Digital contracts are formal agreements created, signed, stored, verified and executed through digital platforms. These contracts require long-term protection because they often contain legally, financially and organisationally sensitive information. However, classical cryptographic methods used in current digital contract systems may become vulnerable with advances in quantum computing. This paper focuses on Quantum Internet of Contracts (QIoCs) as a future direction for preparing digital contracts for the quantum era. It examines post-quantum cryptography, quantum communication, blockchain, smart contracts, digital identity, zero-knowledge proofs and risk-based migration strategies. The paper argues that QIoCs cannot rely on a single security method. Instead, they require a layered approach that combines quantum-resistant blockchain protocols, privacy-preserving data authentication, secure audit trails, legal governance and staged migration from classical systems to quantum-safe contract infrastructures. The paper highlights the need for legal acceptance, governance standards and real-world testing of proposed post-quantum models. Overall, the paper provides a review-based framework for building safer and more reliable digital contracts in a quantum-safe future.
Electronic Healthcare Records (EHRs) provide distributed access to patient and doctor information through pervasive cloud-based storage. As this data is highly sensitive, robust privacy measures are essential to mitigate adversarial impacts. To ensure optimal privacy across multiple shared EHRs, this article proposes a Session-dependent Zero Knowledge Proof Technique (SZKPT). The framework identifies privacy breaches using two truth values: the first representing optimal session closure, and the second reflecting verification at each sharing instance. Both truth values are validated through iterated session validations, which are managed using a deep learning paradigm. During training, different combinations of truth values are employed to maximize privacy during data sharing, while iterative processes train consecutive validation instances to improve breach detection. Truth values are continuously updated to reflect the session closure and the most recent privacy verification. In practice, if either truth value equals zero, the session is suspended; otherwise, if truth values are valid in consecutive iterations, data sharing is delegated to the authorized user. The process is repeatted at regular intervals with updated truth values, ensuring continuous monitoring and adaptive privacy protection. The proposed technique is rigorously evaluated using key performance metrics, including access verification, computational complexity, privacy breach detection, verification time, and access delegation time. Results demonstrate that SZKPT effectively balances privacy preservation with usability, providing a reliable, scalable, and efficient solution for secure EHR management in cloud-based healthcare systems.
Quantum computing’s accelerating trajectory threatens the cryptographic foundations of every major blockchain network. Recent research demonstrates that fewer than 500 000 physical qubits could break ECC-256 in approximately nine minutes, while expert surveys place a 28–49% probability of a cryptographically relevant quantum computer (CRQC) emerging within ten years. This paper presents a layered reference architecture for end-to-end quantum-resilient distributed ledger systems, making three contributions: (1) a structured threat analysis applying STRIDE across blockchain architectural layers and post-quantum cryptography (PQC) migration phases; (2) a seven-layer reference architecture with per-layer interface specifications and dependency graph; and (3) a multi-chain quantum readiness assessment covering twelve major networks with fintech-specific migration strategies for decentralised finance (DeFi), stablecoins, tokenised real-world assets (RWA), and decentralised identity (DID). A critical finding is that blockchain’s primary quantum risk is real-time signature forgery upon CRQC arrival, not retroactive harvest-now-decrypt-later (HNDL) attacks on signatures. Cross-chain bridges, data availability layers, and Lightning Network payment channels are identified as the most critically neglected quantum attack surfaces.
Digital identity management is a cornerstone of effective e-governance, yet centralized identity systems face critical challenges including single points of failure, data breaches, and lack of citizen control over personal information. This paper proposes a blockchain-based Self-Sovereign Identity (SSI) framework for e-governance that enables citizens to own, control, and selectively disclose their identity credentials without relying on centralized authorities. Built on Hyperledger Fabric with W3C Decentralized Identifier (DID) standards and Verifiable Credentials, the framework incorporates zero-knowledge proofs (ZKPs) for privacy-preserving authentication and smart contracts for automated credential verification. Performance evaluation on a 4-organization, 16-peer Hyperledger Fabric network demonstrates a throughput of 4,800 transactions per second with an average identity verification latency of 85 ms, suitable for citizen-scale e-governance applications. Security analysis confirms resistance to identity theft, Sybil attacks, man-in-the-middle attacks, and credential forgery, achieving resistance scores above 94% across all evaluated attack vectors. The framework provides a practical pathway for governments to modernize identity infrastructure while preserving citizen privacy and data sovereignty.
