The response r will always
be different for the same challenge c because in addition to
the physical properties of the corresponding physical object,
the response r also depends on environmental noise (e.g.,
temperature or supply voltage variations) [19]. PUFs can map
different responses r to the same challenge c by using a small
circuit, called Fuzzy Extractor that takes an additional input
w to remove the effects of noise.
A challenge-response protocol for