This work unifies insights from the systems and functional programming communities, in order to enable compositional reasoning about software which is nonetheless efficiently realizable in hardware. It exploits a correspondence between design goals for efficient concurrent data structures and efficient immutable persistent data structures, to produce novel implementations of mutable concurrent trees with low contention and an efficient snapshot operation to support speculative execution models. It also exploits commutativity to characterize a design space for integrating traditional high-performance concurrent data structures into Software Transactional Memory (STM) runtimes, and extends this technique to yield a novel algorithm for concurrent execution of so-called ``smart contracts'' (specialized programs which manipulate the state of blockchain ledgers).
Blockchain or Distributed Ledger Technology is a disruptive technology that provides the infrastructure for developing decentralized applications enabling the implementation of novel business models even in traditionally centralized domains. In the last years it has drawn high interest from the academic community, technology developers and startups thus lots of solutions have been developed to address blockchain technology limitations and the requirements of applications software engineering. In this paper, we provide a comprehensive overview of DLT solutions analyzing the addressed challenges, provided solutions and their usage for developing decentralized applications. Our study reviews over 100 blockchain papers and startup initiatives from which we construct a 3-tier based architecture for decentralized applications and we use it to systematically classify the technology solutions. Protocol and Network Tier solutions address the digital assets registration, transactions, data structure, and privacy and business rules implementation and the creation of peer-to-peer networks, ledger replication, and consensus-based state validation. Scaling Tier solutions address the scalability problems in terms of storage size, transaction throughput, and computational capability. Finally, Federated Tier aggregates integrative solutions across multiple blockchain applications deployments. The paper closes with a discussion on challenges and opportunities for developing decentralized applications by providing a multi-step guideline for decentralizing the design of traditional systems and implementing decentralized applications.
Yibin Xu, Yangyu Huang, Jianhua Shao, George Theodorakopoulos
Blockchain sharding is a promising approach to solving the dilemma between decentralisation and high performance (transaction throughput) for blockchain. The main challenge of Blockchain sharding systems is how to reach a decision on a statement among a sub-group (shard) of people while ensuring the whole population recognises this statement. Namely, the challenge is to prevent an adversary who does not have the majority of nodes globally but have the majority of nodes inside a shard. Most Blockchain sharding approaches can only reach a correct consensus inside a shard with at most $n/3$ evil nodes in a $n$ node system. There is a blockchain sharding approach which can prevent an incorrect decision to be reached when the adversary does not have $n/2$ nodes globally. However, the system can be stopped from reaching consensus (become deadlocked) if the adversary controls a smaller number of nodes. In this paper, we present an improved Blockchain sharding approach that can withstand $n/2$ adversarial nodes and recover from deadlocks. The recovery is made by dynamically adjusting the number of shards and the shard size. A performance analysis suggests our approach has a high performance (transaction throughput) while requiring little bandwidth for synchronisation.
Blockchain enabled digital scarcity has opened up a whole new dimension of possibilities for the token economy, particularly with regards to rights and assets that have not been traded electronically before. Blockchain based tokenization of rights and assets has also brought a new set of legal and regulatory challenges. Regulators and legislators are yet to address many of the issues raised by blockchain based tokenization, from decentralisation and token characterisation to cross border harmonisation and regulatory compliance with traditional market infrastructure. Lack of regulatory alignment can undermine many of the benefits of the token economy. Lack of legal certainty may not only stifle innovation and slow down mainstream adoption of blockchain based tokenization, but can also raise the risks for investors and harm the reputation of the industry. The emerging regulations vary in approach. Liechtenstein became the first country to have comprehensive technology-neutral regulation of the token economy. Malta and Singapore also represent progressive jurisdictions for blockchain regulation. However, most jurisdictions, including the US and the EU, have not yet formed clear policy for blockchain regulation and many legal questions remain open. The paper examines whether there is an emerging predominant regulatory approach or prevailing regulatory direction for the future of the token economy. It also highlights the existing regulatory void and divergent approaches to blockchain based tokenization. Finally, the paper concludes that there is an urgent need to provide a clear legal and regulatory framework if the potential of the token economy is to be realised.
