Personalized quality of service (QoS) prediction plays an important role in helping users build high-quality service-oriented systems. To obtain accurate prediction results, many approaches have been investigated in recent years. However, these approaches do not fully address untrustworthy QoS values submitted by unreliable users, leading to inaccurate predictions. To address this issue, inspired by blockchain with distributed ledger technology, distributed consensus mechanisms, encryption algorithms, etc., we propose a personalized QoS prediction method for web services that we call blockchain-based matrix factorization (BMF). We develop a user verification approach based on homomorphic hash, and use the Byzantine agreement to remove unreliable users. Then, matrix factorization is employed to improve the accuracy of predictions and we evaluate the proposed BMF on a real-world web services dataset. Experimental results show that the proposed method significantly outperforms existing approaches, making it much more effective than traditional techniques.
Blockchain Technology (BCT) is a growing digital technology that in recent years has gained widespread traction in various industries in the public and private sectors. BCT is a decentralized ledger that records every transaction made in the network, known as a ‘block’, the body of which is comprised of encrypted data of the entire transaction history. BCT was introduced as the working mechanism that forms the operational basis of Bitcoin, the first digital cryptocurrency to gain mainstream appeal. The introduction of decentralized data exchange technology in any industry would require strengthened security, enforce accountability, and could potentially accelerate a shift in workflow dynamics from current centralized architectures to a decentralized, cooperative chain of command and affect a cultural and societal change by encouraging trust and transparency. BCT aims at creating a system that would offer a robust self-regulating, self-monitoring, and cyber-resilient data transaction operation, assuring the facilitation and protection of a truly efficient data exchange system. In the state of Florida, climate change and unpredicted weather disasters have put pressure on state and local decision-makers to adapt quick and efficient post-disaster recovery systems. Part of the recovery efforts is the reconstruction of buildings and infrastructure. The introduction of new technologies in the Architecture, Engineering, and Construction (AEC) industry can contribute to addressing recovery and rebuilding after the event of a natural disaster. With parallel technological advancement in geospatial data and Geographic Information System (GIS), as well as worsening climatic conditions, concerns can be suitably addressed by employing an integrated system of both Building Information Modeling (BIM) and BCT. While several potential applications of BIM must provide solutions to disaster-related issues, few have seen practical applications in recent years that indicate the potential benefits of such implementations. The feasibility of BIM-based applications still rests on the reliability of connectivity and cyber-security, indicating a strong use case for using BCT in conjunction with BIM for post-disaster recovery. This research depicts a survey of BCT and its applications in the Architecture, Engineering, and Construction (AEC) industries and examines the potential incorporation within the BIM process to address post-disaster rebuilding problems. Moreover, the study investigates the potential application of BCT in improving the framework for automating the building permitting process using Smart Contract (SC) technologies and Hyperledger Fabric (HLF), as well as discussing future research areas. The study proposes a new conceptualized framework resulting from the integration of BCT and BIM processes to improve the efficiency of building permit processes in post-disaster events.
Cüneyt Gürcan Akçora, Yitao Li, Yulia R. Gel, Murat Kantarcıoğlu
Proliferation of cryptocurrencies (e.g., Bitcoin) that allow pseudo-anonymous transactions, has made it easier for ransomware developers to demand ransom by encrypting sensitive user data. The recently revealed strikes of ransomware attacks have already resulted in significant economic losses and societal harm across different sectors, ranging from local governments to health care. Most modern ransomware use Bitcoin for payments. However, although Bitcoin transactions are permanently recorded and publicly available, current approaches for detecting ransomware depend only on a couple of heuristics and/or tedious information gathering steps (e.g., running ransomware to collect ransomware related Bitcoin addresses). To our knowledge, none of the previous approaches have employed advanced data analytics techniques to automatically detect ransomware related transactions and malicious Bitcoin addresses. By capitalizing on the recent advances in topological data analysis, we propose an efficient and tractable data analytics framework to automatically detect new malicious addresses in a ransomware family, given only a limited records of previous transactions. Furthermore, our proposed techniques exhibit high utility to detect the emergence of new ransomware families, that is, ransomware with no previous records of transactions. Using the existing known ransomware data sets, we show that our proposed methodology provides significant improvements in precision and recall for ransomware transaction detection, compared to existing heuristic based approaches, and can be utilized to automate ransomware detection.
