Wireless sensor networks (WSNs) have been widely used in many areas, such as early earthquake monitoring, building structure monitoring, and military surveillance. In this thesis, we focus on the wireless sensor network deployed in the battlefield, using random key predistribution scheme. Firstly we presented an analysis of the security impacts by node capture attack. Also, based on the node cloning attack, we proposed a new attack scheme, called compromised key redistribution attack, and discussed related attack scenarios. Besides, we have found out and conjectured that, when the overlapping factor of compromised key set is larger than 0.05, it is very possible (almost 90%) that the number of distinct compromised keys is 10.5% of the original key pool. This conjecture helps the adversary estimate the approximated size of original key pool by calculating the overlapping factor, thus calculate the probability that malicious nodes successfully establish connections with legitimate nodes.