Efficient Anonymous Multireceiver Certificateless Encryption

To protect receiver privacy, researchers constructed anonymous multireceiver encryption by implanting anonymity in multireceiver encryption. It allows a sender to produce the identical ciphertext for multiple designated receivers. Every designated receiver can decrypt the ciphertext, but does not know who the other designated receivers are. Recently, several anonymous multireceiver identity (ID)-based encryption (AMIBE) schemes were proposed without the utilization of certificates. However, these AMIBE schemes are not efficient because their decryption cost of each receiver grows linearly with the number of the designated receivers. Moreover, all the ID-based cryptographic schemes suffer from the key escrow problem, which has been resolved by using certificateless public key settings. Very recently, Islam et al. proposed an anonymous multireceiver certificateless encryption (AMCLE) scheme. However, the encryption cost of a sender is quadric with the number of designated receivers, whereas the decryption cost of each receiver is linear with the number. In this paper, we propose an efficient AMCLE scheme with constant decryption cost, namely, the required decryption cost of each receiver is independent of the number of receivers. When compared with previously proposed AMIBE and AMCLE schemes, our scheme solves the key escrow problem and improves the efficiency of encryption/decryption significantly as well.