Web archives store born-digital documents, which are usually collected from the Internet by crawlers and stored in the Web Archive (WARC) format. The trustworthiness and integrity of web archives is still an open challenge, especially in the news portal domain, which face additional challenges of censorship even in democratic societies. The aim of this paper is to present a light-weight, blockchain-based solution for web archive validation, which would ensure that documents retrieved by crawlers are authentic for many years to come. We developed our archive validation solution as an extension and continuation of our work in web crawler development mainly targeting news portals. The system is designed as an overlay over a blockchain with a proof-of-stake (PoS) distributed consensus algorithm. PoS was chosen due to its lower ecological footprint compared to proof-of-work solutions (e.g. Bitcoin) and lower expected investment in computing infrastructure. We based our prototype on the open-source Nxt blockchain and implemented it in Python. The prototype was tested on web archive content crawled from Hungarian news portals at two different timestamps with more than 1 million articles in total. We concluded that the proposed solution is accessible, usable by different stakeholders to validate crawled content, deployable on cheap commodity hardware, tackles the archive integrity challenge and is capable to efficiently manage duplicate documents.
With the rapid advancement of cloud computing, cloud storage services have developed rapidly. One issue that has attracted particular attention in such remote storage services is that cloud storage servers are not enough to reliably save and maintain data, which greatly affects users’ confidence in purchasing and consuming cloud storage services. Traditional data integrity auditing techniques for cloud data storage are centralized, which faces huge security risks due to single-point-of-failure and vulnerabilities of central auditing servers. Blockchain technology offers a new approach to this problem. Many researchers have endeavored to employ the blockchain for data integrity auditing. Based on the search of relevant papers, we found that existing literature lacks a thorough survey of blockchain-based integrity auditing for cloud data. In this paper, we make an in-depth survey on cloud data integrity auditing based on blockchain. Firstly, we cover essential basic knowledge of integrity auditing for cloud data and blockchain techniques. Then, we propose a series of requirements for evaluating existing Blockchain-based Data Integrity Auditing (BDIA) schemes. Furthermore, we provide a comprehensive review of existing BDIA schemes and evaluate them based on our proposed criteria. Finally, according to our completed review and analysis, we explore some open issues and suggest research directions worthy of further efforts in the future.
Whereas the use of distributed ledger technologies has previously been limited to cryptocurrencies, other sectors—such as healthcare, supply chain, and finance—can now benefit from them because of bitcoin scripts and smart contracts. However, these applications rely on oracles to fetch data from the real world, which cannot reproduce the trustless environment provided by blockchain networks. Despite their crucial role, academic research on blockchain oracles is still in its infancy, with few contributions and a heterogeneous approach. This study undertakes a bibliometric analysis by highlighting institutions and authors that are actively contributing to the oracle literature. Investigating blockchain oracle research state of the art, research themes, research directions, and converging studies will also be highlighted to discuss, on the one hand, current advancements in the field and, on the other hand, areas that require more investigation. The results also show that although worldwide collaboration is still lacking, various authors and institutions have been working in similar directions.
Sebastian Müller, Andreas Penzkofer, Nikita Polyanskii, Jonas Theis · 6 authors
The Unspent Transaction Output (UTXO) model is commonly used in the field of Distributed Ledger Technology (DLT) to transfer value between participants. One of its advantages is that it allows parallel processing of transactions, as independent transactions can be added in any order. This property of order invariance and parallelisability has potential benefits in terms of scalability. However, since the UTXO Ledger is an append-only data structure, this advantage is compromised through the presence of conflicting transactions. We propose an extended UTXO Ledger model that optimistically updates the ledger and keeps track of the dependencies of the possible conflicts. In the presence of a conflict resolution mechanism, we propose a method to reduce the extended ledger back to a consistent UTXO Ledger.
