  Internet of Things (IoT) have gained popularity in recent times. With an
increase in the number of IoT devices, security and privacy vulnerabilities are
also increasing. For sensitive domains like healthcare and industrial sectors,
such vulnerabilities can cause havoc. Thus, authentication is an important
aspect for establishing a secure communication between various participants. In
this paper, we study the two recent authentication and key exchange protocols.
We prove that these protocols are vulnerable to replay attack and modification
attack, and also suffer from technical correctness. We then present the
possible improvements to overcome the discussed vulnerabilities. The
enhancement preserves performance of the original protocols.
