Improved Proxy Re-encryption Scheme with Equality Test

Abstract

A proxy re-encryption with keyword search (PRES) provides simultaneously the function of keyword search and flexible sharing of data. The concept is more efficient than the traditional data-sharing method by performing "search-download-decrypt-encrypt." However, a PRES is limited to searching for encrypted keywords using the same public key. To address this problem, Li et al. introduced a new primitive, called proxy re-encryption with equality test (PREET), which can search for ciphertext under different public keys. PREET effectively solves these problems and provides an equality test of keywords under different public keys. Unfortunately, we found that their scheme was unable to effectively verify the integrity of the ciphertext during the verification process of the decryption step. Therefore, we propose an improved scheme to make the verification effectively verify the integrity of the ciphertext. In addition, a security proof is provided to show that our proposed scheme is secure against chosen-ciphertext attacks based on the Diffie–Hellman assumptions under random oracle models.