İbrahim Korkmaz Kahraman, Habib Küçükşahin, Emin ÇAĞLAK
Getirilerin normal dağıldığı varsayımını temel alan öngörü modelleri sığ piyasalarda yeterince başarılı performans sergileyememektedir. Bu modeller, özellikle yüksek oynaklık gösteren piyasalarda ulaşılabilecek uç noktaların öngörüsünde daha fazla başarısızlık göstermekte ve bu durum da yatırımcıları volatilite tahminlemesine yöneltmektedir. Bahsedilen durumlar çerçevesinde, çalışmada finansal yatırımcılar için alternatif yatırım aracı olarak görülen ve piyasalarında yüksek oynaklıkların görüldüğü kripto paraların volatilite tahmininde Tekil Oynaklık Modelleri (ARCH, GARCH, T-GARCH, GARCH-M, E-GARCH, I-GARCH) ile uzun hafıza modelleri (AP-GARCH ve C-GARCH) kullanılmıştır. Ayrıca oynaklık tahmini için yararlanılan modeller arasından en uygun model test edilmeye çalışılmıştır. Bu bağlamda, kripto para piyasası içerisinde en yüksek piyasa değerine sahip, Bitcoin, Ethereum ve Ripple para birimlerinin 24/08/2016-07/05/2018 tarihleri arası fiyat verilerinden yararlanılmıştır. Araştırma sonuçlarına göre, Bitcoin ve Ethereum için şokların volatilite etkisi kalıcı ve pozitif şokların etkisi negatif şokların etkisinden daha fazla iken Ripple için şokların volatiliteye etkisi geçici karakterde ve oynaklığın geçişkenliği kısa dönemli olmaktadır.
Blockchain technology is, in part, a proposal to resolve ‘the political’ through technical means: decentralised networks to solve the problem of authority; cryptography to coordinate and secure the network; and game theory and incentive design to solve network behaviour. This PhD thesis draws on theoretical work by Karen Barad (2007) and Jacques Rancière (Rancière, 2010) to ask the question of what matters politically in blockchain technology – both in the sense of matter as becoming material of a new mediation of the political, but also mattering in the sense of being of political importance to engineers, developers and communities forming around blockchain as a potential. Rather than treating blockchain as coherent thing to be either celebrated or criticised, this thesis proposes and attempts to draw out the ways in which the potentials of blockchain are negotiated as part of its political effects, looking towards these negotiations to understand how political differences are made and sought materialised. Three approaches to the political are articulated to analyse Bitcoin and Ethereum as case studies and shift their terms of debate. Firstly, addressing the question of algorithmic determinacy, an approach is proposed for critically understanding a blockchain proposition that does not immediately revert to a competition of control between ‘human’ and ‘machine’ through the notion of the insensible, drawing on work by geographer of the inhuman Yusoff (2013a). Secondly, drawing on political theorist Rancière (2010) a particular blockchain sensibility is articulated, addressing the question of the particular kind of ‘disruption’ that blockchain presents. Its specific provenance in political histories of decentralised network computation opens up political significance beyond its intersections with financial capitalism. Finally, addressing the question of blockchain as a resolution to the political, the thesis introduces the concept of dissensible as an ongoing potential for incompatible sensibilities and their negotiation.
Blockchain has been around for over a decade, however, the technology does not seem to have been adopted after a long time being in existence. The goal of this thesis was to get to study what are the barriers of the blockchain adoption. Furthermore, the thesis also indicated one use case that seems to stand out from the rest, smart contract, by implementing one specific example for demonstration purpose. \n The thesis went through an in-depth concept of blockchain technology, studied the most well-known use cases being, including cryptocurrency, initial coin offering and smart contract and figured out their limitations particularly and blockchain’s generally. Finally, one example of Ethereum smart contract was implemented to indicate how this particular use case could fit what is needed nowadays. \n As a result, the studies showed that blockchain is promising and can be applied through developing decentralized applications by smart contracts but the use cases must be chosen very carefully due to the problems of privacy and data protection. Otherwise, the main obstacle for the adoption is the lack of serious regulations, resulting the lack of trust, therefore, as long as blockchain-related businesses are not clearly regulated, the mass adoption is probably still far away since no one gets fully protected in the game, neither the companies nor the customers.
