Physical unclonable function system based on capacitance variations

Provided is a physical unclonable function (PUF) system, which includes at least two PUF cells and a control signal generation unit generating a control signal to control the operation of the PUF cells. Each PUF cell includes: a charge sharing circuit operated according to the control signal, and having a circuit with at least two capacitors being arranged in parallel; a comparator detecting a capacitance variation of some of the capacitors in the charge sharing circuit; and a logically exclusive-OR gate performing a logically exclusive-OR operation on an input signal (challenge) and a signal outputted from the comparator to output an output signal (response), which is a result of the logically exclusive-OR operation. Therefore, the PUF cells based on the capacitance variations is achieved using the present invention, to secure the reliability and thus obtain the stable output, without being affected by external environments such as voltage or temperature.