We propose a security approach that uses secret key cryptography and key management along with re-keying support. A salient feature of our approach is that a secret key is embedded in the source code of every node to protect the other keys in its nonvolatile memory. Even the node is captured physically; the sensitive information cannot be retrieved. Our key selection protocol uses the node ID and some basic rotate and multiplication function to select the key for current data transmission. Because of this dynamic key selection, our approach identifies the replay attack, DoS attack and Sybil attack. Our simulation results shows that our security mechanism efficiently controls various attacks with lower resource requirements and the network resilience against node capture is substantially improved.