In a recent paper, Chang et al. proposed an authentication scheme for E-coupon systems and proved that their scheme can prevent a range of attacks. In this paper, we reanalyze the Chang et al.’ scheme and demonstrate that it cannot resist off-line password attack, masquerading shop attack and masquerading customer attack. Moreover, it cannot achieve two security properties that is anonymity and traceability. Meanwhile, Lee proposed an efficient chaotic maps-based authentication and key agreement scheme using smartcards for telecare medicine information systems. In the scheme, we find it also cannot resist off-line password attack, masquerading attack. Unfortunately, it resists an deadly error. So the scheme cannot run.
On the Design of Fine Grained Access Control With User Authentication Scheme for Telecare Medicine Information Systems