As an append-only distributed database, blockchain is utilized in a vast variety of applications including the cryptocurrency and Internet-of-Things (IoT). The existing blockchain solutions show downsides in communication and storage scalability, as well as decentralization. In this article, we propose LightChain , which is the first blockchain architecture that operates over a Distributed Hash Table (DHT) of participating peers. LightChain is a permissionless blockchain that provides addressable blocks and transactions within the network, which makes them efficiently accessible by all peers. Each block and transaction is replicated within the DHT of peers and is retrieved in an on-demand manner. Hence, peers in LightChain are not required to retrieve or keep the entire ledger. LightChain is fair as all of the participating peers have a uniform chance of being involved in the consensus regardless of their influence such as hashing power or stake. We provide formal mathematical analysis and experimental results (simulations and cloud deployment) to demonstrate the security, efficiency, and fairness of LightChain , and show that LightChain is the only existing blockchain that can provide integrity under the corrupted majority power of peers. As we experimentally demonstrate, compared to the mainstream blockchains such as Bitcoin and Ethereum, LightChain requires around 66 times smaller per node storage, and is around 380 times faster on bootstrapping a new node to the system, and each LightChain node is rewarded equally likely for participating in the protocol.
Long Shi, Taotao Wang, Jun Li, Shengli Zhang · 5 authors
As the underlying consensus protocol of Bitcoin and Ethereum blockchains, Proof-of-Work (PoW) features a cryptographic mathematical puzzle whose solution is easy to verify but extremely hard to solve. Under PoW, miners maintain the security of blockchain by devoting computing powers to solve the puzzle; the miner who has solved the puzzle successfully generates a block, along with a reward (e.g., a set of cryptocurrency). The average waiting time to generate a block is inversely proportional to the computing power of the miner. To reduce the average block generation time, a group of individual miners can form a centralized mining pool to aggregate their computing power to solve the puzzle together and share the reward contained in the block. However, if the aggregated computing power of the pool forms a substantial portion of the total computing power in the network, the pooled mining undermines the core spirit of blockchain, i.e., the decentralization, and harms its security. To discourage the pooled mining, we develop a new consensus protocol called Proof-of-Age (PoA) that builds upon the native PoW protocol. The core idea of PoA lies in using Age-of-Work (AoW) to measure the effective mining periods that the miners have devoted to maintaining the security of blockchain. Unlike in the native PoW protocol, in our PoA protocol, miners benefit from its effective mining periods even if they have not successfully mined a block. We first employ a continuous time Markov chain (CTMC) to model the block generation process of the PoA based blockchain. Based on this CTMC model, we then analyze the block generation rates of the mining pool and solo miners respectively. Our analytical results verify that under PoA, the block generation rates of miners in the mining pool are reduced compared to that of solo miners, thereby disincentivizing the pooled mining. Finally, we simulate the mining process in the PoA blockchain to demonstrate the consistency of the analytical results.
First, a big data analysis of the transactions and smart contracts made on the Ethereum blockchain is performed, revealing interesting trends in motion. Next, these trends are compared with the public's interest in Ether and Bitcoin, measured by the volume of online searches. An analysis of the crypto prices and search trends suggests the existence of big players (and not the regular users), manipulating the market after a drop in prices. Lastly, a cross-correlation study of crypto prices and search trends reveals the pairs providing more accurate and timely predictions of Ether prices.
First, a big data analysis of the transactions and smart contracts made on\nthe Ethereum blockchain is performed, revealing interesting trends in motion.\nNext, these trends are compared with the public's interest in Ether and\nBitcoin, measured by the volume of online searches. An analysis of the crypto\nprices and search trends suggests the existence of big players (and not the\nregular users), manipulating the market after a drop in prices. Lastly, a\ncross-correlation study of crypto prices and search trends reveals the pairs\nproviding more accurate and timely predictions of Ether prices.\n
Samuel Asumadu Sarkodie, Maruf Yakubu Ahmed, Phebe Asantewaa Owusu
The COVID-19 global pandemic has disrupted business-as-usual, hence, affecting sustained economic development across countries. However, it appears economic uncertainty following COVID-19 containment measures favor market signals of cryptocurrencies. Here, this study empirically and structurally investigates the implication of COVID-19 health outcomes on market prices of Bitcoin, Bitcoin Cash, Ethereum, and Litecoin. Evidence from the novel Romano-Wolf multiple hypotheses reveal COVID-19 shocks spur Litecoin by 3.20-3.84%, Bitcoin by 2.71-3.27%, Ethereum by 1.43-1.75%, and Bitcoin Cash by 1.34-1.62%.
