An anonymous identifier is a number or string that is unique to the person, but from which it is hard or impossible to determine which person it refers to. It is used in pseudonymised data to help connect together different records that refer to the same individual. Sometimes, the list that connects individuals with identifiers is deleted after use in order to prevent accidental disclosure, but sometimes it has to be retained in order to correctly pseudonymise further data. In these cases the authority file linking ids to people needs to be maintained at a much higher level of security to the pseudonomised data itself.
Used in Chap. 17: page 253
Also known as anonymous id