1. A system-on-chip comprising: a plurality of circuit instances having respectively a first plurality of nodes, wherein the plurality of circuit instances are designed to provide nominally a same value at each of the first plurality of nodes; a selector module configured to generate a first selection signal; a circuit instance module configured to (i) monitor a plurality of states of the first plurality of nodes, and (ii) based on the first selection signal, select (a) two or more of the plurality of states of the first plurality of nodes, or (b) two or more parameter values generated based on the two or more of the plurality of states of the first plurality of nodes; a first comparing module configured to compare (i) the two or more of the states of the first plurality of nodes, or (ii) the two or more parameter values, and based on the comparison, output a first bit of (i) a silicon fingerprint of the system-on-chip, or (ii) a unique response code of the system-on-chip; a second comparing module configured to generate a comparison signal based on a comparison between the silicon fingerprint and the unique response code; a mode module configured to operate in a secure mode based on the comparison signal; and a countermeasure module configured to, based on the comparison signal, perform a countermeasure.