While the Bitcoin and Ethereum are still leading the world of permissionless blockchains, we are increasingly seeing a multipolar ecosystem where new blockchains keep emerging instead of migrating to the two big players. As a result, it is highly desired to enable multiple blockchains to interoperate, e.g., move assets from one blockchain to the other. The crosschain bridge service, as a solution to the blockchain interoperability problem, has been offered by a wide range of service providers. However, the existing bridges either rely on centralised notaries or require complicated preparations, therefore are far from sufficient in practice. In this demo proposal, we highlight the Poly Bridge for heterogeneous blockchains to interoperate with cryptocurrencies. In specific, Poly Bridge is based on an un-derlying Poly Chain and a pair of relays to confirm crosschain transactions and form consensus among relevant parties. More importantly, Poly Bridge delivers extensibility to flexibly inter-face to blockchains with different consensus models and atomicity as well in a way that a sequence of crosschain operations are either all confirmed or all rejected. Poly Bridge is now available as a web application to support crosschain requests with over 200 types of cryptocurrencies on 18 blockchains.
Sharding technique, which divides the whole network into multiple disjoint groups or committees, has been recognized as a revolutionary solution to enhance the scalability of blockchains. For account-based model, state data are partitioned over all committees and organized as Merkle trees to ensure data consistency and immutability. However, existing techniques on Merkle tree-based state storage fail to scale out due to a large amount of network and compute overheads incurred by data migration and Merkle tree reconstruction, respectively. In this paper, we propose $\mathcal{S}$-Store, a scalable data storage technique towards permissioned blockchain sharding based on Aggregate Merkle B+ tree (AMB-tree). $\mathcal{S}$-Store utilizes consistent hashing to reduce data migration among committees and uses split and merge on AMB-tree to decrease Merkle tree reconstruction overheads. $\mathcal{S}$-Store also employs a novel committee addition protocol that guarantees the system service availability during data migration. Extensive experiments show that $\mathcal{S}$-Sotre outperforms existing techniques by one order of magnitude in terms of transaction execution, data transmission, and committee addition.
State-of-the-art blockchain sharding solutions, say Monoxide, can induce imbalanced transaction (TX) distributions among all blockchain shards due to their account deployment mechanisms. Imbalanced TX distributions then cause hot shards, in which the cross-shard TXs may experience an unlimited length of confirmation latency. Thus, how to address the hot-shard issue and how to reduce cross-shard TXs become significant challenges of blockchain state sharding. Through reviewing the related studies, we find that a cross-shard TX protocol that can achieve workload balance among all shards and simultaneously reduce the number of cross-shard TXs is still absent from the literature. To this end, we propose BrokerChain, which is a cross-shard blockchain protocol devised for the account/balance-based state sharding. Essentially, BrokerChain exploits fine-grained state partition and account segmentation. We also elaborate on how BrokerChain handles cross-shard TXs through broker accounts. The security issues and other properties of BrokerChain are analyzed substantially. Finally, we conduct comprehensive evaluations using both a cloud-based prototype and a transaction-driven simulator. The evaluation results show that BrokerChain outperforms other solutions in terms of system throughput, transaction confirmation latency, the queue size of transaction pool, and workload balance.
In this paper, we propose a novel method for academic assessment inspired by the decentralized applications made possible by blockchain technology. The proposed method applies to a wide range of academic material, including assignments, exams, academic papers, etc and tackles issues regarding potential personal bias and makes assessment possible without the need to rely on a few assessors. We examine the challenges and possibilities that arise with this method and further explore more general applications in areas such as education. In the experiments conducted for this research, poll results show generally positive views toward the fairness of this system compared to the traditional methods.
Blockchain has received great attention in academia and industry due to its decentralization and immutability. From the perspective of transaction processing, blockchain is a distributed shared ledger and database with the characteristics of decentralization, traceability, and transparency. These features ensure the security of blockchain’s reliability. However, because a blockchain network requires complex consensus verification between users, it causes problems such as a high cost of data exchange and a low system throughput. Such problems are aggravated when executing a cross-chain transaction, as it is particularly important to ensure the atomicity and isolation of transactions across the blockchain. Considering this, in this paper, we propose the cross-chain transaction processing flow of EOVPC and efficient transaction processing based on version control. Different from the existing cross-chain transaction approaches based on locking, we propose optimistic approaches in which the updated data can be used immediately, with a rolling back procedure that guarantees atomicity. We conducted extensive experiments, which show that our approaches can improve the throughput and success rate significantly.
