Trust-Based Framework for Securing Inter-Fog Communication in Smart City Applications

The proliferation of smart city technologies has accelerated the deployment of fog computing to support low-latency, real-time services. By processing data closer to the source, fog computing reduces dependence on cloud infrastructures. However, decentralized, peer-to-peer inter-fog communication introduces serious security challenges due to the lack of centralized oversight and the involvement of diverse administrative domains. Traditional perimeter-based security models fall short in such environments. Establishing trust defined as confidence in a node’s reliability, behavior, and compliance is critical for securing fog-based interactions. This paper reviews trust-based frameworks tailored for inter-fog communication, including machine learning-driven evaluators, blockchain-enhanced identity systems, game-theoretic models, and reputation-based mechanisms. We assess their scalability, privacy trade-offs, and operational effectiveness in real-time settings. Key challenges such as trust standardization, cold-start issues, privacy risks in feedback systems, and Sybil or bad-mouthing attacks are examined. In response, we propose a conceptual Trust Evaluation and Enforcement Layer (TEEL) that dynamically assesses trust using hybrid behavioral, cryptographic, and reputational metrics. Our recommendations emphasize adaptive trust recalibration, integration with lightweight security orchestration, support for federated trust across domains, and privacy-by-design principles. Trust, we argue, must evolve from a security feature to a foundational architectural requirement in fog-driven smart cities