Doxing is the intentional public release onto the Internet of personal information about an individual by a third party, often with the intent to humiliate, threaten, intimidate, or punish the identified individual. In this paper I present a conceptual analysis of the practice of doxing and how it differs from other forms of privacy violation. I distinguish between three types of doxing: deanonymizing doxing, where personal information establishing the identity of a formerly anonymous individual is released; targeting doxing, that discloses personal information that reveals specific details of an individual’s circumstances that are usually private, obscure, or obfuscated; and delegitimizing doxing, which reveals intimate personal information that damages the credibility of that individual. I also describe how doxing differs from blackmail and defamation. I argue that doxing may be justified in cases where it reveals wrongdoing (such as deception), but only if the information released is necessary to reveal that such wrongdoing has occurred and if it is in the public interest to reveal such wrongdoing. Revealing additional information, such as that which allows an individual to be targeted for harassment and intimidation, is unjustified. I illustrate my discussion with the examples of the alleged identification of the creator of Bitcoin, Satoshi Nakamoto, by Newsweek magazine, the identification of the notorious Reddit user Violentacrez by the blog Gawker, and the harassment of game developer Zoe Quinn in the ‘GamerGate’ Internet campaign.
Permisionless decentralized ledgers ("blockchains") such as the one underlying the cryptocurrency Bitcoin allow anonymous participants to maintain the ledger, while avoiding control or "censorship" by any single entity. In contrast, permissioned decentralized ledgers exploit real-world trust and accountability, allowing only explicitly authorized parties to maintain the ledger. Permissioned ledgers support more flexible governance and a wider choice of consensus mechanisms. Both kinds of decentralized ledgers may be susceptible to manipulation by participants who favor some transactions over others. The real-world accountability underlying permissioned ledgers provides an opportunity to impose fairness constraints that can be enforced by penalizing violators after-the- fact. To date, however, this opportunity has not been fully exploited, unnecessarily leaving participants latitude to manipulate outcomes undetectably. This paper draws attention to this issue, and proposes design principles to make such manipulation more difficult, as well as specific mechanisms to make it easier to detect when violations occur.
In this paper, we reveal the attenuation mechanism of anchor of the commodity money from the perspective of logistics warehousing costs, and propose a novel Decayed Commodity Money (DCM) for the store of value across time and space. Considering the logistics cost of commodity warehousing by the third financial institution such as London Metal Exchange, we can award the difference between the original and the residual value of the anchor to the financial institution. This type of currency has the characteristic of self-decaying value over time. Therefore DCM has the advantages of both the commodity money which has the function of preserving wealth and credit currency without the logistics cost. In addition, DCM can also avoid the defects that precious metal money is hoarded by market and credit currency often leads to excessive liquidity. DCM is also different from virtual currency, such as bitcoin, which does not have a corresponding commodity anchor. As a conclusion, DCM can provide a new way of storing wealth for nations, corporations and individuals effectively.
Luke Anderson, Ralph Holz, Alexander Ponomarev, Paul Rimba · 5 authors
Half a decade after Bitcoin became the first widely used cryptocurrency, blockchains are receiving considerable interest from industry and the research community. Modern blockchains feature services such as name registration and smart contracts. Some employ new forms of consensus, such as proof-of-stake instead of proof-of-work. However, these blockchains are so far relatively poorly investigated, despite the fact that they move considerable assets. In this paper, we explore three representative, modern blockchains---Ethereum, Namecoin, and Peercoin. Our focus is on the features that set them apart from the pure currency use case of Bitcoin. We investigate the blockchains' activity in terms of transactions and usage patterns, identifying some curiosities in the process. For Ethereum, we are mostly interested in the smart contract functionality it offers. We also carry out a brief analysis of issues that are introduced by negligent design of smart contracts. In the case of Namecoin, our focus is how the name registration is used and has developed over time. For Peercoin, we are interested in the use of proof-of-stake, as this consensus algorithm is poorly understood yet used to move considerable value. Finally, we relate the above to the fundamental characteristics of the underlying peer-to-peer networks. We present a crawler for Ethereum and give statistics on the network size. For Peercoin and Namecoin, we identify the relatively small size of the networks and the weak bootstrapping process.
