Equality Test of Ciphertexts in Certificateless Public Key Systems with an Outsourced Revocation Authority

Due to the privacy and confidentiality, users usually encrypt the data before uploading data to the cloud. In the past, there has been research on the cloud server running the equality test of ciphertexts in certificateless public key systems. Based on the results of the equality test of ciphertexts, the cloud server can carry out the application of ciphertext classification without knowing the plaintext, such as the classification of encrypted emails. However, a mechanism for revoking users should exist in any system. In this article, we add an outsourced revocation authority to the equality test of ciphertexts in certificateless public key systems. A concrete scheme is proposed under the elliptic curve. Compared with the existing scheme, our scheme not only retains the features of the existing scheme, but also employs an ORA to perform the task of revoking users.