Protecting Ring Oscillator Physical Unclonable Functions Against Modeling Attacks

One of the most common types of Physical Unclonable Functions (PUFs) is the ring oscillator PUF (RO-PUF), a type of PUF in which the output bits are obtained by comparing the oscillation frequencies of different ring oscillators. One application of RO-PUFs is to be used as strong PUFs: a reader sends a challenge to the RO-PUF and the RO-PUF’s response is compared with an expected response to authenticate the PUF. In this work we introduce a method to choose challenge-response pairs so that a high number of challenge-response pairs is provided but the system has a good tolerance to modeling attacks, a type of attacks in which an attacker guesses the response to a new challenge by using his knowledge about the previously-exchanged challenge-response pairs. Our method targets tag-constrained applications, i.e. applications in which there are strong limitations of cost, area and power on the system in which the PUF has to be implemented.