Husam Al Jawaheri, Mashael Al Sabah, Yazan Boshmaf, Aiman Erbad
With the rapid increase of threats on the Internet, people are continuously seeking privacy and anonymity. Services such as Bitcoin and Tor were introduced to provide anonymity for online transactions and Web browsing. Due to its pseudonymity model, Bitcoin lacks retroactive operational security, which means historical pieces of information could be used to identify a certain user. We investigate the feasibility of deanonymizing users of Tor hidden services who rely on Bitcoin as a payment method by exploiting public information leaked from online social networks, the Blockchain, and onion websites. This, for example, allows an adversary to link a user with @alice Twitter address to a Tor hidden service with private.onion address by finding at least one past transaction in the Blockchain that involves their publicly declared Bitcoin addresses. To demonstrate the feasibility of this deanonymization attack, we carried out a real-world experiment simulating a passive, limited adversary. We crawled 1.5K hidden services and collected 88 unique Bitcoin addresses. We then crawled 5B tweets and 1M BitcoinTalk forum pages and collected 4.2K and 41K unique Bitcoin addresses, respectively. Each user address was associated with an online identity along with its public profile information. By analyzing the transactions in the Blockchain, we were able to link 125 unique users to 20 Tor hidden services, including sensitive ones, such as The Pirate Bay and Silk Road. We also analyzed two case studies in detail to demonstrate the implications of the resulting information leakage on user anonymity. In particular, we confirm that Bitcoin addresses should always be considered exploitable, as they can be used to deanonymize users retroactively. This is especially important for Tor hidden service users who actively seek and expect privacy and anonymity.
Rhys Bowden, Paul Keeler, A. E. Krzesinski, Peter Taylor
Bitcoin is a electronic payment system where payment transactions are verified and stored in a data structure called the blockchain. Bitcoin miners work individually to solve a computationally intensive problem, and with each solution a Bitcoin block is generated, resulting in a new arrival to the blockchain. The difficulty of the computational problem is updated every 2,016 blocks in order to control the rate at which blocks are generated. In the original Bitcoin paper, it was suggested that the blockchain arrivals occur according to a homogeneous Poisson process. Based on blockchain block arrival data and stochastic analysis of the block arrival process, we demonstrate that this is not the case. We present a refined mathematical model for block arrivals, focusing on both the block arrivals during a period of constant difficulty and how the difficulty level evolves over time.
Vehicular Ad Hoc Networks (VANETs) play a vital role in enabling smart transportation systems by facilitating communication between vehicles. However, existing vehicular announcement systems face two major challenges: preserving user privacy and motivating users to share reliable traffic information. In this paper, we propose CreditCoin, a privacy-presing blockchain-based incentive announcement network. The system utilizes an anonymous vehicular announcement aggregation protocol combined with blockchain technology to ensure secure, tamper-resistant, and decentralized communication. Users can broadcast traffic updates anonymously while earning incentives for participation, thereby improving network reliability. A Trace Manager enables conditional privacy by identifying malicious users without compromising honest participants. The proposed system is implemented using Python, Web3, and a simulated VANET environment. Experimental results demonstrate improved efficiency, reduced computation time, and enhanced data reliability compared to traditional approaches. This work contributes toward secure and incentive-driven communication in smart transportation systems. In this paper, we propose CreditCoin, a privacy-preserving blockchain-based incentive announcement network. The system utilizes an anonymous vehicular announcement aggregation protocol combined with blockchain technology to ensure secure, tamper-resistant, and decentralized communication. Users can broadcast traffic updates anonymously while earning incentives for participation, thereby improving network reliability. A Trace Manager enables conditional privacy by identifying malicious users without compromising honest participants. Keywords— VANET; Blockchain; Privacy Preservation; Incentive Mechanism; Smart Vehicles; CreditCoin
Bitcoin and other similar digital currencies on blockchains are not ideal means for payment, because their prices tend to go up in the long term (thus people are incentivized to hoard those currencies), and to fluctuate widely in the short term (thus people would want to avoid risks of losing values). The reason why those blockchain currencies based on proof of work are unstable may be found in their designs that the supplies of currencies do not respond to their positive and negative demand shocks, as the authors have formulated in our past work. Continuing from our past work, this paper proposes minimal changes to the design of blockchain currencies so that their market prices are automatically stabilized, absorbing both positive and negative demand shocks of the currencies by autonomously controlling their supplies. Those changes are: 1) limiting re-adjustment of proof-of-work targets, 2) making mining rewards variable according to the observed over-threshold changes of block intervals, and 3) enforcing negative interests to remove old coins in circulation. We have made basic design checks and evaluations of these measures through simple simulations. In addition to stabilization of prices, the proposed measures may have effects of making those currencies preferred means for payment by disincentivizing hoarding, and improving sustainability of the currency systems by making rewards to miners perpetual.
