Key-aggregate searchable encryption with multi-user authorization and keyword untraceability for distributed IoT healthcare systems

Adopting Internet-of-Things (IoT) enables pervasive computing by integrating distributed healthcare infrastructures to enhance conventional medical services. Integrated healthcare systems store numerous encrypted electronic health records (EHR) on clouds that multiple users frequently access as per delegated access rights. Sharing any group of selected EHR within any group of users involving different encryption keys potentially heightens security and privacy concerns over inadvertent data leaks. This necessitates a searchable encryption mechanism in distributed IoT requiring secure multi-user authorization and efficient searchable keys management with compact trapdoors. Contemporary state-of-the-art protocols utilize large numbers of expensive encryption keys and keyword trapdoors while lacking secure multi-user authorization and keyword untraceability on clouds. This motivates us to design a novel key-aggregate searchable encryption protocol that jointly achieves multi-user authorization and keyword untraceability for distributed IoT applications. Key-aggregation reduces complexity in sharing (n)$$ (n) $$ documents by executing a stand-alone trapdoor, while token-based authorization allows keyword search only to legitimate data users. Additionally, secure dynamic indexing achieves keyword untraceability on clouds. Security analysis illustrates correctness and resilience against typical attacks. Performance and empirical analysis demonstrate a relative advantage in storage, communication, and computational costs while incorporating secure multi-user authorization and keyword untraceability as additional security features.