Kai Lin, Jian Gao, Guangjie Han, Haohua Wang · 5 authors
With the explosive growth of devices and tasks deployed in the industrial Internet of Things (IIoT), the lack of interconnection and collaboration between devices leads to poor timeliness and security in IIoT resource scheduling. This article focuses on the issue of adaptive scheduling of resources in large-scale IIoT. First, a collaborative terminal-edge IIoT architecture is designed, which introduces blockchain and AI technology to support dynamic resource scheduling in untrustworthy environments. Then, a smart contract-based multidimensional resource transaction model is developed to improve the efficiency and security of resource scheduling by establishing a credit-based consensus mechanism. Distributed transaction learning resource scheduling algorithm is further proposed to implement resource-adaptive scheduling between devices in IIoT. Extensive simulation experiments are conducted to evaluate the proposed method with respect to several performance aspects covering the scheduling decision delay, transaction generation ratio, and security. The obtained results demonstrate that the comprehensive scheduling performance of the proposed method outperforms other existing algorithms.
Aimen Djari, Emmanuelle Anceaume, Sara Tucci-Piergiovanni
A recent evolution of the blockchain structure is emerging to address the performance issue of permissionless chain-based ledgers, in particular the small number of transactions confirmed per second. To address such an issue, new designs have been brought forward, including Bitcoin-NG, which favors an off-chain mechanism in which blocks refer to a leader in charge of validating transactions batched in micro-blocks out of the chain [6]; Lightning [10], which follows the same principle but only publishes the outcome of repeated transactions among a set of parties. Others propositions such as HashGraph [2], ByteBall [5], and Iota [4] leverage the presence of well known institutions to get rid of blocks, while Ghost [12] and Spectre [11] protocols family modifies the blockchain data structure from a totally ordered sequence of blocks to a directed graph of blocks. Blocks are built so that they commit the state of the directed graph at the time blocks were created which decreases the opportunity for powerful attackers to create blocks in advance. Regarding the graph-based approach, the absence of mechanisms to prevent the presence of conflicting records (i.e., blocks with conflicting transactions) or the presence of cycles in the directed graph (Spectre [11] organises blocks in a directed, but not acyclic, graph of blocks) require that participants execute a complex algorithm to extract from the graph the set of accepted (i.e., valid) transactions [11]. Sycomore1 is an immutable permissionless distributed ledger whose structure is a particular directed acyclic graph of blocks, called SYC-DAG [1]. Its design differs from existing distributed ledgers in that its graph structure dynamically adapts to fluctuations in transaction submission rates: When the leaf block of a chain (more precisely the last blocks appended to a chain) of the graph exceeds a maximal loading threshold (the load is measured in Bytes), subsequent blocks are partitioned over two sibling chains, and these blocks are mined in parallel (as will be described shortly, even if blocks are appended in parallel to the SYC-DAG they cannot be conflicting, i.e., each valid transaction cannot appear in more than one block). Conversely, when the leaf blocks of two sibling chains (again the last blocks of two sibling chains) fall short of a minimal loading threshold, subsequent blocks will belong to a unique chain. The decision to split a leaf chain of the SYC-DAG or to merge two sibling ones is locally taken by each miner, and soundness of this decision is verifiable by everyone at any time [1]. Actually, Sycomore has been designed to meet the following properties [1]:
Pengfei Wang, Pan Bo, Tao Qian, Yang Changqing · 5 authors
Aiming at the safety and efficiency problems in the whole life cycle management of aviation equipment, propose an efficient solution based on federated blockchain. Firstly, the data collected by the terminal sensing device is hash transformed through the blockchain system, and the initial data security is achieved by using the irreversibility principle of the hash algorithm while reducing the data volume of a single transaction in the block; secondly, the block is generated by the representative nodes elected through the Delegated-Proof of Stake (DPoS), and the consensus algorithm of the blockchain data verification adopts the delegated Byzantine Fault-Tolerance (DBFT) consensus algorithm to improve the consensus efficiency; finally, the transaction time curves are fitted and plotted according to the number of participating nodes, block size and network bandwidth in the simulation experiments to calculate the transaction efficiency under different situations. The experimental results show that the federated chain system is proved to achieve secure and efficient aviation equipment history storage and traceability.
