Applying Incompletely Specified Boolean Functions for Patch Circuit Generation
Anzhela Yu. Matrosova, Viktor A. Provkin · 2021
We consider combination circuit C and some its nodes that faults are detected on the last stages of circuit fabrication. Besides, injections of Trojan Circuits (TCs) in certain circuit C lines may be also detected. (It is assumed that TC payload output is inserted into a line of a combinational circuit). In both cases circuit C improper functions are changed for incompletely specified Boolean functions correlated with the corresponding fault nodes or the circuit lines of correct circuit C. That is why masking of circuit faults and TCs injections may be reduced to implementation of a patch circuit that realizes the correct system of incompletely specified Boolean functions, in particular, depending on internal circuit C variables. The correct system is calculated with using SAT solver. Patch circuit inputs are connected with internal nodes of circuit C that precede both fault nodes and the lines. Patch circuit outputs are connected with nodes that are fed either by fault nodes or by circuit lines in which Trojan circuits are inserted. Experimental results are executed on ISCAS test circuits. The results show that patch circuits as a rule are simpler than duplication subcircuit with fault node as outputs and preceding nodes as inputs.