An anonymous identifier is a number or string that is unique to the person, but from which it is hard or impossibel to determine which person it refers to. It is used, in pseudonymised data to help connect together different record that refer to the same indivdiual. Sometiems, the lost that connects individuals with identifiers is deleted after use in order to prevent accidental disclosure, but sometime sit has to be retaianied in order to correctly pseudonymise further data. In these case the authority file linking ids to people needs to be maintained at a much higher level of security to the pseudonomised data itself.
Used on page 391
Also known as anonymous id