This paper concerns the lightweight cryptography, elliptic curve cryptography on the Internet of Thing (IoT). Most of the system depends on the internet, so it is IoT that is an excellent evolution of technology. Smart home, city, university are some familiar examples of the Internet of Things. It is a great challenge to modernize our world into the smart world from the security perspective. For instance, at the smart home door system, an unauthorized person can easily break the security that means opening the door after trying the password several times. Some security schemes have been proposed to enhance IoT security issues after adopting the public key infrastructure (PKI) system that is either not secure or has complexity. The lightweight nature of the IoT devices often demands different security approaches apart from existing web security that motivates us to enhance IoT security upon different primitive such as elliptic curve cryptography (ECC). Here, we propose sample IoT scenarios to incorporate ECC instead of an existing technique as it has the thin nature in key size, and at the same size of the key ECC show more strength than RSA-driven technique. We evaluate our proposed system based on a smart-door IoT system using a simulation tool, namely Cryptool 2. The contribution of this work is to show how ECC performs better than the Rivest–Shamir–Adleman (RSA) based approach in the considered IoT use-case.