Blockchain is a decentralized ledger that serves as the foundation of Bitcoin and has found applications in various domains due to its immutable properties. It has the potential to change digital transactions drastically. It has been successfully used across multiple fields for record immutability and reliability. The consensus mechanism is the backbone of blockchain operations and validates newly generated blocks before they are added. To verify transactions in the ledger, various peer-to-peer (P2P) network validators use different consensus algorithms to solve the reliability problem in a network with unreliable nodes. The security and reliability of the inherent consensus algorithm used mainly determine blockchain security. However, consensus algorithms consume significant resources for validating new nodes. Therefore the safety and reliability of a blockchain system is based on the consensus mechanism's reliability and performance. Although various consensus mechanisms/algorithms exist, there is no unified evaluation criterion to evaluate them. Evaluating the consensus algorithm will explain system reliability and provide a mechanism for choosing the best consensus mechanism for a defined set of problems. This article comprehensively analyzes existing and recent consensus algorithms' throughput, scalability, latency, energy efficiency, and other factors such as attacks, Byzantine fault tolerance, adversary tolerance, and decentralization levels. The paper defines consensus mechanism criteria, evaluates available consensus algorithms based on them, and presents their advantages and disadvantages.
Mohammad Alshinwan, Ahmed Younes Shdefat, Nour Mostafa, Abdullah A.M AlSokkar · 6 authors
Blockchain technology is one of the crypto-currency technologies that has received a lot of attention. It has also found use in various applications, including the Internet of Things (IoT) and Cloud computing. Nonetheless, Blockchain has a significant scalability issue, restricting its ability to support services with various transactions. On the other hand, cloud computing is the on-demand availability of shared computer system resources, although issues now beset it in automation, processes, management, policies, and human aspects. Combining cloud computing and blockchain technology into a single system can improve network control, task scheduling, data integrity, resource management, pricing, fair payment, and resource allocation. In this article, we offered a comprehensive and up-to-date survey of cloud computing and Blockchain integration, a critical service for business applications due to the benefits of privacy, security, and service support. The lack of a comprehensive assessment examining the significance of BaaS platforms used in cloud computing prompted this review. We focus on the various BaaS tools that are currently in use. This report also examines the most common BaaS platforms incorporating Blockchain as a cloud service, such as Alibaba, Oracle, Azure, Amazon, and IBM. Furthermore, this research highlighted some major technological issues associated with merging Blockchain with cloud computing.
Blockchain consensus protocols are responsible for coordinating the nodes to make agreements on the transaction results. Their implementation bugs, including memory-related and consensus logic vulnerabilities, may pose serious threats. Fuzzing is a promising technique for protocol vulnerability detection. However, existing fuzzers cannot deal with complex consensus states of distributed nodes, thus generating a large number of useless packets, inhibiting their effectiveness in reaching the deep logic of consensus protocols.
Asmaa Aldoubaee, Noor Hafizah Hassan, Fiza Abdul Rahim
Blockchain is an exciting new technology that has garnered attention across multiple industries. This new technology offers several advantages, including decentralization, transparency, and immutability. However, several issues limit the effectiveness of this technology, such as scalability, interoperability, and privacy. A systematic review of blockchain scalability research was conducted using three primary databases: ACM, Science Direct, and IEEE. The review examined the state of the art in blockchain scalability, identifying the most important research trends and challenges. The solutions that have been established can be categorized into two main groups: those that pertain to block storage and those that pertain to the underlying blockchain mechanism. Numerous solutions were suggested for each main group. The most common proposed solutions for improving the scalability of blockchain networks in the literature are improving the consensus algorithm and using sharding. Most of the solutions were proof of concept and need more investigation in the future.
