This document summarizes research on secure data aggregation protocols for wireless sensor networks. It first introduces wireless sensor networks and discusses how data aggregation can help reduce energy usage by aggregating sensor data as it travels towards a base station. However, data aggregation also presents security risks if sensor data is compromised. The document then reviews different types of attacks against wireless sensor networks, such as denial of service attacks and false data injection attacks. It also discusses security goals like data confidentiality, integrity, and availability. Several existing secure data aggregation protocols are then summarized, including techniques using public/private key cryptography and probabilistic encryption to securely aggregate and transmit sensor data while preventing attacks. The document concludes that security is an important challenge for data aggregation in wireless sensor