SEAC: dynamic searchable symmetric encryption with lightweight update-search permission control

Abstract

Sharing electronic protected health information (ePHI) is highly beneficial in public affairs. Constructing a cloud-assisted ePHI retrieval service represents a modern strategy that enhances cost-effectiveness and efficiency, making it a promising solution. However, widespread implementation is hindered by concerns over privacy violations. Symmetric Searchable Encryption (SSE) has emerged as a practical approach for ensuring data privacy and efficient retrieval in the cloud without decryption. Nonetheless, existing SSE schemes encounter challenges, including secure and efficient data updates, effective search-update permission control, and cross-platform adaptability. To address these limitations, we propose a novel variant of Dynamic Searchable Symmetric Encryption known as SEAC, tailored for secure, cloud-assisted sharing of ePHI. SEAC is formalized within a multi-client/single-server model, enabling authorized clients to perform search or update on encrypted data. The concrete construction integrates dynamic cryptographic accumulators with an efficient binding mechanism for index structures, offering two key features: (1) sublinear conjunctive keyword search that ensures forward and Type-II backward privacy, and (2) lightweight, updatable permission control that effectively mitigates read-write confusion while supporting scalable user revocation and re-authorization. We developed both a localized and a web-based implementation, demonstrating its efficiency and scalability in practical applications.