The objective of this paper is to describe the contemporary issues that supply chains face using the information sharing dimension and analyze blockchain technology’s capabilities to address these issues. We discuss select issues in managing contemporary supply chains from an information sharing perspective namely, information coordination challenges, effect of product and service manifestation on information complexity, effect of customer demand manifestation on information flow, outsourcing and globalization effects on information flow, and new emerging threats to supply chains by affecting information vulnerability. These issues are further categorized into- confidentiality and trust issues, inability to share information between supply chain partners, limitations of IT systems and lack of data standards. To address these issues, a unifying framework describing the applicability of blockchain has been presented that will guide companies in designing and implementing potential blockchain solutions to address issues in information exchange among supply chain partners. Blockchain based research is in nascent stages and this paper aims to add to this emerging research paradigm by analyzing blockchain technology through the information sharing dimension of supply chains. (this record is metadata only)
Jan 17, 2018·Peter Krafft, Nicolás Della Penna, Alex Pentland. (2018). An Experimental Study of Cryptocurrency Market Dynamics. ACM CHI Conference on Human Factors in Computing Systems (CHI)
P. M. Krafft, Nicolás Della Penna, Alex Sandy Pentland
As cryptocurrencies gain popularity and credibility, marketplaces for cryptocurrencies are growing in importance. Understanding the dynamics of these markets can help to assess how viable the cryptocurrnency ecosystem is and how design choices affect market behavior. One existential threat to cryptocurrencies is dramatic fluctuations in traders' willingness to buy or sell. Using a novel experimental methodology, we conducted an online experiment to study how susceptible traders in these markets are to peer influence from trading behavior. We created bots that executed over one hundred thousand trades costing less than a penny each in 217 cryptocurrencies over the course of six months. We find that individual "buy" actions led to short-term increases in subsequent buy-side activity hundreds of times the size of our interventions. From a design perspective, we note that the design choices of the exchange we study may have promoted this and other peer influence effects, which highlights the potential social and economic impact of HCI in the design of digital institutions.
A peer-to-peer system of blockchain, originally started for a cryptocurrency Bitcoin, has caused major disruptions in the stock market. It has affected many businesses if not all, but its significance in the financial world is magnanimous. Historical data (daily rates) for the past 23 months are analyzed to understand the market size, market capitalization and price volatility for Bitcoin. Time series data and financial model are applied to realize the shocks. Monte Carlo simulation is applied to assess the dynamic structure of Bitcoin. With greater volume and activity, the banks and financial intermediaries may become outdated, and the middleman will have no place. It seems like a distant thought, but the facts are pointing toward its reality.
The state-of-the-art mobile edge applications are generating intense traffic and posing rigorous latency requirements to service providers. While resource sharing across multiple service providers can be a way to maximize the utilization of limited resources at the network edge, it requires a centralized repository maintained by all parties for service providers to share status. Moreover, service providers have to trust each other for resource allocation fairness, which is difficult because of potential conflicts of interest. We propose EdgeChain, a blockchain-based architecture to make mobile edge application placement decisions for multiple service providers. We first formulate a stochastic programming problem minimizing the placement cost for mobile edge application placement scenarios. Based on our model, we present a heuristic mobile edge application placement algorithm. As a decentralized public ledger, the blockchain then takes the logic of our algorithm as the smart contract, with the consideration of resources from all mobile edge hosts participating in the system. The algorithm is agreed by all parties and the results will only be accepted by majority of the mining nodes on the blockchain. When a placement decision is made, an edge host meeting the consumer's latency and budget requirements will be selected at the lowest cost. All placement transactions are stored on the blockchain and are traceable by every mobile edge service provider and application vendor who consumes resources at the mobile edge.
In this dissertation we will present the Bitcoin and its technology and is supporting feature as a success factor for innovation and entrepreneurship. We will first demonstrate that Bitcoin is a currency and present its history and technology. Then from our literature researches and the interview we have conducted we will try to answer our problematic: Is Bitcoin and the Blockchain supporting entrepreneurship and innovation? Finally after crossing the theoretical and academic lectures with the testimony of the real actors we will present our conclusion and recommendation to the lectors.
