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The blockchain has gained widespread attention due to its decentralized, secure, traceable, and immutable characteristics. However, current consensus protocols face the challenge of limited scalability and inadequate consideration of dynamic node behavior in large-scale networks. They cannot effectively adapt to the increasing number of nodes and the subsequent network traffic surge. Furthermore, their inability to sufficiently address dynamic node behavior poses a risk to the consensus process and compromises the overall reliability of the system. A cluster reputation-based hierarchical consensus model (CRHCM) has been proposed to addresses node dynamics and improves network scalability in this paper. The model introduces a reputation system that updates node reputations based on both current and historical behaviors during the consensus process. Node reputation fluctuations are assessed using a discrete Markov chain, which enables the identification of abnormal nodes and improves overall node reliability. Furthermore, a hierarchical structure has been proposed to improve scalability and reduce the communication complexity of blockchain by assigning nodes to the upper or lower layers through reputation and fluctuation levels. Experimental and theoretical evaluations demonstrate the effectiveness of CRHCM. The model achieves a balanced distribution of reputation values among all nodes and exhibits high scalability. It has excellent performance by comparisons with some other state-of-the-arts. [ABSTRACT FROM AUTHOR]

With the advent of the digital age, traditional lifestyle activities, such as reading books, referencing recipes, and enjoying music, have progressively transitioned from offline to online. However, numerous issues plague the conventional approach to digital copyright protection. This is especially true in the realm of recipe protection, where the rights and interests of original creators are inadequately safeguarded due to the widespread dissemination of a large number of recipes on the Internet. This primarily stems from the high costs of gathering evidence, incomplete coverage of evidence collection, and the inability to identify and halt infringement activities in a timely manner during the process of traditional digital copyright protection. Therefore, this study designs and implements a blockchain-based digital recipe copyright protection scheme to address the issues of insufficient legal evidence and cumbersome processes in traditional digital copyright protection. First, we enhance standard short text similarity calculation method SimHash, boosting the accuracy of text similarity detection. We then utilize the decentralization, immutability, time-stamping, traceability, and smart contract features of blockchain technology for data privacy protection. We employ the Interplanetary File System (IPFS) to store raw data, thereby ensuring user privacy and security. Lastly, we improve the proxy voting node selection in the existing delegated proof of stake (DPOS) consensus mechanism. According thorough evaluation and empirical analysis, the scheme effectively improves the accuracy of text similarity detection. Simultaneously, the enhanced DPOS mechanism effectively rewards nodes with excellent performance and penalizes nodes exhibiting malicious behavior. In this study, we successfully designed and implemented an innovative digital recipe copyright protection scheme. This scheme effectively enhances the accuracy of text similarity detection; ensures the privacy and security of user data; and, through an enhanced DPOS mechanism, rewards well-performing nodes while penalizing those exhibiting malicious behavior. [ABSTRACT FROM AUTHOR]

Motivated from the mean‐square bounded consensus (MSBD) problem of multiagent systems (MASs) with additive noise, this paper studies the joint influence of the agent dynamic structure and communication topology on the consensus. The necessary condition of MSBD is given under the output‐based consensus protocol, which is also sufficient under some mild conditions. Furthermore, the upper consensus bound is given via the solution of the Lyapunov equation. Finally, simulation results are provided to illustrate the theoretical results. [ABSTRACT FROM AUTHOR]

With the increasing growth rate of smart home devices and their interconnectivity via the Internet of Things (IoT), security threats to the communication network have become a concern. This paper proposes a learning engine for a smart home communication network that utilizes blockchain-based secure communication and a cloud-based data evaluation layer to segregate and rank data on the basis of three broad categories of Transactions (T), namely Smart T, Mod T, and Avoid T. The learning engine utilizes a neural network for the training and classification of the categories that helps the blockchain layer with improvisation in the decision-making process. The contributions of this paper include the application of a secure blockchain layer for user authentication and the generation of a ledger for the communication network; the utilization of the cloud-based data evaluation layer; the enhancement of an SI-based algorithm for training; and the utilization of a neural engine for the precise training and classification of categories. The proposed algorithm outperformed the Fused Real-Time Sequential Deep Extreme Learning Machine (RTS-DELM) system, the data fusion technique, and artificial intelligence Internet of Things technology in providing electronic information engineering and analyzing optimization schemes in terms of the computation complexity, false authentication rate, and qualitative parameters with a lower average computation complexity; in addition, it ensures a secure, efficient smart home communication network to enhance the lifestyle of human beings. [ABSTRACT FROM AUTHOR]