After the success of the Bitcoin blockchain, came several cryptocurrencies and blockchain solutions in the last decade. Nonetheless, Blockchain-based systems still suffer from low transaction rates and high transaction processing latencies, which hinder blockchains' scalability. An entire class of solutions, called Layer-1 scalability solutions, have attempted to incrementally improve such limitations by adding/modifying fundamental blockchain attributes. Recently, a completely different class of works, called Layer-2 protocols, have emerged to tackle the blockchain scalability issues using unconventional approaches. Layer-2 protocols improve transaction processing rates, periods, and fees by minimizing the use of underlying slow and costly blockchains. In fact, the main chain acts just as an instrument for trust establishment and dispute resolution among Layer-2 participants, where only a few transactions are dispatched to the main chain. Thus, Layer-2 blockchain protocols have the potential to transform the domain. However, rapid and discrete developments have resulted in diverse branches of Layer-2 protocols. In this work, we systematically create a broad taxonomy of such protocols and implementations. We discuss each Layer-2 protocol class in detail and also elucidate their respective approaches, salient features, requirements, etc. Moreover, we outline the issues related to these protocols along with a comparative discussion. Our thorough study will help further systematize the knowledge dispersed in the domain and help the readers to better understand the field of Layer-2 protocols.
Kyle P. Michelson, Anjali Sridharan, Umut Can Çabuk, Ethan Reesor · 9 authors
The Accumulate Protocol ("Accumulate") is an identity-based, Delegated Proof of Stake (DPoS) blockchain designed to power the digital economy through interoperability with Layer-1 blockchains, integration with enterprise tech stacks, and interfacing with the World Wide Web. Accumulate bypasses the trilemma of security, scalability, and decentralization by implementing a chain-of-chains architecture in which digital identities with the ability to manage keys, tokens, data, and other identities are treated as their own independent blockchains. This architecture allows these identities, known as Accumulate Digital Identifiers (ADIs), to be processed and validated in parallel over the Accumulate network. Each ADI also possesses a hierarchical set of keys with different priority levels that allow users to manage their security over time and create complex signature authorization schemes that expand the utility of multi-signature transactions. A two token system provides predictable costs for enterprise users, while anchoring all transactions to Layer-1 blockchains provides enterprise-grade security to everyone.
Big Data is huge in volume, diverse in information, and growing at flourishing rates. The major distributed file systems in the current market in Big Data Analysis includes Apache Hadoop, Storm, Cassandra, Flink, Cloudera, and many more. Hadoop is an open-source framework divided into Hadoop Distributed File System (HDFS) and Map-Reduce. Hadoop plays a leading role in storing and processing Big Data in contemporary society as it is cost- effective and can manage large volumes of data in low-cost commodity hardware. HDFS is a type of Data Warehouse which is scalable and has fast access to the information. Metadata is the information about the data, such as which block is storing on what datanode, how many replications are that particular block has, and on which datanodes those replications reside. In HDFS, this metadata is stored at a fixed place in namenode, and attackers can access the metadata and modify it without notice. Also, the metadata is mutable, which means that the attacker can erase his presence easily. To resolve this issue, in this paper we have provided a mechanism using blockchain technology that follows a decentralized architecture against the centralized architecture followed by HDFS. Hyperledger Fabric (HLF) is the blockchain proposed to be effective and trusted for such a purpose. HLF is a private blockchain with a distributed immutable ledger. The metadata will be stored in the ledger. If an attacker tries to modify the data, he cannot erase his presence as the ledger is immutable, unlike HDFS. Further, the work proposed in this paper can be extended in real-time HDFS with the secure ledger and multiple nodes.
