 GDPR Data Protection by Design and by Default principles as embodied in pseudonymization require protection of both direct and indirect identifiers so that personal data is not cross-referenceable (or re-identifiable) via the Mosaic Effect without access to “additional information” that is kept separately by the controller.Because access to separately kept “additional information” is required for re-identification, attribution of data to a specific data subject can be limited by the controller to support lawful purposes only.Existing privacy regulations typically protect information that has been modified, so that the data is deemed anonymized, or de-identified.