A Blockchain network consists of a distributed ledger and a set of nodes participating in the network. The consistency in the ledger’s state is maintained by a Blockchain consensus mechanism. This property is essential since it is assumed that the participants in the network do not trust each other. Most Blockchain consensus algorithms are unsuitable for resource-constrained nodes due to their power consumption, storage, network overhead, and computation requirements. Furthermore, many consensus methods do not address the issue of data accountability, which guarantees that an entity will be judged on its performance or conduct concerning a duty they have taken. This study proposes a novel consensus mechanism termed Proof of Block Height (PoBH) that prioritizes accountability for reporting IoT data transactions and considers factors such as low computation cost and energy consumption. The approach relies on a pre-existing comparable deterministic value based on the height of the committed blocks. The model identifies a malicious intent using a set of predicates and consequently incurs a computation penalty to keep such nodes away from the network. As a preventive measure, the model also seeks to increment this penalty appropriately by making the network free from dishonest nodes for as long as possible, thus sanitizing the network. Importantly, the developed method does not augment the basic hierarchy of an IoT network. A formal analysis of the mechanism’s operation shows that the resource and time required to cheat the system grows exponentially with the number of faulty blocks a node tries to append to the shared ledger. The factors affecting the mechanism’s performance, scalability, and effort required (by malicious nodes) to stay within the network are also quantitatively evaluated. [ABSTRACT FROM AUTHOR]

Consensus protocols, as crucial components of blockchain technology, play a vital role in ensuring data consistency among distributed nodes. However, the existing voting-based and proof-based consensus protocols encounter scalability issues within the blockchain system. Moreover, most consensus protocols are serialized, which further limits their scalability potential. To address this limitation, parallelization methods have been employed in both types of consensus protocols. Surprisingly, however, novel fusion consensus protocols demonstrate superior scalability compared with these two types but lack the utilization of parallelization techniques. In this paper, we present PnV, an efficient parallel fusion protocol integrating proof-based and voting-based consensus features. It enhances the data structure, consensus process, transaction allocation, and timeout handling mechanisms to enable concurrent block generation by multiple nodes within a consensus round. Experimental results demonstrate that PnV exhibits superior efficiency, excellent scalability, and acceptable delay compared with Proof of Vote (PoV) and BFT-SMART. Moreover, at the system level, the performance of the PnV-based blockchain system optimally surpasses that of the FISCO BCOS platform. Our proposed protocol contributes to advancing blockchain technology by providing a more efficient and practical solution for achieving decentralized consensus in distributed systems.

In this work, we propose a satellite-aided permissionless consensus protocol for scalable space-terrestrial blockchains. We design its working principle and workflow by taking full advantage of satellites for extensive coverage and ubiquitous connectivity. Based on the proposed protocol, we demonstrate how such a space-terrestrial blockchain grows and evolves through several typical cases in the presence of adversarial nodes, user misbehavior, and transmission outage. Taking proof of work (PoW) as a benchmark, we assess the system security by considering both adversarial miners and possible colluding satellites. Then, we analyze the maximum blockchain throughput under network capacity limits and evaluate the impact of information propagation delay via a Markov model. Simulation results support that the proposed satellite-aided consensus protocol achieves higher throughput and exhibits greater scalability than PoW.

Sharding is a technology that solves the problem of blockchain capacity expansion.However,sharding may make it ea-sier for malicious nodes to be concentrated in a single shard,thus hindering the safe operation of the entire system.This paper proposes a reputation-based sharding consensus protocol(RBSCP),which establishes a reputation mechanism to measure node behavior and encourage nodes to follow the protocol.The reputation level-based sharding method reduces the difference in the reputation level distribution in different shards,so as to prevent malicious nodes from concentrating on a single shard to do evil.A double-chain model combining verification chain and record chain is proposed.Through the differentiated storage of transactions,the storage capacity of the blockchain is expanded while the security of the blockchain is improved.By associating the vo-ting shares with the node reputation and differentiating the node commitments,a reputation-based fast Byzantine fault tolerance(RFBFT) algorithm is proposed,which enables honest nodes to reach consensus faster and reduces the impact of malicious nodes.Security analysis shows that RBSCP can guarantee the rationality of node distribution in shards and the security of consensus process,and prevent double spend attack and nothing at stake attack.Experimental results show that RBSCP can achieve low sharding latency,low consensus latency and high throughput under the premise of ensuring security.

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. [ABSTRACT FROM AUTHOR]

For connected automated vehicles (CAVs), safety and security are two interrelated critical issues since many in-vehicle components are both safety critical and security critical. To achieve both safety and security in the presence of functional failures or cyberattacks, this article proposes a dynamic heterogeneous redundancy (DHR) scheme for CAVs. The basic idea is that each safety- and security-critical in-vehicle component should employ a DHR architecture, which is constructed by multiple heterogeneous executors with the same function. With redundancy, the functional safety can be achieved when one executor fails. Meanwhile, based on the principle that the probability is extremely low that two or more heterogeneous executors with the same function will fail for the same vulnerability, security can be ensured by using simple consensus mechanisms to detect abnormal executors caused by any cyberattacks. A DHR prototype has been designed and installed on an automated bus. Test results show that the proposed DHR is effective in enhancing both safety and security for CAVs. [ABSTRACT FROM AUTHOR]

