Search Results (703)

The rapid advancement of artificial intelligence relies on massive high-quality data, yet increasingly stringent data privacy regulations have exacerbated the problem of data silos. Federated learning enables collaborative training under privacy protection by exchanging model parameters rather than transmitting raw data. Nevertheless, its traditional centralized architecture still suffers from limitations such as single points of failure, lack of trust, and insufficient incentives. The integration of blockchain and federated learning opens new pathways for decentralized, auditable, and secure machine learning systems. This paper systematically reviews research progress in blockchain-enabled federated learning, analyzing technological evolution from three perspectives: system architecture, incentive mechanisms, and privacy enhancement. It further explores critical challenges including efficiency bottlenecks, storage overhead, and the inherent tension between transparency and privacy, while identifying key research directions for building scalable, efficient, and trustworthy decentralized learning systems. Full article

This study presents ZK-EHR, a decentralized access control framework designed to enable secure and privacy-preserving sharing of encrypted electronic health records across institutional boundaries. Unlike existing blockchain-based EHR access control systems that expose user identities on-chain or lack cryptographic privacy guarantees, ZK-EHR decouples authorization from identity disclosure by integrating zk-SNARK-based proofs with blockchain smart contracts to verify policy compliance without revealing user roles, affiliations, or credentials. The framework employs three differentiated actor roles—Patient (Data Owner), Doctor (Care Provider), and Researcher (Authorized Analyst)—with distinct policy-driven access workflows, a custom Groth16 zero-knowledge circuit for role-based constraint enforcement, and a modular architecture combining on-chain verification with off-chain encrypted storage via IPFS. Concrete design proposals for access revocation and replay attack prevention are introduced to address operational security requirements. The system was evaluated under multiple operational and adversarial scenarios. Experimental results indicate consistent on-chain verification latency (approximately 390 ms), reliable rejection of tampered submissions, and per-verification gas consumption of 216,631 gas. A comparative analysis against representative baseline systems demonstrates that ZK-EHR uniquely combines identity anonymity, on-chain cryptographic policy enforcement, and auditable encrypted record retrieval. These findings establish the feasibility of zk-SNARK-based access control for decentralized, verifiable, and privacy-aware EHR management. Full article

This systematic review examines how digital technologies enable circular economy (CE) transitions across sectors and value chains. Analysing 266 peer-reviewed publications (2016–2025), we develop a comprehensive taxonomy of digital enablers—including IoT, AI, blockchain, cloud computing, additive manufacturing, and digital platforms—and map their applications to circular strategies such as reuse, remanufacturing, and recycling. Our findings reveal that data-driven technologies dominate CE implementation, with 89% of studies involving data collection, storage, analysis, or sharing functions. IoT emerges as the foundational technology for real-time tracking and monitoring, while AI and big data analytics optimise circular processes and predict maintenance needs. Blockchain ensures traceability and trust in circular supply chains, and cloud computing provides scalable infrastructure for collaboration. Manufacturing (41%) and construction (15.5%) are the most studied sectors, with strong European research leadership reflecting policy drivers such as Digital Product Passports. We identify three impact types: enabling (process optimisation), disruptive (business model innovation), and facilitating (ecosystem collaboration). Key barriers include technical complexity, organisational resistance, high implementation costs, and regulatory gaps. The review concludes with recommendations for integrated, multi-stakeholder approaches to realise a digitally enabled circular economy. Full article

In this paper, we propose a novel multisecret sharing (MSS) scheme that integrates a recently developed exponential-speedup matrix spectral factorization algorithm into the construction of paraunitary matrices over finite fields. By exploiting the block-matrix generalization of the Janashia-Lagvilava method, we significantly enhance the efficiency and scalability of the MSS scheme. The proposed method ensures perfect secrecy, collusion resistance, and efficient reconstruction, while enabling practical deployment in large-scale distributed systems such as secure cloud storage, IoT networks, and blockchain authentication. Security and performance analyses demonstrate the superiority of the new approach over existing MSS schemes. Full article

Authenticity verification for thangka artworks remains challenging in the market, as traditional physical authentication methods offer limited reliability, while modern spectroscopic and chemical testing technologies are costly and unsuitable for large-scale application. Although deep learning methods can achieve efficient authentication through image features, they rely on centralized databases to store feature information, making them susceptible to tampering risks and undermining the credibility of authentication results. To address these issues, this study proposes a digital authentication method for thangka paintings that integrates blockchain technology. This approach stores image features in the InterPlanetary File System (IPFS) and records their hash values on the blockchain, ensuring the immutability and verifiable evidence of feature data. Simultaneously, it employs convolutional neural networks for feature extraction and similarity analysis of thangka images, constructing an integrated platform system encompassing storage, authentication, and traceability. This enhances the reliability and automation of authentication outcomes. The platform further supports full-process traceability of thangka storage and authentication operations, providing a viable pathway for establishing a scientific and reliable digital authentication system for thangkas. Experimental evaluation on a dataset of 2847 thangka images demonstrates 99.2% authentication accuracy, with a precision of 98.7% and an F1-score of 99.1%, while end-to-end authentication latency averages 1247 ms, validating the system’s effectiveness for practical museum and market deployment scenarios. Full article