Attaining consensus with no constraints on the consensus participation is a fundamental feature of decentralized blockchain solutions such as Bitcoin (Nakamoto, 2008) and Ethereum (Buterin et al., 2013). Unrestricted consensus participation removes the possibility of censorship and a potential single point of failure, but this design has led to a new concern: that of centralization. Centralization in decentralized blockchain refers to the concentration of a large portion of computing resources to a select few participants. In this paper, we identify the restriction on new participation as a critical contributor to the centralization of consensus power towards commercial and large-scale entities. We also examine the cause of the indirect restriction on participation and propose a metric to identify the degree of these indirect restrictions. This new metric may be used as a threat indicator to identify the centralization of decentralized blockchain caused by indirect participation restrictions.
Cryptocurrency marked its presence with the inception of bitcoin in the year 2009. Bitcoin was created as a medium for peer to peer exchange. Cryptocurrency can be defined as money in digital form which can be used for exchange of goods and services. The cryptocurrency was designed to discover a type of currency which is not government regulated or in simpler terms currency whose demand and supply cannot be regulated by authorities. Cryptocurrency use cryptography to generate and allocate currency. The process of cryptography requires different verification of transactions without involving any king of centralized authority. To verify that no currency unit is spent twice, transaction verification authenticates the amount of transaction as well as the ownership of the currency. This step by step process is known as mining. The transaction record of cryptocurrency is stored in a ledger called blockchain. Blockchain can be defined as a distributed ledger which forms the basis for cryptocurrency market but its implication is not restricted to only cryptocurrency, blockchain technology can be used in financial services, supply chain management, government documentation. Mining algorithms in most of the cryptocurrency are public. Cryptocurrency presence was not felt only because of its concept but the controversies associated with it like the money laundering and terrorism activities being funded through its mechanism. The cryptocurrency market has shown turbulent with significant growth as well as downfalls. Since the main purpose of cryptocurrency was to replace real currency the question arises whether it has been able to impact the value of real currency in any significant way or not. This research aims at studying the correlation between cryptocurrencies namely Bitcoin, Bitcoin Cash, Neo, Ripple, Ethereum, Tron, Litecoin, Dash, Monero, IOTA and real currencies namely Australian dollar, Canadian dollar, Euro, Pound sterling, Japanese yen, Chinese yuan and commodities namely gold, silver keeping united states dollar as base for all conversions.
José Augusto Fontoura Costa, Leonardo Albuquerque Marques
portuguesO artigo expoe e discute os cenarios possiveis de interpretacao de contratos em ambiente de computacao descentralizada em blockchain. Parte-se de um caso ocorrido em 2016 no ambiente de transacoes do Ethereum, no qual a aplicacao de um contrato inteligente poderia ter levado a consequencias contraintuitivas e desastrosas, capazes de causar um prejuizo de cerca de cento e sessenta milhoes de dolares a investidores. Nesse caso, o potencial prejuizo foi contornado a luz de uma “intervencao humana” na codificacao de um contrato inteligente. Abordam-se as limitacoes dos contratos inteligentes (smart contracts) e das OAD a partir do argumento do quarto chines de John Searle, segundo o qual o modus operandi da computacao de maquinas e diverso da interpretacao humana. Em um segundo momento, procura-se fazer uma reflexao sobre como essa ideia pode ser confrontada com o principio contratual da autonomia da vontade em um cenario em que soberanias estatais praticamente nao tem como agir em ambientes de transacao em computacao descentralizada e outra reflexao sobre que tipo de consequencias podem ser esperadas a partir dai. Em seguida, a partir da Nova Economia Institucional e da eficiencia adaptativa, avaliam-se os caminhos possiveis para a decidibilidade de conflitos contratuais em computacao descentralizada, que se encontram em ambientes quase imunes a soberania estatal. EnglishThe article discusses the interpretation of contracts in the blockchain decentralized computing environment. To do so, it does analyse a 2016 case on a transaction that took place in the Ethereum environment. In this instance, the use of smart contracts would have led to counter-intuitive and disastrous consequences, particularly a loss of about one hundred and sixty million dollars. The potential loss was circumvented thanks to “human intervention” to a codified smart contract. The limits of smart contracts and DAO are addressed through the John Searle’s Chinese Room Argument, according to which there is an essential gap between machine computing and human understanding. It also seeks to challenge the Principles of Private Autonomy and Freedom of Contract in an environment marked by the decentralization of operations and their deleterious consequences to state control. As it is concluded, the New Institutional Economics and the concept of adaptive efficiency may help to understand and set possible ways to settling private controversies backed by contracts in an almost stateless scenario.
