A Question about Research mi_lira_2021: Why is logpdf used instead of logcdf?

[axelabb]

Hi,
I have a question regarding how the score for the offline attack is calculated in the Research mi_lira_2021 code.

In the code the score is calculated using logpdf

score = scipy.stats.norm.logpdf(sc, mean_out, std_out+1e-30)

but if I understand correctly this does not match equation 4 in the paper that describes how the score should be calculated. The equation looks like this $\Lambda = 1- Pr[Z > \phi (f(x)_{y} ) ]$, where $Z \sim \mathcal{N} (\mu_o, \sigma^2_o)$ which should mean that cdf should be used and not pdf. Is there any particular reason for why the pdfis used in the implementation over cdf?