Blockchain has attracted lots of attention in recent years. However, the performance of blockchain cannot meet the requirement of massive Internet of Things (IoT) devices. One of the important bottlenecks of blockchain is the limited computing resources on a single server while executing transactions. To address this issue, we propose Aeolus blockchain to achieve the distributed execution of blockchain transactions. There are two key challenges to achieving this for IoT blockchain: transaction structure and state consistency. Facing these challenges, we first propose a distributed blockchain transaction structure, which imports extra parameters to divide the transaction execution into different stages to enable distributed execution. Second, we propose distributed state update sharding, which equips each blockchain peer with its own master and shard servers. In this way, each blockchain peer can be considered as a cluster that distributes the transaction to shorten the processing time and reach the consensus finally. We implement Aeolus on Go-Ethereum to evaluate its feasibility, on a testbed including 132 cloud servers. Our system runs stably for more than 8 h under the workload of 190 000 000 real-world user transactions. Experimental results show the efficiency that Aeolus can achieve more than 100 000 transactions/s of blockchain transactions, which is 15.6 times the throughput of the original blockchain.
Non-fungible tokens have been a unique transformation in the implementation of the concept of distributed ledger technology in digital assets. NFTs are said to be non-interchangeable, which distinguishes its value from fungible tokens like Bitcoin (Btc). Scammers are utilizing the open source nature of the blockchain to victimize users and steal their NFTs, leaving NFT collectors with infringed artwork. In a bid to eliminate security vulnerability and attack in NFT platform, we implemented a smart contract verification model. Our verification model is a 2-pronged approach that utilized F*, functional programming language. We presented two tools that translated solidity source code and EVM bytecode to solidity* and EVM* respectively. The EVM decompiler analyzes contracts in which the solidity source codes are unavailable as well as low level properties of contracts. The EVM* and Solidity* tools helped to check the equivalence between a solidity program and the bytecode output from the solidity compiler in order to avoid bugs and preserve verified properties at the source level. In this paper, Etherscan token tracker was used to verify and authenticate NFT token before buying or minting such NFT. Keywords: Non-Fungible Tokens (NFTs), The NFT- marketplace (NFTM), Ethereum
Blockchain sharding technology randomly divides all nodes in the blockchain system into multiple shardings. This design aims to solve the scalable problem when there are too many access nodes in the blockchain network, by significantly reducing the complexity of reaching consensus and improving the throughput and efficiency of transactions in the blockchain system. However, if too many malicious nodes are allocated or the number of nodes is not enough, it may bring security risks to sharding. This paper analyzes the sharding security of blockchain systems with PBFT consensus under non-cross sharding transaction and cross sharding transaction. Simulation results show that both the number of nodes in a sharding and the number of malicious nodes affect the sharding security. In the case of cross-sharding, we can increase the number of cross-sharding validation nodes to improve the success rate of consensus.
In a world where privacy and authenticity get questioned at every turn, technologies like Blockchain exist to help assist the digital information’s integrity to remain. The healthcare industry is a volatile and sensitive industry, which is seen as an avenue for multiple technological ideas and advancements. With privacy being the main concern, work talks about the importance of its resolution, putting users and their needs first through user research, and further implementing a secure and effective Blockchain file storage system using IPFS and Ethereum, accessed via an interactive web application and using a secure backend for user information integrity within the system.
The key features that distinguish blockchain as one of the most secure technologies are - decentralization, privacy, and immutability. It has converted a low-trust centralized ledger held by a single third party into a high-trust decentralized ledger held by multiple entities. The main contribution of blockchain is the consensus protocol, which ensures the stable operation of the blockchain system. Consensus occurs when all nodes in a blockchain network agree on a common state of the ledger. Thus, a consensus must prohibit malicious actors from controlling the network while also granting equal rights to all nodes and mandating their participation in the consensus process. Existing algorithms such as proof of work and proof of stake are vulnerable to future attacks such as 51% attack. The proposed algorithm solves issues such as unfair miner selection, 51%-attack, forking, double spending problem with minimal computational resources. It provides adequate protection regardless of the attacker's hashing ability or currency holdings and also resolves the enormous waiting time issue for transaction confirmation.
