Format-preserving encryption for PII in Polars: FF3-1 vs FF1 for RUT, CPF, and DNI

You need to hand a dataset of Chilean RUTs to an outside analytics team. They will join it against other tables by identifier, run the cohort analysis, and hand back a model. They do not need to know, and should never learn, who any of these people are. Asterisk the RUT column and the join dies on c