Securing wireless sensor networks against node capture is a challenging task. All well-known random key pre-distribution systems, including the Eschenauer and Gligor's pioneering scheme, its extensions, as well as threshold schemes, become insecure when a large number of nodes are captured. We propose a general technique, called virtual key ring, that can effectively strengthen the resilience of random key predistribution systems against node capture attacks by reducing the pre-loaded keying material while maintaining secure connectivity of the network. The technique is general and applicable to many key predistribution systems. We however focus on the original EG scheme and propose a virtual key ring system based on this pioneering scheme. We provide detailed mathematical analysis and a security proof for the system, and use extensive simulation to validate the analysis and to compare performance of the new system with the original EG scheme. We also present simulation results f...