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.