Hyeong Joon Kim, Hye Hyeon Kim, Hosuk Ku, Kyung Don Yoo · 11 authors
BACKGROUND: ) for data privacy and participatory medicine; however, its fully decentralized architecture has come at the expense of decentralized data management and data provenance. OBJECTIVE: The introduction of blockchain and smart contract technologies to the legacy Health Avatar Platform with a clinical metadata registry remarkably strengthens decentralized health data integrity and immutable transaction traceability at the corresponding data-element level in a privacy-preserving fashion. A crypto-economy ecosystem was built to facilitate secure and traceable exchanges of sensitive health data. METHODS: The Health Avatar Platform decentralizes patient data in appropriate locations (ie, on patients' smartphones and on physicians' smart devices). We implemented an Ethereum-based hash chain for all transactions and smart contract-based processes to guarantee decentralized data integrity and to generate block data containing transaction metadata on-chain. Parameters of all types of data communications were enumerated and incorporated into 3 smart contracts, in this case, a health data transaction manager, a transaction status manager, and an application programming interface transaction manager. The actual decentralized health data are managed in an off-chain manner on appropriate smart devices and authenticated by hashed metadata on-chain. RESULTS: Metadata of each data transaction are captured in a Health Avatar Platform blockchain node by the smart contracts. We provide workflow diagrams each of the 3 use cases of data push (from a physician app or an intelligent agents to a patient Avatar), data pull (request to a patient Avatar by other entities), and data backup transactions. Each transaction can be finely managed at the corresponding data-element level rather than at the resource or document levels. Hash-chained metadata support data element-level verification of data integrity in subsequent transactions. Smart contracts can incentivize transactions for data sharing and intelligent digital health care services. CONCLUSIONS: Health Avatar Platform and interconnected patient Avatars, physician apps, and intelligent agents provide a decentralized blockchain ecosystem for health data that enables trusted and finely tuned data sharing and facilitates health value-creating transactions with smart contracts.
Guntur Dharma Putra, Volkan Dedeoglu, Salil S. Kanhere, Raja Jurdak · 5 authors
Authorization or access control limits the actions a user may perform on a computer system, based on predetermined access control policies, thus preventing access by illegitimate actors. Access control for the Internet of Things (IoT) should be tailored to take inherent IoT network scale and device resource constraints into consideration. However, common authorization systems in IoT employ conventional schemes, which suffer from overheads and centralization. Recent research trends suggest that blockchain has the potential to tackle the issues of access control in IoT. However, proposed solutions overlook the importance of building dynamic and flexible access control mechanisms. In this paper, we design a decentralized attribute-based access control mechanism with an auxiliary Trust and Reputation System (TRS) for IoT authorization. Our system progressively quantifies the trust and reputation scores of each node in the network and incorporates the scores into the access control mechanism to achieve dynamic and flexible access control. We design our system to run on a public blockchain, but we separate the storage of sensitive information, such as user's attributes, to private sidechains for privacy preservation. We implement our solution in a public Rinkeby Ethereum test-network interconnected with a lab-scale testbed. Our evaluations consider various performance metrics to highlight the applicability of our solution for IoT contexts.
Data analytics based on the produced data from the Internet of Things (IoT) devices is expected to improve the individuals' quality of life. However, ensuring security and privacy in the IoT data aggregation process is a non-trivial task. Generally, the IoT data aggregation process is based on centralized servers. Yet, in the case of distributed approaches, it is difficult to coordinate several untrustworthy parties. Fortunately, the blockchain may provide decentralization while overcoming the trust problem. Consequently, blockchain-based IoT data aggregation may become a reasonable choice for the design of a privacy-preserving system. To this end, we propose PrivDA, a Privacy-preserving IoT Data Aggregation scheme based on the blockchain and homomorphic encryption technologies. In the proposed system, each data consumer can create a smart contract and publish both terms of service and requested IoT data. Thus, the smart contract puts together into one group potential data producers that can answer the consumer's request and chooses one aggregator, the role of which is to compute the group requested result using homomorphic computations. Therefore, group-level aggregation obfuscates IoT data, which complicates sensitive information inference from a single IoT device. Finally, we deploy the proposal on a private Ethereum blockchain and give the performance evaluation.