Vyper has been proposed as a new high-level language for Ethereum smart\ncontract development due to numerous security vulnerabilities and attacks\nwitnessed on contracts written in Solidity since the system's inception. Vyper\naims to address these vulnerabilities by providing a language that focuses on\nsimplicity, auditability and security. We present a survey where we study how\nwell-known and commonly-encountered vulnerabilities in Solidity feature in\nVyper's development environment. We analyze all such vulnerabilities\nindividually and classify them into five groups based on their status in Vyper.\nTo the best of our knowledge, our survey is the first attempt to study security\nvulnerabilities in Vyper.\n
Shreya Banerjee, Arghya Mukherjee, Prasanta K. Panigrahi
This paper proposes a protocol to prepare a blockchain using quantum tools which maintains the distributive nature of the blockchain and provides security against a quantum attacker. The authors provide an example of a two blockchain prepared in IBM 5 qubit quantum computer, as a proof of concept with fidelity close to 0.9548.
Muhammad Salek Ali, Massimo Vecchio, Guntur Dharma Putra, Salil S. Kanhere · 5 authors
Within the Internet of Things (IoT) and blockchain research, there is a growing interest in decentralizing health monitoring systems, to provide improved privacy to patients, without relying on trusted third parties for handling patients' sensitive health data. With public blockchain deployments being severely limited in their scalability, and inherently having latency in transaction processing, there is room for researching and developing new techniques to leverage the security features of blockchains within healthcare applications. This paper presents a solution for patients to share their biomedical data with their doctors without their data being handled by trusted third party entities. The solution is built on the Ethereum blockchain as a medium for negotiating and record-keeping, along with Tor for delivering data from patients to doctors. To highlight the applicability of the solution in various health monitoring scenarios, we have considered three use-cases, namely cardiac monitoring, sleep apnoea testing, and EEG following epileptic seizures. Following the discussion about the use cases, the paper outlines a security analysis performed on the proposed solution, based on multiple attack scenarios. Finally, the paper presents and discusses a performance evaluation in terms of data delivery time in comparison to existing centralized and decentralized solutions.
Muhammad Umar Javed, Mubariz Rehman, Nadeem Javaid, Abdulaziz Aldegheishem · 6 authors
In this paper, a blockchain-based secure data sharing mechanism is proposed for Vehicular Networks (VNs). Edge service providers are introduced along with ordinary nodes to efficiently manage service provisioning. The edge service providers are placed in the neighborhood of the ordinary nodes to ensure smooth communication between them. The huge amount of data generated by smart vehicles is stored in a distributed file storage system, known as Interplanetary File System (IPFS). It is used to tackle the issues related to data storage in centralized architectures, such as data tampering, lack of privacy, vulnerability to hackers, etc. Monetary incentives are given to edge vehicle nodes to motivate them for accurate and timely service provisioning to ordinary nodes. In response, ordinary nodes give reviews to the edge nodes against the services provided by them, which are further stored in a blockchain to ensure integrity, security and transparency. Smart contracts are used to automate the system processes without the inclusion of an intermediate party and to check the reviews given to the edge nodes. To optimize gas consumption and to enhance the system performance, a Proof of Authority (PoA) consensus mechanism is used to validate the transactions. Moreover, a caching system is introduced at the edge nodes to store frequently used services. Furthermore, both security and privacy are enhanced in the proposed system by incorporating a symmetric key cryptographic mechanism. A trust management mechanism is also proposed in this work to calculate the nodes’ reputation values based upon their trust values. These values determine the authenticity of the nodes involved in the network. Eventually, it is concluded from the simulation results that the proposed system is efficient for VNs.
Klitos Christodoulou, Elias Iosif, Antonios Inglezakis, Marinos Themistocleous
The inception of Bitcoin as a peer-to-peer payment system, and its underlying blockchain data-structure and protocol, has led to an increased interest in deploying scalable and reliable distributed-ledger systems that build on robust consensus protocols. A critical requirement of such systems is to provide enough fault tolerance in the presence of adversarial attacks or network faults. This is essential to guarantee liveness when the network does not behave as expected and ensure that the underlying nodes agree on a unique order of transactions over a shared state. In comparison with traditional distributed systems, the deployment of a distributed-ledger system should take into account the hidden game theoretical aspects of such protocols, where actors are competing with each other in an environment which is likely to experience various well-motivated malicious and adversarial attacks. Firstly, this paper discusses the fundamental principles of existing consensus protocols in the context of both permissioned and permissionless distributed-ledger systems. The main contribution of this work deals with observations from experimenting with Ripple’s consensus protocol as it is embodied in the XRP Ledger. The main experimental finding suggests that, when a low percentage of malicious nodes is present, the centralization degree of the network can be significantly relaxed ensuring low convergence times. Those findings are of particular importance when engineering a consensus algorithm that would like to balance security with decentralization.
