SSE-CTC: Search Over Encrypted Data With Owner-Enforced and Complete Time Constraints

Searchable symmetric encryption (SSE) is a technique that enables secure outsourcing of data to an untrusted cloud server without sacrificing search functionality. Recently, multi-user SSE schemes for data sharing, which support access control from various users, have gained attention. However, the access control mechanisms in existing schemes are not adequate for realistic data-sharing scenarios as they do not consider time constraints or only partially address them, making these mechanisms unsuitable for SSE schemes. To address this issue, we first highlight the importance of time constraints in multi-user SSE and propose a completely time-constrained SSE scheme under a two-server model. By taking advantage of the Lagrange interpolation and pre-computation, our proposed scheme enables searching over time-related encrypted data with owner-enforced time constraints. Additionally, we employ the blinding technique with the assistance of a semi-honest time server to ensure the completeness of time constraints, which is not guaranteed in existing works. Based on the leakage function, we prove the security of our proposed scheme in the simulation-based security model. Furthermore, extensive experiments demonstrate the practicality of our scheme in supporting time-constrained functions.