Kurz nach der Veröffentlichung des White Papers zu Bitcoin im Jahr 2008 wurde Blockchain zu einer der am meisten diskutierten und gehypten Technologien der letzten zwei Jahrzehnte. Bitcoin führte eine kryptografisch gesicherte dezentrale Plattform für die Übertragung digitaler Vermögenswerte (die Kryptowährung Bitcoin) mit freiem Zugriff für alle ein. Einige Jahre später ging ein neuer „Player“ einen Schritt weiter: Ethereum führte die Idee eines Blockchain-basierten globalen, dezentralen Computers ein, auf dem jeder Programme auf beobachtbare und transparente Weise bereitstellen und ausführen kann. Diese als Smart Contracts (SCs) bezeichneten Programme sind zwar in der Lage, jedes entscheidbare Problem zu berechnen, sie ermöglichen jedoch in erster Linie Parteien, ein Rahmenwerk für Verträge einzurichten, ohne dass ein vertrauenswürdiger Vermittler erforderlich ist. Tatsächlich verlagert sich das Vertrauen dadurch zu den transparenten Mechanismen der Blockchain. In dieser Arbeit untersuchen wir das Ökosystem von Ethereum hinsichtlich der auf der Mainchain bereitgestellten SCs und legen einen Fokus auf die in den SCs verwendeten Authentifizierungsmuster. Diese Muster beschränken einige Funktionen der SCs, indem sie nur bestimmten Adressen erlauben, den abgesicherten Teil der Funktion auszuführen. Als Methoden für unsere Analyse führen wir die symbolische Ausführung und die Taint-Analyse ein, welche Werkzeuge sind, mit denen der Bytecode eines Programms semantisch analysiert wird. Basierend auf diesen Tools schlagen wir heuristische Erkennungsstrategien vor, um automatisch vier Authentifizierungsmuster zu erkennen, die wir im Ethereum-Bytecode von SCs finden. Darüber hinaus bewerten wir die Erkennungsstrategien anhand eines Testsatzes manuell klassifizierter SCs.
The Android platform is undoubtedly the most popular platform for smartphones, with thousands of new applications becoming available daily and billions of app installations each year. Ethereum is the most popular smart contract platform, with thousands of applications on the blockchain serving as trading platforms and providing other functionalities. Due to these platforms’ popularity, security issues in their applications may reach a catastrophic scale with ease. Several prominent automated techniques help to reveal security problems in applications at the early stages of expansion. One such technique is static analysis. This thesis focuses on the design of static analysis techniques for Android apps and smart contracts distributed in the form of low-level code (bytecode).After installation, an Android app may get access to a set of sensitive information sources (e.g., location data). Unfortunately, exposure of such information to third parties has led in the past to several cases of privacy breach, and continues to be a serious threat. In this thesis, we tackle information flow propagation in the bytecode of Android applications by sound Horn-clause based abstraction techniques. This work will be the first to use Horn-clause based techniques in the context of security analysis. Moreover, we prove that our approach is sound, that is, our approach provides guarantees for its results. As a consequence, it can be used to show the absence of explicit data leaks in an app. Furthermore, Horn-clause based abstraction techniques are not limited to information propagation tasks, that is, our techniques can be used to show any kind of program property expressed as a reachability property. In addition, our Horn-clause based techniques scale to large codebases, benefit from the advancements in Satisfiability Modulo Theory solving, and allow for favorable performance with respect to the state-of-the-art. We instantiate the principles that were obtained while developing the analysis techniques for Android applications in the context of Ethereum smart contracts distributed in the form of Ethereum Virtual Machine (EVM) bytecode. Smart contracts are programs mainly used to perform financial operations (e.g., auctions) on cryptocurrency blockchains (e.g., Ethereum). Recent attacks demonstrate that certain vulnerabilities in smart contracts might cause severe money loss and an overall decrease of trust in the technology. Therefore, security analysis of EVM bytecode is in the focus of the research community. This thesis presents two results which establish the foundations for sound security analysis of EVM bytecode. First, the semantics of EVM bytecode is mechanized for the first time and tested against the official Ethereum test suite. This result facilitates both the design of analysis techniques and establishing their correctness properties. Second, this thesis provides the first sound Control Flow Graph reconstruction solution for EVM bytecode, that is, our analysis guarantees that reachable parts of the code are never pruned. This guarantee is required by a number of security properties for smart contracts. We also develop a tool implementing our analysis and successfully evaluate it on a big collection of real-world contracts.