While the practical Byzantine fault tolerance (PBFT) consensus algorithm provides excellent theoretical fault tolerance, its performance in practical blockchain applications is often constrained by high communication overhead, especially in scenarios with limited node resources and high mobility, such as Vehicular Ad hoc Networks (VANETs). To address these blockchain-specific limitations without sacrificing the fundamental safety guarantees against arbitrary Byzantine failures, this paper proposes a novel PBFT-optimized consensus algorithm based on a dynamic reputation tree (DRT-PBFT). First, to address the issue of limited storage resources, we propose a block synchronization method based on differentiated storage of reputation values. The lower-reputation nodes retain only “micro-blocks” that contain essential information of the complete block, while the higher-reputation nodes store and synchronize complete blocks, significantly reducing the storage overhead. Second, on the basis of the reputation values, we construct a tree communication topology from the leaf node layer in a bottom-up manner. Messages are transmitted from multiple child nodes to their parent node, resolving the problem of a single message source in the tree structure. Additionally, we optimize the consensus process, reducing the number of mutual communications between nodes to a linear level. Finally, to address the problem of malicious nodes in the tree structure, we introduce a dynamic reconstruction mechanism for the reputation tree. When child node messages are inconsistent, the parent node splits the child nodes to mitigate the influence of malicious nodes, enhancing both the security and scalability of the consensus process. The experimental results show that, compared with typical improved PBFT algorithms, the proposed algorithm improves the average throughput by 34.1% and reduces the average latency by 27.4%. Moreover, compared with the full replication block synchronization method, the differentiated storage method reduces the storage overhead by 26.3%, making it potentially more suitable for large-scale VANET scenarios. Full article

Smart grids require real-time ancillary services from large-scale distributed energy storage (DES), creating a conflict between second-scale physical response needs and the slow confirmation of trust mechanisms like blockchain. Traditional VPPs lack scalability and trust for massive participation, while decentralized approaches struggle with mismatched time scales. We propose a framework that decouples real-time dispatch from asynchronous settlement. An off-chain matcher uses a physics-aware model, including a novel “service holding time” ($T^{\mathrm{service}}$) constraint and power (kW) envelopes, for fast assignments. A separate on-chain proof-of-stake (PoS) layer handles incentives and penalties (slashing) asynchronously. We formulate the MILP dispatch problem and provide a fast online heuristic alongside a MINLP decomposition benchmark. Co-simulations (IEEE 33-node) show that our scheme significantly outperforms baselines in success rate and latency, is robust against non-compliant nodes due to the PoS mechanism, and thereby offers a scalable and trustworthy solution. Full article

In blockchain–IPFS-based systems, full nodes maintain complete ledger replicas, whereas light nodes retain only essential information such as block headers to reduce storage and computation overhead. Due to the absence of full data replicas, light nodes are unable to support full-data queries, which limits their applicability in practical financial data sharing scenarios. Moreover, conventional blockchain storage mechanisms rely on synchronous confirmation across multiple nodes, resulting in limited throughput and poor responsiveness under high-concurrency and burst-traffic conditions. To address these issues, this paper proposes a blockchain–IPFS-based storage and query scheme for banking credit data that integrates multi-level caching, non-blocking asynchronous processing, and a Cuckoo filter–based lightweight query mechanism. The proposed scheme enables light nodes to efficiently verify the existence of credit files and retrieve associated metadata without maintaining complete ledger replicas, while a coordinated caching–asynchronous architecture decouples user requests from on-chain and off-chain persistence operations to improve system throughput and robustness. A prototype system is implemented and evaluated under varying file sizes and concurrency levels. Experimental results show that, for files smaller than 100 MB, the proposed scheme reduces storage latency by approximately 35–99% and improves query response time by more than 95%, compared with conventional blockchain–IPFS-based solutions. In addition, download latency is reduced by 20–31% for small and medium-sized files. The results further confirm that the proposed approach effectively supports full-data queries for light nodes and demonstrates strong resilience under burst traffic conditions, indicating its practical feasibility for secure financial credit data sharing. Full article

