As wireless sensor network is resource-constrained, reliability and security of broadcasted data become major issue in these types of network. In order to overcome security and integrity issues, a secure authentication and integrity technique is proposed. In this technique, shared keys are used for providing authentication. Here, mutual authentication technique allows the sender and recipient to share a common key matrix as an authentication key. Both sender and recipient chose a random noise matrix and verification is done based on hamming weight. To increase authentication and integrity, a hybrid offline and online signcryption technique is proposed which is a cryptographic method that satisfies both the function of digital signature and public key encryption in a logical single step. By simulation results, we show that the proposed technique provides security in terms of increased packet delivery ratio and reduced compromised communications.