Abstract The block chain technology enjoys a promising development prospect. As one of the most popular technologies, block chain has been heatedly studied and researched by people from all walks of life. Based on an introduction to the technical background and basic concepts of block chain, by analyzing the technical architecture and working principle of block chain, this paper systematically explains the key technologies of block chain, namely decentralization, proof of work (POW), smart contract and Ethereum, and further discusses the development of the block chain technology, 5G, the Internet of Things and the future wireless network.
Lodovico Giaretta, Ioannis Savvidis, Thomas Marchioro, Šarūnas Girdzijauskas · 7 authors
We envision PDS<sup>2</sup>, a decentralized data marketplace in which consumers submit their tasks to be run within the platform, on the data of willing providers. The goal of PDS2is to ensure that users maintain full control on their data and do not compromise their privacy, while being rewarded for the value that their data generates. In order to achieve this, our marketplace architecture employs blockchain technology, privacy-preserving computation and decentralized machine learning. We then compare different potential solutions and identify the Ethereum blockchain, trusted execution environments and gossip learning as the most suitable for the implementation of PDS<sup>2</sup>. We also discuss the main open challenges that are left to tackle and possible directions for future work.
Academic degrees are subject to corruptions, system flaws, forgeries, and imitations. In this paper we propose to develop a blockchain smart contract-based application using Ethereum Platform, to store, distribute and verify academic certificates. It constitutes a trusted, decentralized certificate’s management system that can offer a unified viewpoint for students, academic institutions, as well as for other potential stakeholders such as employers. The article describes the implementation of three main parts of our proposed solution that includes: verification application, university interface and accreditor interface. This application avoids administrative barriers, makes the process of deployment, verification, and validation of certificates faster, efficient, and more secure. Additionally, it offers confidentiality of the data by using AES encryption algorithm before creating transactions and allows bulk submission of multiple academic certificates.
5G and beyond (B5G) networks are leading a digital revolution in telecommunication in both academia and industry. It brings new paradigms in many aspects of people's daily lives due to its advantages. However, it still leaves some issues in terms of security and privacy as challenges. Blockchain, the public database, is an alternative to the traditional centralized systems, serving as the backbone technique in many systems, including manufacturing, economics, and industry. Blockchain is promising in solving the security issues in the sense that it provides desirable properties including decentralization, transparency, immutability, and so on. In this article, we investigate typical security and privacy issues in edge intelligence in B5G networks and devise a framework to integrate blockchain with such systems, which can provide guaranteed security as well as privacy. We also illustrate several possible solutions to these security and privacy issues in edge intelligence in B5G systems based on blockchain and Ethereum to show how blockchain contributes to the coming B5G networks.
Financial Regulation is a form of compliance system that subjects financial institutions to certain requirements and restrictions. Investment Compliance is an example that involves investment restrictions and monitoring on behalf of investors. Hedge Funds differ from other traditional funds such as mutual funds because of their ability to employ complex investment and hedging techniques. These are private entities with few public disclosure requirements. This is useful in a way as the strategies used are confidential which allows financial agents to participate in the financial markets without any fear of information leakage, hence promoting liquidity. However, this is often implied as a lack of transparency. Hedge Funds are expected to produce higher returns, but sometimes investors seek a risk guarantee in addition to higher returns. However, too much transparency rules out the incentives financial entities have by participating in the first place. On the other hand, too much secrecy may give rise to malicious entities that can break the rules due to a lack of compliance. We aim to solve this problem of protecting investors while ensuring the privacy of financial bodies using zero knowledge proofs. Proofs can be visualized as a way of providing enough information to investors while the zero-knowledge property of proofs maintains the privacy of the fund manager’s strategies. We propose a protocol to address this scenario using Zokrates, a framework for verifiable computation using Zk-SNARKs on Ethereum, to encode the constraints and export the verifier. Based on our implementation and analysis, it can be concluded that zero knowledge proofs provide us with a variety of ways to develop compliance systems.
