5. The following questions are about PUF-based applications: (a) What applications do you know about PUFs? (b) Can you describe in your own words about what is PUF-based key generation? (c) Why do we say that PUF-based key generation can tolerate ZERO bit flip errors? (d) In the model-building attacks, the adversary who has access to a PUF instance could collect a subset of challenge-response pairs with which to train a machine learning algorithm (ML) to build an accurate model of the PUF instance. Why do we say that model-building attack is NOT APPLICABLE to PUF-based key generation?