Abstract This study investigates how twelve cryptocurrencies with large capitalization get influenced by the three cryptocurrencies with the largest market capitalization (Bitcoin, Ethereum, and Ripple). Twenty alternative specifications of ARCH, GARCH as well as DCC-GARCH are employed. Daily data covers the period from 1 January 1 2018 to 16 September 2018, representing the intense bearish cryptocurrency market. Empirical outcomes reveal that volatility among digital currencies is not best described by the same specification but varies according to the currency. It is evident that most cryptocurrencies have a positive relationship with Bitcoin, Ethereum and Ripple, therefore, there is no great possibility of hedging for crypto-currency portfolio managers and investors in distressed times.
The patients' medical image data are one of the most important data in e-health. Medical image data usually play a crucial role in disease diagnosis and implicate unpredictable potential values for improving diagnostic methods and adjusting diagnostic results. To exploit their incredible potential values, medical images need to be shared among different hospitals, medical institutions and insurance companies and others. But how to securely and effectively share these medical image data becomes a challenging problem. In this paper, we proposed to combine encryption and digital watermark technology to achieve a secure and privacy-preserving medical image sharing method. The QR code image of the concatenation of authoritative diagnosis results and the hash of the original medical image is generated as the watermark image. The Discrete cosine transform (DCT) and Inverse DCT (IDCT) algorithms are utilized to embed the watermark image. As the watermarked medical images are desensitized, they are stored to a smart contract based blockchain, such as Ethereum, to achieve secure and fair sharing between data owners and users. The experimental results show that the proposed method can resist several attacks meanwhile it is efficient in medical image sharing.
Open access
Advanced Steganography and Watermarking Techniques
Pol Alemany, Ricard Vilalta, RaĂŒl Muñoz, Ramon Casellas · 5 authors
This paper presents a non-hierarchical architecture to deploy End-to-End Network Slices in a multi-domain network using an Ethereum-based Blockchain to manage the Network Slicing requests across domains. The use of Blockchain aims to look towards a collaboration vision to deploy Networks Slices using the resources to deploy them as if they would be placed under the domain of the Network Slice requester. The authors describe a possible instantiation procedure and they present results showing how much the use of Blockchain might increase the deployment time of an End-to-End Network Slice.
It is widely accepted that Ethereum mining is highly centralized. Nonetheless, centralization has been mostly characterized by exclusively looking at the influence that independent miners or mining pools can have over the network. Moreover, models of mining behavior assume that miners are either unrelated or only relate via mining pools under highly structured and transparent agreements. If these assumptions and the predictions they entail were to be completely accurate, there would not be any evidence of on-chain transactions between miners, other than the ones expected from mining pool payouts. By looking at on-chain transactions between miners in the Ethereum Network we find that aside from the payouts from mining pools to small miners, there are also transactions that define relationships between mining pools, independent miners and between independent miners and mining pools. Furthermore, by characterizing the topology of the network of miner transactions, we find the emergence of highly connected clusters that control significant amounts of hashing power and exhibit relationships in the opposite direction of what theoretical models predict. This more nuanced characterization of mining centralization can help identify network vulnerabilities and inform protocol redesigns.
Advancements in distributed ledger technologies are rapidly driving the rise of decentralized crowdsourcing systems on top of open smart contract platforms like Ethereum. While decentralized blockchain-based crowdsourcing provides numerous benefits compared to centralized solutions, current implementations of decentralized crowdsourcing suffer from fundamental scalability limitations by requiring all participants to pay a small transaction fee every time they interact with the blockchain. This increases the cost of using decentralized crowdsourcing solutions, resulting in a total payment that could be even higher than the price charged by centralized crowdsourcing platforms. This paper proposes a novel suite of protocols called NF-Crowd that resolves the scalability issue by reducing the lower bound of the total cost of a decentralized crowdsourcing project to O(1). NF-Crowd is a highly reliable solution for scaling decentralized crowdsourcing. We prove that as long as participants of a project powered by NF-Crowd are rational, the O(1) lower bound of cost could be reached regardless of the scale of the crowd. We also demonstrate that as long as at least one participant of a project powered by NF-Crowd is honest, the project cannot be aborted and the results are guaranteed to be correct. We design NF-Crowd protocols for a representative type of project named crowdsourcing contest with open community review (CC-OCR). We implement the protocols over the Ethereum official test network. Our results demonstrate that NF-Crowd protocols can reduce the cost of running a CC-OCR project to less than $2 regardless of the scale of the crowd, providing a significant cost benefit in adopting decentralized crowdsourcing solutions.