In the field of cryptoeconomics the Ethereum (Ethereum Foundation) project gave opportunity to create “own” cryptocurrency – new token based on its smart-contract platform to everyone without lowlevel programming skills. Then it became obvious that tokens could be used for crowdfunding as the Ethereum did in 2014. Unregulated and easy to access such scheme became popular among related to the blockchain tech startups. It was named Initial Coin Offering (ICO/or ITO). Despite its name, which is similar to IPO, this scheme is usually used for venture funding of a new project instead of expanding already well-established working business. The authors use machine-learning algorithms to classify ICOs and estimate ROI based on public digital data and web-sources. The goal of the research is to develop sustainable and efficient model, which will predict target profit ROI (profit trends) of ICO startup. Data collection and analysis period: Feb-Mar 2018. The prediction model and the application (service) of ICO startups’ selection are developed as the result of the study. Results. There were over 3000 samples of ICO-startups in the research dataset. After cleaning and elimination of outliers, it contained only 518. The number of samples with positive ROI (which means that these ICOs were profitable) was 234. Cross validation metric was confirmed to be accurate. The model achieved 79 % accuracy (average value). To prove this score separated prediction was executed the metrics: for test dataset AUC is 0.78; for profitable samples Precision: 0.76; Recall: 0.9 for profitable; F1-score: 0.82. Discussions. In order to achieve the objectives of this study, various IT components of the service architecture (applications) were developed to monitor, analyze and predict the risks of ICO startups. An artificial neural network was developed to solve the problem of ROI classification and prediction. The average ROI among profitable ICOS was 47 %. Taking into consideration that the crypto market is highly volatile and that there is a possibility that such investments will not bring any profit, this model of monitoring, analysis and prediction can be very valuable for the purposes of critical selection (exclusion) of a number of ICO projects from potential investment. Conclusion. The developed components can be used as a basis of monitoring service of ICO startups. The risk-forecasting model can be improved, foremost, by using the most complete (and wider) set of data. In this case, individual data collection and processing tasks can be performed manually, which will require additional resources. It should be noted that other types of neural networks can be developed for both text analysis and trading data analysis. This may lead to the logic of using a combination of models, which will potentially help to provide the most accurate predictions.
The feedback control loop is the atomic unit in a control system. Typically, feedback control loops are rigid objects that involve a dynamical system, or plant, which has a set of its output states measured by dedicated sensors, which in turn feed a processing unit, known as controller, that calculates actions to be applied as inputs to the plant, via elements known as actuators, in order to drive the outputs to a desired value or trajectory. The appearance of the Internet of Things (IoT) paradigm, where a large number of sensors and processing units interact over a communication network, offers an underlying infrastructure to operate and configure control loops using a different logic: an on-demand strategy. This work introduces the concept of on-demand control loop, and proposes the use of blockchain technology as the enabling infrastructure for generating on-demand control loops over large-scale IoT environments. General design guidelines are given and a simple implementation example over the Ethereum blockchain is presented, which shows the feasibility of the proposed technique.
The purpose of this research is to demonstrate how public blockchains offer a greater degree of censorship resistance over traditional web-based information broadcasting mechanisms, and a comparison of existing options. Public blockchains present a means to mitigate censorship from nation states through both a broadcasting and data storage mechanism. They are costly to attack and difficult to remove from the public due to their distributed and accessible nature. A recent incident in China proved the worth of public blockchains by forcing the distribution of a censored letter describing harassment by Peking University into an Ethereum transaction by an anonymous individual or party. The Chinese government censored the letter on popular centralized services such as WeChat, but was unable to censor it once posted to the Ethereum blockchain. Through the demonstration of the letter’s presence on Ethereum as well as the act of placing it on other public blockchains, this research highlights the importance of how public blockchains will continue to be a vessel for the protection of information well into the future.
