One feature pertains to an integrated circuit (IC) that includes a first plurality of ring oscillators configured to implement, in part, a physically unclonable function (PUF). The IC further includes a second plurality of ring oscillators configured to implement, in part, an age sensor circuit, and also a ring oscillator selection circuit that is coupled to the first plurality of ring oscillators and the second plurality of ring oscillators. The ring oscillator selection circuit is adapted to select at least two ring oscillator outputs from at least one of the first plurality of ring oscillators and/or the second plurality of ring oscillators. Notably, the ring oscillator selection circuit is commonly shared by the PUF and the age sensor circuit. Also, the IC may further include an output function circuit adapted to receive and compare the two ring oscillator outputs and generate an output signal.