Knowing millions of students too well: High-entropy scores as deterministic quasi-identifiers for re-identification and data leakage in the Brazilian high school exam

Researchers found that high-entropy scores (statistical measurements of randomness or uniqueness in data) from Brazilian high school exam results can act as quasi-identifiers (partial pieces of information that can identify individuals when combined with other data), allowing attackers to re-identify students and leak their personal data even when direct identifiers like names are removed. The study shows that seemingly anonymous datasets can still expose millions of students' information through these numerical patterns.