Mohammad Javad Amiri, Sujaya Maiyya, Divyakant Agrawal, Amr El Abbadi
Large scale data management systems utilize State Machine Replication to provide fault tolerance and to enhance performance. Fault-tolerant protocols are extensively used in the distributed database infrastructure of large enterprises such as Google, Amazon, and Facebook, as well as permissioned blockchain systems like IBM's Hyperledger Fabric. However, and in spite of years of intensive research, existing fault-tolerant protocols do not adequately address all the characteristics of distributed system applications. In particular, hybrid cloud environments consisting of private and public clouds are widely used by enterprises. However, fault-tolerant protocols have not been adapted for such environments. In this paper, we introduce SeeMoRe, a hybrid State Machine Replication protocol to handle both crash and malicious failures in a public/private cloud environment. SeeMoRe considers a private cloud consisting of nonmalicious nodes (either correct or crash) and a public cloud with both Byzantine faulty and correct nodes. SeeMoRe has three different modes which can be used depending on the private cloud load and the communication latency between the public and the private cloud. We also introduce a dynamic mode switching technique to transition from one mode to another. Furthermore, we evaluate SeeMoRe using a series of benchmarks. The experiments reveal that SeeMoRe's performance is close to the state of the art crash fault-tolerant protocols while tolerating malicious failures.
Stanisław Drożdż, Ludovico Minati, Paweł Oświȩcimka, Marek Stanuszek · 5 authors
Based on the high-frequency recordings from Kraken, a cryptocurrency exchange and professional trading platform that aims to bring Bitcoin and other cryptocurrencies into the mainstream, the multiscale cross-correlations involving the Bitcoin (BTC), Ethereum (ETH), Euro (EUR) and US dollar (USD) are studied over the period between 1 July 2016 and 31 December 2018. It is shown that the multiscaling characteristics of the exchange rate fluctuations related to the cryptocurrency market approach those of the Forex. This, in particular, applies to the BTC/ETH exchange rate, whose Hurst exponent by the end of 2018 started approaching the value of 0.5, which is characteristic of the mature world markets. Furthermore, the BTC/ETH direct exchange rate has already developed multifractality, which manifests itself via broad singularity spectra. A particularly significant result is that the measures applied for detecting cross-correlations between the dynamics of the BTC/ETH and EUR/USD exchange rates do not show any noticeable relationships. This could be taken as an indication that the cryptocurrency market has begun decoupling itself from the Forex.
Sebastien Lugan, Paul Desbordes, Luis Xavier Ramos Tormo, Axel Legay · 5 authors
Distributed learning across a coalition of organizations allows the members of the coalition to train and share a model without sharing the data used to optimize this model. In this paper, we propose new secure architectures that guarantee preservation of data privacy, trustworthy sequence of iterative learning and equitable sharing of the learned model among each member of the coalition by using adequate encryption and blockchain mechanisms. We exemplify its deployment in the case of the distributed optimization of a deep learning convolutional neural network trained on medical images.
In economic development, transactions have become the routine of the people. Currently there are many transactions that are growing, one of which is Bitcoin. Bitcoin is one of the technologies of cryptocurreny which is then used. Bitcoin is a digital currency in the open source P2P payment network system. But the value of the Bitcoin body is not fixed, Bitcoin values often change over time. One of the causes of changing the value of Bitcoin is VGA. This role of VGA card to process Bitcoin encryption data because GPU (brain of VGA) has more core to process CPU, increase Bitcoin value and influence graphics card price. In this paper will rise the value of rising and falling value of Bitcoin which affects the price of the graphics card.Keyword: Bitcoin, Cryptocurrency, VGA, GPUAbstrakDalam perkembangan ekonomi, transaksi sudah menjadi rutinitas masyarat. Saat ini sudah banyak jenis transaksi yang berkembang, salah satunya adalah Bitcoin. Bitcoin merupakan salah satu teknologi dari cryptocurreny yang sering digunakan. Bitcoin adalah mata uang digital yang berada di dalam system jaringan pembayaran open source P2P. Namun nilai dari suatu Bitcoin tidak tetap, nilai Bitcoin sering berubah seiring berjalannya waktu. Salah satu penyebab berubahnya nilai dari Bitcoin adalah VGA. Peran VGA card ini untuk memproses enkripsi data Bitcoin karena GPU (otak dari VGA) mempunyai core yang lebih banyak untuk memproses instruksi dalam satu waktu dibandingkan CPU, sehingga naiknya nilai Bitcoin juga mempengaruhi harga kartu grafis. Dalam paper ini akan mengevaluasi perbandingan naik dan turunnya nilai Bitcoin yang mempengaruhi harga kartu grafis.Kata Kunci: Bitcoin, Cryptocurrency, VGA, GPU
Sujaya Maiyya, Victor Zakhary, Mohammad Javad Amiri, Divyakant Agrawal · 5 authors
The uprise of Bitcoin and other peer-to-peer cryptocurrencies has opened many interesting and challenging problems in cryptography, distributed systems, and databases. The main underlying data structure is blockchain, a scalable fully replicated structure that is shared among all participants and guarantees a consistent view of all user transactions by all participants in the system. In this tutorial, we discuss the basic protocols used in blockchain, and elaborate on its main advantages and limitations. To overcome these limitations, we provide the necessary distributed systems background in managing large scale fully replicated ledgers, using Byzantine Agreement protocols to solve the consensus problem. Finally, we expound on some of the most recent proposals to design scalable and efficient blockchains in both permissionless and permissioned settings. The focus of the tutorial is on the distributed systems and database aspects of the recent innovations in blockchains.
