RESUMO
It is not always possible for a patient to go to a doctor in critical or urgent period. Telecare Medical Information Systems (TMIS) provides a facility by which a patient can communicate to a doctor through a medical server via internet from home. To hide the secret information of both parties (a server and a patient), an authentication mechanism is needed in TMIS. In 2013, Khan and Kumari proposed the authentication schemes for TMIS. In this paper, we have shown that Khan and Kumari's scheme is insecure against off-line password guessing attack. We have also shown that Khan and Kumari's scheme does not provide any security if the password of a patient is compromised. To improve the security and efficiency, a new authentication scheme for TMIS has been proposed in this paper. Further, the proposed scheme can resist all possible attacks and has better performance than the related schemes published earlier.