Shelly Grossman, Ittai Abraham, Guy Golan-Gueta, Yan Michalevsky · 7 authors
Callbacks are essential in many programming environments, but drastically\ncomplicate program understanding and reasoning because they allow to mutate\nobject's local states by external objects in unexpected fashions, thus breaking\nmodularity. The famous DAO bug in the cryptocurrency framework Ethereum,\nemployed callbacks to steal $150M. We define the notion of Effectively Callback\nFree (ECF) objects in order to allow callbacks without preventing modular\nreasoning.\n An object is ECF in a given execution trace if there exists an equivalent\nexecution trace without callbacks to this object. An object is ECF if it is ECF\nin every possible execution trace. We study the decidability of dynamically\nchecking ECF in a given execution trace and statically checking if an object is\nECF. We also show that dynamically checking ECF in Ethereum is feasible and can\nbe done online. By running the history of all execution traces in Ethereum, we\nwere able to verify that virtually all existing contracts, excluding the DAO or\ncontracts with similar known vulnerabilities, are ECF. Finally, we show that\nECF, whether it is verified dynamically or statically, enables modular\nreasoning about objects with encapsulated state.\n
The emergence of distributed ledger technology (DLT) based upon a blockchain data structure, has given rise to new approaches to identity management that aim to upend dominant approaches to providing and consuming digital identities. These new approaches to identity management (IdM) propose to enhance decentralisation, transparency and user control in transactions that involve identity information; but, given the historical challenge to design IdM, can these new DLT-based schemes deliver on their lofty goals? We introduce the emerging landscape of DLT-based IdM, and evaluate three representative proposals: uPort; ShoCard; and Sovrin; using the analytic lens of a seminal framework that characterises the nature of successful IdM schemes.
Digital currencies, such as Bitcoin, have emerged as an alternative form of money, untethered to traditional money and largely unregulated. As such, digital currency represents a wild frontier for investors who might otherwise be shopping for gold or foreign currencies, with serious risks. The present work considers digital currency from a traditional asset pricing perspective. Setting aside risks of seller fraud or currency theft, we examine fluctuation and systematic risk in the price of Bitcoin. From this perspective, Bitcoin does not appear to carry much systematic risk -- despite its high volatility -- and so is a reasonable candidate for inclusion in investors’ portfolios. Some illustrative examples suggest that the optimal amount of Bitcoin to include in investor portfolios may be tiny or instead substantial - as high as 21 percent of total financial assets.
Large-scale rumor spreading could pose severe social and economic damages. The emergence of online social networks along with the new media can even make rumor spreading more severe. Effective control of rumor spreading is of theoretical and practical significance. This paper takes the first step to understand how the blockchain technology can help limit the spread of rumors. Specifically, we develop a new paradigm for social networks embedded with the blockchain technology, which employs decentralized contracts to motivate trust networks as well as secure information exchange contract. We design a blockchain-based sequential algorithm which utilizes virtual information credits for each peer-to-peer information exchange. We validate the effectiveness of the blockchain-enabled social network on limiting the rumor spreading. Simulation results validate our algorithm design in avoiding rapid and intense rumor spreading, and motivate better mechanism design for trusted social networks.
In this paper, we investigate the use of decentralized blockchain mechanisms for delivering transparent, secure, reliable, and timely energy flexibility, under the form of adaptation of energy demand profiles of Distributed Energy Prosumers, to all the stakeholders involved in the flexibility markets (Distribution System Operators primarily, retailers, aggregators, etc.). In our approach, a blockchain based distributed ledger stores in a tamper proof manner the energy prosumption information collected from Internet of Things smart metering devices, while self-enforcing smart contracts programmatically define the expected energy flexibility at the level of each prosumer, the associated rewards or penalties, and the rules for balancing the energy demand with the energy production at grid level. Consensus based validation will be used for demand response programs validation and to activate the appropriate financial settlement for the flexibility providers. The approach was validated using a prototype implemented in an Ethereum platform using energy consumption and production traces of several buildings from literature data sets. The results show that our blockchain based distributed demand side management can be used for matching energy demand and production at smart grid level, the demand response signal being followed with high accuracy, while the amount of energy flexibility needed for convergence is reduced.