Ankur Sharma, Felix Schuhknecht, Divya Agrawal, Jens Dittrich
Within the last few years, a countless number of blockchain systems have emerged on the market, each one claiming to revolutionize the way of distributed transaction processing in one way or the other. Many blockchain features, such as byzantine fault tolerance, are indeed valuable additions in modern environments. However, despite all the hype around the technology, many of the challenges that blockchain systems have to face are fundamental transaction management problems. These are largely shared with traditional database systems, which have been around for decades already. These similarities become especially visible for systems, that blur the lines between blockchain systems and classical database systems. A great example of this is Hyperledger Fabric, an open-source permissioned blockchain system under development by IBM. By implementing parallel transaction processing, Fabric's workflow is highly motivated by optimistic concurrency control mechanisms in classical database systems. This raises two questions: (1)~Which conceptual similarities and differences do actually exist between a system such as Fabric and a classical distributed database system? (2)~Is it possible to improve on the performance of Fabric by transitioning technology from the database world to blockchains and thus blurring the lines between these two types of systems even further? To tackle these questions, we first explore Fabric from the perspective of database research, where we observe weaknesses in the transaction pipeline. We then solve these issues by transitioning well-understood database concepts to Fabric, namely transaction reordering as well as early transaction abort. Our experimental evaluation under the Smallbank benchmark as well as under a custom workload shows that our improved version Fabric++ significantly increases the throughput of successful transactions over the vanilla version by up to a factor of 12x, while decreasing the average latency to almost half.
A new framework for a secure and robust consensus in blockchain-based IoT networks is proposed using machine learning. Hyperledger fabric, which is a blockchain platform developed as part of the Hyperledger project, though looks very apt for IoT applications, has comparatively low tolerance for malicious activities in an untrustworthy environment. To that end, we propose AI-enabled blockchain (AIBC) with a 2-step consensus protocol that uses an outlier detection algorithm for consensus in an IoT network implemented on hyperledger fabric platform. The outlier-aware consensus protocol exploits a supervised machine learning algorithm which detects anomaly activities via a learned detector in the first step. Then, the transactions go through the inherent Practical Byzantine Fault Tolerance (PBFT) consensus protocol in the hyperledger fabric for ledger update. We measure and report the performance of our framework with respect to the various delay components. Results reveal that our implemented AIBC network (2-step consensus protocol) improves hyperledger fabric performance in terms of fault tolerance by marginally compromising the delay performance.
Satoshi Nakamoto's Blockchain allows to build publicly verifiable and almost immutable ledgers, but sometimes privacy has to be factored in. In this work an original protocol is presented that allows sensitive data to be stored on a ledger where its integrity may be publicly verified, but its privacy is preserved and owners can tightly manage the sharing of their information with efficient revocation.
Governance issues limit blockchains' ability to evolve and face unforeseen challenges. It seems possible to argue that this impasse is because most blockchains lack meta-rules. This work considers blockchains as a socio-technical system of rules, in order to draw a comparison with legal systems. Following the comparison, one finds that most blockchains lack what, in legal theory, are considered secondary rules. That is, the meta-rule of the system.