Healthcare data is among the most sensitive and frequently targeted information in the digital era. Existing centralised Electronic Health Record (EHR) systems are vulnerable to data breaches, unauthorised access, and single-point failures. This paper introduces a blockchain-based privacy-preserving framework for healthcare data management that integrates smart contracts, attribute-based encryption (ABE), and zero-knowledge proofs (ZKP) to ensure tamper-proof, role-gated data access. Our system is deployed on a permissioned Hyperledger Fabric network with a RESTful API gateway and a React-based patient portal. Experimental evaluations show that the proposed system achieves 99.2% access-control policy enforcement, reduces unauthorised access incidents to near zero, and maintains record retrieval latency under 180 ms at the 95th percentile. The framework also supports HIPAA and GDPR compliance through immutable audit trails and consent lifecycle management
Zero-knowledge succinct non-interactive arguments of knowledge (zk-SNARKs) allow for elegant, privacy-preserving validation of computations. PLONK, a subclass of the zk-SNARKs, is certainly useful, but its complex interactions with permutation arguments, lookup tables, and blinding, among other considerations, make the protocol difficult to follow, let alone understand. This paper describes a framework centered around the core components of zk-SNARKs. In particular, we detail the construction of arithmetic gate constraints, representation of witness polynomials, and the Kate-Zaverucha-Goldberg (KZG) commitment scheme. By removing permutation proofs, lookup, and blinding, we aim to simplify the pedagogy of zk-SNARKs and preserve their essential properties of soundness and completeness. We describe a Python module from the ground up that demonstrates the generation and validation of proofs in a PLONK-modified zk-SNARK. We validate the framework and its foundations with a benchmark of a module generating and validating proofs in a PLONK-modified zk-SNARK. We validate the module against a circuit of 1,000 gates and demonstrate that the system correctly rejects all invalid witnesses. We illustrate the expected asymptotic behavior, with a pro tor of tight the module is quasi-linear, and verification, tight. We justify the foundations of the module and describe tight with zero private inputs. We have also bridged the gap between abstract zk-SNARK theoretical arguments and their practical implementation and research. We have provided a simple, empirically grounded mechanism that describes the key components of PLONK. We have done this in such a way that researchers, developers, and teachers can build on this base module and create production-ready systems without the abstraction.
This is Paper 6 of a series of formally-verified analyses of masked NTT hardware for post-quantum cryptography; Paper 1 [1] established structural dependency analysis of the QANARY platform, and Paper 2 [2] quantified security margins under partial NTT masking. Boolean masking composition is well-understood through NI, SNI, and PINI. Arithmetic masking over $\mathbb{Z}_q$ for prime $q$, the foundation of NTT-based post-quantum cryptography, has lacked an analogous theory. We prove, to our knowledge, the first machine-checked composition theorems for arithmetic masking over prime fields. Our key insight is the renewal argument: when a fresh random mask is applied between two pipeline stages, the intermediate wire becomes perfectly uniform regardless of Stage 1's security parameter. For two PF-PINI gadgets with parameters $k_1$ and $k_2$, the composed two-stage pipeline with fresh masking satisfies PF-PINI($k_2$), Stage 1's multiplicity is completely erased from the composed output. Without fresh masking, intermediate wires have multiplicity up to $k_1$, creating a necessary condition for differential power analysis. We formalize both theorems in Lean 4 with 18 machine-checked proofs and zero sorry stubs. We formally bridge the algebraic and hardware-faithful arithmetic models of Barrett reduction, and instantiate the theorems to formally diagnose Microsoft's Adams Bridge PQC accelerator: its absence of fresh inter-stage masking leaves Barrett output wires non-uniform under the first-order probing model, the same architectural flaw that two independent empirical analyses [3, 4] and our own prior structural analysis [1] identified. Computational evidence further suggests the 1-Bit Barrier is universal across Barrett and Montgomery reductions.