<em>This paper aims to identify the practices involved in the formation of smart contracts and the limitations that are faced by the organizations through development of smart contracts in business. The Smart contract is developed based on specific criteria in the business. The smart chain in the business identify the block chains that are developed in the business to resolve different financial issues in the company. In this report, the elements of smart contracts are evaluated and analyzed along with a discussion of previous researchers on the same criteria. This study identifies that smart contracts become essential for business practices with development of technology. The form of smart contracts has captured the attention of legal attorney and its impact on contract law of business. This report implements the descriptive methodology approach in which the secondary data is analyzed to identify the formation of smart contracts and its liability on business. Additionally, the research data is analyzed through secondary qualitative analysis. </em>
We examine blockchain technologies, especially smart contracts, as a platform for decentralized applications. By providing a basis for consensus, blockchain promises to upend business models that presuppose a central authority. However, blockchain suffers from major shortcomings arising from an over-regimented way of organizing computation that limits its prospects. We propose a sociotechnical, yet computational, perspective that avoids those shortcomings. A centerpiece of our vision is the notion of a declarative, violable contract in contradistinction to smart contracts. This new way of thinking enables flexible governance, by formalizing organizational structures; verification of correctness without obstructing autonomy; and a meaningful basis for trust.
Bitcoin, as well as many of its successors, require the whole transaction record to be reliably acquired by all nodes to prevent double-spending. Recently, many blockchains have been proposed to achieve scale-out throughput by letting nodes only acquire a fraction of the whole transaction set. However, these schemes, e.g., sharding and off-chain techniques, suffer from a degradation in decentralization or the capacity of fault tolerance. In this paper, we show that the complete set of transactions is not a necessity for the prevention of double-spending if the properties of value transfers is fully explored. In other words, we show that a value-transfer ledger like Bitcoin has the potential to scale-out by its nature without sacrificing security or decentralization. Firstly, we give a formal definition for the value-transfer ledger and its distinct features from a generic database. Then, we introduce an off-chain based scheme with a shared main chain for consensus and an individual chain for each node for recording transactions. A locally executable validation scheme is proposed with uncompromising validity and consistency. A beneficial consequence of our design is that nodes will spontaneously try to reduce their transmission cost by only providing the transactions needed to show that their transactions are double-spending-proof. As a result, the network is sharded as each node only acquires part of the transaction record and a scale-out throughput could be achieved, which we call "spontaneous sharding".
This paper examines factors that influence prices of most common five cryptocurrencies such Bitcoin, Ethereum, Dash, Litecoin, and Monero over 2010-2018 using weekly data. The study employs ARDL technique and documents several findings. First, cryptomarket-related factors such as market beta, trading volume, and volatility appear to be significant determinant for all five cryptocurrencies both in short- and long-run. Second, attractiveness of cryptocurrencies also matters in terms of their price determination, but only in long-run. This indicates that formation (recognition) of the attractiveness of cryptocurrencies are subjected to time factor. In other words, it travels slowly within the market. Third, SP500 index seems to have weak positive long-run impact on Bitcoin, Ethereum, and Litcoin, while its sign turns to negative losing significance in short-run, except Bitcoin that generates an estimate of -0.20 at 10% significance level. Lastly, error-correction models for Bitcoin, Etherem, Dash, Litcoin, and Monero show that cointegrated series cannot drift too far apart, and converge to a long-run equilibrium at a speed of 23.68%, 12.76%, 10.20%, 22.91%, and 14.27% respectively.
Blockchain technology, popularized by Bitcoin cryptocurrency, is characterized as an open-source, decentralized, distributed database for storing transaction information. Rather than relying on centralized intermediaries (e.g., banks) this technology allows two parties to transact directly using duplicate, linked ledgers called blockchains. This makes transactions considerably more transparent than those provided by centralized systems. As a result, transactions are executed without relying on explicit trust [of a third party], but on the distributed trust based on the consensus of the network (i.e., other blockchain users). Applying this technology to improve supply chain transparency has many possibilities. Every product has a long and storied history. However, much of this history is presently obscured. Often, when negative practices are exposed, they quickly escalate to scandalous, and financially crippling proportions. There are many recent examples, such as the exposure of child labor upstream in the manufacturing process and the unethical use of rainforest resources. Blockchain may bring supply chain transparency to a new level, but presently academic and managerial adoption of blockchain technologies is limited by our understanding. To address this issue, this research uses the Unified Theory of Acceptance and Use of Technology (UTAUT) and the concept of technology innovation adoption as a foundational framework for supply chain traceability. A conceptual model is developed and the research culminates with supply chain implications of blockchain that are inspired by theory and literature review.
We discuss the issue of what we call {\em incentive mismatch}, a fundamental problem with public blockchains supported by economic incentives. This is an open problem, but one potential solution is to make application portable. Portability is desirable for applications on private blockchains. Then, we present examples of middleware designs that enable application portability and, in particular, support migration between blockchains.