The present paper aims to design and simulate an adversarial strategy where a swarm of quadrotor UAVs is herding anti-aircraft land vehicles (AALV) that actively oppose the swarm's objective by potentially taking them down. The main strategy is to block the AALVs' line of sight to their goal zone (AALVs' objective), shifting its trajectory so it reaches a kill zone instead (UAVs' objective). The counter-swarm strategy performed by the AALVs consists of taking down the closest aerial units to the goal zone. As a result, a consensus algorithm is executed by the UAVs in order to assess the communication network and re-group. Consensus is based on the propagation of local observations that converge into a global agreement on a communication graph. Re-grouping is done via positioning around the kill zone vector or preferring an anti-clockwise formation to better close gaps. The adversarial strategy was tested in an empty arena and urban setting, the latter making use of a path-planning procedure that re-routes the AALV trajectory based on its current destination. Simulation results show a maximum UAV mission success rate converging to roughly 80% in the empty arena. When targeted elimination procedures are executed, UAV mission performance drops 5%, making no distinction between re-grouping strategies in the empty arena. The urban setting shows lower performance due to navigation complexity but favors the decision to re-group based on a formation that close gaps rather than positioning around the kill zone vector. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) is a network of smart objects connected via the Internet, where each object is identified by a unique, accessible, and programmable address, while Blockchain is a technology for storing and transmitting information based on a decentralized system such that the centralized validation of transactions is replaced by a consensus mechanism. The integration of these two technologies requires consensus protocols to overcome the major challenges encountered in IoT systems, including issues related to security, storage capacity limits, computing power, etc. Therefore, different consensus algorithms have been implemented. For this purpose, this paper presents a research study on the criteria that would render a Blockchain consensus algorithm suitable for IoT networks, namely, computing power, latency, storage capacity, and security. [ABSTRACT FROM AUTHOR]

This paper proposes a variant of the recently reported pool mining approach and provides a reduction in the energy that is consumed by the blockchain consensus protocol. The novelty of the proposed architecture lies in the employment of an innovative cryptographic puzzle that is based on stream ciphering. This enables flexibility in setting the difficulty parameter of the protocol, and allows for the separation of the energy and memory resources that are required for the puzzle solving. The proposed approach provides high resistance against the following malicious activities of miners in public blockchain systems: (i) the submission of fake work and fictitious computation results; and (ii) some well-known attacks that target the blockchain incentive mechanism. We experimentally evaluate the power consumption of the proposed consensus protocol and compare it with the traditional proof-of-work protocol based on hashing. The obtained results point out the gain that the proposed pool mining provides compared with the traditional types. [ABSTRACT FROM AUTHOR]

Aiming at the problem that the classical blockchain consensus mechanism is under the threat of quantum computing attacks,a quantum-secured Byzantine fault tolerant consensus mechanism is proposed.Firstly,to solve the security threat of public key digital signature,this paper proposes a multilinear hash-unconditionally secure signature(MH-USS) signature scheme based on quantum key distribution (QKD) and multilinear hash function family.In this scheme,quantum keys are distributed through QKD network,messages and signatures are transmitted through classical network,and the simplified USS signature scheme is adopted as the main framework,combined with the family of multiple linear hash functions,to generate a new USS scheme.This signature scheme has the characteristics of unforgeability,non-repudiation and transferability.Moreover,this scheme can be implemented on existing equipment and has high practical value.Secondly,in view of the relatively low consensus efficiency of the classical Byzantine fault-tolerant consensus mechanism PBFT,this paper proposes the quantum secured-byzantine fault tolerance(QS-BFT) consensus mechanism.By adding “fast-normal” consensus mode and allowing nodes to vote on empty blocks,the system communication times are reduced and the view conversion process is avoided.It has been proved that this scheme not only guarantees the safety and liveness,but also effectively reduces message complexity and improves consensus efficiency.The simulation and performance test for this scheme indicate that the throughput of this scheme is higher and the delay is lower compared with the PBFT consensus mechanism which is based on the MH-USS signature scheme.

In large-scale energy storage system, the large number of energy storage units leads to inconsistent of State of Charge and unbalanced sharing of output power. In order to solve this problem, a consensus control protocol design and analysis method based on specified sampled-data is proposed. The consensus of SOC and output power (normalization) of each energy storage unit in large-scale energy storage system has been achieved. Firstly, according to the definition of lithium battery SOC and discharge mechanism, a system model of large-scale energy storage system is established. Based on specified sampled-data control, consensus control protocol of multi-agent of energy storage units is designed, and system convergence analysis is carried out. Meantime, the constraints of sampling period T are derived. It is proved that local energy storage unit agent can generate local energy storage unit control signal only when it receives the state information of adjacency energy storage unit agent at a specified sampling time point. In this way, the problem of too much computation caused by the complex communication of large-scale energy storage system is solved. Considering specified sampled-data control and system requirements, the system control parameters are designed. This method is simple in control and takes up less system communication resources. Finally, the simulation results are shown that the method is effective in different application scenarios.

