Wireless sensor networks (WSNs) when combined with Internet-of-things (IoT) enable a wide range of applications across multiple domains. Sensor nodes in these wireless sensor networks like any other Internet-connected device are resource constrained and vulnerable to a variety of malicious attacks thereby compromising security. Consequently, a secure and efficient lightweight cryptographic protocol is required that can provide a balance between end-to-end security offering all features but yet lightweight. For secure data transmission and access, newer multi-factor authentication and key management features must be developed as majority of existing techniques have high computational overheads and are vulnerable to a wide range of attacks. In this paper, we propose a Rabin-assisted three-factor authentication protocol that uses the computational asymmetry of Rabin cryptosystem in addition to user password, smartcard and biometric for increased security. NS2 based simulation proves that the proposed protocol outperforms the baseline ad-hoc on-demand distance vector (AODV) protocol in terms of throughput, computation cost, and delay performance. Also, it has the ability to tolerate most common attacks and offers additional functionality features thereby offering a lightweight and highly secure protocol that can be extended to other critical domains like Smart Transportation Systems (STS), Smart grids, Smart buildings etc.