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Tham khảo tài liệu 'emerging communications for wireless sensor networks part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Secure Data Aggregation in Wireless Sensor Networks 193 is threatened by some malicious activities. To put in another way this verification phase is used to validate the aggregation results or the aggregator behaviour by using methods such as interactive protocols between the base station or the querier and normal sensor nodes. We provide insights into the aggregation phase verification phase security primitives used to defeat the considered adversary security services offered and weaknesses of each protocol. Due to lack of space we discuss eight representative protocols in detail four for each model and summarize other protocols in subsections 4.1.5 and 4.2.5. 4.1 Single Aggregator Model The aggregation process in this model takes place once between the sensing nodes and the base station or the querier. All individual collected physical phenomena PP in WSNs therefore travel to only one aggregator point in the network before reaching the querier. This aggregator node should be powerful enough to perform the expected high computation and communication. The main role of the data aggregation might not be fully satisfied since redundant data still travel in the network for a while until they reach the aggregator node as shown in Figure 2-A. This model is useful when the network is small or when the querier is not in the same network. However large networks are unsuitable places for implementing this model especially when data redundancy at the lower levels is high. Examples of secure data aggregation protocols that follow the one aggregator model are Du et al. s protocol 2003 Przydatek et al. s protocol 2003 Mahimkar and Rappaport s protocol 2004 and Sanli et al. s protocol 2004 . These protocols are discussed in the following subsections. 4.1.1 Witness-based Approach for Data Fusion Assurance in WSNs Du et al. 4.1.1.1 Description Du et al. proposed a witness-based approach for data fusion assurance in WSNs 2003 . The protocol enhances the assurance of aggregation .