In recent years, with the definition and expansion of a new phenomenon called cryptocurrencies, we have witnessed scientific discussions and challenges in the field of accurate thematics of this phenomenon and the jurisprudential and religious implications of their transactions under Islamic economy. Although the phenomenon began with the introduction of Bitcoin in 2008, in the last decade with the expansion of technologies and consensus protocols, there has been a significant growth in this with the consequence of more than seventeen thousand (17,000) cryptocurrencies of different natures being formally listed. Since one of the important issues in Shari'a and Islamic ruling is the complete knowledge of the subject and its varieties, in this research, an attempt has been made to provide an accurate thematics of these seventeen thousand codes and then according to the principles, rules and criteria about money in the general framework of the Islamic monetary system, different types of cryptocurrencies should be analyzed and examined. The results show that, firstly, from a technical point of view, according to the protocols of consensus and support, cryptocurrencies can be divided into two general categories: stable and unstable. Secondly, from an economic point of view, some cryptocurrencies are monetary in nature and others are asset in nature. Thirdly, among the types of cryptocurrencies, those that are designed to be stable and backed by assets or goods, are more closely related to and observe better the principles and rules of the Islamic monetary system.

The consensus protocol is the core of blockchain systems. The existing hybrid committee-based consensus protocol is one of the important ways to improve the permissionless blockchain system. But the presence of malicious nodes, it can interfere with the normal operation of the committee. However, there is a deficiency in the existing mechanism to ensure the efficient and secure operation of the committee. Therefore, a reliable committee consensus protocol (DCCP) for permissionless blockchain is proposed. The protocol guarantees the operation of the committee in three ways. First, a reliability evaluation model is designed based on the performance of committee members. Second, a reliable node selection strategy is proposed by combining the mining process and node reliability value. Third, a malicious node replacement mechanism is proposed to optimize the committee operation. Finally, a delayed reward mechanism is designed in order to encourage node participation. The experiment shows that the DCCP protocol can effectively inhibit the entry of malicious nodes and can improve the throughput by 12% in the presence of malicious nodes, with high throughput and security. [ABSTRACT FROM AUTHOR]

Blockchain technology has aroused great interest from society and academia since the inception of Bitcoin. Its de-centralization and non-tampering can apply in broader scenarios, such as the Internet of Things, smart cities, and cloud computing. Among various core components, the consensus protocol is the core of maintaining blockchain networks' performance, stability, and security. However, with the increase of network nodes and the improvement of network complexity, these properties are difficult to meet simultaneously. In this paper, we propose an advancement of the practical Byzantine consensus algorithm (LRBFT). The algorithm uses Lagrange interpolation that all backups can participate in to generate random seeds, uses the seeds to optimize the election process of the primary set, improves consensus efficiency through delegated nodes, and prevents the primary from doing evil through the supervisory mechanism. The generation of random seeds has the characteristics of full participation, unpredictability, and verifiability. The election process of the primary set has randomness, uniform distribution, and supervision. Furthermore, we proved the feasibility of our proposed algorithm through theoretical analysis and experimental evaluations. Experimental analysis shows that when there are 70 nodes in the practical Byzantine fault tolerance (PBFT) consensus protocol. If LRBFT selects only 7 nodes as delegated nodes, the time it takes for LRBFT to reach 100 consensuses is only 0.83% of that of PBFT. [ABSTRACT FROM AUTHOR]

A multi‐agent consensus protocol is investigated over noisy undirected connected graphs. It is supposed that each agent can know her neighbors' states with bounded noise. A theoretical stopping rule having a probabilistic guarantee is established for the consensus protocol, which explicitly relates the number of iterations with the closeness of the agreement. The stopping rule is derived by utilizing Bernstein inequality that deals with a given noise bound explicitly. The sample complexity with respect to the number of agents is also investigated, where it is shown that the number of iterations required by the proposed stopping rule based on the bound of noise itself is generally smaller than that of the conventional stopping rules that utilize bound of noise variance. The results are demonstrated through numerical examples. [ABSTRACT FROM AUTHOR]

Consensus algorithms are applied in the context of distributed computer systems to improve their fault tolerance. The explosive development of distributed ledger technology following the proposal of 'Bitcoin' led to a sharp increase in research activity in this area. Specifically, public and permissionless networks require robust leader selection strategies resistant to Sybil attacks in which malicious attackers present bogus identities to induce byzantine faults. Our goal is to analyse the entire breadth of works in this area systematically, thereby uncovering trends and research directions regarding Sybil attack resistance in today's blockchain systems to benefit the designs of the future. Through a systematic literature review, we condense an immense set of research records (N = 21,799) to a relevant subset (N = 483). We categorise these mechanisms by their Sybil attack resistance characteristics, leader selection methodology, and incentive scheme. Mechanisms with strong Sybil attack resistance commonly adopt the principles underlying 'Proof-of-Work' or 'Proof-of-Stake' while mechanisms with limited resistance often use reputation systems or physical world linking. We find that only a few fundamental paradigms exist that can resist Sybil attacks in a permissionless setting but discover numerous innovative mechanisms that can deliver weaker protection in system scenarios with smaller attack surfaces. [ABSTRACT FROM AUTHOR]

