A Convertible Multi-Authenticated Encryption scheme for group communications

Recently, Wu et al. proposed a Convertible Multi-Authenticated Encryption (CMAE) scheme, which allows a signing group with multiple signers to generate a multi-authenticated ciphertext signature on the chosen message so that only a designated verifier can recover and verify the message. In case of later dispute, the verifier can convert the multi-authenticated ciphertext signature into an ordinary one that can be verified by anyone. In this study, a CMAE scheme for group communications is proposed. This is presented by first reviewing the concepts of group-oriented encryption schemes and the merits of Wu et al.’s scheme. This shows that not only can a multi-authenticated ciphertext signature be generated by a signing group, but also the message can be recovered and verified by a verifying group with multiple verifiers. The security of the proposed scheme is based solely on the DDH problem, which provides higher security confidence than using the CDH problem in Wu et al.’s CMAE scheme.