Distributedly and Provably Continuous Storage Scheme With Forward Secure for IoT Healthcare Data

The proliferation of healthcare devices enabled by consumer electronics has led to the generation of massive volumes of sensitive data, posing significant challenges for secure and continuous storage. While distributed edge storage offers scalability and accessibility, existing provable continuous storage schemes must predefine the entire storage period and precompute all audit proofs by repeatedly evaluating trapdoor-based Verifiable Delay Functions (VDF), incurring preprocessing costs that scale linearly with storage time and audit frequency. Moreover, once these proofs are generated, these schemes become inherently static - any data update invalidates all precomputed proofs and necessitates the regeneration of the entire preprocessing phase, which renders real-time updates impractical. In this paper, we propose a Distributedly and Provably Continuous Storage Scheme (DPCSS) tailored for healthcare data. DPCSS enables periodic integrity verification without trusted auditors by combining VDF with homomorphic authenticators. To eliminate the inefficiency of local pre-verification, DPCSS introduces a cross-validation method among edge servers that allows sequentially proving and then verifying. Furthermore, a structural interaction protocol is designed to reduce communication overhead, and puncturable key wrapping is leveraged to enable efficient, real-time data and key updates with forward security. Formal security analysis demonstrates that DPCSS ensures confidentiality, forward security, and secure against forgery attack, and experimental results show that our DPCSS achieves low verification cost and constant-time preprocessing that is independent of storage time and audit frequencies, where DPCSS improves the preprocessing time by about 1.4 times compared to the state-of-the-art scheme.