Cette thèse de doctorat se compose de 6 chapitres. Dans le premier chapitre, en guise d'introduction, nous donnons un aperçu des objectifs généraux et des motivations des réseaux décentralisés et permissionless, ainsi que des obstacles auxquels ils sont confrontés. Dans l'introduction, nous évoquons également la solution irrationnelle et illogique, connue sous le nom de « blockchain permissioned », qui a été proposée pour améliorer les performances des réseaux similaires à Bitcoin. Cette question a été détaillée au chapitre 5. Dans le chapitre 2, nous rendons clairs et intelligibles les systèmes que l'idée proposée, « Parallel Committees », est basée sur de tels réseaux. Nous détaillons les fonctionnalités indispensables et les défis essentiels des systèmes de réplication. Ensuite, dans le chapitre 3, nous discutons des limitations de scalabilité et du faible débit des systèmes de réplication qui utilisent des mécanismes de consensus pour traiter les transactions et comment ces problèmes peuvent être améliorés en utilisant des techniques de sharding. Nous décrivons les défis les plus importants dans le sharding des systèmes de réplication distribuée, une approche qui a déjà été mise en œuvre dans plusieurs systèmes de réplication basés sur la blockchain et, bien qu'elle ait montré un potentiel significatif pour améliorer les performances et la scalabilité, les techniques de sharding actuelles ont encore des limitations de scalabilité et des défis de sécurité. Nous expliquons pourquoi la plupart des protocoles de sharding actuels utilisent une approche d'allocation aléatoire pour distribuer les nœuds entre les shards pour des raisons de sécurité. Nous décrivons également comment traiter une transaction dans un système de réplication partitionné basé sur les protocoles de sharding actuels. Nous expliquons comment un « shared-ledger » partagé sur les shards impose des limitations de scalabilité et des défis de sécurité au réseau, et expliquons pourquoi les transactions « cross-shards » ou « inter-shards » sont indésirables et plus coûteuses en raison des problèmes qu'elles causent, y compris « atomicity failure » et les défis de « state transition », ainsi qu'une passe en revue des solutions proposées. Nous passons également en revue certains des travaux récents les plus remarquables qui utilisent des techniques de sharding pour les systèmes de réplication. Cette partie de l'ouvrage a été publiée sous la forme d'un chapitre de livre (peer-reviewed) in « Building Cybersecurity Applications with Blockchain Technology and Smart Contracts » (Springer, 2023). Dans le chapitre 4, nous proposons une nouvelle technique de sharding, « Parallel Committees », prenant en charge à la fois le « processing-sharding » et le « storage/state sharding », pour améliorer la scalabilité et les performances des systèmes de réplication distribués qui utilisent des mécanismes de consensus pour traiter les demandes des clients (client requests). Nous introduisons une approche innovante et originale pour répartir les nœuds entre les shards à l'aide d'un processus de génération de clé publique qui atténue simultanément l'attaque Sybil et sert de mécanisme de preuve de travail (proof-of-work). Notre approche réduit efficacement les transactions « inter-shards » indésirables, qui sont plus complexes et coûteuses à traiter que les transactions « intra-shards ». L'idée proposée a été publiée dans la conférence IEEE BCCA 2023. Nous expliquons ensuite pourquoi nous n'utilisons pas la structure de la blockchain dans l'idée proposée, un sujet abordé en détail au chapitre 5. Cette explication et clarification a été publiée dans le Journal of Software (JSW), Volume 16, Number 3, May 2021. Et dans le dernier chapitre de cette thèse, le chapitre 6, nous résumons les points importants et les conclusions de cette recherche.
Blockchain technology has emerged as a promising solution to secure and decentralized platforms. However, blockchain technology has high computational requirements, latency, and low throughput, particularly for single or multi-query processing. Lightweight blockchain has emerged as a solution to overcome these problems. It addresses performance and efficiency issues and can provide convenience in the query process. This paper proposed a novel high-performance data structure for multi-query processing based on a lightweight blockchain, namely Multi-State Merkle Patricia Trie (MSMPT). MSMPT combines Merkle Patricia Trie (MPT) based indexing and linked-list storage to achieve high performance. MPT has been used on the Ethereum network with a Key-Value database approach. The key field in this proposal is used as crucial user data. The value field is changed to the head of the linked list, and the following data elements will store a summary of the data based on the specified category. In this paper, a blockchain simulator was built to discover the performance of the proposed systems. This simulator will simulate creating blocks in a blockchain network using existing and modified blockchain data structures. The blocks created will be compared using the query process from the conventional and proposed systems. The experimental findings demonstrate that MSMPT outperforms existing blockchain-based data structures by requiring only about one millisecond in query processing performance and less than 500 bytes of additional storage. The MSMPT provides a promising solution for efficient and scalable data management in lightweight blockchain, particularly for multi-query processing.