Interoperability of patient files between hospitals continues to present significant obstacles. Health systems frequently utilize central EHR systems that could suffer malfunctions, data breaches, and unauthorized access by third parties. Not only does this jeopardize patient confidentiality, but it also hinders the efficient operations of hospital processes.Blockchain technology is viewed as a prospective remedy for the issue. Blockchain keeps its data differently, allowing users to store data securely and make changes difficult. In this study, we analyze research works published between 2016 and 2023 regarding blockchain-based hospital-to-hospital data exchange.The methodologies differ widely: there are cases where researchers use smart contracts in Ethereum, build a system on Hyperledger Fabric, and deploy IPFS. Moreover, certain studies incorporate encryption methods, machine learning algorithms, and more. In summary, the results show that blockchain allows for improved data protection and transparency while giving patients more control over their personal information. Still, some issues persist, such as scalability, expenses, integration with existing infrastructure, and adherence to GDPR and HIPAA requirements. For future work, more improvements are necessary. For instance, zero-knowledge proofs, cybersecurity measures for new technologies, and using artificial intelligence to audit and validate smart contracts may be promising solutions.
Financial privacy protocols on public blockchains protect transaction linkability but offer no defense when users are physically compelled to reveal their credentials — the "$5 wrench attack." This paper presents a complete solution in two integrated parts. Part I provides the formal cryptographic foundation: dual-nullifier arithmetic selectors within Groth16 zk-SNARK circuits, where path selection between real and decoy funds is computed entirely within the zero-knowledge witness without conditional branching. The R1CS structure is identical for both execution paths (<8% overhead), and the resulting proof is computationally indistinguishable regardless of whether coercion resistance was activated. We formalize peace of mind as a protocol design principle, prove coercion resistance through a four-game sequence-of-games reduction under the Sponge PRF and q-SDH assumptions, and prove withdrawal soundness, double-spend prevention, and front-running resistance. Part II presents ZK-Sentinel V11: a Diamond EIP-2535 architecture with 10 independently upgradeable facets and 104 functions; Stealth Shielded Transfers eliminating temporal correlation at ~60% lower gas cost; 92 privacy pools across 12 tokens on two networks; and a Multi-Tier Compliance Oracle with 4 KYC levels. Indistinguishability is confirmed empirically: a Random Forest classifier trained on 10,000 simulated transactions achieves 50.3% accuracy (AUC-ROC 0.501, p=0.87), consistent with random guessing. To our knowledge, this is the first work providing both a formal coercion resistance proof and a production-scale multi-asset deployment validated across all 12 tokens on two networks.
We prove three impossibility theorems establishing fundamental limits on universal AML compliance in zero-knowledge financial systems. T1 (Completeness Impossibility): no ZK compliance system achieves complete coverage of illicit transactions under rational adversarial behavior. T2 (Oracle Integrity Impossibility): no decentralized oracle network achieves integrity guarantees when state-level adversaries control oracle nodes — cryptographically valid compliance proofs can be semantically false by construction. T3 (Sovereignty Gap Impossibility): no voluntary international compliance framework achieves universal participation when sovereign defection is individually rational. These theorems are not engineering limitations addressable by better cryptography — they are structural properties of the compliance problem under adversarial conditions. Validated empirically against the Tornado Cash OFAC designation (T3) and the Lazarus Group / Ronin Bridge exploit (T2). The theorems characterize the residual attack surface that any compliance architecture must acknowledge and bound rather than claim to eliminate.
