Improved Hwang et al.'s Convertible Authenticated Encryption Scheme with Message Linkages for Message Flows

An authenticated encryption scheme is very useful for transmitting a confidential message in insecure communication networks. In 2010, Rasslan et al.'s pointed out that HWang et al.'s authenticated encryption scheme is not secure by presenting another message forgery attack. However, Rasslan et al. do not proposed a countermeasure of the HWang et al.'s scheme. This paper proposes an improvement of HWang et al.'s scheme that can withstand Rasslan et al.'s proposed message forgery attacks. Unlike HWang et al.'s scheme, the proposed scheme was added conversion phase to provide non-repudiation when the signer repudiates his/her signature. As a result, the proposed scheme is more practical than HWang et al.'s scheme because it not only provides computational efficiency but also achieves all security requirements.