The invention of the Internet has changed the way social resistance, revolutionary movements and terror groups are organized with new features such as loose network organization, netwars, social media campaigns, and lone wolf attacks. This article argues that blockchain technology will lead to more far-reaching changes in the organization of resistance to authority. Blockchain is a distributed ledger that records transactions using a consensus protocol, and when it meets objective conditions, it also enables smart contracts that execute transactions. Blockchain technology is not only a system for transferring value, but also it is a trustless system in which strangers can cooperate without the need for having to trust each other, as computer code governs their interactions. Blockchain will not only allow resistance/ terror organizations to easily receive donations globally, to have assets that a government can easily confiscate, and to disseminate censorship-resistant propaganda, but more importantly, to operate and cooperate across the world in a truly leaderless, coordinated, and highly decentralized fashion. Governments will need to be more proactive in the area of blockchain technology to mitigate some of the dangers to political stability that may emerge from it.
Critical infrastructure sectors are increasingly adopting enterprise Distributed Ledgers (DL) to host long-term assets, systems, and information that is considered vital to an organization’s ability to operate without clear or public plans and strategies to migrate safely and timely to Post Quantum Cryptography (PQC). A quantum computer (QC) compromised DL would allow, eavesdropping, unauthorized client authentication, signed malware, cloak-in encrypted session, a man-in-the-middle attack (MITM), forged documents and emails. These attacks can lead to disruption of service, damage of reputation and trust, injury to human life, and the loss of intellectual property, assets, regulated data, and global economic security. In 2018, Gartner revealed that a QC is a digital disruption that organizations may not be ready and prepared, and CIOs may not see coming. On September 18, 2019, IBM announced the largest universal QC available for commercial use would be available in October 2019. On October 23, 2019, Google officially announced “Quantum Supremacy,” “by performing a calculation in 200 seconds that would take a classical supercomputer approximately 10,000 years.” DL Cyber Resilience requires “reasonable” measures, policies, procedures, strategies, and risk management before large-scale deployment. Cyber Resilience implementations must be a critical component during the design and building phase, or during the initialization phase. The most significant existing attack vectors for enterprise DLs is the Public Key Infrastructure (PKI), which is fundamental in securing the Internet and enterprise DLs and is a core component of authentication, data confidentiality, and data and system integrity [1] [2]. Effectively implementing and managing a quantum-resistant PKI solution requires adherence to PKI standards, industry requirements, potential government mandates, certificate management policies, training personnel, and data recovery policies that currently do not exist. This research discusses security risks in enterprise DL PKI, areas that can be compromised, and provides an idea of what should be in a PKI DL Risk Management Framework plan.
As the indispensable trading platforms of the ecosystem, hundreds of cryptocurrency exchanges are emerging to facilitate the trading of digital assets. While, it also attracts the attentions of attackers. A number of scam attacks were reported targeting cryptocurrency exchanges, leading to a huge mount of financial loss. However, no previous work in our research community has systematically studied this problem. In this paper, we make the first effort to identify and characterize the cryptocurrency exchange scams. We first identify over 1,500 scam domains and over 300 fake apps, by collecting existing reports and using typosquatting generation techniques. Then we investigate the relationship between them, and identify 94 scam domain families and 30 fake app families. We further characterize the impacts of such scams, and reveal that these scams have incurred financial loss of 520k US dollars at least. We further observe that the fake apps have been sneaked to major app markets (including Google Play) to infect unsuspicious users. Our findings demonstrate the urgency to identify and prevent cryptocurrency exchange scams. To facilitate future research, we have publicly released all the identified scam domains and fake apps to the community.
