Clock synchronization is of critical importance for several applications in wireless and mobile sensor networks; for example to determine the order and time of events. Although several protocols to achieve clock synchronization have been developed, they may not be secure. For instance, a link controlled by an attacker could delay packets it forwards in ways which would cause the nodes sharing that link to obtain faulty time estimates. In this paper, we propose a secure network-wide clock synchronization protocol. It also allows nodes to securely discover the network topology by detecting and isolating links that behave inconsistently. This networkwide clock synchronization protocol is built on ideas in  where inconsistent attacks are detected using timing information alone under certain conditions. The proposed protocol has been implemented and the results of experimentation on a twenty-five node network are presented.