De-Identification Handbook
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## Glossary

anonymization: process by which personal data is irreversibly altered in such a way that a data subject can no longer be identified directly or indirectly, either by the data controller alone or in collaboration with any other party (Source: (ISO 25237, 2017).

Note 1: The term is defined in a similar way under the PIPL (Art. 73(4)).

Note 2: An absolute concept of anonymization is not feasible in practice. This book interprets it as a relative concept, where the risk of re-identification, even with reasonable additional information, is minimized to a very low level.

anonymous identifier: identifier of a person which does not allow the identification of the natural person(Source: (ISO 25237, 2017)).

data linking: matching and combining data from multiple databases (Source: (ISO 25237, 2017)).

Note 1: The term "data linking" is identical to the term "linking" defined in the (ISO/IEC 20889, 2018).

data subject: person to whom data refer (Source: (ISO 25237, 2017)).

Note 1: The term "data subject" is identical to the term "data principal" defined in the (ISO/IEC 20889, 2018).

de-identification: general term for any process of reducing the association between a set of identifying data and the data subject. (Source: (ISO 25237, 2017)).

Note 1: The term "de-identification" is distinguished from the term "anonymization" under the PIPL(PIPL, 2021). De-identification under the PIPL is similar to the concept of pseudonymization in this book.

Note 2: The term "de-identification" in this handbook is identical to the definition of "de-identification process" within the (ISO/IEC 20889, 2018).

direct identifier: data that directly identifies a single individual. (Source: (ISO 25237, 2017)).

Note 1: Direct identifiers are those data that can be used to identify a person without additional information or with cross-linking through other information that is in the public domain.

Note 2: The term “directly identifying data” in (ISO 20237,2017) has been simplified according to (ISO/IEC 20889, 2018).

identifiable natural person: one who can be identified, directly or indirectly, in particular by reference to an identifier such as a name, an identification number, location data, an online identifier or to one or more factors specific to the physical, physiological, genetic, mental, economic, cultural or social identity of that natural person. (Source: GDPR Art 4(1)).

Note 1: Similar to the concept of identifiable person within (ISO 25237, 2017).

imputed value: plausible substitutes generated by applying statistical methods to replace sensitive, missing, or identifying data points, preserving data utility and privacy.

indirect identifier: data that can identify a single person only when used together with other indirectly identifying data. (Source: (ISO 25237, 2017)), modified).

Note 1: Indirect identifiers can reduce the population to which the person belongs, possibly down to one if used in combination.

Note 2: The term "indirectly identifying data" in (ISO 25237, 2017) has been simplified according to (ISO/IEC 20889, 2018).

Note 3: The term "indirect identifier" in this handbook is identical to the definitions of "indirect identifier" and "quasi-identifier".

Example Postcode, sex, age, date of birth.

irreversibility: situation when, for any passage from identifiable to pseudonymous, it is computationally unfeasible to trace back to the original identifier from the pseudonym (Source: (ISO 25237, 2017)).

linkability: property for a dataset that it is possible to associate (by linking) a record concerning a data subject with a record concerning the same data subject in a separate dataset. (Source: (ISO/IEC 20889, 2018)).

microdata: dataset comprised of records related to individual data principals (Source: (ISO/IEC 20889, 2018)).

natural person: real human being as opposed to a legal person which may be a private or public organization (Source:(ISO 25237, 2017)).

personal identifier: information with the purpose of uniquely identifying a person within a given context (Source: (ISO 25237, 2017)).

Note 1: Personal identifier can be used to directly identify a person, therefore is also directly identifying data.

pseudonym: personal identifier that is different from the normally used personal identifier and is used with pseudonymized data to provide dataset coherence linking all the information about a subject, without disclosing the real world person identity (Source: (ISO 25237, 2017)).

Note 1: This may be either derived from the normally used personal identifier in a reversible or irreversible way or be totally unrelated.

Note 2: Pseudonym is usually restricted to mean an identifier that does not allow the direct derivation of the normal personal identifier. Such pseudonymous information is thus functionally anonymous. A trusted third party may be able to obtain the normal personal identifier from the pseudonym.

pseudonymization: particular type of de-identification that both removes the association with a data subject and adds an association between a particular set of characteristics relating to the data subject and one or more pseudonyms. (Source: (ISO 25237, 2017)).

Note 1: This includes irreversible and reversible pseudonymization which is similar to the concept of pseudonymization under the GDPR.

Note 2: The pseudonymized data can no longer be attributed to a specific data subject without the use of additional information, but could be attributed to a natural person by the use of additional information (Source: GDPR Recital 26).

Note 3: The term defined in the handbook is different from the definition specified in the (ISO/IEC 20889, 2018) where "pseudonymization" refers to a type of de-identification technique.

re-identification: process of associating data in a de-identified dataset with the original data subject (Source: (ISO/IEC 20889, 2018)).

Note 1: A process that establishes the presence of a particular data subject in a dataset is included in this definition.

re-identification attack: action performed on de-identified data by an attacker with the purpose of re-identification (Source: (ISO/IEC 20889, 2018)).

re-identification risk: risk of a successful re-identification attack (Source: (ISO/IEC 20889, 2018)).