Consensus protocol is challenging due to the poor node reliability, low efficiency and decentralization. A comprehensive reputation based Practical Byzantine Fault Tolerance consensus method (CRPBFT) has been proposed. Comprehensive reputation model has been developed to evaluate the credibility of each node from service behavior and consensus process at first. The nodes with higher reputation are selected to participate in the consensus process, which helps to reduce the probability of consensus failure caused by the existence of malicious nodes. A consensus communication structure is optimized by replacing the whole network broadcast structure in the commit phase with a star one. It can be applied to degrade the network communication overhead and improve consensus efficiency. A rotation mechanism for replacing the consensus nodes regularly has been proposed to increase the degree of decentralization and enhance the robustness and dynamic of the consensus network. Some experimental results demonstrate that the developed method has excellent performance by comparisons with some state-of-the-arts. [ABSTRACT FROM AUTHOR]

Industrial Internet of Things (IIoT) and fifth generation (5G) network have fueled the development of Industry 4.0 by providing an unparalleled connectivity and intelligence to ensure timely (or real time) and optimal decision-making. Under this umbrella, the edge intelligence is ready to propel another ripple in the industrial growth by ensuring the next generation of connectivity and performance. With the recent proliferation of blockchain, edge intelligence enters a new era, where each edge trains the local learning model, then interconnecting the whole learning models in a distributed blockchain manner, known as blockchain-assisted federated learning. However, it is quiet challenging task to provide secure edge intelligence in 5G-enabled IIoT environment alongside ensuring latency and throughput. In this article, we propose a proof-of-learning consensus protocol that considers the reputation opinion for edge blockchain to ensure secure and trustworthy edge intelligence in IIoT. This protocol fetches each edge’s reputation opinion by executing a smart contract, and partly adopts the winner’s learning model according to its reputation opinion. By quantitative performance analysis and simulation experiments, the proposed scheme demonstrates the superior performance in contrast to the traditional counterparts. [ABSTRACT FROM AUTHOR]

Crowdsourcing is an effective technique that allows humans to solve complex problems that are hard to accomplish by automated tools. Some significant challenges in crowdsourcing systems include avoiding security attacks, effective trust management, and ensuring the system’s correctness. Blockchain is a promising technology that can be efficiently exploited to address security and trust issues. The consensus protocol is a core component of a blockchain network through which all the blockchain peers achieve an agreement about the state of the distributed ledger. Therefore, its security, trustworthiness, and correctness have vital importance. This work proposes a Secure and Trustworthy Blockchain-based Crowdsourcing (STBC) consensus protocol to address these challenges. Model checking is an effective and automatic technique based on formal methods that is utilized to ensure the correctness of STBC consensus protocol. The proposed consensus protocol’s formal specification is described using Communicating Sequential Programs (CSP#). Safety, fault tolerance, leader trust, and validators’ trust are important properties for a consensus protocol, which are formally specified through Linear Temporal Logic (LTL) to prevent several security attacks, such as blockchain fork, selfish mining, and invalid block insertion. Process Analysis Toolkit (PAT) is utilized for the formal verification of the proposed consensus protocol.

We introduce the theoretical foundations of the Tangle 2.0, a probabilistic leaderless consensus protocol based on a directed acyclic graph (DAG) called the Tangle. The Tangle naturally succeeds the blockchain as its next evolutionary step as it offers features suited to establish more efficient and scalable distributed ledger solutions. Consensus is no longer found in the longest chain but on the heaviest DAG, where PoW is replaced by a stake- or reputation-based weight function. The DAG structure and the underlying Reality-based UTXO Ledger allow parallel validation of transactions without the need for total ordering. Moreover, it enables the removal of the intermediary of miners and validators, allowing a pure two-step process that follows the propose-vote paradigm at the node level and not at the validator level. We propose a framework to analyse liveness and safety under different communication and adversary models. This allows providing impossibility results in some edge cases and in the asynchronous communication model. We provide formal proof of the security of the protocol assuming a common random coin.

Aggregators can be effective in organizing distributed energy resources (DERs) for smart grids and electricity markets. The recent development of blockchain and peer-to-peer (P2P) networks provides a new ecosystem for aggregating DERs. Initial studies have mainly used off-the-shelf consensuses, which may struggle to balance node sizes and computational intensities. Moreover, the dynamics of DERs changing their selection among multiple aggregators over time are rarely considered in most related literature. This freedom of selection, which is encouraged by the electricity market, can be better activated by a blockchain. In this study, a game-dynamic-based selection framework for multiple aggregators of DERs is proposed in a decentralized blockchain ecosystem. First, a proof-of-dual-credibility (Po2C) protocol is established so that DERs in such an aggregator can reach consensus. At the same time, for one DER node, both an unavoidable objective credit and a malicious subjective credit constitute its credibility with different weights. Then, a function with triple payoffs motivates DERs in terms of both the physical characteristics of being power supply devices and P2P nodes, the latter including consensus winning and data propagation. Third, the selection game of DERs among aggregators is modeled as an evolutionary game under replicator dynamics to find equilibrium. Numerical simulations with two and four aggregators show general stability in the selection game of DERs. Performance achieved with different consensuses and incentives are compared as well. The framework shows its great potential to organize DERs in a decentralized but aggregated mechanism in open electricity markets.