The global maritime industry, a critical pillar of international trade, continues to face persistent challenges in ensuring the integrity, security, and transparency of containerized cargo data, particularly during ocean transport. Traditional container tracking systems at sea often lack the reliability and resilience required to prevent data tampering, cyber threats, and operational inefficiencies. As supply chains become more complex and interconnected, the demand for robust, end-to-end data security solutions becomes more pressing. A promising technological advancement in this area is the convergence of smart containers, equipped with Internet of Things (IoT) sensors for real-time condition monitoring, and blockchain technology (BCT) for secure data validation. These IoT devices facilitate continuous tracking of critical parameters such as location, temperature, humidity, tilt, and the like. However, the data they generate remains vulnerable to cyberattacks, signal disruptions, and unauthorized alterations. Blockchain’s decentralized and tamper-evident architecture addresses these vulnerabilities by enabling secure data immutability, transparent audit trails, and enhanced stakeholder trust. Despite its potential, the practical integration of blockchain with smart container systems in maritime logistics remains largely underexplored. To bridge this gap, this paper proposes a blockchain-enabled smart container monitoring system that combines container real-time data with secure physical tracking. Furthermore, to ensure scalability and efficient in data storage, hybrid on/off-chain architecture is introduced, balancing blockchain integrity with performance and resource optimization. Full article

Modern permissioned blockchain systems increasingly adopt hybrid data architectures in which critical metadata are anchored on-chain, while large or sensitive payloads are stored off-chain using infrastructures such as IPFS and cloud services. Although this paradigm improves scalability and cost efficiency, it introduces a coupled design challenge where latency, operational cost, and security must be balanced simultaneously. Existing Layer-2 and data-availability approaches primarily focus on throughput and verification, leaving data placement decisions in enterprise permissioned environments insufficiently explored. This paper formulates hybrid on-chain, IPFS, and cloud data placement as a multi-objective optimization problem that jointly encodes storage location, transaction execution mode, and key blockchain parameters, aiming to minimize latency and cost while maximizing integrity and resilience. To explore this high-dimensional design space without costly physical deployment, a digital-twin-based evaluation framework is proposed to approximate the performance, cost, and security behavior of a Fabric-class permissioned blockchain integrated with IPFS and cloud storage. The optimization problem is solved using NSGA-II, yielding a Pareto front that reveals fundamental trade-offs among hybrid configurations. The results demonstrate that hash-anchored off-chain storage consistently outperforms purely on-chain and purely off-chain strategies by reducing latency and cost while preserving strong integrity and replication guarantees. The proposed framework provides practical decision support for data-availability-aware permissioned blockchains in domains such as supply chains, healthcare, and disaster response. Full article

The integration of distributed data storage, P2P networks, consensus mechanisms, cryptography and other technologies, the application of blockchain technology has expanded from the initial financial field to many other areas, such as logistics and auditing. The consensus mechanism is the soul of blockchain technology, and it is of great significance to conduct a rigorous mathematical analysis. As far as we know, the Proof of Stake (PoS) consensus mechanism is only a qualitative description of the rich and the poor, the rich are richer, the poor are poorer, and there is no quantitative mathematical analysis. This paper presents a novel quantitative framework to quantitatively analyze the PoS consensus mechanism. Under the premise of not carrying out the attack, we use the expected reward and the reward ratio as the evaluation indicators, quantitatively analyze the optimal fund allocation strategy of the two parties game under the PoS consensus mechanism from the perspective of rich miners, and construct the reward function as the objective function. The inequality constrains the optimization problem and solves it using the Karush-Kuhn-Tucker condition. We consider the two schemes of assignment strategy and random strategy, and get the optimal fund allocation strategy. At the same time, it is compared with the general strategy to obtain the optimization effect of the optimal strategy. After that, we compare the situation in which both sides of the game use the optimal strategy. We found that for assignment strategy, the mining activity will not indicate that the rich are richer and the poor are poorer. However, for the random strategy, this will not happen. The random strategy is also the most common strategy in practice. We also use Markov decision process (MDP) to give the optimal strategy calculation method under the rational miner game, which is also applicable to the n-parties game. The work of this paper helps the blockchain developers to analyze the PoS consensus mechanism, and the adoption strategy of the assignment strategy and the random strategy can be used as the future research direction. Full article