Scholarship management is a crucial aspect of higher education systems, aimed at supporting deserving students and reducing financial barriers. However, traditional scholarship management processes often suffer from challenges such as a lack of transparency, inefficient communication, and difficulty tracking and verifying scholarship applications. Recently, Blockchain technology has emerged as a potential solution to address these issues, offering a decentralized, transparent, and secure framework for scholarship management. Blockchain technology has emerged as a promising solution to address the challenges faced in scholarship management. However, existing literature lacks comprehensive solutions in critical areas such as scholarship management, storage facilities, payment systems, monitoring and auditing, and experimental validation. This research introduces an innovative smart scholarship management system leveraging Blockchain technology to overcome these limitations. The research presents an Ethereum-based implementation utilizing Solidity for backend smart contracts and ReactJS for the front end. Experimental evaluation validates the transaction execution gas costs and deployment cost.
Distributed filesystem architectures use commodity hardware to store data on a large scale with maximum consistency and availability. Blockchain makes it possible to store information that can never be tampered with and incentivizes a traditional decentralized storage system. This project aimed to implement a decentralized filesystem that leverages the blockchain to keep a record of all the transactions on it. A conventional filesystem viz. GFS [1] or HDFS [2] uses designated servers owned by their organization to store the data and are governed by a master service. This project aimed at removing a single point of failure and makes use of participating users’ machines to store data. The implemented file system uses a distributed hash table to evenly store data on multiple machines and efficiently look up, track, maintain, and persist the data. The data stored on the file system is made easily and readily accessible to a user ensuring its soundness. Finally using smart contracts enabled incentives and increased the integrity and reliability of storing data by recording all the transactions. The project functions autonomously by coordinating multiple participant machines in the network to store data and monetize unused storage space on the machines. It supports the basic functionalities of a filesystem which include storing, deletion, and reading a file as desired. The filesystem’s performance was tested with files of different sizes and a variable number of nodes. The current file system is able to store files as big as 100 MB within 12 seconds and 300 MB in less than 25 seconds. This is significantly faster than Storj [3] which nearly takes more than a minute for a similar operation. The tests also provided observations on the average gas consumed during transactions.
As the digitalization in the architecture, engineering, and construction (AEC) industry has been rapidly progressing, building end users will require more coverage of quality data for their built environment. Despite its obvious need, it is seldom for the building information modeling (BIM) to be distributed for such broad use cases thus far. A potential reason for the situation is the lack of the public repository that can provide the adequate access control for various users. Distributed Ledger Technology (DLT), including blockchain, is one of the promising resolutions for the problem. Numbers of preceding proposals for DLT-based BIM repository systems (BIM-DLT system) have proved the utility to date. Understanding the statistical facts of their configurations will become a significant assistance to determine the plausible data distribution system, and thus, to strengthen the project information life cycle. This article aims to build a representative framework through the integrated literature review (ILR). The review results showed that the systemÂs data flow was classified into two patterns. The judgment criteria for selecting the pattern of the system are expected to depend on the purpose of system implementation, and the purpose of automation through smart contracts is more important than the oracle problem.
Open-source systems help to manage the rapid development of software, while governing open-source systems properly can effectively promote software and software engineering. However, some significant problems, such as code controls, incentives, interaction and cooperation, automation, transparency and fairness of rights and responsibilities, cannot be properly solved by traditional methodologies. The decentralization, immutability, change in trust mode and smart contract programming of blockchain provide new solutions. In order to solve the problems of traditional centralized open-source governance, this paper proposes a decentralized open-source coordination management system using a novel triple-blockchain architecture. Through the analysis of traditional and blockchain-based research, the business and technical issues that need to be addressed in decentralized open-source governance systems have been emphatically studied. Combined with triple-blockchain architecture, smart contracts, oracles and continuous integration tools, we study the decentralization of open-source businesses and make them more trustworthy, automated and coordinated. An identity authentication mechanism is designed for permission control and inter-community collaboration. A decentralized open-source reputation is proposed for incentive and reference. We also improved the DPoS (Delegated Proof of Stake) consensus under triple-blockchain architecture to reduce repeated elections. By constructing the OSCMS prototype based on the proposed architecture model, many comparative experiments were conducted under different parameters and conditions and showed good feasibility, scalability, reliability and performance. The OSCMS not only solves the shortcomings of previous research but also provides a comprehensive and feasible reference for the decentralized practice of open-source governance.
