes on Ethereum, analysing their behaviour and their impact from various viewpoints.

Xiang Li

In December 2013 the People's Bank of China announced the restriction of Bitcoin from being involved in any services offered by financial institutions in China, fearing that the speculative risks inherent in Bitcoin is too new for Chinese investors and may endanger the national financial system. This article reviews the Bitcoin's evolvement both as currency and as investment asset around the world. Also, the regulatory treatment for Bitcoin in America is discussed. Then I used detrended ratios to compare the volatility of Bitcoin market and China's stock market, concluding that the risks inherent in Bitcoin are not unacceptable for Chinese investors. Moreover, I searched into the relationship between Bitcoin return and some fundamental economic variables, finding that Bitcoin doesn't have enough correlation with the national economic system to depress investors further during an economic downturn and that Bitcoin actually has excellent diversification benefit as portfolio component.

Julie A. Maupin

No abstract is available for this record.

Nir Kshetri, Jeffrey Voas

Incidents of ransomware have been escalating, which could be fueled in part by the diffusion of crypto-currencies. Without crypto-currencies, the creation of ransomware is less desirable because other forms of payment are more traceable. The risk from ransomware can be considerable, and some companies hold supplies of bitcoins in reserve to pay extortionists if necessary. Here, the authors examine crypto-currencies’ effects on ransomware and look at what might influence a victim’s decision to pay.

Luca Brunoni, Olivier Beaudet-Labrecque

The purpose of this paper is to provide a brief explanation regarding the authors’ current research in the field of the possible uses of smart contracts in cybercrime, focusing in particular on how the technology could provide a substitute for trust both in client-criminal transactions and in transactions taking place within criminal organizations. The authors share the conviction put forward by Alharby and Moorsel [1] in their 2017 analysis of blockchainbased smart contracts that there is a ”lack of studies on criminal activities in smart contracts”: while quality research does exist, including a paper by Juels et al. [2] detailing three types of such activities that can be facilitated by the technology, it is evident that the subject deserves a more widespread attention. Quality research, in fact, could play an important role in aiding authorities and regulators to understand the issue and react accordingly.

Deborah Farringer

Part I of this Article describes how the healthcare industry has arrived in this place of vulnerability, including (1) the history of the movement toward EHRs through HIPAA, (2) HIPAA’s meaningful use regulations and the background of current ransomware attacks, and (3) the distinctions between these attacks and other security breaches that have plagued large insurers and health systems within the last five years. Next, Part II will examine current industry culture when it comes to cybersecurity and review current legal and business approaches to address this growing threat. Then, Part III will argue that, while the current laws—including HIPAA and HITECH—are a good start, they do not go far enough to curb the current ransomware attacks and thus, should be amended. It will further argue that such amendments cannot be the only solution. Rather, the healthcare industry has to spur its own movement toward better and tighter security over its healthcare technology. Lastly, this Article will conclude with some suggestions and recommendations for how industry and government regulators can work together to assure that hospitals and health systems are not faced with the dilemma of having to choose between patient safety and the payment of a bitcoin ransom.