Current research in consent management techniques focuses on isolated aspects of data security, privacy, or auditability, but important issues like (i) dynamically integrating regulatory updates into form generation, (ii) support in content generation with verifiable audit trails, and (iii) tools that make compliance reasoning transparent for non-legal users are not yet addressed. This paper introduces CONSENT, an architecture that integrates AI-based consent reasoning using Large Language Models (LLMs) for automated consent-form drafting and compliance evaluation, alongside blockchain technology for secure and auditable storage. The architecture builds on prior work to address the aforementioned issues by introducing three supporting mechanisms: (a) Specialized AI models coordinated through expert routing which coordinate subtasks such as automation in form generation and regulatory compliance, (b) Retrieval-Augmented Generation (RAG) that supports the integration of regulatory updates into forms, and (c) Explainable AI (XAI) for the reasoning behind form content and compliance assessments. CONSENT architecture is evaluated through 250 test cases and a pilot case study for clinical trial consent management involving 20 engineers and attorneys, who evaluated the prototype on form quality (i.e., coherence, conciseness, factuality, fluency, and relevance) as well as time and effort efficiency. Results show that CONSENT substantially reduces the manual effort in consent-form creation while providing transparent, audit-ready compliance assessments, highlighting its potential for dynamic, user-centric consent management. Full article

This study investigates the potential adoption of blockchain technology within the Indonesian electricity sector to address key challenges in digital infrastructure. Blockchain technology has the potential to address the challenges by facilitating immutable and distributed storage of data across multiple network points. A two-stage methodology comprising a comprehensive literature review and selection of case studies is employed to conduct the survey. Research from reputable databases is reviewed by focusing on blockchain applications in energy systems. Key criteria such as Regulation, Implementation Readiness, Urgency, Technology Readiness Level, and Business Maturity Level are analyzed to assess deployment readiness across the main use cases in the Indonesian landscape. The review finds that five main use cases in Indonesia can be enhanced by blockchain technology, including peer-to-peer energy trading, renewable energy certificate trading, electronic billing of electricity, microgrid transactions, and electric vehicle charging transactions. Furthermore, the deployment readiness analysis suggests that electronic billing and electric vehicle charging transactions emerge as the most viable options. It is supported by conducive regulations, high urgency, and existing technological infrastructure. Full article

The rapid expansion of the Internet of Things (IoT) has led to billions of interconnected devices generating and exchanging sensitive data across diverse domains, which introduces challenges in identity management (IdM) regarding privacy, scalability, and verifiability. While blockchain technology provides decentralization and tamper resistance, its transparency and increasing on-chain storage demands make it unsuitable for large-scale IoT identity ecosystems. To overcome these challenges, IoT-SBIdM is proposed as a lightweight, privacy-preserving, and stateless blockchain-based identity management framework designed for IoT environments. This framework incorporates Elliptic Curve Cryptography (ECC)-based accumulators and Zero-Knowledge Proofs (ZKPs) to facilitate selective disclosure, enabling entities to prove credential authenticity without exposing sensitive identity information. Furthermore, the framework adopts W3C-compliant Decentralized Identifiers (DIDs) and Verifiable Credentials (VCs) to promote interoperability and user-controlled identity ownership. The experimental results indicate that IoT-SBIdM achieves efficient smart contract execution by reducing gas costs through optimized registry logic. Moreover, the system maintains a compact block size of only 45 MB at higher block heights, outperforming comparable schemes in storage efficiency by achieving a 55% reduction relative to recent models and an approximate 94% reduction relative to older systems, thereby demonstrating superior scalability and storage efficiency, making it suitable for identity management solutions for IoT environments. Full article

Blockchain technology, with its characteristics of decentralization, immutability, auditability, and traceability, has gradually become a core infrastructure in the digital economy era, demonstrating great potential in fields such as finance, government services, and the Internet of Things (IoT). However, as the scale of blockchain networks expands and data volumes surge, issues such as full-node storage redundancy, limited transaction throughput, and inefficient synchronization of historical data have become increasingly prominent, severely restricting the large-scale application of blockchain systems. The storage scalability problem faced by blockchain is therefore becoming more critical. To address the challenge in which on-chain storage expansion still cannot meet the demand for large-scale data storage, a storage method combining the InterPlanetary File System (IPFS) with blockchain, referred to as IPFS-BC, is proposed. In IPFS-BC, large-scale raw data are stored in the decentralized and content-addressable IPFS network, while the blockchain only retains the unique content identifier (CID) hash and related metadata. Through smart contracts enabling dynamic permission management and fine-grained access control, efficient interaction and collaborative storage between on-chain and off-chain systems are achieved. In this work, file upload simulation experiments were conducted, and two evaluation indicators—storage space consumption and storage performance (file read/write time and speed)—were used to compare three storage approaches: Distributed Hash Table (DHT)-based off-chain storage, Financial Blockchain Shenzhen Open Source (FISCO BCOS) on-chain storage, and the IPFS-BC on-chain/off-chain collaborative storage model. Experimental results show that the IPFS-BC model reduces storage space consumption by approximately 75% compared with FISCO BCOS blockchain storage when storing file data, significantly decreasing data redundancy. Moreover, IPFS-BC ensures system security during the on-chain process, and through the automated management and auditing provided by smart contracts, it effectively enhances system security and realizes scalable on-chain/off-chain collaborative storage. Full article