Efficient Convertible Multi-authenticated Encryption Scheme for Group Communications

In 2008, a convertible multi-authenticated encryption (CMAE) scheme for group communications is proposed by Ting-Yi Chang. Chang´s mechanism enables multiple signers to generate a multi-authenticated cipher text associated with the targeted message or document. After receiving this multi-authenticated cipher text, multiple verifiers can recover and verify the message from it. If those signers deny the message was sent by them afterward, the verifiers can convert the corresponding multi-authenticated signature into a traditional one and then submit it to the trusted third party to resolve the dispute. In this study, we propose a new CMAE scheme for group communications based on one-way hash function and discrete logarithm problem (DLP). The proposed scheme is more efficient than Chang´s scheme in terms of computation cost. In addition, security robustness of the proposed CMAE scheme is evaluated under four general attack patterns.