This paper studies how a simple approach based on fuzzing testing can help authors of Solidity contracts to accurately estimate the gas cost of services specified in a contract. Our fuzzer creates a private blockchain and randomly generates transactions. Such an environment is meant to simulate large scale behavior that may be seen in a public blockchain. Our fuzzer handles Ethereum starting and target endpoints in a transaction to accommodate requirements expressed in financial contracts. By comparing the gas computation made by the Ethereum Solidity compiler and the actual consumption during our fuzzing, we are able to find discrepancies between predicted and real gas consumption. Our findings are beneficial to transaction authors to correctly predict the computing resources of Ethereum miners.
Ethereum is the largest blockchain platform that supports smart contracts. Users deploy smart contracts by publishing the smart contract's bytecode to the blockchain. Since the data in the blockchain cannot be modified, even if these contracts contain bugs, it is not possible to patch deployed smart contracts with code updates. Moreover, there is currently neither a comprehensive classification framework for Ethereum smart contract bugs, nor detailed criteria for detecting bugs in smart contracts, making it difficult for developers to fully understand the negative effects of bugs and design new approaches to detect bugs. In this paper, to fill the gap, we first collect as many smart contract bugs as possible from multiple sources and divide these bugs into 9 categories by extending the IEEE Standard Classification for Software Anomalies. Then, we design the criteria for detecting each kind of bugs, and construct a dataset of smart contracts covering all kinds of bugs. With our framework and dataset, developers can learn smart contract bugs and develop new tools to detect and locate bugs in smart contracts. Moreover, we evaluate the state-of-the-art tools for smart contract analysis with our dataset and obtain some interesting findings: 1) Mythril, Slither and Remix are the most worthwhile combination of analysis tools. 2) There are still 10 kinds of bugs that cannot be detected by any analysis tool.
O dinheiro eÌ indispensaÌvel para o ser humano e apresenta constantes evoluçoÌes. Com o avanço da tecnologia, diversos meios de pagamento surgiram e dentre eles eÌ possiÌvel destacar as criptomoedas, um assunto recente que tem sido apresentado em diversos meios, sobretudo, como uma possibilidade de investimento. Nesse contexto, o presente trabalho tem como objetivo analisar as caracteriÌsticas tecnoloÌgicas chaves das treÌs criptomoedas que ocupam, atualmente, os maiores iÌndices de capitalizaçaÌo de mercado, sendo elas: Bitcoin, Ethereum e XRP. Para atingir tal objetivo, assumiu-se nesta pesquisa um posicionamento de natureza qualitativa. Aplicou-se teÌcnicas descritivas para retraçar os histoÌricos e a descriçaÌo de suas tecnologias chave. Como resultados, a presente pesquisa demonstrou que as criptomoedas apresentam objetivos diferentes, no entanto, utilizam-se da mesma tecnologia de transaçaÌo, a peer-to-peer. As tecnologias de blockchain, mineraçaÌo e proof-of-work saÌo utilizadas de maneiras distintas por cada uma das criptomoedas. Por fim, considera-se que trabalhos como esse saÌo importantes por colocarem luz nas tecnologias implementadas. Como limitaçoÌes, ressalta-se o estudo em treÌs casos. Abstract Money is indispensable for humans and is constantly evolving. With the advancement of technology, several payment methods have emerged and among them it is possible to highlight cryptocurrencies, a recent subject that was presented in various media, mainlyas a possibility of investment. Therefore, this paper aims to analyze the three cryptocurrencies that occupy the highest market capitalization indexes, namely: Bitcoin, Ethereum and XRP. To achieve this goal, a qualitative approach was assumed in this research. Descriptive techniques were applied to retrace the histories and the description of their key technologies. As a result, the present research demonstrated that cryptocurrencies have different objectives, however, it uses the same peer-to-peer transaction technology. Blockchain, mining and proof-of-work technologies are used in different ways. Finally, it is considered that works like this are important because they shed light on the implemented technologies. Limitations include the application in three cases. Keywords:Tecnologies; Criptocurrencies; Blockchain; Bitcoin; Payment.
