Contributed by Hassan Salmani; University of Connecticut
The Trojan trigger consists of two comparators and one flip-flop at the output of each comparator. The comparators drive the clock inputs of the flip-flops. The data input of the first flip-flop is '1' and the output of the first flip-flop is connected to the data input of the second flip-flop. The output of the second flip-flop is gated by the inverted test enable signal to ensure Trojan activation only in the functional mode. The Trojan payload is a MUX on an output port. Unless the Trojan gets activated, the output port functions as normal; otherwise, the output port leaks an internal signal.