Riaz Ahmad Ziar, Syed Irfanullah, Wajid Ullah Khan, Abdus Salam
Blockchain technology provides several suitable characteristics such as immutability, decentralization and verifiable ledger. It records the transactions in a decentralized way and can be integrated into several fields like eHealth, e-Government and smart cities etc. However, blockchain has several privacy and security issues, one of them is the on-chain data privacy. To deal with this issue we provide a privacy-preserving solution for permission less blockchain to empower the user to take control of transaction data in the open ledger. This work focuses on designing and developing the peer-to-peer system using symmetric cryptography and ethereum smart contract. In this scheme, we create smart contracts for the interaction of the data provider, data consumer, and access control list. Data providers register authorized users in the access control list. Data consumers can check their validity in the access control list. After successful validation, data consumers can request the security key from data providers to access secret information. Based on successful validation, a smart contract that is created between the data provider and data consumer is executed to send a key to the data consumer for accessing the secret information. The smart contracts of this proposed model are modeled in solidity, and the performance of the contracts is assessed in the Ropsten test network.
Ahmed Jeribi, Yasmine Snene Manzli, Islem Khefacha
Abstract Using the DCC-GARCH (1.1) model, we investigate the dynamic conditional correlations between Tunisian indices, digital assets, and gold prices for the period ranging from 4 January 2016 to 30 April 2020. Our findings reveal that digital assets (Bitcoin, Ripple, Ethereum, and Dash) and gold can be considered as hedge and diversifier assets before the 2020 global pandemic. Contrarily to Ripple which can be a safe haven asset for the Tunisian investors in early 2020, Monero can be considered as a diversifier asset more than a hedge. Finally, our results can be useful to Tunisian investors when accounting for implementing hedging strategies. JEL classification: C22, C5, G1
Objective: creating the corporate governance structure and legal regulation mechanism of blockchain protocols.Methods: dialectical approach to cognition of social phenomena, allowing to analyze them in historical development and functioning in the context of the totality of objective and subjective factors, which predetermined the following research methods: formal-logical, comparative-legal, and sociological.Results: Blockchain technology was born out of a Cypherpunk vision for regulation without sacrificing privacy. This vision feeds a call by some in the blockchain technology ecosystem to view computer code as the only law applicable to blockchain protocols, transactions conducted on the protocols, and DAOs. The code of certain protocols, such as the Bitcoin blockchain and Ethereum, currently embody their Cypherpunk cultural origins, placing a premium on privacy and governance mechanisms that preserve privacy. But that code can change. In fact, laws enacted and enforced by governments may act as the stimuli for such change. Indeed, such stimuli, for better or worse, are already in play, with coders ceasing work for fear of legal repercussions. Adopting a contract-based governance system in which the rules and expectations are clearly defined empowers blockchain protocol communities to preserve as much of their cultures and visions as possible. Adopting these contracts also requires blockchain communities to engage in open, active, and thoughtful conversation about their collective culture and vision. Further, basing blockchain governance structures in contracts that loosely resemble corporate governance structures allows such communities to tap into centuries of scholarship and experimentation in a functionally equivalent governance arena. Scientific novelty: the work proves that the biggest cultural impact of (un)corporate crypto-governance may be on the culture of traditional corporations. Indeed, one significant lesson of a corporate governance model for off-chain governance may be a sharpened recognition that “code as law” is a subsystem of regulatory norms within the greater legal system. Viewed through systems analysis, the result is a two-way recognition of the interconnected roles of code and law in limiting behavior within the blockchain ecosystem. In other words, the code informs the law and its application to a blockchain ecosystem. Meanwhile, law informs behavior and activities undertaken through the code. The result is that the intersection of code and law can impact our understanding of how to apply the law in more traditional scenarios as well.Practical significance: the main provisions and conclusions of the article can be used in scientific, pedagogical and law enforcement activities when considering issues related to (un)corporate crypto-governance.