Bulletproofs is a widely used zero-knowledge range proof system with logarithmic proof size and no trusted setup, but its proving phase remains computationally expensive. This work demonstrates that NTT-based polynomial acceleration is ineffective for Bulletproofs due to fundamental structural mismatch. An NTT-integrated implementation is constructed and evaluated within the Bulletproof proving pipeline. Both theoretical analysis and empirical results show that NTT introduces additional overhead without improving performance. The dominant bottleneck is identified as multi-scalar multiplication (MSM) rather than polynomial computation. Further evaluation of MSM optimization strategies shows that simple analytical models fail to outperform existing heuristic implementations due to implementation-level constraints. Based on these observations, a unified analytical framework is proposed to explain optimization mismatch across protocols. The results demonstrate that effective optimization must align with the dominant computational structure of the protocol.
<sec> <title>BACKGROUND</title> Self-sovereign identity (SSI) provides a decentralized approach to digital identity management, enabling individuals to control their personal data without reliance on centralized authorities. Blockchain technology offers a tamper-resistant and distributed infrastructure that can support secure and verifiable identity systems. In health care, where identity fragmentation, privacy risks, and interoperability challenges persist, blockchain-enabled SSI (BC-SSI) has been proposed as a potential solution. However, existing research remains heterogeneous, with varying levels of technical maturity and limited evidence of real-world deployment. </sec> <sec> <title>OBJECTIVE</title> This study conducts a scoping review to systematically map BC-SSI applications in health care and to analyze their application domains, development stages, study aims, targeted challenges, and technological infrastructures. In addition, this study aims to identify structural gaps in current research and assess the readiness of BC-SSI systems for clinical deployment. </sec> <sec> <title>METHODS</title> This review followed the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews) methodology. A comprehensive literature search conducted between September 2024 and August 2025 identified 37 peer-reviewed studies that met predefined inclusion criteria. Data were extracted and synthesized using descriptive and thematic analyses across application areas, system maturity, technological components, and reported challenges. </sec> <sec> <title>RESULTS</title> The findings indicate that BC-SSI research in health care remains at an early stage of maturity, with most studies proposing conceptual models or prototype implementations and limited real-world validation. Applications predominantly focus on identity verification, credential management, and privacy-preserving data exchange across domains such as electronic health records, mobile health, and access control systems. Commonly used technologies include decentralized identifiers, verifiable credentials, smart contracts, and privacy-enhancing mechanisms such as zero-knowledge proofs and selective disclosure. Despite rapid technical development, persistent challenges include interoperability limitations, governance gaps, usability concerns, and insufficient integration with health care infrastructures. Notably, a structural gap was identified between technological capability and system-level readiness for clinical deployment. </sec> <sec> <title>CONCLUSIONS</title> BC-SSI technologies demonstrate potential for enabling secure, interoperable, and patient-centric identity management in health care. However, current research is predominantly technology-driven and lacks sufficient system-level validation. This study highlights the need for integrated architectural approaches, governance frameworks, and real-world evaluation to bridge the gap between conceptual innovation and clinical implementation. Advancing BC-SSI toward health care adoption will require coordinated progress across technical, organizational, and regulatory dimensions. </sec>
Rajkishor Yadav, Preeti Yadav, K C Nithin Kumar, Vinay Kumar · 5 authors
The rapid enhancement in the use of Internet of Things (IoT) devices has introduced the issues viz privacy, scalability, and computational efficiency. Conventional blockchain solutions only provide decentralization and security. But they result in significant overhead and hence, not found suitable for resource-constrained IoT environments. This work proposes ZK-EdgeChain, an edge-assisted blockchain framework by integrating the lightweight Zero Knowledge Proofs (ZKPs) with edge computing to enable privacy preserving and scalable IoT system. The proposed framework offloads computationally intensive proof generation and verification to edge nodes while maintaining decentralized trust through blockchain. The paper also presents a formal mathematical model and optimized verification algorithm. The results validate a 75% reduction in communication overhead and 44% reduction in energy consumption compared to traditional approaches. The results demonstrate that the ZK-EdgeChain significantly improves efficiency, scalability, and privacy preservation in IoT networks.