Yijun Yu, Danny Barthaud, Blaine Price, Arosha K. Bandara · 6 authors
Unmanned Aerial Vehicles (UAVs), or drones, are increasingly expected to operate in spaces populated by humans while avoiding injury to people or damaging property. However, incidents and accidents can, and increasingly do, happen. Traditional investigations of aircraft incidents require on-board flight data recorders (FDRs); however, these physical FDRs only work if the drone can be recovered. A further complication is that physical FDRs are too heavy to mount on light drones, hence not suitable for forensic digital investigations of drone flights. In this paper, we propose a self-adaptive software architecture, LiveBox, to make drones both forensic-ready and regulation compliant. We studied the feasibility of using distributed technologies for implementing the LiveBox reference architecture. In particular, we found that updates and queries of drone flight data and constraints can be treated as transactions using decentralised ledger technology (DLT), rather than a generic time-series database, to satisfy forensic tamper-proof requirements. However, DLTs such as Ethereum, have limits on throughput (i.e. transactions-per-second), making it harder to achieve regulation-compliance at runtime. To overcome this limitation, we present a self-adaptive reporting algorithm to dynamically reduce the precision of flight data without sacrificing the accuracy of runtime verification. Using a real-life scenario of drone delivery, we show that our proposed algorithm achieves a 46% reduction in bandwidth without losing accuracy in satisfying both tamper-proof and regulation-compliant requirements.
With the recent trend on blockchain, many users want to know more about the important players of the chain. In this study, we investigate and analyze the Ethereum blockchain network in order to identify the major entities across the transaction network. By leveraging the rich data available through Alethio's platform in the form of RDF triples we learn about the Hubs and Authorities of the Ethereum transaction network. Alethio uses SANSA for effcient reading and processing of such large-scale RDF data (transactions on Ethereum blockchain) in order to perform analytics e.g. finding top accounts, or typical behavior patterns of exchanges' deposit wallets and more.
Blockchain has received increased attention from both the academic and practitioner worlds. Numerous papers have been written on how blockchain works and its potential applications. However, few studies have focused on fraudulent activities on blockchain. The purpose of this study is to understand common issues and scams related to blockchain. A literature review was conducted to identify top security issues on blockchain. In addition, we collected tweets on blockchain fraud discussion from November 6, 2018 to December 31, 2008. The results of tweets analysis show that the most frequently mentioned words in tweets include scams, crypto/cryptocurrency, ICO, Bitcoin, Ethereum, combat/fight, Asia, Japan, and Germany. The top mentioned sentiment words include scam, combat, guilty, prevent, solution, tired, and fake. In addition, a sentiment analysis shows that the majority of the tweets (69%) on the discussion on blockchain fraud are negative. The findings also shows the majority of top influencers of the topic are the companies that have developed blockchain-based platforms/applications.
Katharina Zeuch, Kai Hendrik Wöhnert, Volker Skwarek
Due to increasing security requirements e. g. for transaction based smart-x-technologies in distributed systems, blockchain technologies are predestined for secure data exchange and keeping in distributed systems. Although the underlying principle of almost every blockchain is the Byzantine fault tolerance (BFT), its implementation differs significantly between the technologies so that migration or interoperability between systems is nearly impossible. Additionally, this missing interoperability also reduces the chance for scalability between different extents of implementation as there is usually not a one-size-fits-all-blockchain: Different technologies have their advantages for different systems. Therefore scalability and interoperability are tightly coupled. As a basis for further research on and the derivation of generally scalable and interoperable architectures of blockchains, current technologies have to be made comparable and interoperability criteria have to be developed. This paper analyses current literature and introduces technical criteria for the comparison of blockchainand distributed ledger technologies (BC/DLT).With a list of eleven criteria popular BC/DLTs such as Bitcoin, Ethereum, Hyperledger Fabric, Ripple and Corda are compared regarding general features.
Trusted Execution Environments (TEEs), such as Intel SGX enclaves, use hardware to ensure the confidentiality and integrity of operations on sensitive data. While the technology is available on many processors, the complexity of its programming model and its performance overhead have limited adoption. TEEs provide a new and valuable hardware functionality that has no obvious analogue in programming languages, which means that developers must manually partition their application into trusted and untrusted components. This paper describes an approach that fully integrates trusted execution into a language. We extend the Go language to allow a programmer to execute a goroutine within an enclave, to use low-overhead channels to communicate between the trusted and untrusted environments, and to rely on a compiler to automatically extract the secure code and data. Our prototype compiler and runtime, GOTEE, is a backward-compatible fork of the Go compiler. The evaluation shows that our compiler-driven code and data partitioning efficiently executes both microbenchmarks and applications. On the former, GOTEE achieves a 5.2×throughput and a 2.3× latency improvement over the Intel SGX SDK. Our case studies, a Go ssh server, the Go tls package, and a secured keystore inspired by the go-ethereum project, demonstrate that minor source-code modifications suffice to provide confidentiality and integrity guarantees with only moderate performance overheads.
Open access
Security and Verification in Computing
Advanced Malware Detection Techniques
Physical Unclonable Functions (PUFs) and Hardware Security