An access point and a sensor node are disclosed for use within a wireless sensor network. The wireless sensor network includes at least one access point adapted to securely communicate with at least one of the sensor nodes using an encryption mechanism that uses a nonce and an encryption key to encrypt the plaintext at the sensor node to create the cipher text included in the data payload of a message sent to the access point. The sensor node does not send the nonce. The access point uses the same nonce to decipher to the received message's data payload, but generates the nonce internally without receiving it from the sensor node.