Problem Explaining: Nowadays the financial system has been affected dramatically by the development in the era of information and communication technology. One of these phenomena, is Crypto Currency Bitcoin is the most famous among them. In the reviews of Crypto Currency and Bitcoin, we can pay special attention to the public opinion, because it can have a significant impact on the future of money. Purpose: The aim of this study is to identify the preferences of people using Bitcoin as a novel product introduced by human into the financial system. For this purpose, the important factors in choosing Bitcoin have been checked. In terms of practical purpose and collecting descriptive information, this research is survey - correlation. Design/methodology/approach: In this study the important factors in the selection of Bitcoin through the investigation of the opinions of experts and consumers, offering model by patterning the technology acceptance and innovation publication models, interviewing with experts using a questionnaire and the analysis of the model through PLS partial least square method using Version 2 SMARTPLS software. Findings: The results show that the variables of infrastructure, structural, individualistic and cultural factors through perceived value have a significant and positive impact on the intention of using people. Meanwhile cultural factor has had the largest share, but innovative, political and environmental factors haven’t had any significant effect. The results of this research indicate the effective factors in the users’ tendency to use Bitcoin. Originality/value: The main question in this research is that: Is there any significant relationship between the values perceived by the consumer from Bitcoin and the intention of using it?
Crypto-currencies like Bitcoins are relatively recent phenomena on the online Internet landscape and an emerging force in the financial sector. While not conforming to traditional institutional practices, they are gaining increasing acceptance as viable commercial currencies. In this conceptual paper we discuss the potential impact of digital currency technology on the Australian economy, including the (i) payments sector, (ii) retail sector, and (iii) banking sector; and explore potential ways in which Australia can take advantage of digital currency technology to establish itself as a market leader in this field. The emergence of this new and potentially disruptive technology provides both opportunities as well as risks. In order to support innovation and the needs of the growing Australian digital currency industry it is important to define digital currencies and examine the impact regulatory frameworks could have on the further adoption and diffusion of the technology.
Bitcoin is the most important and well known form of digital currency. It is not produced or backed by any single entity. Its production takes place in a decentralised manner and its value derives only from the fact that there is a growing community that attributes value to it and chooses to transact using this innovative means of payment. However, its importance is increasing, especially in the field of e-commerce. The main aim of this article is to examine the consumer’s right of withdrawal, as it is regulated in the Consumer Rights Directive (Directive 2011/83/EU), in case of payments with bitcoins. More specifically, it is examined whether a consumer’s payment with bitcoins can be a hindrance to the consumer’s protection, with respect to the withdrawal right provided by the aforementioned Directive in cases of distance and off-premises contracts. Furthermore, the consequences of the exercise of the withdrawal right are examined, particularly with regards to reimbursement. The main concerns derive from the bitcoin’s disputed legal nature and its high value volatility. Keywords Bitcoin Consumer Rights Directive consumer’s right of withdrawal e-commerce digital currency
Dominic Wörner, Thomas von Bomhard, Yan-Peter Schreier, Dominik Bilgeri
The Bitcoin ecosystem has grown tremendously in recent years.While the main sectors of growth and venture capital funding have been infrastructure for the Bitcoin ecosystem itself as well as financial services, there is also a more recent evolution in sectors beyond financial services.We classify the venture-capital backed start up ecosystem accordingly and present its evolution over time.Thereby, we identify interesting sectors, i.e. digital assets, marketplaces, and notary services.Each sector is further subdivided, and six representative venture-backed start-up companies are presented in comprehensive case studies.We extract the core innovations and Bitcoin features on which these are based.Finally, we critically discuss their disruptive potential.
Ikuo Magaki, Moein Khazraee, Luis Vega Gutierrez, Michael Taylor
GPU and FPGA-based clouds have already demonstrated the promise of accelerating computing-intensive workloads with greatly improved power and performance. In this paper, we examine the design of ASIC Clouds, which are purpose-built datacenters comprised of large arrays of ASIC accelerators, whose purpose is to optimize the total cost of ownership (TCO) of large, high-volume chronic computations, which are becoming increasingly common as more and more services are built around the Cloud model. On the surface, the creation of ASIC clouds may seem highlyimprobable due to high NREs and the inflexibility of ASICs. Surprisingly, however, large-scale ASIC Clouds have already been deployed by a large number of commercial entities, to implement the distributed Bitcoin cryptocurrency system. We begin with a case study of Bitcoin mining ASIC Clouds, which are perhaps the largest ASIC Clouds to date. From there, we design three more ASIC Clouds, including a YouTube-style video transcoding ASIC Cloud, a Litecoin ASIC Cloud, and a Convolutional Neural Network ASIC Cloud and show 2-3 orders of magnitude better TCO versus CPU and GPU. Among our contributions, we present a methodology that given an accelerator design, derives Pareto-optimal ASIC Cloud Servers, by extracting data from place-and-routed circuits and computational fluid dynamic simulations, and then employing clever but brute-force search to find the best jointly-optimized ASIC, DRAM subsystem, motherboard, power delivery system, cooling system, operating voltage, and case design. Moreover, we show how data center parameters determine which of the many Pareto-optimal points is TCO-optimal. Finally we examine when it makes sense to build an ASIC Cloud, and examine the impact of ASIC NRE.
