Certificateless cryptography, which solves the key escrow problem and avoids the complexity of certificate management, is an important part of public key cryptography. In the multi-user scenarios, broadcast encryption can improve computational efficiency and reduce communication cost. Moreover, there may be some malicious users in the above scenarios, and the decryption permissions of these users need an effective mechanism to revoke them. In this paper, a revocable certificateless encryption scheme for multi-user (RCLE-MU) is proposed to address this issue. In the scheme, the Cloud Server Provider (CSP) utilizes the master time key to periodically generate time keys for legitimate users. For illegitimate users, their decryption privileges are revoked since they are unable to obtain the time keys. Then this new scheme is proved to be ciphertext indistinguishable under selected identity and chosen-ciphertext attacks (sID-CCAs). Finally, compared with several other schemes, the new scheme has more efficiency advantage. So it is suitable for multi-user scenarios.
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