  The smart card based authentication schemes are designed and developed to
ensure secure and authorized communication between remote user and the server.
In recent times, many smart card based authentication schemes for the telecare
medical information systems (TMIS) have been presented. In this article, we
briefly discuss some of the recently published smart card based authentication
schemes for TMIS and try to show why efficient login and password change phases
are required. In other word, the study demonstrates how inefficient password
change phase leads to denial of server attack and how inefficient login phase
increase the communication and computation overhead and decrease the
performance of the system.
