A PUF authentication protocol could follow the following steps.

C $->$ S: ID $=$ get PUF ID

S $->$ A : send$($ID$)$

A $->$ S: $\{$CRP$\}$

S: select challenge c$1$ and associated r$1$

S $->$ C: send challenge c$1$

C: r$2=$ F$($c$1)$

C $->$ S: send r$2$

S: d $=$ HD$($r$1,$ r$2)$

S: check d $$ dth where S is the server, C is the client, A is the certification authority, and hth is Hamming distance threshold. Explain possible weaknesses of this protocol.