A multi-receiver certificateless public-key searchable encryption: Field-free subset conjunctive and disjunctive

Cloud-based telemedicine uses powerful data processing technology to improve remote healthcare services. This helps make healthcare more accessible, efficient, and beneficial for both patients and healthcare providers. However, the security and privacy of patients sensitive data, especially when outsourcing to the cloud, remain significant concerns. To address this issue, patient data is stored in encrypted format on the cloud server. A searchable encryption mechanism is employed to enable efficient search on the encrypted data without compromising information confidentiality. While most searchable encryption schemes support conjunctive field keyword search in both single receiver and multi-receiver scenarios, they often result in partial information leakage related to the searched keywords. Additionally, a new scheme based on the Lagrange polynomial concept was developed to support conjunctive field-free search in a single receiver scenario. However, it is unsuitable for multi-receiver scenarios and suffers from certification management challenges. To overcome these limitations, we propose an innovative approach called "Multi-receiver Certificateless Public-key Searchable Encryption: Field-free Subset Conjunctive and Disjunctive." Our scheme is constructed upon reciprocal maps and leverages Lagrange polynomials as a fundamental tool. It offers several advantages, including cipher-index indistinguishability against chosen keyword attacks, utilizing the hardness of the decisional linear Diffie-Hellman assumption. Theoretical and experimental analyses demonstrate that our proposed scheme achieves comparable performance to existing works in terms of computational efficiency and communication overhead.