AbstntclSensor networks include nodes with limited computation and communication capabilities, One of the basic functions of sensor networks is to sense and transmit data to the end users. The 1·esource constraints and security issues pose a challenge to information aggregation in large sensor networks. Bootstrapping keys is another challenge because public key cryptosystems are unsuitable for use in resource-constrained sensor networks. In this paper, we propose a solution by dividing the problem in two domains. First, we present a protocol for establishing cluster keys in scnso1· networks using verifiable secret sharing. We chose elliptic curve cryptosystems for security because of their smaller key size, faster computations and reductions in processing power. Second, we develop 11 Secure Data Agg1·egation and Verification (SecureDAV) protocol that ensures that the base station never accepts faulty aggregate readings. Integrity check of the readings is done using Merkle Hash Trees avoiding over-reliance on the cluster-heads.