Efficient Policy-Hiding and Large Universe Attribute-Based Encryption with Public Traceability for Internet of Medical Things

Modern day medical systems are closely integrated and interconnected with other systems, such as those comprising Internet-of-Medical Things (IoMT) devices that facilitate remote healthcare services, say during pandemics (e.g., COVID-19). Attribute-based encryption (ABE) is a promising cryptographic primitive to support fine-grained access control in the ciphertext environment; in other words, ABE can potentially be used to ensure data confidentiality and user privacy in the IoMT ecosystem. In this article, we propose an efficient partially-policy-hidden and large universe ABE scheme with public traceability to construct a practical IoMT system (hereafter referred to as PTIoMT). The system is designed to achieve the following features: 1) the access policy is partially hidden: only nonsensitive attribute labels/names are displayed, while sensitive attribute values are hidden in the encrypted electronic health records (EHRs); 2) the number of the attributes is independent of the public parameters and, thus, can be arbitrarily large; 3) any user who discloses the decryption key can be efficiently tracked; and 4) fewer bilinear pairing operations are required during the decryption process. The security analysis and performance evaluation demonstrate the security and efficiency of PTIoMT.