As multifactor authentication has massively spread over almost every security-critical application, electronic devices gained a key role providing a "something only the user has" evidence. Rather than storing a secret key inside a device, as it is usually done, a promising alternative is the employment of so-called Physical Unclonable Functions (PUFs). PUFs exploit physical randomness of a device in order to create a secure challenge-response authentication mechanism. A PUF is therefore a function which associates each challenge to a response, according to some physical and immutable properties of a device. PUFs can be divided into weak and strong ones. The former are characterized by a large set of challenge-response pairs (CRP) and can be used for both authentication and identification.