  Authentication schemes are practised globally to verify the legitimacy of
users and servers for the exchange of data in different facilities. Generally,
the server verifies a user to provide resources for different purposes. But due
to the large network system, the authentication process has become complex and
therefore, time-to-time different authentication protocols have been proposed
for the multi-server architecture. However, most of the protocols are
vulnerable to various security attacks and their performance is not efficient.
In this paper, we propose a secure and energy-efficient remote user
authentication protocol for multi-server systems. The results show that the
proposed protocol is comparatively ~44% more efficient and needs ~38% less
communication cost. We also demonstrate that with only two-factor
authentication, the proposed protocol is more secure from the earlier related
authentication schemes.
