Abstract: The development of Internet of things (IoT) has always been faced with serious security threats and challenges. The security sharing and fine-grained access control of data in the IoT is one of the security issues that urgently need to deal with. In order to solve this problem, an attribute-based encryption (ABE) scheme with the hidden access structure for data security sharing of IoT is proposed. This scheme can achieve fine-grained access control of ciphertext and guarantee data privacy. In this paper, a universal method to convert identity-based encryption (IBE) into ciphertext-policy attribute-based encryption (CP-ABE) is proposed, which supports AND-gate access structure with multiple values. The converted CP-ABE can inherit the characteristics of IBE. Then, the receiver anonymous IBE scheme proposed by Wee is converted to the CP-ABE scheme with the hidden access structure based on the conversion method, which realizes the fixed length of ciphertext, user secret key, public key and master secret key, and only needs one bilinear pairing computation in the decryption phase. The converted scheme is applied to the intelligent medical application scene and the system model and application steps are given. Finally, the results of theoretical analysis and experimental simulation show that the proposed scheme implements the hidden access structure and has advantages in computing efficiency, storage burden and security. It is more efficient and secure when the scheme is applied to the IoT environment.

Key words: Internet of things (IoT), privacy protection, data sharing, ciphertext-policy attribute-based encryption (CP-ABE), hidden access structure