33 Bits of Entropy: Myths and Fallacies of "Personally Identifiable Information"

Data is the currency of the digital economy, but increasing data collection by companies and sharing with third parties threatens privacy. \Anonymization" is the usual answer to privacy concerns, typically implemented via removal of \personally identiable information." Sweeney’s work on reidentication of Massachusetts hospital records showed that naive deidentication via PII removal can be reversed [3]. That led to a cat-and-mouse game between deidentication