Cho Nwe Zin Latt, Sandi Rahmadika, Kyung-Hyune Rhee
The Myanmar rice cycle’s existing system is still relying on a third party to manage every rice data information from several organizations. It is inconvenient to supervise simultaneously due to the unreliability of information provided by organizations. Thus, the rice cycle’s original data is challenging to be utterly trusted since irresponsible parties can manipulate the current state of information. Moreover, the applied system does not preserve a proper incentive for the involved parties. In this paper, we leverage the Ethereum blockchain to be adopted to tackle the aforementioned issues. The main objective is to build trust between parties in the Myanmar rice cycle system. Our proposed scheme allows customers to check and trace information about the rice cycle information without worrying about the integrity of the data. Furthermore, the authorized parties are also rewarded by the government through Ethereum smart contract features. Eventually, our scheme achieves traceability in the rice chain system and leads to the complete digitization and automation of the rice cycle information.
Borcun kaynaklarından biri olan sözleşmelerin temelinde tarafların sözleşme yapmak konusunda iradelerini açıklamaları ve bu iradelerin birbiri ile uyuşması yatar. Sözleşmesel yükümlülüklerin sözleşmelerde düzenlenen şekilde yerine getirilmesi önemlidir. Bu nokta, taraflarının iradelerine tabi olup ve birbirlerine yönelik karşılıklı güvenlerine dayanır. Sözleşmelerin gereği gibi ifası, dayanağı ve kaynağı bakımından hassas, zayıf ve kırılgandır. Zira, taraflar her zaman birbirlerinin iradelerini tam ve doğru şekilde anlayamayabilir. Yine böylesine akitlerde taraflar, aradan geçen zamanın veya değişen şartların etkisiyle yahut ortada bunun için zorlayıcı bir sebep yokken bile sözleşmeye yansıyan iradesine konu taahhüdünü tam veya zamanında yerine getirmekten kaçınabilir. Güven esasına dayanan sözleşmelerin ifası itimat asimetrisi riskine ve taraf iradesinin zaaflarına tabidir. Teknoloji, güven ve sözleşmelerin ifa edilmesine dair bu risklerin giderilmesine çözüm getirebilir mi? İşte bu soru, Bitcoin ile ortaya çıkan Blokzincir teknolojisini pek çok yönden daha ileri taşıyan Ethereum ile birlikte daha fazla tartışılır, merak edilir hale gelmiştir. Ethereum ile beraber tekrar hatırlanan ve Blokzincir teknolojisi ile yeniden yorumlanan akıllı sözleşme kavramı mezkur sözleşmenin, taraflarının karşılıklı, subjektif güvenine mahkum edilmeden, kendi kendini ifa edebilmesinin yeniden tartışılmasına ve heyecanla karşılanmasına yol açmıştır. Bu makalede, Ethereum üzerinde geliştirilebilen ve uygulanabilen akıllı sözleşmelerin ne anlama geldiği, kendi kendini nasıl ifa edebildiği, gelecekteki teknoloji ve hukuk işbirliğine dair hangi etkileşimleri yarattığı ve bunların hukuki sonuçlarına incelenmektedir.
Proof-of-Work (PoW) is the most widely adopted incentive model in current blockchain systems, which unfortunately is energy inefficient. Proof-of-Stake (PoS) is then proposed to tackle the energy issue. The rich-get-richer concern of PoS has been heavily debated in the blockchain community. The debate is centered around the argument that whether rich miners possessing more stakes will obtain higher staking rewards and further increase their potential income in the future. In this paper, we define two types of fairness, i.e., expectational fairness and robust fairness, that are useful for answering this question. In particular, expectational fairness illustrates that the expected income of a miner is proportional to her initial investment, indicating that the expected return on investment is a constant. To better capture the uncertainty of mining outcomes, robust fairness is proposed to characterize whether the return on investment concentrates to a constant with high probability as time evolves. Our analysis shows that the classical PoW mechanism can always preserve both types of fairness as long as the mining game runs for a sufficiently long time. Furthermore, we observe that current PoS blockchains implement various incentive models and discuss three representatives, namely ML-PoS, SL-PoS and C-PoS. We find that (i) ML-PoS (e.g., Qtum and Blackcoin) preserves expectational fairness but may not achieve robust fairness, (ii) SL-PoS (e.g., NXT) does not protect any type of fairness, and (iii) C-PoS (e.g., Ethereum 2.0) outperforms ML-PoS in terms of robust fairness while still maintaining expectational fairness. Finally, massive experiments on real blockchain systems and extensive numerical simulations are performed to validate our analysis.