Incentive (or point) systems are widely deployed across industries such as retail, tourism, and finance to enhance customer loyalty and create benefits for service providers. However, their operation typically requires the collection and processing of sensitive customer data, leading to significant privacy concerns. Existing privacy-preserving incentive systems predominantly rely on bilinear pairings and the discrete logarithm assumption, which, while efficient in classical settings, are vulnerable to quantum adversaries and thus lack long-term security guarantees. To address this limitation, we present LatInc, a practical lattice-based privacy-preserving incentive system. LatInc integrates state-of-the-art lattice-based signatures with efficient protocols, the ABDLOP commitment, and efficient lattice zero-knowledge proofs, achieving a robust balance between post-quantum security and efficiency. Relying on the hardness of the MLWE and MSIS problems, we formally prove that LatInc achieves unforgeability, anonymity, and framing-resistance in the random oracle model. We implement a demo of the system and evaluate its performance on a standard laptop platform. Experimental results show that the communication overheads for the Earning and Spending protocols are approximately 99 KB and 140 KB, respectively, with execution times of 610 ms and 900 ms, highlighting significant efficiency gains over previous lattice-based incentive constructions.
The modular invariance and automorphism group rigidity of vertex operatoralgebras provide a profound mathematical foundation for constructing novel postquantum cryptographic systems. However, a significant theoretical and engineeringgap exists between mathematical theorems and deployable cryptosystems. Thispaper does not propose new cryptographic protocols but rather systematicallyexamines the core challenges encountered in engineering vertex operator algebracryptography: the discrete selection of parameter spaces and their quantitativerelationship with security strength, the computational resource requirements ofcandidate algebraic families (lattice vertex operator algebras, WZW models, andmoonshine vertex operator algebras), the assessment of security boundaries underquantum attack models, and the practical overhead of auxiliary mechanisms suchas zero-knowledge proofs. The objective is to provide a clear problem inventoryand a feasibility analysis framework for future research, rather than to claim anyimmediately usable security parameters. The article concludes by summarizing thecurrent technology readiness levels and identifying the key breakthroughs requiredto advance from a theoretical framework toward a practical system.
Digital signature schemes derived from non-interactive zero-knowledge (NIZK) proofs are rapidly gaining prominence within post-quantum cryptography. CROSS is a promising new code-based post-quantum digital signature scheme based on the NIZK framework. It is currently in the second round of the NIST’s additional call for standardization for post-quantum digital signatures. However, CROSS’s reference implementation has a substantially large memory footprint. This makes its deployment on resource-constrained platforms prohibitively difficult.In particular, we identified the most memory-intensive areas such as Merkle and GGM tree structures, and zero-knowledge proof commitment generation. We propose several novel algorithms and implementation strategies to reduce the memory requirement of these components. Apart from these, we also propose several memory optimization techniques, such as just-in-time hashing and execution flow analysis. As a result, our implementation reduces the memory footprint of Key Generation, Signature Generation, and Verification of the CROSS reference code by as much as 95%, 92%, and 85%, respectively. This results in a suite of implementations in which all variants are under 128kB (for all security levels of KeyGen/Sign/Verify) and six variants under 32kB. Our memory optimization techniques are not specific to CROSS, but can be applied to other NIZK-based signature schemes.Regarding efficiency, matrix multiplications are crucial to the performance of CROSS. We show how the Digital Signal Processing (DSP) instructions on ARM Cortex-M4, specifically packing and multiplying, can be utilized to efficiently implement matrix operations over finite fields. The DSP optimizations combined with the memory reductions improve the efficiency of CROSS by up to 32% and 33% in Signature Generation and Verification respectively.