Nelson Bore, Andrew Kinai, Peninah Waweru, Isaac Wambugu · 8 authors
Farm records hold the static, temporal, and longitudinal details of the farms. For small-scale farming, the ability to accurately capture these records plays a critical role in formalizing and digitizing the agriculture industry. Reliable exchange of these record through a trusted platform could unlock critical and valuable insights to different stakeholders across the value chain in agriculture eco-system. Lately, there has been increasing attention on digitization of small scale farming with the objective of providing farm-level transparency, accountability, visibility, access to farm loans, etc. using these farm records. However, most solutions proposed so far have the shortcoming of providing detailed, reliable and trusted small-scale farm digitization information in real time. To address these challenges, we present a system, called Agribusiness Digital Wallet (ADW), which leverages blockchain to formalize the interactions and enable seamless data flow in small-scale farming ecosystem. Utilizing instrumentation of farm tractors, we demonstrate the ability to utilize farm activities to create trusted electronic field records (EFR) with automated valuable insights. Using ADW, we processed several thousands of small-scale farm-level activity events for which we also performed automated farm boundary detection of a number of farms in different geographies.
Wangze Ni, Han Wu, Peng Cheng, Lei Chen · 8 authors
By allowing users to obscure their transactions via including "mixins" (chaff coins), ring signature schemes have been widely used to protect a sender's identity of a transaction in privacy-preserving blockchain systems, like Monero and Bytecoin. However, recent works point out that the existing ring signature scheme is vulnerable to the "chain-reaction" analysis (i.e., the spent coin in a given ring signature can be deduced through elimination). Especially, when the diversity of mixins is low, the spent coin will have a high risk to be detected. To overcome the weakness, the ring signature should be consisted of a set of mixins with high diversity and produce observations having "similar" distributions for any two coins. In this paper, we propose a notion, namely $ε$-coin-indistinguishability ($ε$-CI), to formally define the "similar" distribution guaranteed through a differential privacy scheme. Then, we formally define the CI-aware mixins selection problem with disjoint-superset constraint (CIA-MS-DS), which aims to find a mixin set that has maximal diversity and satisfies the constraints of $ε$-CI and the budget. In CIA-MS-DS, each ring signature is either disjoint with or the superset of its preceding ring signatures. We prove that CIA-MS-DS is NP-hard and thus intractable. To solve the CIA-MS-DS problem, we propose two approximation algorithms, namely the Progressive Algorithm and the Game Theoretic Algorithm, with theoretic guarantees. Through extensive experiments on both real data sets and synthetic data sets, we demonstrate the efficiency and the effectiveness of our approaches.
This study empirically investigates the effects of crypto-currencies trading on the energy consumption as an important consequence of blockchain technology on climate change. In this article, we use the data of Bitcoin trading volume as well as all crypto-currencies trading volumes for the period going from 2014M1 to 2017M12 to investigate the effects on the primary energy consumption. Our empirical results show a positive correlation between crypto-currencies trading volumes and the energy consumption. Moreover, the crypto-currencies trading volume has a Granger-causality to energy consumption in the period of study indicating that these two variables have a long-run co-integration. In other words, our findings show a significant positive (and increasing) influence of cryptocurrency activities on the energy consumption in both short-run and long-run. This study investigates one step further in examining the effects of residuals of the crypto-currencies trading volume on the residuals in energy consumption to confirm that a higher trading volume in cryptocurrencies might cause a higher energy consumption. Our findings show a negative influence of the trading of crypto-currencies - precisely, the higher the crypto-currency activities are, the higher the energy consumption is, affecting therefore the environment.Keywords: Crypto-currencies, Environment; Energy consumption; Innovation.JEL Classifications: Q40, Q51, Q54, Q55, Q56DOI: https://doi.org/10.32479/ijeep.9258
This research was conducted to analyze cryptocurrency volatility. Gold, Dollar Index, and Composite Stock Prices Index in the Indonesia Stock Exchange (IDX) variable are used as independent variables. The cryptocurrency objects in this study are Bitcoin and Ethereum which have the largest market capitalization. The data used in this study is from 1st January 2017 to 31st December 2019. This study uses GARCH analysis. The result of this study indicates that the volatility of Bitcoin and Ethereum is not influenced by other variables, but it is influenced by the prices of each Bitcoin and Ethereum at past prices. This shows that the cryptocurrency market is an inefficient market.