The development of financial technology arrived at a new form, namely cryptocurrency. The development of cryptocurrency with an increasingly widespread network and its autonomous nature cannot be controlled by the state, which makes China implement policies to block all domestic cryptocurrency activities. The policy becomes unnatural when China occupies the top position in the developing global digital currency market. This anomaly is interesting to study further to find reasons that motivate China to take firm policy when in a safe position as a center of production and global crypto currency transactions. To explain this reason, national interest theory and rational choice are used as the main tools in analyzing this problem. The national interest theory and rational choice explain that the policies taken by China are motivated by economic and security interests, as well as rational calculations of the advantages and disadvantages of those policies
Amos Fiat, Anna R. Karlin, Ηλίας Κουτσουπιάς, Christos H. Papadimitriou
The Bitcoin protocol induces miners, through monetary rewards, to expend energy in order to add blocks to the chain. We show that, when energy costs are substantial and taken into account, counterintuitive and unintended strategic behavior results: In a simple bounded-horizon setting with two identical miners there is a unique pure symmetric equilibrium in which both miners first "slow down" in order to decrease the crypto complexity and then take advantage of this decrease. If miners have different energy efficiencies and are restricted to choose the same hash rate for many epochs, there is a unique pure equilibrium in which miners either participate at low levels that depend in intricate ways on all the other miners' efficiencies, or choose to abstain from mining if their efficiency is too low. In the general setting in which miners can adapt their hash rates over time, we show that, unless the number of miners is very small, the only possible pure equilibria are rather chaotic, with miners quitting and starting again periodically --- or there is no pure equilibrium at all. We discuss the implications of these results for the stability of proof-of-work protocols.
The research focuses on identifying Bitcoin ecosystem factors and modeling a causal loop diagram of the complete ecosystem. Bitcoin is a complex social, economical and technical system and a brand. Defining Bitcoin is very hard or even impossible, as it is a peer-to-peer phenomenon without central authority or formal definition. System dynamics methods are used to create a causal loop diagram of the Bitcoin ecosystem. Semi-structured expert interviews are used to improve and validate the CLD model and to gain insight about what is Bitcoin, why and how it works and generally about factors related to Bitcoin. Results, in addition to the CLD model, show that Bitcoin is a complex phenomenon without definition and with loads of subjective opinions about what it really is.
Smart contracts are written in programming languages rather than in natural languages. This might seem to insulate them from ambiguity, because the meaning of a program is determined by technical facts rather than by social ones. It does not. Smart contracts can be ambiguous, too, because technical facts depend on socially determined ones. To give meaning to a computer program, a community of programmers and users must agree on the semantics of the programming language in which it is written. This is a social process, and a review of some famous controversies involving blockchains and smart contracts shows that it regularly creates serious ambiguities. In the most famous case, The DAO hack, more than $150 million in virtual currency turned on the contested semantics of a blockchain-based smart-contract programming language.
Min Choi, Rupali Shinde, Sechang Oh, Oh‐Young Kwon
In this paper, we present a badge awarding system for performance assessment in education using blockchain technology. Learners will be awarded badges, which are certified for a predetermined level of progress in terms of learning. All the badges are stored in a backpack, which is an environment for storing and presenting the obtained badges. Badges are immutable and verifiable as well as rigid. The use of badges in the education system makes education more interesting, skill-based, and adaptable to changes. The key contribution of our work is in terms of compatibility with Openbadge specification and integrated cooperating platform between digital badge awarding and blockchaining. Our system implementation is compatible with Open Badges of IMS Global Learning Consortium, which is used to earn, issue, and award badges across various platforms. The badges are trusted by the IMS standard, the criteria to earn a badge is verified through the network, and the overall process is transparent compared to the traditional education system. Moreover, all badge awarding events in our system are recorded in a blockchain. Once stored, the contents cannot be tampered with. Thereafter, anyone can check the validity of the badge through the blockchain. Our platform will be useful for distance learning as well as time and location independent learning. The experimental results are as follows. On a Bitcoin-based digital badge publishing platform, the execution time required to award the badge is 24.53 s, while on the Ethereum-based digital badge publishing platform, the execution time to award the badge is only 3.86 s. It can also be used for career management and personal history. The learners can obtain the current knowledge required for a job. Lifelong learning will be also possible with this platform.
El bitcoin es una criptomoneda que ha tomado cada vez mayor importancia en terreno económico y financiero; fue creada para usos potenciales como moneda de compra y venta de bienes y servicios y como una base para aplicaciones, pero últimamente se ha estado convirtiendo en una reserva de valor en tiempos de crisis. Las plantas de minado, están proliferando siendo consideradas un modelo de negocio; estas funcionan a través de nodos que forman una red descentralizada. No obstante, la gran cantidad de energía eléctrica utilizada en la producción y protección de las criptomonedas, les genera altos costos y esto podría ser su talón de Aquiles. Además, está causando polémica porque podría invalidar los esfuerzos hechos para la producción sostenible de la energía, a causa del crecimiento exponencial de la demanda de energía que se está gestando en los centros de datos dedicados al minado. Esta investigación tiene el objetivo de elaborar un análisis y una revisión de la creación y desenvolvimiento de la primera criptomoneda, su oferta y la demanda exponencial de energía que pone en entredicho la factibilidad de su crecimiento y desarrollo en el tiempo por factores económicos y de sostenibilidad.