This thesis addresses computer security problems in: Access Control, Ethereum Smart Contracts, Cloud VM Scheduling, and Logic Locking. These problems are solved using polynomially timed reductions to 2 complexity classes: PSPACE-Complete and NP-Complete. This thesis is divided into 2 parts, problems reduced to: Model Checking (PSPACE-Complete) and Integer Linear Programming (ILP) (NP-Complete). The PSPACE-Complete problems are: Safety Analysis of Administrative Temporal Role Based Access Control (ATRBAC) Policies, and Safety Analysis of Ethereum Smart Contracts. The NP-Complete problems are: Minimizing Information Leakage in Virtual Machine (VM) Cloud Environments using VM Migrations, and Attacking Logic Locked Circuits using a Reduction to Integer Linear Programming (ILP). \n \nIn Chapter 3, I create the Cree Administrative Temporal Role Based Access Control (ATRBAC)-Safety solver. Which is a reduction from ATRBAC-Safety to Model Checking. I create 4 general performance techniques which can be utilized in any ATRBAC-Safety solver. \n \n 1. Polynomial Time Solving, which is able to solve specific archetypes of ATRBAC-Safety policies using a polynomial timed algorithm. \n 2. Static Pruning, which includes 2 methods for reducing the size of the policy without effecting the result of the safety query. \n 3. Abstraction Refinement, which can increase the speed for reachable safety queries by only solving a subset of the original policy. \n 4. Bound Estimation, which creates a bound on the number of steps from the initial state, where a satisfying state must exist. This is directly used by the model checker's bounded model checking mode, but can be utilized by any solver with a bound limiting parameter. \n \nIn Chapter 4, I analyze ATRBAC-Safety policies to identify some of the ``sources of complexity'' which make solving ATRBAC-Safety policies difficult. I provide analysis of the sources of complexity that exists in the previously published datasets [128,90,54]. I perform analysis of Cree's performance techniques on the previous datasets. I create 2 new datasets, which are shown to be hard instances of ATRBAC-Safety. I analyze the new datasets to show how they achieve this hardness and how they differ from each other and the previous datasets. \n \nIn Chapter 5, I create a novel reduction from a Reduced-Solidity Smart Contract, subset of available Solidity features, to Model Checking. This reduction reduces Reduced-Solidity Smart Contract into a Finite State Machine and then reduces to an instance of a Model Checking problem. This provides the ability to test smart contracts published on the Ethereum blockchain and test if there exists bugs or malicious code. I perform empirical analysis on select Smart contracts. \n \nIn Chapter 6, I create 2 methods for generating instances of ATRBAC policies into Solidity Smart Contracts. The first method is the Generic ATRBAC Smart Contract. This method requires no modification before deployment. After deployed the owner is able to create, and maintain, the policy using special access functions. The special action functions are automated with code that converts an ATRBAC policy into a series of transactions the owner can run. The second method is the Baked ATRBAC Smart Contract. This method takes an ATRBAC policy and reduces it to a Smart Contract instance with no special access functions. The smart contract can then be deployed by anyone, and that person will have no special access. I perform an empirical analysis on the setup costs, transaction costs, and security each provides. \n \nIn Chapter 7, I create a new reduction from Minimizing Information Leakage via Virtual Machine (VM) Migrations to Integer Linear Programming (ILP). I compare a polynomial algorithm by Moon et. al. [71], my ILP reduction, and a reduction to CNF-SAT that is not included in this thesis. The polynomial method is faster, but the problem is NP-Complete thus that solution must have sacrificed something to obtain the polynomial time speed (unless P = NP). I show instances in which the polynomial time algorithm does not produce the minimum total information leakage, but the ILP and CNF-SAT reductions are able to. In addition to this, I show that Total Information Leakage also has a security vulnerability for non-zero information leakage using the <R,C> model. I propose an alternative method to Total Information Leakage, called Max Client-to-Client Information Leakage, which removes the vulnerability at the cost of increased total information leakage. \n \nIn Chapter 8, I create a reduction from the Key Recovery Attack on Logic Locked Circuits to Integer Linear Programming (ILP). This is a recreation of the ``SAT Attack'' using ILP. I provide an empirical analysis of the ILP attack and compare it to the SAT-Attack. I show that ``ILP Attack'' is a viable attack, thus future claims of ``SAT-Attack Resistant Logic Locking Techniques'' need to also show resistance to all potential NP-Complete attacks.
Blockchain technology, beyond cryptocurrencies, is called to be the new information exchange ecosystem due to its unique properties, such as immutability and transparency. The main objective of this work is to introduce the design of a decentralized rental system, which leverages smart contracts and the Ethereum public blockchain. The work started from an exhaustive investigation on the Ethereum platform, emphasizing the aspect of cryptography and all the technology behind this platform. In order to test the proposed scheme in a realistic use, the implementation of a web application for the rental of vehicles has been carried out. The application covers the entire vehicle rental process offered in traditional web applications, adding more autonomy and ease of use to users. Following Ethereum application development guidelines, all business logic is located in the smart contracts implemented in the Ethereum network, where these contracts control the entire vehicle rental system of customers. While this is a work in progress, the results obtained in the first proof of concept have been very promising.
