The sensor networks application domain continues to increase with the need for an

effective security mechanism. The fact that WSN often deal with sensitive data operating in

hostile and unexpected environments, makes the concept of security considered essential.

However, because of limited resources and low computing capacity of a sensor node, the

development of a mechanism that ensures security is a real design challenges.

In this report we have tried to propose a new security mechanism dedicated to WSN. Our

main objective is to secure the process of transferring data to the base station. The proposed

protocol protects transferred data against intruder nodes attacks, using a security

mechanism based on the use of control message MAC (Message Authentication Code) for

authentication. Our protocol performances are evaluated using the simulator NS2.