Improvement of Convertible Authenticated Encryption Schemes

A convertible authenticated encryption scheme simultaneously provides the functions of integration, authentication, confidentiality, and non-repudiation. In this paper, we first separately point out that any adversary can forge a converted signature in Araki’s scheme and MaChen’s scheme. Moreover, we further improve the weakness in WuHsu’s scheme, which is to convert the signature into an ordinary one should divulge the message. Our improved scheme not only solves the weakness but also reduces the computational complexities in both sides of signer and recipient.