Dan McGinn, David Birch, David Akroyd, Miguel Molina-Solana · 6 authors
This work presents a systemic top-down visualization of Bitcoin transaction activity to explore dynamically generated patterns of algorithmic behavior. Bitcoin dominates the cryptocurrency markets and presents researchers with a rich source of real-time transactional data. The pseudonymous yet public nature of the data presents opportunities for the discovery of human and algorithmic behavioral patterns of interest to many parties such as financial regulators, protocol designers, and security analysts. However, retaining visual fidelity to the underlying data to retain a fuller understanding of activity within the network remains challenging, particularly in real time. We expose an effective force-directed graph visualization employed in our large-scale data observation facility to accelerate this data exploration and derive useful insight among domain experts and the general public alike. The high-fidelity visualizations demonstrated in this article allowed for collaborative discovery of unexpected high frequency transaction patterns, including automated laundering operations, and the evolution of multiple distinct algorithmic denial of service attacks on the Bitcoin network.
Tendermint is a new protocol for ordering events in a distributed network under adversarial conditions. More commonly known as consensus or atomic broadcast, the problem has attracted significant attention recently due to the widespread success of digital currencies, such as Bitcoin and Ethereum, which successfully solve the problem in public settings without a central authority. Tendermint modernizes classic academic work on the subject to provide a secure consensus protocol with accountability guarantees, as well as an interface for building arbitrary applications above the consensus. Tendermint is high performance, achieving thousands of transactions per second on dozens of nodes distributed around the globe, with latencies of about one second, and performance degrading moderately in the face of adversarial attacks.
We revisit the fundamental question of Bitcoin's security against double spending attacks. While previous work has bounded the probability that a transaction is reversed, we show that no such guarantee can be effectively given if the attacker can choose when to launch the attack. Other approaches that bound the cost of an attack have erred in considering only limited attack scenarios, and in fact it is easy to show that attacks may not cost the attacker at all. We therefore provide a different interpretation of the results presented in previous papers and correct them in several ways. We provide different notions of the security of transactions that provide guarantees to different classes of defenders: merchants who regularly receive payments, miners, and recipients of large one-time payments. We additionally consider an attack that can be launched against lightweight clients, and show that these are less secure than their full node counterparts and provide the right strategy for defenders in this case as well. Our results, overall, improve the understanding of Bitcoin's security guarantees and provide correct bounds for those wishing to safely accept transactions.
The American corporate graveyard is littered with prior darlings of Wall Street and pillars of the New York Stock Exchange, such as Kodak and Polaroid (both photography pioneers). More recently, other businesses and entire industries that were once household names have similarly experienced plummeting demand: pay telephone manufacturers; travel agencies; wrist watch manufacturers; print news media such as newspapers and magazines; and many traditional brick and mortar retailers (replaced by Amazon). The common characteristic is that all of these businesses have become completely or substantially obsolete due to digitized technology.Now, the equivalent disruptive technological revolution in financial services is underway. During recent years, rapid technological advances have resulted in a sea change to the way most of the world conducts and regulates financial services. While the implications are vast and the ultimate ramifications are largely unknown at this time, this article: examines the brief but important history of virtual currencies in general; considers the impact of Bitcoin in particular; and explores the promise for widespread application of Bitcoin’s underlying blockchain technological platform to the financial services industry.This brief article proceeds in five parts, as follows. First, there is a discussion of disruptive changes taking place in financial services. Second, the article briefly explores virtual currencies and the genesis of Bitcoin. Third, there is an explanation of blockchain technology - what it is and why it is important. Fourth, the article discusses recent developments that provide a validation of blockchain application to financial services markets. Finally, there is a brief review of regulatory challenges to the adoption of this new technology. A purpose of this article is to enhance the reader’s understanding of the promises and challenges faced by financial service providers due to these rapid advances in technology.
