Today’s life cannot be imagined without smart homes, which are designed to provide both convenience and automation. Unfortunately, the security gaps that exist in the infrastructure frameworks of smart homes can lead to significant loss of property and even life. These settings depend on devices on the Internet of Things (IoT), which have some of the most serious security issues, especially with respect to device authentication and key management. Although traditional cryptographic methods could work, they are often too slow and overly complicated for basic IoT gadgets. This article proposes a lightweight authentication scheme based on Shamir’s Secret Sharing (SSS), cryptographic hash functions (SHA-3), and an XOR based session key generation. The proposed system is capable of securely distributing the secrets of authentication and provides pseudonyms to the reconstructed secrets through Lagrange interpolation. The system exploits hashing and XOR to deliver fast authentication while being not vulnerable to MITM, replay, or key compromise attacks. The security evaluation proves the effectiveness and dependability of the protocol and its applicability in IoT settings with limited resources.