A multi-die device a first die containing a plurality of first die signal path elements configured to propagate a stimulus signal and a second die containing a plurality of second die signal path elements configured to propagate the stimulus signal. The multi-die device further includes an interposer configured to establish signal communication between the first die and the second die so as to deliver the stimulus signal from the plurality of first die signal path elements to the plurality of second die signal path elements to generate a propagation delay. The propagation delay is used to generate a single unified PUF response that is indicative of the authenticity of the multi-die device.