Due to limited energy capacity of batteries, the function lifetime of sensor networks in general is longer than the operational lifetime of single nodes. Therefore, to keep the network working, multiple deployments of sensor nodes are needed. Due to their nature and their operational resource constraints, sensor networks are vulnerable to various types of attacks. Key pre-distribution has been shown to be an effective way to establish secure communication in sensor networks. However, existing schemes of key pre-distribution assume the use of the same pools in various deployments of sensors. We analyzed the vulnerability of the existing key pre-distribution schemes arising out of the repeated use of fixed key information through multiple deployments. We also developed SCON, an approach for key management that provides a significant improvement in security through the use of a unique key pool for each phase of deployment. Nodes of different deployments connect through special nodes call...