PPO-LIGHT MED: A QUANTUM-SAFE BLOCKCHAIN-ENABLED LIGHTWEIGHT FRAMEWORK FOR SECURE EMR SHARING IN FOG-ASSISTED IOT–CLOUD ENVIRONMENTS

The rapid pace of the development of IoT-based healthcare systems requires efficient, secure, and privacy-sensitive systems of electronic medical records (EMRs) sharing. In an attempt to solve the issue of latency, computational cost, and unauthorized access, the present paper presents Policy-private outsourced Lightweight medical data security (PPO-LightMED), a policy-privately outsourced lightweight medical data security architecture, which is a combination of fog computing, blockchain, and quantum-safe cryptography. The model uses a quantum-safe verifiable outsourced ciphertext-policy attribute-based encryption (QS-VO-CPABE) scheme to provide an access control scheme on a fine-grained basis to offload heavy encryption workloads to fog nodes. Privacy-preserving access is decentralized through a zero-knowledge attribute verification (ZK-AttrVerify) protocol and ephemeral decryption tokens (EDTs) with the help of blockchain smart contracts. There is also an epoch-based revocation mechanism, which allows updating to policies and users dynamically without full re-encryption. Through experiment, there are substantial improvements: 55% reduction in encryption latency, 70% faster revocation and 30% higher throughput than any other models. PPO-LightMED provides a secure and scaled architecture as well as a quantum-resilient architecture for reliable healthcare data sharing in fog-assisted IoT cloud environments.