Heterogeneous and plaintext checkable signcryption for integrating IoT in healthcare system

Preserving the confidentiality and integrity of data transmission is paramount in the Internet of Things (IoT)-based healthcare systems. Current encryption techniques that allow plaintext checks primarily serve a specific cryptosystem, lacking the adaptability to work with a diverse system incorporating various cryptographic methods. To address this, we present a unique online/offline heterogeneous signcryption scheme with plaintext checkable encryption (HOOSC-PCE). This approach enables the transition of signcrypted messages from an identity-based cryptosystem (IBC) to a public key infrastructure (PKI) system, improving information interoperability. A key aspect of our scheme is its capacity to allow cloud servers to perform plaintext queries, facilitating efficient data searches using plaintext keywords over encrypted data. Furthermore, the signcryption process is divided into online and offline phases. The online phase handles tasks that require fewer resources, while the offline phase carries out more resource-intensive preparatory tasks. We rigorously tested the HOOSC-PCE scheme's security by proving it secure under the Random Oracle Model (ROM). Meanwhile, compared to similar work, it effectively reduces computation costs by 46.39%, 19.45%, 18.73%, and 13.25% across offline encryption, online encryption, decryption, and search algorithms. The results indicate that the HOOSC-PCE is secure and efficient, confirming its feasibility for IoT-based healthcare systems.