Ray Neiheiser, Gustavo Inácio, Luciana Rech, Carlos Montez · 6 authors
Most permissionless blockchains inherently suffer from throughput limitations. Layer-2 systems, such as side-chains or Rollups, have been proposed as a possible strategy to overcome this limitation. Layer-2 systems interact with the main-chain in two ways. First, users can move funds from/to the main-chain to/from the layer-2. Second, layer-2 systems periodically synchronize with the main-chain to keep some form of log of their activity on the main-chain - this log is key for security. Due to this interaction with the main-chain, which is necessary and recurrent, layer-2 systems impose some load on the main-chain. The impact of such load on the main-chain has been, so far, poorly understood. In addition to that, layer-2 approaches typically sacrifice decentralization and security in favor of higher throughput. This paper presents an experimental study that analyzes the current state of Ethereum layer-2 projects. Our goal is to assess the load they impose on Ethereum and to understand their scalability potential in the long-run. Our analysis shows that the impact of any given layer-2 on the main-chain is the result of both technical aspects (how state is logged on the main-chain) and user behavior (how often users decide to transfer funds between the layer-2 and the main-chain). Based on our observations, we infer that without efficient mechanisms that allow users to transfer funds in a secure and fast manner directly from one layer-2 project to another, current layer-2 systems will not be able to scale Ethereum effectively, regardless of their technical solutions. Furthermore, from our results, we conclude that the layer-2 systems that offer similar security guarantees as Ethereum have limited scalability potential, while approaches that offer better performance, sacrifice security and lead to an increase in centralization which runs against the end-goals of permissionless blockchains.
Avni Rustemi, Fisnik Dalipi, Vladimir Atanasovski, Aleksandar Risteski
In the past few years, there has been significant progress made in the area of blockchain. The use of blockchain technology has the potential to revolutionize the educational system by providing individuals with innovative and cost-effective ways to learn, as well as by altering the way teachers and students work together. Additionally, blockchain technology can be utilized for the issuing of unchangeable digital certificates, and it can enhance the present limitations of the existing certificate verification systems by making them quicker, more reliable, and independent of the central authority. The application of blockchain in the context of education has generated significant scientific interest in this field. Nonetheless, research endeavors on the adoption of blockchain in the verification of academic credentials are still in the development phase. In order to shed more light on the field, in this paper we focus on extensively reviewing the body of knowledge on blockchain-based systems for academic certificate verification. Hence, the purpose of this survey is to compile all relevant research into a systematic literature review, highlighting the key contributions from various researchers throughout the years with a focus on the past, present, and future. In this work, we have identified 34 relevant studies out of 1744 papers that were published between 2018 and 2022 by employing the PRISMA framework. We distinguished six major themes covered by the research articles analyzed and also identified research gaps that need to be addressed and explored by the research community. Based on the findings of this review, we provide some recommendations for future research directions and practical applications that can assist researchers, policymakers, and practitioners in the field.
Mohammad Madine, Khaled Salah, Raja Jayaraman, Mohamed Jamal Zemerly
Software licenses are legal agreements of sale and usage among software developers and clients. Such legal agreements are crucial to effectively manage ownership and protect the rights of involved parties. Today’s software licensing mechanisms are mostly centralized and do not address the ever-increasing issues and complexities of modern software that may include multiple licenses, open-source distribution, rewarding other contributors of external software libraries, and utilizing royalty payments for monetization. As a result, developers have lost confidence in the existing software licensing models, and many software projects are failing due to lack of funding and royalty payments. This paper addresses such issues and complexities by proposing a novel decentralized software licensing system based on Non-Fungible Tokens (NFTs) and blockchain. The proposed licensing system is applicable to both commercial and open-source software. We use NFTs as digital tokens that encapsulate software code and their artifacts by minting them as unique valuable assets that allow developers to store and manage them on a blockchain ledger. With NFTs, developers can register and license their code, monetize it on NFT marketplaces, and earn royalties from other software projects that use their code. We present system architecture, relevant sequence diagrams, and develop aggregation algorithms for Ethereum smart contracts with ERC-1155 NFTs. Furthermore, we perform functional validation of our system and analyze the cost of its adoption. We also analyze the security of the solution and show how its applicability can be generalized and extended. We have made our smart contract code and related testing scripts publicly available on GitHub.