Crowdfunding is an innovative way of financing projects that allows anyone to contribute money online and support various initiatives, such as businesses, causes, or solutions. However, traditional crowdfunding platforms face some challenges, such as lack of transparency and security, high fees, and limited control over the funds by the contributors and the project owners. Blockchain technology, which is a P2P, decentralized ledger, which is distributed can offer a more reliable, secure, and transparent solution for crowdfunding. Blockchain-based crowdfunding can leverage smart contracts, which are self-executing agreements that encode the rules and conditions of the funding process and ensure that the funds are released only when the predefined criteria are met. This paper aims to propose a concept for designing efficient smart contracts for crowdfunding, which can enable both the contributors and the project owners to have more control and influence over the funds and the project outcomes. Unlike the existing literature-based ideas, our proposed method not only allows the contributors to invest their own money, but also guarantees them that their token values will be preserved. This method can be integrated without disrupting the existing logic of the blockchain. The methodology provides higher control and transparency for all the parties involved in the crowdfunding process.
The video created by a surveillance cameras plays a crucial role in crime prevention and examinations in smart cities. The closed-circuit television camera (CCTV) is essential for a range of public uses in a smart city; combined with Internet of Things (IoT) technologies they can turn into smart sensors that help to ensure safety and security. However, the authenticity of the camera itself raises issues of building up integrity and suitability of data. In this paper, we present a blockchain-based system to guarantee the trustworthiness of the stored recordings, allowing authorities to validate whether or not a video has been altered. It helps to discriminate fake videos from original ones and to make sure that surveillance cameras are authentic. Since the distributed ledger of the blockchain records the metadata of the CCTV video as well, it is obstructing the chance of forgery of the data. This immutable ledger diminishes the risk of copyright encroachment for law enforcement agencies and clients users by securing possession and identity.
Open access
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
We conduct a systematic study on the light client of permissionless blockchains, in the setting where the full nodes and the light clients are rational. Under such a game-theoretic model, we design a superlight-client protocol to enable a client to employ some relaying full nodes (e.g. two or one) to read the blockchain. The protocol is "generic", i.e., it can be deployed disregarding the underlying consensuses, and also "superlight", i.e., the computational cost of the light client to predicate the (non)existence of a transaction in the blockchain becomes a small constant. Since our protocol resolves a fundamental challenge of broadening the usage of blockchain technology, it captures a wide variety of important use-cases such as multi-chain wallets, DApp browsers and more.
Increasingly growing Cryptocurrency markets have become a hive for scammers to run pump and dump schemes which is considered as an anomalous activity in exchange markets. Anomaly detection in time series is challenging since existing methods are not sufficient to detect the anomalies in all contexts. In this paper, we propose a novel hybrid pump and dump detection method based on distance and density metrics. First, we propose a novel automatic thresh-old setting method for distance-based anomaly detection. Second, we propose a novel metric called density score for density-based anomaly detection. Finally, we exploit the combination of density and distance metrics successfully as a hybrid approach. Our experiments show that, the proposed hybrid approach is reliable to detect the majority of alleged P & D activities in top ranked exchange pairs by outperforming both density-based and distance-based methods.
Ningyu He, Ruiyi Zhang, Lei Wu, Haoyu Wang · 8 authors
The EOSIO blockchain, one of the representative Delegated Proof-of-Stake (DPoS) blockchain platforms, has grown rapidly recently. Meanwhile, a number of vulnerabilities and high-profile attacks against top EOSIO DApps and their smart contracts have also been discovered and observed in the wild, resulting in serious financial damages. Most of EOSIO's smart contracts are not open-sourced and they are typically compiled to WebAssembly (Wasm) bytecode, thus making it challenging to analyze and detect the presence of possible vulnerabilities. In this paper, we propose EOSAFE, the first static analysis framework that can be used to automatically detect vulnerabilities in EOSIO smart contracts at the bytecode level. Our framework includes a practical symbolic execution engine for Wasm, a customized library emulator for EOSIO smart contracts, and four heuristics-driven detectors to identify the presence of four most popular vulnerabilities in EOSIO smart contracts. Experiment results suggest that EOSAFE achieves promising results in detecting vulnerabilities, with an F1-measure of 98%. We have applied EOSAFE to all active 53,666 smart contracts in the ecosystem (as of November 15, 2019). Our results show that over 25% of the smart contracts are vulnerable. We further analyze possible exploitation attempts against these vulnerable smart contracts and identify 48 in-the-wild attacks (25 of them have been confirmed by DApp developers), resulting in financial loss of at least 1.7 million USD.
