In wireless sensor networks securing code update is essential for many crucial military applications. The nodes deployed in border areas in the military region called the border sensor nodes are the more sensitive nodes. The border sensor nodes need to do some special tasks compared to other intermediate sensor nodes. So the code update to be sent to the border nodes will be different from the other intermediate nodes. Thus, the code updates that need to be sent to the border sensor nodes should be highly confidential.
The confidentiality of these code updates cannot be compromised at any cost, hence Key management is also an important issue. A protocol is developed to securely send the code update to the border sensor nodes via intermediate nodes. The Protocol is implemented using necs on TinyOS platform and evaluated the performance.