Hardware trojan detection and prevention is paid more and more attention in recent years due to the great potential threat imposed by hardware trojan to the whole integrated circuit industry. Using a combination of new design techniques and new memory technologies, we present a new approach that detects a wide variety of hardware Trojans during IC testing and also during system operation in the field. It can also prevent a wide variety of attacks during synthesis, place-and-route, and fabrication of ICs. It can be applied to any digital system. This project demonstrate its applicability for both application-specified integrated circuits and field-programmable gate arrays. Using fabricated test chips with Trojan emulation capabilities and also using simulations, we demonstrate: 1) our approach can prevent 99.98% of specific attacks (simulated) that utilize detailed knowledge of the design being attacked 2) our approach never produces any false positives, i.e., it does not report attacks when the IC operates correctly.