Recently smart services, which are a global issue, aims to provide convenience, instructiveness, and safety to users by sharing data through communication between various devices connected to the internet and analyzing and processing collected data to provide useful information to users. However, in order to securely provide a variety of services to users by interconnecting a large number of devices, important key management function as well as mutual authentication between devices must be applied to the smart service environments. In this paper, we propose a secret key updating method based on devices using dynamic session key. This method can be applied to secure services on smart city such as authentication and key update between repeaters and street lights or between CCTV cameras and various sensors and also applicable to secure services on smart home such as authentication and key update between gas detector and gas breaker.