Blockchain technology has been prominent recently due to its applications in cryptocurrency. Numerous decentralized blockchain applications have been possible due to blockchains’ nature of distributed, secured, and peer-to-peer storage. One of its technical pillars is using public-key cryptography and hash functions, which promise a secure, pseudoanonymous, and distributed storage with nonrepudiation. This security is believed to be difficult to break with classical computational powers. However, recent advances in quantum computing have raised the possibility of breaking these algorithms with quantum computers, thus, threatening the blockchains’ security. Quantum-resistant blockchains are being proposed as alternatives to resolve this issue. Some propose to replace traditional cryptography with postquantum cryptography—others base their approaches on quantum computer networks or quantum internets. Nonetheless, a new security infrastructure (e.g., access control/authentication) must be established before any of these could happen. This article provides a theoretical analysis of the quantum blockchain technologies that could be used for decentralized identity authentication. We put together a conceptual design for a quantum blockchain identity framework and give a review of the technical evidence. We investigate its essential components and feasibility, effectiveness, and limitations. Even though it currently has various limitations and challenges, we believe a decentralized perspective of quantum applications is noteworthy and likely.

With the rapid advancement and wide application of blockchain technology, blockchain consensus protocols, which are the core part of blockchain systems, along with the privacy issues, have drawn much attention from researchers. A key aspect of privacy in the blockchain is the sensitive content of transactions in the permissionless blockchain. Meanwhile, some blockchain applications, such as cryptocurrencies, are based on low-efficiency and high-cost consensus protocols, which may not be practical and feasible for other blockchain applications. In this paper, we propose an efficient and privacy-preserving consensus protocol, called Delegated Proof of Secret Sharing (DPoSS), which is inspired by secure multiparty computation. Specifically, DPoSS first uses polynomial interpolation to select a dealer group from many nodes to maintain the consensus of the blockchain system, in which the dealers in the dealer group take turns to pack the new block. In addition, since the content of transactions is sensitive, our proposed design utilizes verifiable secret sharing to protect the privacy of transmission and defend against the malicious attacks. Extensive experiments show that the proposed consensus protocol achieves fairness during the process of reaching consensus.

The profitability of a supply chain (SC) is proportional to the stability of all its stakeholders as well as their consistent information sharing with an effective and efficient communication mechanism. Various inefficiencies, such as the bullwhip effect (BWE) and product unavailability, may be caused by a lack of coordination in an SC. The importance of sharing consumer demand has been quantified by comprehensive studies under the assumption that all SC participants will access the same information. However, only a few studies have studied the effect of minimal coordination or limited visibility of information while considering their effect on the overall efficiency of an SC. This work primarily leverages blockchain technology (BCT) to create a simulation model. To do this, an SC BWE-based model is initially developed. Following that, a blockchain-based robust information sharing system is simulated. Furthermore, information sharing is challenging, and SC stakeholders may not really trust each other and hence be reluctant to share sensitive information. Considering that, this paper propose an improved proof-of-authority (PoA) consensus algorithm that will increase trust in a decentralized SC model. Multiple experiments are carried out to demonstrate the effectiveness of our approach, and the simulation results clearly demonstrate the effectiveness of information sharing in a supply chain via blockchain, as well as that trust between partners tends to increase overall SC efficiency and reduce BWE.

Blockchain technology has recently attracted tremendous interest due to its potential to revolutionize the industry by achieving decentralization while increasing the number of data sources, transparency, reliability, auditability, and trustworthiness. However, one of the major barriers to the widespread adoption of blockchain applications is the lack of mutual consensus and management across blockchains. Cross-blockchain consensus refers to one blockchain network reaching a consensus with another blockchain network to provide the ability to interact and share data. In this paper, we propose a secure management scheme with symmetric cross-blockchain communication and certificateless signature primitives, in which two heterogeneous blockchains are linked by a relay chain to simultaneously deliver cross-blockchain transaction security, achieve compatibility among various blockchains, and ensure the consistency of data exchanged, in practice. Additionally, our evaluation and security analysis shows the practicability and security of our proposed management scheme and demonstrates that a common test platform based on Ethereum can achieve acceptable computation costs. [ABSTRACT FROM AUTHOR]

