With the increasing use of Wireless Sensor Networks (WSN) in more and more fileds, security of data transfer becomes a major concern in research filed . The secret key cryptography is not able to provide a sense of security in WSN given the nature of deployment area in the most of the applications. Key distribution remains a major problem in secret key cryptography . Recently many public key cryptography based algorithms have been defined. In these foremost is homomorphic algorithms but they are very costly on scarce resource in WSN i.e. Battery life. This paper proposes a new encryption scheme for achieving energy efficiency and security for LEACH-C  protocol in wireless sensor network. The proposed scheme uses a hybrid scheme comprising both type of encryption schemes i.e. Secrete key cryptography and public key cryptography both. In the proposed scheme the session key is distributed to various nodes using public key cryptography scheme which enhances security of network and also consumes less energy. For data aggregation plain method (in-network data aggregation) is used. The proposed method is compared with public key cryptography with concealed data aggregation and in network data aggregation. The result shows that the proposed scheme achieved higher energy efficiency as compared to other two comparable schemes without compromising security environment in data transfer.