Blockchain is the vehicle on which cryptocurrencies run, and it canât be regulated by any legal entity during its operation.The huge growth in various cryptocurrency segments in 10 years has created the controversy of an inevitable bubble. A bubble can be generated either by queer herd behaviour or logical secular movement. Traces of evident bubbles have been a certainty and they take the perceived valuation of crypto to figures far away from its true value. This sudden diversion can be lethal due to the illogical, irrational propensity of regular market participants. This study observes ten cryptos under surveillance from September 2014 to August 2019. The selected ten (Monero, Bitcoin, XRP Ripple, Litecoin, Dogecoin, Monacoin, Ethereum, Bytecoin, Digibite, Potcoin) cryptocurrencies were studied for the last five years using Right Tailed ADF Test. Prominent traces of the rational bubble in all the underlying cryptocurrencies were found and have been considered for the study.
This article proposes a self-organizing collaborative computing network with an approach to enhance the expectation of a collaborating node for joining the self-organizing network. The proposed approach relies on Ethereum cryptocurrency and Smart Contract to enhance the expectation of collaborating nodes by monetizing the services provided to the self-organizing network. Furthermore, an escrow based smart contract is formalized in the proposed framework to sustains the monetary trust issue between collaborating nodes. The proposed scheme can enforce an autonomic incentive management mechanism to any type of self-organizing networks such as self-organizing clouds, ad-hoc networks, self-organizing federated cloud networks, self-organizing federated learning networks, and self-organizing D2D networks to name a few. Considering the distributed nature of these self-organizing networks and the Ethereum blockchain network, a distributed agent-based methodology is materialized in the proposed framework. Following this, a proof of concept implementation for the general case of a self-organizing cloud is presented. Lastly, the article provides some insights into possible future directions using the proposed framework.
The appearance of so-called block chains or Blockchain with the promise of transforming trust and the way value is exchanged, joins the expansion of the technological capabilities of organizations to achieve higher levels of productivity and innovation. This is how Blockchain-based techniques are being applied to many fields, focusing in this article on the public sector, as a possible solution to the demands for transparency, participation and citizen cooperation that society demands; due to the possibility of disintermediation based on automated transactions and on the responsibility and security in the management of official blockchain records. This could obstruct corruption and make government services more transparent and efficient. Although, it investigates about applications in the public sector under the Blockchain system, such as transactions, agreements, property registries and innovations, developments and other assets; Special emphasis is placed on the possibility of implementing Smart Contracts (mechanisms that aim to eliminate intermediaries to simplify processes) in public procurement procedures, given that it is in this type of activity where high levels of corruption are generated. It is concluded then that Europe has the largest number of blockchain initiatives worldwide, while Latin America, except for the case of Peru, lacks this type of applications, being this continent exactly where there are the countries with the highest levels of corruption. It concludes with a recommendation to use blockchain along with smart contracts through platforms such as Ethereum or Lisk, mainly given its flexibility and current development on topics with similar functionalities.
Aug 25, 2020·ÂThe Âinternational archives of the photogrammetry, remote sensing and spatial information sciences/International archives of the photogrammetry, remote sensing and spatial information sciences
Abstract. Blockchain is an emerging immature technology that disrupt many well established industries nowadays, like finance, supply chain, transportation, energy, official registries (identity, vehicles, âŠ). In this contribution we present a smart contracts library, named Crypto-Spatial, written for the Ethereum Blockchain and designed to serve as a framework for geospatially enabled decentralized applications (dApps) development. The main goal of this work is to investigate the suitability of Blockchain technology for the storage, retrieval and processing of vector geospatial data. The design and the proof-of-concept implementation presented are both based on the Open Geospatial Consortium standards: Simple Feature Access, Discrete Global Grid Systems (DGGS) and Well Known Binary (WKB). Also, the FOAM protocol concept of Crypto-Spatial Coordinate (CSC) was used to uniquely identify spatial features on the Blockchain immutable ledger. The design of the Crypto-Spatial framework was implemented as a set of smart contracts using the Solidity object oriented programming language. The implemented library was assessed toward Etheruemâs best practices design patterns and known security issues (common attacks). Also, a generic architecture for geospatially enabled decentralized applications, combining blockchain and IPFS technologies, was proposed. Finally, a proof-of-concept was developed using the proposed approach which main purpose is to port the UN/FAO-SOLA to Blockchain techspace allowing more transparency and simplifying access to users communities. The smart contracts of this prototype are live on the Rinkeby testnet and the frontend is hosted on Github pages. The source code of the work presented here is available on Github under Apache 2.0 license.