In this paper, a novel framework that uses wireless mobile miners (MMs) for computation purposes in a blockchain system is proposed. In the introduced system, the blockchain ledger is located at the communication nodes (CNs), and the MMs associated with CNs process the blockchain's proof-of-work (PoW) computation to verify the originality of the data. The MM that is the first to finish its PoW will receive a reward by sending its computing result to the CNs that are connected to other MMs. In the considered scenario, a blockchain forking event occurs if the MM having the shortest PoW delay fails to be the first to update its computing result to other MMs. To enable such mobile operations for a blockchain with minimum forking events, it is imperative to maintain low-latency wireless communications between MMs and CNs. To analyze the sensitivity of the system to latency, the probability of occurrence of a forking event is theoretically derived. The system is then designed so as to compute the forked block's PoW again to recover from a forking event. For this case, the average energy consumption of an MM is derived as a function of the system parameters such as the number of MMs and power consumed by the computing, transmission, and mobility processes of the MMs. Simulation results verify the analytical derivations and show that using a larger number of MMs can reduce the energy consumption by up to 94.5% compared to a blockchain system with a single MM.
Abstract\nThis paper applies cointegration tests to identify cryptocurrency pairs which can be used in pairs trading strategies. The aim of this research is twofold. First, I want to examine cointegration in a system of bitcoin, dashcoin, dogecoin and litecoin. In the second part, I create pairs trading strategies in order to determine whether excess return can be made, compared to a simple buy and hold approach. The results find evidence of cointegration between the cryptocurrencies and positive profitability using pairs trading. By creating a portfolio in which the funds are equally allocated to the strategies with an open position, excess return can be made.
In the era of rapid technological progress, the legislators of individual countries face the challenge of submitting new technological phenomena to the legal framework. The business operation in the field of virtual currencies (cryptocurrencies),widely, in the financial technology sector (hereinafter referred to in as “fintech”), create a chance to attract investors and develop the economy. On the other hand, the same might be misused for illegal purposes, such as, in particular,money laundering or financing of terrorism. This study provides for an overview of the legal regulations of selected states in the field of virtual currencies (cryptocurrencies). Although, presented laws and regulations herein are in favour of thecryptocurrencies, the scope of implemented acts varies significantly.
We describe MaGPoS, a novel consensus mechanism which is well suited to decentralized blockchain based protocols. MaGPoS is based on a combination of the well known physics of nano-scale magnetism, and previous implementations of proof of stake. This system has been studied by hundreds of thousands of scientists worldwide for over a hundred years, giving it an extreme level of reliability that is needed for a consensus mechanism. We start by explaining the physics, and study the properties that make it particularly beneficial for use in a consensus mechanism. We then show how to apply the physical model to a decentralized network of nodes, each with their own copy of a blockchain. After this, we describe some example calculations that a node in the decentralized network would make, and provide pseudo code for implementation. Finally, we discuss the how the model achieves all of the important properties that one expects of a consensus mechanism.
Stefanos Leonardos, Daniel Reijsbergen, Georgios Piliouras
The rapid evolution of blockchain technology has brought together stakeholders from fundamentally different backgrounds. The result is a diverse ecosystem, as exemplified by the development of a wide range of different blockchain protocols. This raises questions for decision and policy makers: How do different protocols compare? What are their trade-offs? Existing efforts to survey the area reveal a fragmented terminology and the lack of a unified framework to reason about the properties of blockchain protocols. In this paper, we work towards bridging this gap. We present a five-dimensional design space with a modular structure in which protocols can be compared and understood. Based on these five axes -- Optimality, Stability, Efficiency, Robustness and Persistence -- we organize the properties of existing protocols in subcategories of increasing granularity. The result is a dynamic scheme -- termed the PREStO framework -- which aids the interaction between stakeholders of different backgrounds, including managers and investors, and which enables systematic reasoning about blockchain protocols. We illustrate its value by comparing existing protocols and identifying research challenges, hence making a first step towards understanding the blockchain ecosystem through a more comprehensive lens.
Ashutosh Dhar Dwivedi, Lukáš Malina, Petr Dzurenda, Gautam Srivastava
There continues to be a recent push to taking the cryptocurrency based ledger system known as Blockchain and applying its techniques to non-financial applications. One of the main areas for application remains Internet of Things (IoT) as we see many areas of improvement as we move into an age of smart cities. In this paper, we examine an initial look at applying the key aspects of Blockchain to a health application network where patients health data can be used to create alerts important to authenticated healthcare providers in a secure and private manner. This paper also presents the benefits and also practical obstacles of the blockchain-based security approaches in IoT.