In this paper, a new scheme to enhance security of Wireless Sensor Network (WSN) gateway is presented. Security in WSN is a challenging task due to its limitation towards the low latency in processing speed and power. Preliminary results show the proposed scheme that does not have application dependency and have potential in integrated with any application of wireless sensor network. However, the technique used in encryption algorithm is Advanced Encryption Standards (AESs) and sleep scheduler for key management combined and operated with the same key size to provide node authentication and secure key exchange.