We empirically examine the initial returns of Initial Coin Offerings (ICOs) and show that ICO underpricing is enormous, which implies that cryptocurrency markets are inefficient. Moreover, we find that having a short offering phase, not holding a presale, a precisely written whitepaper, and the creation of an independent blockchain all have a positive impact on ICOsâ initial returns. Our results also suggest that the driving factor behind initial returns is the movement of the cryptocurrency markets, measured by both Bitcoin and Ethereum returns. In addition, whether or not the jurisdiction has cryptocurrency regulations is an influential indicator. ICOs that belong to the high-tech services and platform industries have higher initial returns. Conventional financial assets, such as the stock market and gold, have a positive influence on ICOsâ initial returns.
As the use of online transaction is increasing day by day, the security measure parameter is difficult to manage. In that case, Blockchain enables peer-to-peer transfer of digital assets without any intermediaries in a secure manner with the use of verification and validation operation by different miner nodes of decentralized network. Blockchain technology also supports cryptocurrencies like
bitcoin and ethereum for amount transfer digitally with secure communication.
There are thousands of projects worldwide based primarily on blockchain technology. These have a large number of users and hundreds of use cases. One of the most popular is the use of cryptocurrencies and their benefits against money without intrinsic value (fiat money) and centralized financial solutions. However, although thousands of new transactions are carried out daily in different platforms, uniform and standardized information does not exist to be able to manage the large amount of data that is generated and exchanged between users through transactions and the generation of new blocks. This research reports the development of BLONDiE, an ontology that allows the semantic representation of knowledge to describe the native structure and related information of the three most relevant blockchain projects to date: Bitcoin, Ethereum and in the recent 1.0 version extends its definitions to include Hyperledger, specifically the Hyperledger Fabric infrastructure. Its use allows having common data formats of different platforms for further processing, such as the execution of semantic queries.
Abstract This paper evaluates the presence of regime changes in the logâreturns volatility dynamics of cryptocurrencies using MarkovâSwitching GARCH (MSâGARCH) models. The empirical study compares the prediction performance of MSâGARCH against traditional singleâregime GARCH methods for oneâ, fiveâ and tenâstepsâahead volatility forecasting of six leading digital coins such as Bitcoin, Dashcoin, Ethereum, Litecoin, Monero and Ripple. Using a Bayesian approach, different MSâGARCH structures are estimated considering specifications up to three regimes, three scedastic functions and six error distributions, resulting in a total of 54 models for each cryptocurrency. Forecasts are compared according to an economic criterion, that is, through the estimation of ValueâatâRisk (VaR) and Expected Shortfall (ES) risk measures. The results support the evidence of regime changes in the volatility process of selected cryptocurrencies and show that MSâGARCH models do provide more accurate VaR and ES forecasts than their singleâregime counterparts.
We test whether the selected cryptocurrencies exhibit long memory behavior in returns and volatility. We use data on five most traded cryptocurrencies: Bitcoin, Litecoin, Ethereum, Bitcoin Cash, and XRP. Using recent tests of long memory developed against persistent and nonlinear alternatives, this paper finds that long memory is mostly rejected in returns. The tests fail to reject the null hypothesis of long memory in most cases across different volatility proxies and cryptocurrencies. The estimated memory parameters show that volatility is persistent, and when volatility is measured by log range, it is borderline nonstationary.
The financial crime landscape is evolving along with the digitization in financial services. In this context, laws and regulations cannot efficiently cope with a fast-moving industry such as finance, which translates in late adoption of measures and legal voids, providing a fruitful landscape for malicious actors. In parallel, blockchain technology and its promising features such as immutability, verifiability, and authentication, enhance the opportunities of financial forensics. In this paper, we focus on an embezzlement scheme and we provide a forensic-by-design methodology for its investigation. In addition, the feasibility and adaptability of our approach can be extended and embrace digital investigations on other types of schemes. We provide a functional implementation based on smart contracts and we integrate standardised forensic flows and chain of custody preservation mechanisms. Finally, we discuss the benefits and challenges of the symbiotic relationship between blockchain and financial investigations, along with future research directions.