In recent years, Internet of Things(IoT) gained popularity due to its enormous applications in many fields. IoT network comprises heterogeneous devices to a great scale, which creates numerous security threats. In this paper, a smart home based on IoT architecture is considered, where the IoT smart Hub(ISH) communicate with the cloud in one hand, and home appliances and smart devices on the other. The IoT smart Hub(ISH) receives commands from the smart phone which is connected to the cloud through the internet, where lies the possibility of an external attack. This paper proposes a secure authentication protocol between smart phone and ISH, which supports ISH for ensuring security in the smart home scenario.