Glossary
Pseudonymization
Pseudonymization replaces a direct identifier with a substitute value, where the mapping back to the original identifier is held separately and can be used to reverse the substitution by whoever controls that mapping. This is meaningfully different from genuine anonymization, which is meant to be irreversible by design — pseudonymized data is still, in principle, tied back to a real individual for anyone holding the corresponding key.
Because the mapping itself is what actually protects a pseudonym from being reversed, that mapping deserves the same access-control rigor as any other sensitive credential — pseudonymization provides essentially no protection if the mapping between pseudonym and real identity is left about as exposed as the original identifier would have been.