Privacy

Pseudonymization

Processing personal data so it can no longer be attributed to a specific person without additional information kept separately.

Pseudonymization is a data protection technique where personal data is processed in such a manner that it can no longer be attributed to a specific data subject without the use of additional information, provided that such additional information is kept separately.

Key Characteristics

  • The data remains personal data — it is not the same as anonymization
  • A lookup key or table exists that can re-identify the individual
  • The key must be stored separately with appropriate access controls
  • Pseudonymized data is still subject to the GDPR

Examples

  • Replacing names with random identifiers in a research dataset
  • Using hashing to replace email addresses with hash values
  • Replacing user IDs with pseudonyms in analytics

GDPR Article 4(5). Encouraged by Articles 25 and 32.

Related Terms

Personal DataPrivacy

Any information that can identify a living individual, directly or indirectly.

Privacy by DesignPrivacy

An approach that embeds privacy protections into systems and processes from the start, rather than adding them later.

AnonymizationPrivacy

The irreversible process of altering data so that individuals can no longer be identified, even indirectly.

HashingTechnical

A one-way mathematical function that converts data into a fixed-length string — used for password storage and data integrity.

ProfilingPurpose Limitation