Industrial operational technology systems are becoming more intelligent and interconnected, requiring remote maintenance and multiparty collaboration. While traditional approaches improve efficiency, they introduce risks like data leakage and unauthorized operations. Existing access control schemes struggle with compliance verification and auditing while ensuring privacy. A novel access control scheme was proposed that combines zero-knowledge proof with the publicly verifiable covert security model. The scheme features a dual-layer verification mechanism: a basic layer using zero-knowledge proof to protect identities and permissions during remote maintenance and an enhanced layer for high-risk operations that uses oblivious transfer and digital signatures to detect malicious behavior and generate cheating certificates. Security analysis showed the scheme ensures privacy, access legitimacy, and non-repudiation. Experiments demonstrated the scheme had faster proof generation and verification compared to existing methods with effective malicious behavior detection and accountability.
A novel blockchain-based smart contract framework is proposed and designed to mitigate financial product fraud by enhancing transparency, auditability, and trust in advisory processes. The framework introduces a unique dual-contract architecture that combines product and authorization smart contracts, along with a challenge-response verification protocol that ensures both product authenticity and advisor legitimacy. The system is implemented and tested on the Ethereum blockchain, demonstrating operational feasibility through real-world transaction simulations and a corresponding gas cost analysis. By leveraging immutability, the framework preserves data integrity, while cryptographic signatures enable privacy protection without exposing sensitive data on-chain. It is designed to support multi-institutional environments, allowing various financial institutions to issue products and authorize advisors under a unified, fraud-resistant platform. Experimental results confirm the system’s effectiveness in preventing common fraud scenarios, while maintaining low transaction costs and high security.
The rapid growth of cloud computing has significantly transformed the way digital data is stored, managed, and accessed, enabling efficient sharing of information across distributed environments; however, this advancement introduces serious concerns related to data security, privacy, and trust, particularly when sensitive information is involved. Many cloud-based systems rely on centralized architectures, which increase the risk of single points of failure, unauthorized access, data tampering, and limited transparency in tracking data activities. These systems often depend on basic encryption techniques without strong auditing or verification mechanisms, making them vulnerable to insider misuse and external cyber threats, while the absence of immutable records reduces accountability and weakens user confidence. Such limitations highlight the need for a secure and transparent data-sharing framework that ensures confidentiality, integrity, and traceability of data transactions. To address these challenges, the proposed system introduces a secure cloud data sharing model developed using the Django framework, integrating Elliptic Curve Cryptography (ECC), blockchain technology, and the InterPlanetary File System (IPFS) to enhance data protection and decentralization. In this approach, ECC is used to generate cryptographic keys and encrypt user files before storage, ensuring that only authorized users can decrypt the data using the corresponding private key. The encrypted files are stored using IPFS for distributed and content-addressable storage, while file metadata such as username, filename, and timestamp is recorded on the blockchain through smart contracts using Web3, providing a decentralized and tamper-resistant record of all transactions. The system also supports user registration, authentication, secure file upload, and controlled file download functionalities, ensuring secure access and traceability. During file access, encrypted data is retrieved from IPFS and decrypted using ECC to maintain end-to-end security. By combining cryptographic encryption, decentralized storage, and blockchain-based verification, the proposed system enhances data confidentiality, prevents unauthorized modifications, and establishes a reliable and transparent framework for secure cloud data sharing.