In Mobile Crowd Sensing (MCS), the power of the crowd, jointly with the sensing capabilities of the smartphones they wear, provides a new paradigm for data sensing. Scenarios involving user behavior or those that rely on user mobility are examples where standard sensor networks may not be suitable, and MCS provides an interesting solution. However, including human participation in sensing tasks presents numerous and unique research challenges. In this paper, we analyze three of the most important: user participation, data sensing quality and user anonymity. We tackle the three as a whole, since all of them are strongly correlated. As a result, we present PaySense, a general framework that incentivizes user participation and provides a mechanism to validate the quality of collected data based on the users' reputation. All such features are performed in a privacy-preserving way by using the Bitcoin cryptocurrency. Rather than a theoretical one, our framework has been implemented, and it is ready to be deployed and complement any existing MCS system.
Bitcoin is without a doubt the most successful cryptocurrency in circulation today, making it an extremely valuable target for attackers. Indeed, many studies have highlighted ways to compromise one or several Bitcoin nodes. In this paper, we take a different perspective and study the effect of large-scale network-level attacks such as the ones that may be launched by Autonomous Systems (ASes).
We show that attacks that are commonly believed to be hard, such as isolating 50% of the mining power, are actually within the reach of anyone with access to a BGP-enabled network and hijacking less than 900 prefixes. Once on path, AS-level adversaries can then partition the Bitcoin network or delay block propagation significantly. The key factors that enable these attacks are the extreme centralization of Bitcoin, both from a routing and a mining perspective, along with the fact that Bitcoin messages are sent unencrypted, without integrity guarantees.
We demonstrate the feasibility of large-scale attacks in practice against the deployed Bitcoin software and quantify their disruptive network-wide impact. The potential damage to Bitcoin is severe. By isolating a part of the network or delaying the propagation of blocks, network-level attackers can cause a significant amount of mining power to be wasted, leading to revenue losses and enabling a wide range of attacks such as double spending. We provide several suggestions on approaches to mitigate such attacks employing both short-term and long-term measures.
As the most successful cryptocurrency to date, Bitcoin constitutes a target of choice for attackers. While many attack vectors have already been uncovered, one important vector has been left out though: attacking the currency via the Internet routing infrastructure itself. Indeed, by manipulating routing advertisements (BGP hijacks) or by naturally intercepting traffic, Autonomous Systems (ASes) can intercept and manipulate a large fraction of Bitcoin traffic. This paper presents the first taxonomy of routing attacks and their impact on Bitcoin, considering both small-scale attacks, targeting individual nodes, and large-scale attacks, targeting the network as a whole. While challenging, we show that two key properties make routing attacks practical: (i) the efficiency of routing manipulation; and (ii) the significant centralization of Bitcoin in terms of mining and routing. Specifically, we find that any network attacker can hijack few (<100) BGP prefixes to isolate ~50% of the mining power---even when considering that mining pools are heavily multi-homed. We also show that on-path network attackers can considerably slow down block propagation by interfering with few key Bitcoin messages. We demonstrate the feasibility of each attack against the deployed Bitcoin software. We also quantify their effectiveness on the current Bitcoin topology using data collected from a Bitcoin supernode combined with BGP routing data. The potential damage to Bitcoin is worrying. By isolating parts of the network or delaying block propagation, attackers can cause a significant amount of mining power to be wasted, leading to revenue losses and enabling a wide range of exploits such as double spending. To prevent such effects in practice, we provide both short and long-term countermeasures, some of which can be deployed immediately.
Address clustering tries to construct the one-to-many mapping from entities to addresses in the Bitcoin system. Simple heuristics based on the micro-structure of transactions have proved very effective in practice. In this paper we describe the primary reasons behind this effectiveness: address reuse, avoidable merging, super-clusters with high centrality, and the incremental growth of address clusters. We quantify their impact during Bitcoin's first seven years of existence.
Most popular blockchain solutions, like Bitcoin, rely on proof-of-work, guaranteeing that the output of the consensus is agreed upon with high probability. However, this probability depends on the delivery of messages and that the computational power of the system is sufficiently scattered among pools of nodes in the network so that no pool can mine more blocks faster than the crowd. New approaches, like Ethereum, generalise the proof-of-work approach by letting individuals deploy their own private blockchain with high transaction throughput. As companies are starting to deploy private chains, it has become crucial to better understand the guarantees blockchains offer in such a small and controlled environment. In this paper, we present the \emph{Blockchain Anomaly}, an execution that we experienced when building our private chain at NICTA/Data61. Even though this anomaly has never been acknowledged before, it may translate into dramatic consequences for the user of blockchains. Named after the infamous Paxos anomaly, this anomaly makes dependent transactions, like "Bob sends money to Carole after he received money from Alice" impossible. This anomaly relies on the fact that existing blockchains do not ensure consensus safety deterministically: there is no way for Bob to make sure that Alice actually sent him coins without Bob using an external mechanism, like converting these coins into a fiat currency that allows him to withdraw. We also explore smart contracts as a potential alternative to transactions in order to freeze coins, and show implementations of smart contract that can suffer from the Blockchain anomaly and others that may cope with it.
