On the security of two authenticated encryption schemes

An authenticated encryption scheme is a message transmission, which sends messages in secure and authentic way. It is very suitable to mobile device. Recently, C.S.Ma and K.F.Chen give a new authenticated encryption scheme, and Hung-Yu Chien also give a convertible authenticated encryption scheme. However, our analysis shows that the two schemes are extremely insecure. The common flaw of the two schemes is forgeability and repudiation. After we give the corresponding attack to the two authenticated encryption schemes respectively, we propose two secure publicly verifiable authenticated encryption schemes to overcome the flaws of MC scheme and Hung-Yu Chien Scheme. As for efficiency, the computation cost and communication overhead of our proposed schemes are as small as the two original schemes: the MC scheme and the Hung-Yu Chien scheme. Finally, we give secure proof to the proposed schemes.