Blockchain is a decentralised and distributed ledger technology that enables multiple participants to collectively maintain a secure and tamper-resistant record of transactions without relying on trusted central authorities. It has several potential features, including decentralisation, immutability, transparency and security. Beyond its original use in cryptocurrencies, blockchain has facilitated a diverse range of applications, including decentralised finance, supply chain tracking, digital identity management, secure voting systems and decentralised autonomous organisations, where transparency, trustlessness and data integrity are critical. Structurally speaking, a blockchain consists of an ordered sequence of blocks, each containing a set of validated transactions. Every block incorporates a cryptographic hash of its previous block, linking them into an immutable chain that maintains chronological ordering and prevents tampering. At its foundation, a blockchain relies on the consensus mechanism that ensures all untrusted participants agree on a consistent ledger state, despite network latency or malicious behaviour. Up to now, widely adopted consensus algorithms include proof-of-work (PoW), which relies on computationally intensive puzzles, and proof-of-stake (PoS), which utilises economic incentives based on stake ownership. Unlike PoW, PoS consumes less energy, achieves faster block finalisation with lower latency and lowers participation barriers, enhancing efficiency, scalability and decentralisation without compromising security.Digital signatures are fundamental cryptographic primitives essential for establishing trust and ensuring security in digital communications. By using a secret key to generate signatures on given messages, anyone who knows the corresponding public key can check the validity of signature candidates. This cryptographic process provides critical guarantees such as authentication, data integrity and non-repudiation, making them integral to secure communication and a wide range of cryptographic protocols. In PoS blockchain protocols, digital signatures play a crucial role not only in authenticating transactions but also in validating the participation of stakeholders in consensus processes, such as block proposals and block attestations. Advanced signature schemes, including forwardsecure signatures or puncturable signatures, are often employed to prevent long-range attacks caused by secret key leakage, preserving the immutability of PoS blockchain protocols. Furthermore, threshold or weighted threshold signatures are frequently deployed in PoS-based protocols to aggregate multiple block attestations into a single compact one efficiently, enhancing scalability while maintaining robust security guarantees.This thesis focuses on advanced digital signature schemes deployed in proof-of-stake blockchain protocols, with particular emphasis on puncturable signatures and weighted threshold signatures. To be more specific, the main contributions of this thesis are outlined as follows.First, we focus on puncturable signatures and propose the first generic construction derived from identity-based signatures by treating identities as to-be-punctured prefixes. Based on this framework, we give concrete puncturable signature instantiations over bilinear maps, lattices and multivariate polynomials, respectively. More specifically, the pairing-based instantiation is proven secure based on the computational Diffie-Hellman (CDH) assumption in the standard model. The lattice-based instantiation achieves provable security under the short integer solution (SIS) assumption in the random oracle model. The multivariate-based instantiation is analysed against some best-known attacks in multivariate public key cryptography. All of the proposed schemes support efficient puncture operations, while the lattice-based and multivariate-based ones additionally enjoy post-quantum security.Second, we adopt a different approach to constructing puncturable signatures supporting compact secret keys that serve as an effective mitigation against long-range attacks caused by secret key leakage in PoS blockchains. Specifically, we propose a new generic construction of puncturable signatures from delegated (key-policy) constrained signatures. Such a framework is inspired by an observation that matching between messages and constraints can be converted to equality tests between prefixes of to-be-signed messages and punctured prefixes. The key delegation property of (key-policy) constrained signatures enables repeated key puncture operations. Building on our framework, we give a concrete lattice-based instantiation that is proven secure based on the SIS assumption in the standard model. Our proposed scheme features small secret key sizes, particularly for the initial secret key, which is beneficial for users to join PoS blockchains without requiring a significant commitment in the initial phase.Third, we revisit the notion of puncturable signatures and find their vulnerability in mitigating long-range attacks caused by secret key leakage in PoS blockchains. Despite their key evolving property, compromising previous secret keys enable adversaries to forge branches in PoS blockchains, bypassing the security guarantees provided by puncturable signatures. It is essential to invalidate previous secret keys, regardless of whether they have been securely deleted. Therefore, we integrate key puncture and signing operations into a unified Sign-and-Pun algorithm. By publishing punctured prefixes and providing additional proofs, our strengthened puncturable signatures ensure that no malicious signers can generate valid signatures using previous secret keys. Furthermore, we propose a concrete lattice-based construction that is provably secure under the SIS assumption in the standard model.Finally, we focus on weighted threshold signatures for block attestations in PoS blockchain protocols, where validators are assigned different weights to reflect their varying impacts on consensus decisions. Specifically, we present the first weighted threshold signature scheme over lattices, which is a combination of multi-signature and non-interactive inner product arguments. In our proposed scheme, the weights of signers are public and work as a separate checking condition in threshold signature verification. We show that our scheme is provably secure under the module short integer solution (MSIS) assumption in the random oracle model. Furthermore, we demonstrate how to integrate our scheme into PoS blockchains for block attestation. Moreover, we implement our scheme in the C programming language and present an experimental evaluation of its practical efficiency.
