In recent years, Wireless sensor networks (WSN) are extensively exploited in terms of their enormous applicability and are widely used from mere public branches like hospitals, banks, Institutes to defense and research wings of the country. Pointing that it can contain public or private (sensitive) information or both correspondingly which means authentication among user, nodes and gateways is a must based on a trust metric(s) or a common cryptographic key. WSNs act as a beehive of storming information that is continuous or timed periodically. An unsecure network is highly prone to outsider as well as insider attacks and then here comes the role of authentication protocols that act as a shield of defense because traditional security methods are not directly applicable on IOT’s WSNs due to increasing heterogeneity of components. In this paper, We revisit the authentication protocol provided by Amin and Biswas in 2016 and we propose an improved authentication protocol based on two factor namely rabin cryptosystem and hashing that aim to provide enhanced security features with secure common session key generation and address some of the previous un-addressed attacks.