We examine a protocol $\pi_{\text{beacon}}$ that outputs unpredictable and publicly verifiable randomness, meaning that the output is unknown at the time that $\pi_{\text{beacon}}$ starts, yet everyone can verify that the output is close to uniform after $\pi_{\text{beacon}}$ terminates. We show that $\pi_{\text{beacon}}$ can be instantiated via Bitcoin under sensible assumptions; in particular we consider an adversary with an arbitrarily large initial budget who may not operate at a loss indefinitely. In case the adversary has an infinite budget, we provide an impossibility result that stems from the similarity between the Bitcoin model and Santha-Vazirani sources. We also give a hybrid protocol that combines trusted parties and a Bitcoin-based beacon.
Blockchain is essentially a set of protocols previously known as a “distributed ledger” system. An Economist article published in March 2016, describes it well: <em>Blockchain is… a database that is maintained not by a single actor, such as a bank, but collaboratively by a number of participants. Their respective computers regularly agree on how to update the database using a “consensus mechanism”, after which the modifications they have settled on are rendered unchangeable with the help of complex cryptography. Once information has been immortalised in this way, it can be used as proof of ownership.</em> The reason why this has become such a hot topic is that technologists and business people see, in these basic characteristics, immense potential for using blockchain beyond the financial services sector where it was conceived, in many different areas of the economy from energy to health, from transport to music and even as a form of digital democracy in society as a whole. The key characteristics that are attracting so much attention are the efficiencies to be derived from a network that is distributed and not centralised, combined with the permanence of the record or ledger at its heart that is cryptographically secured. This attracts those that see profound ideological implications in something that is an alternative to systems that are controlled from a single central point. For the music industry, some of these characterstics might mean that creators could, in theory, radically reduce the cost of unit transactions, thus potentially enabling content licensing for very small sums to be viable. Equally, the transparent record keeping inherent in the system has the potential to lead incrementally to the creation of a Global Repertoire Database (GRD), a kind of holy grail of the digital music industry. Some other functions that potentially could be performed on blockchain networks could relate to the establishment, validation and tracking of identities, so that individuals could be uniquely identified (e.g., as the performer on a recording). Equally good behaviour in, for example, transactions or in rights distribution speediness could contribute to developing an online reputation, which in turn could effect the sorts of terms that are made available for a particular individual or business. This paper takes a look at how bitcoin and blockchain captured the public imagination, some of the technology issues at the heart of blockchain and a key dispute that is taking the bitcoin community in different directions and has a bearing on any possible music applications. The paper explores the initially superficial ways in which blockchain represented an attractive technology and then captures some of the voices that have been generating so much deeper interest in the subject in relation to music. The paper concludes with an assessment of opportunities and obstacles.
Bitcoin was recently introduced as a peer-to-peer electronic currency in order to facilitate transactions outside the traditional financial system. The core of Bitcoin, the Blockchain, is the history of the transactions in the system maintained by all miners as a distributed shared register. New blocks in the Blockchain contain the last transactions in the system and are added by miners after a block mining process that consists in solving a resource consuming proof-of-work (cryptographic puzzle). The reward is a motivation for mining process but also could be an incentive for attacks such as selfish mining. In this paper we propose a solution for one of the major problems in Bitcoin : selfish mining or block-withholding attack. This attack is conducted by adversarial or selfish miners in order to either earn undue rewards or waste the computational power of honest miners. Contrary to recent solutions, our solution, ZeroBlock, prevents block-withholding using a technique free of timestamp that can be forged. Moreover, we show that our solution is compliant with nodes churn.
Irni Eliana Khairuddin, Corina Sas, Sarah Clinch, Nigel Davies
This paper presents an exploratory study focusing on user experience with Bitcoin technology. We describe interviews with 9 Bitcoin users and report findings related to users' motivations for buying and using bitcoins. Our initial findings capture three main motivations such as Bitcoin's predicted role in a monetary revolution, users' increased empowerment, and their perception of a real value of Bitcoin currency. We conclude with reflections on the value of these findings for HCI researchers.