A Lightweight Public Key Encryption Scheme with Equality Test for Distributed Healthcare System

Abstract Most of the healthcare systems electronics medical records (EMRs) are inefficient , and innovation in this domain is slow. Recently, researchers have proposed distributed EMRs using blockchain, in which healthcare system medical data of patients is publicly available for doctors and researchers to improve health quality of patients. Patient medical data are very private information, but blockchain does not provide full anonymity to medical data in distributed EMR of health-care systems. To overcome this issue, this paper presents an application scenario of distributed healthcare record and medical network (DHRMN), in which we make blockchain fully anonymous by utilizing the equality test property of Public Key Encryption with Equality Test (PKEET). However, most existing PKEET schemes have two main issues: (1) Once a server gets the trapdoor from a user to perform equality test, then the server can perform equality test on all ciphertexts of that user without further authorization; (2) Previous schemes require significant computation cost to perform equality test because they used bilinear pairing to perform equality test. These aforementioned two issues of PKEET might lead to privacy leakage or make DHRMN slow. Therefore, this paper presents the first secure lightweight public key encryption with equality test (LW-PKEET), where each trapdoor can only be used to perform the equality test on a particular ciphertext of any user, and to improve the performance, bilinear pairing operation is not used in key generation, encryption, decryption, trapdoor or equality test procedure of the proposed scheme. Moreover, we prove that the security of our LW-PKEET scheme is one-way secure against chosen ciphertext attacks (OW-CCA) in the random oracle model (ROM) under the Computational Diffie-Hellman (CDH) assumption.