Introduction: Intelligent room systems are experiencing a surge in demand within the Healthcare 4.0 ecosystem. The integration of Federated Learning (FL) and Data-Centric AI has led to substantial enhancements in the predictive capabilities of machine learning models while maintaining data privacy. However, centralized aggregation in FL remains a single point of failure and is vulnerable to poisoning attacks. Methods: This paper presents a novel, privacy-preserving architecture for Ambient Intelligence (AmI) that integrates Distributed Ledger Technology (DLT). Results: We explicitly note that while DLT does not preemptively prevent the generation of poisoned gradients, it provides an immutable, cryptographically secure audit trail. This ensures the trustworthiness and traceability of model updates for post-hoc detection, strict accountability, and targeted model rollbacks. Discussion: By fusing Data-Centric AI for quality assurance with a Blockchain-enabled FL framework, we propose a scalable, low-cost solution for real-time patient monitoring in diverse economic settings.
Collins Izuchukwu Okafor, Love Allen Chijioke Ahakonye, Dong‐Seong Kim, Jae Min Lee
Vehicular-to-Everything (V2X) communications promise unprecedented safety and efficiency gains but remain vulnerable to confidentiality breaches such as eavesdropping, traffic analysis, and man-in-the-middle attacks. We propose ConfidSPEC-V2X, a focused hybrid framework that integrates continuous-variable quantum key distribution (CV-QKD), a multi-agent deep reinforcement learning (DRL), and an Ethereum-based permissioned blockchainPureChainpublic-key infrastructure (PKI) to deliver information-theoretic secrecy, dynamic traffic obfuscation, and tamper-proof key management. In the quantum module, CV-QKD transceivers embedded in On-Board Units (OBUs) and Roadside Units (RSUs) establish symmetric keys resilient to passive interception and capable of immediate eavesdropping detection. The Artificial Intelligence (AI) module employs multi-agent DRL agents at RSUs to learn optimal dummy-traffic injection policies that obfuscate real V2X message patterns against statistical inference. The blockchain module leverages PureChain smart contracts to register, rotate, and timestamp vehicle public keys, ensuring that any man-in-the-middle attempt to forge or replay keys is invalidated. We implement and evaluate ConfidSPEC-V2X within an OMNeT++/Veins simulation under realistic urban mobility scenarios, measuring the quantum bit error rate, key generation throughput, obfuscation entropy, and key management latency. Results demonstrate that our framework achieves robust confidentiality protection with minimal performance overhead.
In the classic model, data integrity assumes a simple sender-receiver channel where threats are limited and verifications are straightforward. However, the modern Internet has reshaped this paradigm. In an era of viral misinformation, encrypted messaging, and decentralized finance, integrity is no longer about just who sent the data, but what it really means and whether it can be trusted. For instance, can we verify the authenticity of a direct message screenshot? Is Signal's end-to-end encryption truly end-to-end when a central server distributes users' keys? Can decentralized protocols, which have attracted four trillions in capital, sustain trust under attacks that wipe out millions?In response, we present a modern perspective on data integrity across diverse systems, arguing for the need of comprehensive innovations from theory to practice along three axes: cryptographic foundation in which we borrow ideas from theoretical research and develop interesting cryptographic tools, protocol design in which we find and achieve novel application goals, and empirical security analysis in which we critically evaluate deployed systems to understand their strengths and exploit their blind spots.To ground these ideas, we discuss three cases: Cauchyproofs as a batch-updatable vector commitment, an analysis of proxying in TLS oracles revealing subtleties in AEAD context unforgeability, and attacks and improvements on the Tor directory protocol. These case studies illustrate both the fragility and opportunity in today's integrity landscape, and how an integrated approach can help guide us forward.