Lei Xu, Lin Chen, Zhimin Gao, Shouhuai Xu · 5 authors
Public blockchains provide a decentralized method for storing transaction data and have many applications in different sectors. In order for users to track transactions, a simple method is to let them keep a local copy of the entire public ledger. Since the size of the ledger keeps growing, this method becomes increasingly less practical, especially for lightweight users such as IoT devices and smartphones. In order to cope with the problem, several solutions have been proposed to reduce the storage burden. However, existing solutions either achieve a limited storage reduction (e.g., simple payment verification), or rely on some strong security assumption (e.g., the use of trusted server). In this paper, we propose a new approach to solving the problem. Specifically, we propose an \underline{e}fficient verification protocol for \underline{p}ublic \underline{b}lock\underline{c}hains, or EPBC for short. EPBC is particularly suitable for lightweight users, who only need to store a small amount of data that is {\it independent of} the size of the blockchain. We analyze EPBC's performance and security, and discuss its integration with existing public ledger systems. Experimental results confirm that EPBC is practical for lightweight users.
Blockchain is the core technology used to create the cryptocurrencies, like bitcoin. As part of the fourth industrial revolution since the invention of steam engine, electricity, and information technology, blockchain technology has been applied in many areas such as finance, judiciary, and commerce. The current paper focused on its potential educational applications and explored how blockchain technology can be used to solve some education problems. This article first introduced the features and advantages of blockchain technology following by exploring some of the current blockchain applications for education. Some innovative applications of using blockchain technology were proposed, and the benefits and challenges of using blockchain technology for education were also discussed.
The blockchain activity within the energy sector is high, and the list of use cases is continuouslygrowing. The distributed and immutable nature of blockchain technology could potentially beleveraged to accelerate the ongoing transition to more decentralized and digitalised energy systemsand to address some of the challenges the industry is facing. However, blockchain is an emergingtechnology and it is seen as a critical uncertainty by many incumbents as the challenges andopportunities of implementation are still largely unknown. There is thus a lack of knowledge andscarcity of decision-making tools for understanding why, when and how the technology can addprofound value. This study sets out to explore how utilities can evaluate and prioritize amongblockchain-based use cases and gain practical knowledge about how blockchain could beimplemented.In the first part of the study, a broad initial scope was applied as a large part of the blockchain-baseduse cases within the energy market were inventoried and grouped into clusters based on their overallarea of use. Each cluster was analysed and evaluated to best fit both the strategy of the commissioningcompany and the criteria for using blockchain technology. After the first stage of the use caseevaluation approach, four clusters most suited to the specified selection criteria were selected. Theseare P2P Energy Trading, EV Charging & Management, Grid Stabilization & Management andEnvironmental Commodity Management & Trading. Given a final evaluation based on the overallmaturity of the clusters, EV Charging & Management and more specifically, the use case of EmobilityRoaming, was prioritized and selected for further evaluation given the high market relevanceof the use case.In the second part of the study, both the business and the functional layers of the e-mobility roamingcase were investigated. By adding an additional blockchain layer to the current solution, fourscenarios for blockchain implementation were identified. Several observations were made from thedevelopment of the scenarios and the evaluation of their impact on the business and the functionallayers within the e-mobility market. It became evident that many of the current functions andprocesses could be automated with the use of blockchain. As the technology allows for instantaneoussettlement of transactions, the current manual and time-consuming process of exchanging chargedetail records and the following billing and settlement functions could be removed. This further hasimplications on the market environment as some of the responsibilities of the incumbent marketplayers could become obsolete. By evaluating the scenarios based on the technology, market,customer and regulatory aspects it became clear that the scenarios based on a permissionlessblockchain are further away from commercialization in the energy sector due to the volatile nature ofcryptocurrencies, scalability issues, and regulatory constraints compared to a permissioned consortiumblockchain. On the other hand, these scenarios are easier to start exploring until the technology ismature, since it does not require any initial investment to start building Proof of Concepts foreducational purposes.In conclusion, the industry interest and dedication towards blockchain is high as both incumbents andstart-ups are investigating the potential of the technology. However, given the high complexity of thetechnology, it is essential for companies to evaluate both the technology and the applications beforeinitiating projects and taking investment decisions. It can additionally be seen that while blockchainhas a significant potential to provide scalable and automated solutions with lower transaction costs,the technology is currently not mature enough to do so. There are still issues concerning scalability aswell as a lack of a coherent policy mix in place limiting the development of commercial applications.However, as the adoption of EVs is increasing and interesting technologies such as machine-tomachinepayments and inductive charging are being investigated, value lies in taking a proactivestance and to start exploring scalable and automated solutions.