[ref] https://www.iacr.org/archive/ches2011/69170391/69170391.pdf
Example: we designed a PUF function in someway.
The function generate 50 responses, saying '1011101' and '1001001' are two of the responses.
The hamming distance is 2 and the normalized hamming distance is 2/7 = 0.285. Keep on calculating all the responses and construct a histogram like Fig. 1.
The mean value of this histogram is the uniqueness of this PUF, i.e. about 46% with std of 3.8%.