Unlike conventional cryptocurrencies, Islamic ones are new technologies backed by tangible assets and are characterised by their fundamental values. After the COVID-19 outbreak, cryptocurrency responses have shown different behaviour to stock market reactions. However, there is a lack of studies on the efficiency of Islamic and green cryptocurrencies during the pandemic. This paper attempts to analyse the behaviour of three typical families of cryptocurrencies (conventional, Islamic, and green) extracted according to their availability in daily frequencies during COVID-19. For this purpose, their efficiency levels are studied before and after the outbreak by employing multifractal detrended fluctuation analysis (MFDFA) to make the best predictions and strategies. The inefficiency of the cryptocurrencies is assessed through a magnitude of long-memory (MLM) efficiency index, and the impact of COVID-19 on their efficiency is evaluated. The primary results show that HelloGold was the most efficient market before the COVID-19 outbreak and that subsequently Ethereum has been the most efficient. In addition, the findings reveal that the cryptocurrency reactions are not similar and show more resilience in the Ethereum and Litecoin markets than in other cryptocurrency markets. The main contribution of this study is the evaluation of the impact of COVID-19 on the various classes of crypto money. This work has practical implications, as it provides new insights into trading opportunities and market reactions. Moreover, he work has theoretical implications based on its evaluation of three distinct models from different doctrine viewpoints.
Matheus V. X. Ferreira, Daniel J. Moroz, David C. Parkes, Mitchell Stern
In recent years, prominent blockchain systems such as Bitcoin and Ethereum have experienced explosive growth in transaction volume, leading to frequent surges in demand for limited block space and causing transaction fees to fluctuate by orders of magnitude. Existing systems sell space using first-price auctions; however, users find it difficult to estimate how much they need to bid in order to get their transactions accepted onto the chain. If they bid too low, their transactions can have long confirmation times. If they bid too high, they pay larger fees than necessary. In light of these issues, new transaction fee mechanisms have been proposed, most notably EIP-1559, aiming to provide better usability. EIP-1559 is a history-dependent mechanism that relies on block utilization to adjust a base fee. We propose an alternative design -- a {\em dynamic posted-price mechanism} -- which uses not only block utilization but also observable bids from past blocks to compute a posted price for subsequent blocks. We show its potential to reduce price volatility by providing examples for which the prices of EIP-1559 are unstable while the prices of the proposed mechanism are stable. More generally, whenever the demand for the blockchain stabilizes, we ask if our mechanism is able to converge to a stable state. Our main result provides sufficient conditions in a probabilistic setting for which the proposed mechanism is approximately welfare optimal and the prices are stable. Our main technical contribution towards establishing stability is an iterative algorithm that, given oracle access to a Lipschitz continuous and strictly concave function $f$, converges to a fixed point of $f$.
Tzung‐Her Chen, Ting-Le Zhu, Fuh-Gwo Jeng, Chien-Lung Wang
Although encryption and signatures have been two fundamental technologies for cryptosystems, they still receive considerable attention in academia due to the focus on reducing computational costs and communication overhead. In the past decade, applying certificateless signcryption schemes to solve the higher cost of maintaining the certificate chain issued by a certificate authority (CA) has been studied. With the recent increase in the interest in blockchains, signcryption is being revisited as a new possibility. The concepts of a blockchain as a CA and a transaction as a certificate proposed in this paper aim to use a blockchain without CAs or a trusted third party (TTP). The proposed provably secure signcryption scheme implements a designated recipient beforehand such that a sender can cryptographically facilitate the interoperation on the blockchain information with the designated recipient. Thus, the proposed scheme benefits from the following advantages: (1) it removes the high maintenance cost from involving CAs or a TTP, (2) it seamlessly integrates with blockchains, and (3) it provides confidential transactions. This paper also presents the theoretical security analysis and assesses the performance via the simulation results. Upon evaluating the operational cost in real currency based on Ethereum, the experimental results demonstrate that the proposed scheme only requires a small cost as a fee.