Consensus protocols are currently the bottlenecks that prevent blockchain systems from scaling. However, we argue that transaction execution is also important to the performance and security of blockchains. In other words, there are ample opportunities to speed up and further secure blockchains by reducing the cost of transaction execution. Our goal is to understand how much we can speed up blockchains by exploiting transaction concurrency available in blockchain workloads. To this end, we first analyze historical data of seven major public blockchains, namely Bitcoin, Bitcoin Cash, Litecoin, Dogecoin, Ethereum, Ethereum Classic, and Zilliqa. We consider two metrics for concurrency, namely the single-transaction conflict rate per block, and the group conflict rate per block. We find that there is more concurrency in UTXO-based blockchains than in account-based ones, although the amount of concurrency in the former is lower than expected. Another interesting finding is that some blockchains with larger blocks have more concurrency than blockchains with smaller blocks. Next, we propose an analytical model for estimating the transaction execution speed-up given an amount of concurrency. Using results from our empirical analysis, the model estimates that 6x speed-ups in Ethereum can be achieved if all available concurrency is exploited.
The recent development of payment channels and their extensions (e.g., state channels) provides a promising scalability solution for blockchains which allows untrusting parties to transact off-chain and resolve potential disputes via on-chain smart contracts. To protect participants who have no constant access to the blockchain, a watching service named as watchtower is proposed -- a third-party entity obligated to monitor channel states (on behalf of the participants) and correct them on-chain if necessary. Unfortunately, currently proposed watchtower schemes suffer from multiple security and efficiency drawbacks. In this paper, we explore the design space behind watchtowers. We propose a novel watching service named as fail-safe watchtowers. In contrast to prior proposed watching services, our fail-safe watchtower does not watch on-chain smart contracts constantly. Instead, it only sends a single on-chain message periodically confirming or denying the final states of channels being closed. Our watchtowers can easily handle a large number of channels, are privacy-preserving, and fail-safe tolerating multiple attack vectors. Furthermore, we show that watchtowers (in general) may be an option economically unjustified for multiple payment scenarios and we introduce a simple, yet powerful concept of short-lived assertions which can mitigate misbehaving parties in these scenarios.
Frank Yeong‐Sung Lin, Danny Chung, Conrad Shayo, F De Beer
With the introduction of Bitcoin by Nakamoto (2008), came a key underlying technology that holds great disruptive promise to many crucial industries: Blockchain. The nature of a decentralized, distributed ledger will truly change the way we currently trade and interact through its clear transparency and high integrity (Casey & Vigna, 2018; Sullivan, 2015). Based on trust, Blockchain allows various parties to be involved in transacting with each other without the need to know each other (Botsman, 2017; Deloitte, 2016; Drescher, 2017; Mauri, 2017). The purpose of this paper is to provide a framework for Blockchain by focusing on how Blockchain technology can be integrated and implemented into real world applications (Harvey, Moorman & Toledo, 2018; Iansiti & Lakhani, 2017). As this secure, robust and flexible technology can be applied to numerous industries with a plethora of applications and use cases, Blockchain for business can tremendously save costs, save time and mitigate risk (Gupta, 2017; Mauri, 2017). In particular, we will explore how the premise of provenance in traceability and tractability will affect our supply chains of today and tomorrow (Carson, Romanelli, Walsh, & Zhumaev, 2018; Casey & Wong, 2017; Yiannas, 2018). We will also discuss the technological limitations, the regulations and the social challenges that revolve around Blockchain and its adoption (Commission Nationale de l'Informatique et des Libertés, 2018; Croman, Decker, Eyal, Gencer, Juels, Kosba, Miller, Saxena, Shi, Sirer, Song, & Wattenhofer, 2016; Iansiti & Lakhani, 2017; Global Legal Research Center, 2018). In addition, we aimed to examine the interaction of between Blockchain and various relevant and pertinent emerging technologies such as artificial intelligence, quantum computing, 5G, IoT and among others (Carmichael & Lakhani, 2017; Loukides & Lorica, 2018). Further, we identify the conceivable implications – such as the effect on the workforce, among other concerns – both positive and negative, and how these would affect us in both the short term and the long term (Schwartz, Wooll, & Monahan, 2019). Lastly, we investigate how and where Blockchain would evolve in the near and far future.