Mithilesh Pawar, Rudraksh Balkar, Vijay Pawar, Saurav Roy
Blockchain technology is poised to bring about a paradigm shift in the business environment, offering substantial benefits in the near future. Non-fungible Tokens are digital representations of material possessions like artwork, recordings, assets within the game, and films. These tokens are traded via the internet with multiple cryptocurrencies. NFTs have their own distinct characteristics from fungible tokens, which may be traded without restriction on numerous centralized or decentralized exchanges.Each NFT carries a unique digital signature that precludes its exchange for another NFT, and its value is determined by factors such as metadata, creator, and features.
Itzhak Aviv, Artem Barger, Alexander Kofman, Roye Weisfeld
The blockchain paradigm and its application of Distributed Ledger Technology (DLT) are now enabling technologies for the worldwide development of trustworthy and decentralized solutions. DLT offers enormous potential to accommodate the intricate architectural patterns of individual Distributed Information Systems (DIS). Despite its immense potential, the current research effort is not focused on deploying DLT inside the DIS area. We identified sixteen essential DIS Architectural Properties (APs) that offer issues for DIS system architects using Grounded Theory. Then, we assessed the capabilities of the major DLT platform and highlighted its prospects and limits with regard to supporting DIS APs. Using the meta-analysis research technique, we demonstrated that DLT might serve as a development platform for a blockchain-native DIS (BN-DIS) that enables design and development processes. A BN-DIS utilizes DLT infrastructure and blockchain design principles to expand internationally, support thousands of distributed nodes, and employ DIS APs unique to the Blockchain. Lastly, we give a case study illustrating how DLT handles DIS APs in a real-world context, giving empirical proof of the DLT’s efficacy in servicing DIS APs.
Ethereum is one of the first blockchains executing smart contracts (financial applications directly executed on the ledger using a virtual machine). The performance of the Ethereum virtual machine has become a bottleneck caused by high volumes of transactions due to blockchain applications, including decentralized finance and non-fungible tokens. Hence, there is a need to detail the execution characteristics of the Ethereum virtual machine before its performance can be improved. This work introduces an off-line Ethereum virtual machine tracer called EVMTracer that produces runtime data dependence graphs from executed transactions as an alternative program representation. From the runtime dependence graphs, we can deduce valuable metrics about program execution characteristics, including the degree of parallelization and computational redundancies in smart contracts. Our experiments encompass all blocks up to 12M on the Ethereum mainnet. We found a geometric mean of 1.90× theoretical maximum speedup when executing the smart contracts in parallel and identified 34.97% of SLOAD instructions as redundant.
Nana Kwadwo Akrasi‐Mensah, Andrew Selasi Agbemenu, Henry Nunoo‐Mensah, Eric Tutu Tchao · 9 authors
Blockchain-IIoT integration into industrial processes promises greater security, transparency, and traceability. However, this advancement faces significant storage and scalability issues with existing blockchain technologies. Each peer in the blockchain network maintains a full copy of the ledger which is updated through consensus. This full replication approach places a burden on the storage space of the peers and would quickly outstrip the storage capacity of resource-constrained IIoT devices. Various solutions utilizing compression, summarization or different storage schemes have been proposed in literature. The use of cloud resources for blockchain storage has been extensively studied in recent years. Nonetheless, block selection remains a substantial challenge associated with cloud resources and blockchain integration. This paper proposes a deep reinforcement learning (DRL) approach as an alternative to solving the block selection problem, which involves identifying the blocks to be transferred to the cloud. We propose a DRL approach to solve our problem by converting the multi-objective optimization of block selection into a Markov decision process (MDP). We design a simulated blockchain environment for training and testing our proposed DRL approach. We utilize two DRL algorithms, Advantage Actor-Critic (A2C), and Proximal Policy Optimization (PPO) to solve the block selection problem and analyze their performance gains. PPO and A2C achieve 47.8% and 42.9% storage reduction on the blockchain peer compared to the full replication approach of conventional blockchain systems. The slowest DRL algorithm, A2C, achieves a run-time 7.2 times shorter than the benchmark evolutionary algorithms used in earlier works, which validates the gains introduced by the DRL algorithms. The simulation results further show that our DRL algorithms provide an adaptive and dynamic solution to the time-sensitive blockchain-IIoT environment.
