In recent years, development of wireless communications and ability to design and manufacture of sensors with low energy usage, small size and low cost, cause these networks to be used widely. Energy, process and memory constraints, as major restrictions in these networks need researchers’ efforts to achieve new and creative solutions. Access to the secure networks, particularly is vital consistent to having low energy consumption. One of the important problems of these networks is synchronization of the nodes. Precise and synchronized clocks can be more important in sensor networks than the others. Adversary tries to disturb time synchronization by altering and faking messages, delaying or replying them, compromising the nodes and sending false messages via them. In addition to the importance of secure synchronization, in some secure applications and cryptographic protocols, synchronization is needed. So, there is a trade off between security and synchronization. In this thesis, we have focused on secure synchronization. Up to now, there is not any method that be able to provide both synchronization and security needs of sensor networks simultaneously. In the other word, there has not been any efficient technique that be resist against all attacks including inciders via compromised nodes yet. In the thesis, in this way, we study at first requirements of secure time synchronization in context of sensor networks then the available solutions along with their weaknesses. The suggested method is capable to provide precise synchronization, low communication and computational overhead, low convergence time and high security against internal and external attacks. This method uses broadcast authentication to prevent altering and faking the messages as well as comparing measured delay with a given threshold to object intentional delay. In comparison with TESLA method, that is an efficient broadcast authentication method, the suggested authentication method has some advantages. The most important one is that it do not need initial synchronization. Also redundancy helps this method to be resilient against compromised nodes. Simulations show that our synchronization method has good precision and convergence time. Moreover, the communication and computational overheads in our scheme are absolutely mild. Keywords: wireless sensor network, synchronization, secure synchronization, authentication, pulse delay, compromised node.
