A Blockchain Footprint for Authentication of IoT-Enabled Smart Devices in Smart Cities State-of-the-art, Advancement, Challenges and Future Research Directions

A Blockchain Footprint for Authentication of IoT-Enabled Smart Devices in Smart Cities State-of-the-art, Advancement, Challenges and Future Research Directions
Abstract
The rapid proliferation of heterogeneous IoT devices across smart-city deployments has amplified the need for robust, scalable, and tamper-resistant authentication frameworks. Traditional centralized authentication schemes struggle with single points of failure, scalability bottlenecks, and trust assumptions that are unsuitable for highly distributed urban infrastructures. This work presents a blockchain-footprint approach for authentication of IoT-enabled smart devices in smart cities, combining decentralized ledger immutability, lightweight identity anchors (device fingerprints / NFTs), and edge-assisted verification to provide provable device identity, auditability, and revocation capabilities. We review the state-of-the-art in blockchain-enabled authentication, identify practical constraints (transaction latency, energy and storage overhead, consensus suitability for constrained devices), and classify existing solutions by architecture (public, private, consortium blockchains; on-chain vs off-chain credentialing). Finally, we propose a hybrid architecture that leverages permissioned blockchains, off-chain credential storage, and lightweight consensus/sharding for throughput, together with smart contracts and zero-knowledge proofs for privacy-preserving authentication. Evaluation directions and future research avenues—adaptive consensus, interoperability standards, and post-quantum resilience—are discussed. ResearchGate+2MDPI+2

Existing system
Current smart-city IoT authentication largely relies on centralized Public Key Infrastructure (PKI), cloud-based device management systems, or gateway-mediated trust models. These approaches provide familiar tools (certificates, access control lists, and centralized revocation), but they inherit critical weaknesses: single points of failure, third-party trust assumptions, inconsistent device identity lifecycle management, and limited auditability across administrative domains. Attempts to decentralize trust using naïve blockchain deployments have shown promise—immutability and decentralized verification improve audit trails and cross-domain trust—but introduce new constraints. Primary practical limitations observed in the literature include poor scalability for high-volume IoT telemetry due to blockchain throughput and latency, energy and storage costs for constrained devices, and privacy exposures when sensitive identity data is placed on-chain. Moreover, consensus mechanisms used in public blockchains (PoW, some PoS variants) are often unsuitable for resource-limited IoT contexts, while naïve on-chain credential storage raises GDPR and privacy concerns in urban deployments. These limitations create a gap between theoretical blockchain benefits and deployable authentication systems for large-scale smart cities. ScienceDirect+2ScienceDirect+2

Proposed system

We propose a hybrid blockchain-footprint authentication architecture tailored for smart-city IoT: (1) a permissioned/consortium blockchain layer operated by municipal stakeholders for ledgering device identity events (onboarding, ownership transfers, revocation), (2) off-chain credential stores (e.g., distributed object storage or secure edge vaults) that hold private device metadata and sensitive keys, and (3) lightweight on-device identity anchors implemented as compact cryptographic fingerprints or tokenized non-fungible identifiers (NFT-style device IDs) that are registered on the ledger as immutable references. Authentication flows combine edge-assisted challenge–response (to keep real-time latency low) with on-chain verification of the device’s footprint via merkle proofs and short smart-contract routines for policy checks. To mitigate scalability and resource constraints, the design employs sharding or layer-2 state channels for high-frequency microtransactions, energy-efficient consensus (e.g., permissioned BFT or DPoS variants adapted for IoT), and selective audit logging to preserve privacy. Privacy is further protected using selective disclosure and zero-knowledge proofs so that entitlement checks can be validated without revealing sensitive attributes on the public ledger. This hybrid model balances decentralization, auditability, latency, and device constraints—making blockchain a practical trust backbone rather than an on-chain data store—while enabling cross-domain device authentication and streamlined revocation in smart-city ecosystems

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