Wireless sensor networks (WSNs) consist of sensor nodes and these nodes can vary from a few numbers to a highly dense number. Data aggregation is a very important technique in wireless sensor networks through which diverse parameters performance can be increased effectively. Energy consumption by nodes can be decreased using data aggregation technique by eliminating redundancy because these parameters play a vital role in MANET. Wireless sensor nodes are very tiny in size and have limited processing capability very low battery power. This diminution of low battery power makes the sensor network vulnerable to failure. Sensor networks consist of several sensor nodes which co-operatively send sensed data to base station. One of the critical constraints of sensor nodes is the power consumption requirement. As sensor nodes are battery driven, an efficient utilization of power is essential to reduce data traffic inside sensor networks thus reduce the amount of data that need to send to base station thereby enhancing the network lifetime. In this survey paper, our main focus is to know data aggregation, data aggregation strategies, private key, public key, and security concept how to data can be a guard from hackers or malicious nodes. Networks have huge application in habitat monitoring, disaster management, security, and military, etc.