Partially Programmable Circuit Design Oriented to masking Trojan Circuits
The enhanced utilization of outsourcing services for a part of VLSIs (Intellectual Property cores, reprogramming components based on FPGA and so on) to cut VLSI cost increases risk of inserting Trojan Circuits (TCs) that may destroy VLSI or provide leakage of confidential information. TCs as a rule act in rare operation situations, therefore they are not detectable neither during VLSI verification nor VLSI testing. The approach to partially programmable circuit design from gates, programmable LUTs and MUXs oriented to masking TCs is suggested. The approach allows getting a circuit that masks TC when it has been found or deriving a circuit that is tolerant to TCs actions. The method of reprogramming LUTs for masking TCs is developed. The condition of replacing a function corresponding to free LUT input is formulated. It is based on using incompletely specified Boolean functions of internal nodes of the circuit. The functions are obtained with using operations on ROBDDs corresponding to the circuit fragments. The operations have a polynomial complexity.