The aim of the paper is to present the new factors of ERP (Enterprise Resource Planning system) implementation related to the usage of cloud-based and blockchain information technology and to discover potential possibilities of using cloud computing, big data, and blockchain technologies in the methodology of ERP implementation. The article covers the characteristics of the current implementation methodologies and also discusses how these technologies can be adopted in the implementation process. During the study, a literature review was carried out and survey-based interviews with project managers were performed. Previous studies examined in the literature review have some limitations. Most of them are focused on ERP performance in the cloud or measure success factors of ERP implementation. A research gap exists regarding the impact of technologies in the implementation process and the results of this process. The research shed some light on cloud computing and blockchain in ERP implementation. The conclusions are as follows: (1) Some methods of sustainable methods of ERP implementation with the use of cloud technologies, blockchain, and big data have been examined in research studies, but there is still a lack of publications with in-depth analyses of the impact of blockchain on ERP implementation success. (2) The practitioners recommended the new technologies based on cloud computing and big data in the process of ERP implementation, and more knowledge about blockchain would have a positive impact on the success of sustainable ERP implementation as well as on the willingness to adopt the new technologies.
Akram Alofi, Mahmoud A. Bokhari, Rami Bahsoon, Robert Hendley
Blockchain technology has gained recognition in industrial, financial, and various technological domains for its potential in decentralizing trust in peer-to-peer systems. A core component of blockchain technology is a consensus algorithm, most commonly Proof of Work (PoW). PoW is used in blockchain-based systems to establish trust among peers; however, it does require the expenditure of an enormous amount of energy that affects the environmental sustainability of blockchain-based systems. Energy minimization, whilst ensuring trust within blockchain-based systems that use PoW, is a challenging problem. The solution has to consider how energy consumption can be minimized without compromising trust, whilst still ensuring, for instance, scalability, security, and decentralization. In this paper, we represent the problem as a subset selection problem of miners in a blockchain-based system. We formulate the problem of blockchain energy consumption as a Search-Based Software Engineering problem with four objectives: energy consumption, carbon emission, decentralization, and trust. We propose a model composed of multiple fitness functions. The model can be used to explore the complex search space by selecting a subset of miners that minimizes the energy consumption without drastically impacting the primary goals of the blockchain technology (i.e., security/trustworthiness and decentralization). We integrate our proposed fitness functions into five evolutionary algorithms to solve the problem of blockchain miners selection. Our results show that the environmental sustainability of blockchain-based systems (e.g. reduced energy use) can be enhanced with little degradation in other competing objectives. We also report on the performance of the algorithms used.
Nguyen Khoi Tran, Muhammad Ali Babar, Andrew J. Walters
Blockchain network deployment and evaluation have become prevalent due to the demand for private blockchains by enterprises, governments, and edge computing systems. Whilst a blockchain network's deployment and evaluation are driven by its architecture, practitioners still need to learn and carry out many repetitive and error-prone activities to transform architecture into an operational blockchain network and evaluate it. Greater efficiency could be gained if practitioners focus solely on the architecture design, a valuable and hard-to-automate activity, and leave the implementation steps to an automation framework. This paper proposes an automation framework called NVAL (Network Deployment and Evaluation Framework), which can deploy and evaluate blockchain networks based on their architecture specifications. The key idea of NVAL is reusing and combining the existing automation scripts and utilities of various blockchain types to deploy and evaluate incoming blockchain network architectures. We propose a novel meta-model to capture blockchain network architectures as computer-readable artefacts and employ a state-space search approach to plan and conduct their deployment and evaluation. An evaluative case study shows that NVAL successfully combines seven deployment and evaluation procedures to deploy 65 networks with 12 different architectures and generate 295 evaluation datasets whilst incurring a negligible processing time overhead.