Hardware Trojan Prevention and Detection by Filling Unused Space Using Shift registers, Gate-chain and Extra Routing

Nowadays the security of the design is so important because of the different available attacks to the system. the main aim of this paper is to improve the security of the circuit design implemented on FPGA device. Two approaches are proposed for this purpose. The first is to fill out empty space using flipflops and LUTs so that there is no available space for inserting a hardware Trojan. We name this filling structure as Gatechain. The second approach increases the security of the implemented design by identifying the low observable/controllable points of the main design and wiring them to the unused ports or the predesigned Gatechains. The proposed solutions not only prevent Trojan insertion but also increase the Trojan detection capabilities. Simulation results on Xilinx devices implementing different benchmarks show that the proposed method incurs dynamic power overhead just in test mode with less than one percent of delay overhead for critical path in normal mode.