Removal, Masking, Encryption, Hashing, or Replacement of Direct Identifiers
LOW MODERATE HIGHRequirements NIST SOURCE
Remove, mask, encrypt, hash, or replace direct identifiers in a dataset.
Discussion (NIST Supplemental Guidance)
There are many possible processes for removing direct identifiers from a dataset. Columns in a dataset that contain a direct identifier can be removed. In masking, the direct identifier is transformed into a repeating character, such as XXXXXX or 999999. Identifiers can be encrypted or hashed so that the linked records remain linked. In the case of encryption or hashing, algorithms are employed that require the use of a key, including the Advanced Encryption Standard or a Hash-based Message Authentication Code. Implementations may use the same key for all identifiers or use a different key for each identifier. Using a different key for each identifier provides a higher degree of security and privacy. Identifiers can alternatively be replaced with a keyword, including transforming "George Washington" to "PATIENT" or replacing it with a surrogate value, such as transforming "George Washington" to "Abraham Polk."
Implementation Guidance
Original engineering commentary written for this explorer — not NIST source text and not authoritative guidance.
No engineering interpretation has been authored for SI-19(4) yet. This section is architected to receive it — see the Requirements and Assessment sections above for the authoritative NIST source content in the meantime.
Assessment
Assessment Objectives
- direct identifiers in a dataset are removed, masked, encrypted, hashed, or replaced.
Examine
[SELECT FROM: System and information integrity policy; system and information integrity procedures; personally identifiable information processing policy; de-identification procedures; system configuration; documentation of de-identified datasets; tools for the removal, masking, encryption, hashing or replacement of direct identifiers; system security plan; privacy plan; privacy impact assessment; privacy risk assessment documentation; other relevant documents or records].
Interview
[SELECT FROM: Organizational personnel responsible for de-identifying the dataset; organizational personnel with information security and privacy responsibilities].
Test
[SELECT FROM: Automated mechanisms supporting and/or implementing the removal, masking, encryption, hashing or replacement of direct identifiers].
STIGs & CCIs
No STIG checks or CCI mappings are currently loaded for SI-19(4). This section is architected to display, per product: STIG ID, Finding ID, Severity, Title, Description, Check, Fix, CCI, and NIST control mapping — but nothing is populated here until a real DISA STIG/CCI dataset is ingested.
Learn more about STIG/CCI integration →Evidence
Categorized from the SP 800-53A "Examine"/"Test" artifact list above by keyword — not an authoritative NIST evidence list.
Policy
- System and information integrity policy
- personally identifiable information processing policy
- system security plan
- privacy plan
Configuration
- system configuration
Testing
- Automated mechanisms supporting and/or implementing the removal, masking, encryption, hashing or replacement of direct identifiers
Other Records
- system and information integrity procedures
- de-identification procedures
- documentation of de-identified datasets
- tools for the removal, masking, encryption, hashing or replacement of direct identifiers
- privacy impact assessment
- privacy risk assessment documentation
- other relevant documents or records