Improve Two Remote User Authentication Scheme Using Smart Card

The password authentication of smart card has become popularized in current network environment. In 2011, Chen et al. proposed an enhancement on an improvement on two remote user authentication schemes using smart cards. Their scheme can resist the parallel session attack and impersonation attack. However, there are some loopholes in Chen et al.´s scheme that we find their scheme can not resist the off-line password guessing attack and suffer from the time asynchronous. In this paper, we analyze Chen et al.´s security problem and propose an improvement scheme.