Proof of work (PoW), as the representative consensus protocol for blockchain, consumes enormous amounts of computation and energy to determine bookkeeping rights among miners but does not achieve any practical purposes. To address the drawback of PoW, we propose a novel energy-recycling consensus mechanism named platform-free proof of federated learning (PF-PoFL), which leverages the computing power originally wasted in solving hard but meaningless PoW puzzles to conduct practical federated learning (FL) tasks. Nevertheless, potential security threats and efficiency concerns may occur due to the untrusted environment and miners’ self-interested features. In this paper, by devising a novel block structure, new transaction types, and credit-based incentives, PF-PoFL allows efficient artificial intelligence (AI) task outsourcing, federated mining, model evaluation, and reward distribution in a fully decentralized manner, while resisting spoofing and Sybil attacks. Besides, PF-PoFL equips with a user-level differential privacy mechanism for miners to prevent implicit privacy leakage in training FL models. Furthermore, by considering dynamic miner characteristics (e.g., training samples, non-IID degree, and network delay) under diverse FL tasks, a federation formation game-based mechanism is presented to distributively form the optimized disjoint miner partition structure with Nash-stable convergence. Extensive simulations validate the efficiency and effectiveness of PF-PoFL. [ABSTRACT FROM AUTHOR]

As a promising solution to blockchain scalability, sharding divides blockchain nodes into small groups called shards, splitting the workload. Existing works for sharding, however, are limited by cross-shard transactions, since they need to split each cross-shard transaction into multiple sub-transactions, each of which costs a consensus round to commit. In this paper, we introduce PYRAMID, a novel sharding system based on the idea of layered sharding. In PYRAMID, the nodes with better hardware are allowed to participate in multiple shards and store the blockchains of these shards thus they can validate and execute the cross-shard transactions without splitting. Next, to commit the cross-shard transactions with consistency among the related shards, we design a cooperative cross-shard consensus based on collective signature-based inter-shard collaboration. Furthermore, we present an optimization framework to compute an optimal layered sharding strategy maximizing the transaction throughput with the constraint of system security and node resource. Finally, we implement a prototype for PYRAMID based on Ethereum and the experimental results reveal the efficiency of PYRAMID in terms of performance and scalability, especially in workloads with a high percentage of cross-shard transactions. PYRAMID improves the throughput by up to 3.2 times compared with the state-of-the-art works and achieves about 3821 transaction per seconds for 20 shards. [ABSTRACT FROM AUTHOR]

In this article, a credit identity ring optimization blockchain algorithm (CRBFT) based on practical Byzantine fault tolerance (PBFT) is proposed to address the security problem for the network of Internet of Things (IoT). The contributions of this work are given as follows. First, combined with the edge computing architecture, CRBFT introduces the improved credit grading protocol and the improved ring signature scheme into the blockchain network, rewards or punishes the nodes through their behavior, changes the way of selecting the primary node, and ensures that the identity of the primary node will not be disclosed, so as to prevent the primary node from adaptive attack by Byzantine nodes, improve the reliability of the nodes participating in the consensus, and enhance the security of the system. Second, in order to reduce the communication traffic among nodes, CRBFT optimizes the consensus protocol, which not only reduces the time complexity of the traffic in the consensus stage from O (${n}^{{2}}$) to O (${n}$) but also improves the consensus efficiency of the system while ensuring the system security. Finally, CRBFT aims to measure the performance of CRBFT. This article is simulated and tested in three aspects: throughput (transactions per second), consistency delay, and communication overhead. Performance evaluation shows that CRBFT achieves lower communication overhead than PBFT. When the number of nodes is the same, CRBFT can obtain higher TPS and lower consistency delay. The results show that compared with PBFT, CRBFT can provide very competitive results. [ABSTRACT FROM AUTHOR]

Blockchain has been utilized to manage distributed multicloud storage in the industrial Internet of Things. Existing approaches commonly use trusted third-party servers or middlewares to search data allocation strategies and use blockchain to enhance security. However, finding a fair data allocation strategy is hard when the third-party brokers are manipulated. Moreover, the complex computing in generating blocks reduces efficiency and heavy communication cost in consensus leads to critical challenges to scalability. To address that, this article proposes a scalable two-layer blockchain system for distributed multi-cloud storage (STSM). We design a novel consensus mechanism called proof of storage allocation, which integrates data placement problems into leader selection to achieve fair strategy and high QoS of data storage. We also incorporate asynchronous consensus groups into the consensus process to enhance scalability. Extensive experiments verify that STSM gains high scalability and increases efficiency while achieving high QoS in distributed multicloud data allocation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Different control strategies for microgrid applications have been developed in the last decade. In order to enhance flexibility, scalability and reliability, special attention has been given to control organisations based on distributed communication infrastructures. Among these strategies, the implementation of consensus protocol stands out to cooperatively steer multi-agent systems (i.e., distributed generators), which is justified by its benefits, such as plug and play capability and enhanced resilience against communication failures. However, as the consensus protocol has a long trajectory of development in different areas of knowledge including multidisciplinary subjects, it may be a challenge to collect all the relevant information for its application in an emerging field. Therefore, the main goal of this paper is to provide the fundamentals of multi-agent systems and consensus protocol to the electrical engineering community, and an overview of its application to control systems for microgrids. The fundamentals of consensus protocol herein cover the concepts, formulations, steady-state and stability analysis for leaderless and leader-following consensus problems, in both continuous- and discrete-time. The overview of the applications summarises the main contributions achieved with this technique in the literature concerning microgrids, as well as the associated challenges and trends. [ABSTRACT FROM AUTHOR]

