Proxy re-encryption with equality test for secure data sharing in Internet of Things-based healthcare systems

The integration of the Internet of Things (IoT) and cloud computing brings tremendous convenience and efficiency to process and store growing sensor data in healthcare systems. For the security of sensor data collected by healthcare systems, encrypting data before uploading is necessary. Nevertheless, these encrypted form sensor data make it a research challenge to achieve efficient data search and data sharing on the cloud-assisted IoT simultaneously. Encrypting data by public key encryption with equality test (PKE-ET) scheme, identified as a viable solution, is capable to search data encrypted with different keys efficiently. However, how to efficiently share searched healthcare record on the cloud server is still an unsettled problem. To address this problem, we combine the concepts of proxy re-encryption (PRE) and PKE-ET to obtain proxy re-encryption with equality test (PRE-ET). Inheriting the advantages of PKE-ET and PRE, the user can search the required healthcare record data from data encrypted under different public keys. Meanwhile, the searched healthcare record can be shared securely and flexibly without disclosing the secret key and plaintext. We prove the security of our PRE-ET construction based on divisible computation Diffie-Hellman assumption in the random oracle model. Eventually, the proposed scheme is proven useful according to extensive efficiency analysis and comparison.