Wireless sensor networks have proved to be useful in several applications, such as environment monitoring, Traffic Control, Defence etc. In a large sensor network, in-network data aggregation (i.e., combining partial results at intermediate nodes during message routing) significantly reduces the amount of communication and energy consumption. Recently, the research community has proposed a robust aggregation framework called synopsis diffusion which combines multipath routing schemes with duplicate-insensitive algorithms to accurately compute aggregates (e.g., Count, Sum) in spite of message losses resulting from node and transmission failures. However, this aggregation framework does not address the problem of false sub aggregate values contributed by compromised nodes resulting in large errors in the aggregate computed at the base station, which is the root node in the aggregation hierarchy. This is an important problem since sensor networks are highly vulnerable to node compromises due to the unattended nature of sensor nodes and the lack of tamper-resistant hardware. Since packet losses and node failures are relatively common in WSNs. Several researchers proposed to use a ring topology instead of a tree topology, where a node on the aggregation hierarchy is allowed to have multiple parents. In a ring based aggregation algorithm, an individual node's contribution to the aggregate reaches the base station possibly via multiple paths through the intermediate nodes. In the subsequent query aggregation phase, starting in the outermost ring, each node generates a local synopsis relevant to the query, and broadcasts it to its neighbours. There would be possibility of different attacks like Falsified sub aggregate attack, Falsified local value attack etc. in the process of computing aggregates. The objective of this research is to design an efficient attack resilient computation algorithm, so that the algorithm would guarantee the successful computation of the aggregate even in the presence of an attack. Copyright © 2015 American Scientific Publishers All rights reserved.