Kashif Mehboob Khan, Muhammad Abdullah Hayat, Rana Muhammad Ibrahim
In the current era, blockchain has emerged as one the best and promising technology. All the cryptocurrencies have also gained a lot of popularity around the globe which are based on blockchain technology. Blockchain provides a distributed architecture, in which transactions are verified by different validators using different algorithms and then are stored in distributed ledger. The verification of transactions is done using consensus algorithms which verifies that incoming transaction is correct and reliable by different distributed nodes working in a peer-to-peer network. Consensus algorithms ensure the integrity and security of blockchain. There are various types of consensus algorithms used in blockchain technology which are used depending on the architecture and usage, some of the consensus algorithms are Proof of Work (PoW), Proof of Stake (PoS) etc. The Proof of Work algorithm is most widely used across the globe by the community. It is used by many popular cryptocurrency networks like Litecoin and Bitcoin. It requires larger computation power while verifying transactions. The selection of a consensus algorithm is one the most important parts of blockchain, as the consensus mechanism is considered to be the core of a network. It is easier to predict and guarantee the security, reliability, fault tolerance, and recoverability of the system if the correct consensus protocol is selected. A single algorithm can never fulfill all the requirements, there is always a tradeoff in the selection of consensus algorithms. Therefore, it is very important to select the best suited consensus algorithm for the network as the consensus mechanism validates transactions without any third-party platform and prevents malicious activities in the network. This paper investigates the comparison among types of consensus algorithms and their effectiveness and viability.
The scalability problem has been one of the most significant barriers limiting the adoption of blockchains. Blockchain sharding is a promising approach to this problem. However, the sharding mechanism introduces a significant number of cross-shard transactions, which are expensive to process. This paper focuses on the transaction allocation problem to reduce the number of cross-shard transactions for better scalability. In particular, we systematically formulate the transaction allocation problem and convert it to the community detection problem on a graph. A deterministic and fast allocation scheme TxAllo is proposed to dynamically infer the allocation of accounts and their associated transactions. It directly optimizes the system throughput, considering both the number of cross-shard transactions and the workload balance among shards. We evaluate the performance of TxAllo on an Ethereum dataset containing over 91 million transactions. Our evaluation results show that for a blockchain with 60 shards, TxAllo reduces the cross-shard transaction ratio from 98% (by using traditional hash-based allocation) to about 12%. In the meantime, the workload balance is well maintained. Compared with other methods, the execution time of TxAllo is almost negligible. For example, when updating the allocation every hour, the execution of TxAllo only takes 0.5 seconds on average, whereas other concurrent works, such as BrokerChain (INFOCOM'22) leveraging the classic METIS method, require 422 seconds.
Blockchain has become a popular emergent technology in many industries. It is suitable for a broad range of applications, from its base role as an immutable distributed ledger to the deployment of distributed applications. Many organizations are adopting the technology, but choosing a specific blockchain implementation in an emerging field exposes them to significant technology risk. Selecting the wrong implementation could expose an organization to security vulnerabilities, reduce access to its target audience, or cause issues in the future when switching to a more mature protocol. Blockchain interoperability aims to solve this adaptability problem by increasing the extensibility of blockchain, enabling the addition of new use cases and features without sacrificing the performance of the original blockchain. However, most existing blockchain platforms need to be designed for interoperability, and simple operations like sending assets across platforms create problems. Cryptographic protocols that are secure in isolation may become insecure when several different (individually secure) protocols are composed. Similarly, utilizing trusted custodians may undercut most of the benefits of decentralization offered by blockchain-based systems. Even though there is some research and development in the field of blockchain interoperability, a characterization of the interoperability solutions for various infrastructure options is lacking. This paper presents a methodology for characterizing blockchain interoperability solutions that will help focus on new developments and evaluate existing and future solutions in this space.