Per-regime identifier catalogs

Full per-regime enumerations behind pii-categories.md. The cross-jurisdiction map there is the fast scoping tool; this file holds the detail behind each column.

GDPR - personal data (Article 4(1))

Definition (Article 4(1)): "any information relating to an identified or identifiable natural person ('data subject')" (gdpr-info.eu/art-4-gdpr/).

The article enumerates identifiers that make a person identifiable:

Source: Article 4(1) GDPR (gdpr-info.eu/art-4-gdpr/).

GDPR Article 9 - special categories of personal data

Article 9(1) lists categories whose processing is prohibited by default unless one of the Article 9(2) exceptions applies:

• Racial or ethnic origin
• Political opinions
• Religious or philosophical beliefs
• Trade-union membership
• Genetic data (defined in Art. 4(13))
• Biometric data processed for unique identification (defined in Art. 4(14))
• Data concerning health (defined in Art. 4(15))
• Data concerning a natural person's sex life or sexual orientation

A masking pipeline for an EU dataset must apply at least the broader Art. 4(1) rules and stricter rules to any field falling under Art. 9 (special categories carry higher fines and must be either redacted or fully anonymised, not merely pseudonymised).

GDPR Article 4(5) - pseudonymisation vs anonymisation

"Pseudonymisation" (Art. 4(5)) keeps data attributable to a subject with additional information, kept separately. Pseudonymised data is still personal data under GDPR - it remains in scope.

Anonymised data (no longer linkable to a subject under any reasonably likely method, per Recital 26) falls out of GDPR scope. The masking pipeline must mark which output is which (masking-techniques.md explains the techniques).

CCPA / CPRA - personal information

Definition (Cal. Civ. Code § 1798.140(v)(1), as amended by CPRA): "information that identifies, relates to, describes, is reasonably capable of being associated with, or could reasonably be linked, directly or indirectly, with a particular consumer or household" (oag.ca.gov/privacy/ccpa).

Statutory categories enumerated in § 1798.140(v)(1)(A) - (K):

CPRA - sensitive personal information (SPI)

CPRA added a subcategory of personal information requiring extra protection (Cal. Civ. Code § 1798.140(ae)):

• Government identifiers - SSN, driver's licence, state ID, passport number
• Account log-in + password / financial account / debit-card / credit-card number with security code
• Precise geolocation (≤1,850 ft / 1,850 ft radius)
• Racial / ethnic origin, religious / philosophical beliefs, union membership
• Contents of mail, email, text messages (where the business isn't the intended recipient)
• Genetic data
• Biometric information processed to uniquely identify a consumer
• Health information (collected by businesses, distinct from HIPAA PHI)
• Sex life or sexual orientation

Citation: oag.ca.gov/privacy/ccpa "Sensitive Personal Information" (oag.ca.gov/privacy/ccpa).

NIST SP 800-122 - PII

Definition (citing OMB Memorandum 07-16, reproduced in NIST SP 800-122 Section 2.1): "information which can be used to distinguish or trace an individual's identity, such as their name, social security number, biometric records, etc., alone, or when combined with other personal or identifying information which is linked or linkable to a specific individual, such as date and place of birth, mother's maiden name, etc."

Citation: NIST SP 800-122:2010 §2.1, fetched from csrc.nist.gov/pubs/sp/800/122/final.

Linked vs linkable

NIST 800-122 §2.2 introduces a crucial distinction:

• Linked information is information about or related to an individual that is logically associated with other information about the individual.
• Linkable information is information about or related to an individual for which there is a possibility of logical association with other information about the individual.

A masking pipeline must consider linkable fields (e.g., birth date alone isn't identifying, but date + zip + sex is - the Sweeney 87 % rule). The pipeline shouldn't only protect direct identifiers.

Confidentiality impact levels

NIST 800-122 §3 names six factors that drive the PII confidentiality impact level (low / moderate / high):

1. Identifiability - how directly the PII identifies
2. Quantity - how many individuals' data
3. Data field sensitivity - what specific fields (SSN > name)
4. Context of use - what the PII is used for
5. Obligation to protect confidentiality - legal duty
6. Access to and location of PII - where stored, who can access

Masking aggressiveness scales with impact level.

HIPAA Safe Harbor - 18 identifiers (45 CFR § 164.514(b)(2))

For health data (PHI), the HIPAA Privacy Rule defines two de-identification methods (Expert Determination, 45 CFR § 164.514(b)(1), and Safe Harbor, 45 CFR § 164.514(b)(2)). Safe Harbor requires removing all of these 18 identifiers (per HHS guidance, hhs.gov/hipaa/for-professionals/privacy/special-topics/de-identification):

1. Names
2. All geographic subdivisions smaller than a state (street, city, county, precinct, ZIP - except first 3 digits of ZIP if population > 20,000)
3. All elements of dates (except year) directly related to the individual, including birth, admission, discharge, death; all ages over 89 → "90 or older"
4. Phone numbers
5. Fax numbers
6. Electronic mail addresses
7. Social Security numbers
8. Medical record numbers
9. Health plan beneficiary numbers
10. Account numbers
11. Certificate / licence numbers
12. Vehicle identifiers (incl. licence plate)
13. Device identifiers and serial numbers
14. Web URLs
15. IP addresses
16. Biometric identifiers (fingerprints, voiceprints)
17. Full-face photos and comparable images
18. Any other unique identifying number, characteristic, or code

A masking pipeline operating on health data must catch all 18; a detector configured only for GDPR's broader categories will miss HIPAA-required identifiers (e.g., medical record number is not explicit in GDPR Art. 4(1) - covered by "identification number" but a detector may not flag it without a HIPAA-specific recogniser).