The penetration of distributed generators increases the significance of virtual power plants (VPP) in the electricity market paradigm. The conventional VPP energy management system relies on a trustable centralized coordinator, which is vulnerable to single-point failure and requires a high-bandwidth communication network. This article proposes a robust, fully distributed consensus-based algorithm (RFDCA) for optimal dispatch of VPP participants in power systems with a practical communication network, which considers noise, communication delay, and a dynamically switching communication topology. The profit maximization problem is decomposed into subproblems using dual decomposition and solved using a double consensus approach, which uses a monotonically decreasing consensus gain function to suppress the adverse effects of communication delay and noise. One of the main advantages of this method is that the VPP participants need not share their private information with anyone, thereby preserving their privacy. Another advantage of the proposed approach is that it can deal with networks of different sizes and topologies. Simulations are carried out on standard 15-node VPP and IEEE 39-bus test systems to illustrate the efficacy of the RFDCA approach. The algorithm removes the need for a central controller in the VPP system, and the faster convergence of the algorithm extends its application in real-time energy management. [ABSTRACT FROM AUTHOR]

Following the widespread application of blockchain, a variety of consensus protocols have been proposed recently for different scenarios. Proof of Authority (PoA) is a newly proposed Byzantine Fault Tolerant (BFT) consensus protocol for permissioned blockchains. It relies on a set of trusted nodes to generate blocks and adopts the longest-chain rule to reach consensus. However, the protocol suffers from performance and security issues due to its simple design. This paper proposes CoPoA, a novel proof-of-authority protocol that aims to improve performance and security. In terms of performance, we allow all authority nodes to generate blocks concurrently and process all types of blocks to improve throughput and feedback their blockchain information to the rest of the nodes on time to provide fast confirmation. In terms of security, we select the leader by a random number and set a tight confirmation boundary to protect the protocol from attack. We make a theoretical analysis to prove the safety and liveness properties of the protocol and demonstrate its performance through a prototype implementation and multiple tests. In our experiments, when the number of authority nodes is 9, CoPoA achieves 2x throughput improvement and 5x latency reduction compared to the original PoA protocol. [ABSTRACT FROM AUTHOR]

This article develops a novel hybrid switching control (HSC) approach to the consensus of multiagent systems (MASs), and the objective is to further improve the transient consensus performance compared with a reset control approach in recent results. First, a hybrid switched controller is introduced, which consists of two working modes: 1) reset control mode and 2) gain mode. Through appropriate switching mechanism design, the controller output signal can be guaranteed to be continuous, and the input–output of the switched controller always has the same sign. Then, HSC is applied to the consensus of MAS, and a consensus protocol consisting of proportional control part and HSC part is proposed. By introducing binary-value variables, an appropriate closed-loop model is constructed, and the Lyapunov-based consensus analysis results are obtained. Finally, an example is provided to show the superiority of the proposed approach. [ABSTRACT FROM AUTHOR]

With the popularization of network equipment and the rapid development of information technology, the scale and complexity of wireless sensor networks (WSNs) continue to expand. How to effectively locate link failures has become a challenging problem in WSNs. In this paper, we propose a novel method of locating link failures based on distributed cluster consensus protocol and graph decomposition technique. In our method, the initial data is injected into sensor nodes for distributed interactions, and then link failures can be located by observing and comparing the output data of the nodes. The proposed method is suitable for the situations with both single-link failure and multi-link failures, and has no limitations on the number, distribution and correlation of link failures. Necessary and sufficient conditions are provided to guarantee the accuracy of the proposed method in locating link failures. At last, the effectiveness of the proposed method is verified by both real and simulation experiments. [ABSTRACT FROM AUTHOR]

This article aims to establish an appointed-time observer-based framework to efficiently address the resilient consensus control problem of linear multiagent systems with malicious attacks. The local appointed-time state observer is skillfully designed for each agent to estimate the agent’s actual state value at the appointed time, even in the presence of unknown malicious attacks. Based on the state estimation, a new kind of resilient control strategy is proposed, where a virtual system is constructed for each agent to generate an ideal state value such that the consensus of normal agents can be achieved with the exchange of ideal state values among neighboring agents. To specify the consensus trajectory while achieving resilient consensus, the leader–follower resilient consensus is further studied, where the leader is assumed to be a trusted agent with a bounded control input. Compared with the existing results on the resilient consensus, the proposed distributed resilient controller design reduces the requirement on communication connectivity significantly, where the allowable communication graph is only assumed to contain a directed spanning tree. To verify the theoretical analysis, numerical simulations are finally provided. [ABSTRACT FROM AUTHOR]