There are GDPR articles which relate to a persons ownership about their data e.g. Art. 17 GDPR Right to erasure (‘right to be forgotten’) and Art. 20 GDPR Right to data portability. In case one would anonymize the data without a way to "restore" the relation between the person (name + e-mail adress) (which in turn would allow handling of the person specific data) I'd say this would conflict with these GDPR articles. Are there data anonymization techniques which allow to "restore" the relation between name + contact e-mail after the data has been anonymized? This would allow to satisfy these GDPR rules.


Formally speaking, this is clarified in the GDPR Recital 26, unofficially titled Not Applicable to Anonymous Data:

  1. The principles of data protection should therefore not apply to anonymous information, namely information which does not relate to an identified or identifiable natural person or to personal data rendered anonymous in such a manner that the data subject is not or no longer identifiable.
  2. This Regulation does not therefore concern the processing of such anonymous information, including for statistical or research purposes.

Informally speaking, the claim that data anonymization would violate the data subject's rights to data erasure and portability, hence we should seek to use reversible anonymization techniques, sounds awkward, and against the very spirit of GDPR; and the official interpretation regarding anonymization is very clear:

Effective data anonymization is made up of two parts:

  • It is irreversible.
  • It is done in such a way that it is impossible (or extremely impractical) to identify the data subject.

In other words:

  • if a subject's data have been effectively anonymized, they are no longer personal data, hence they are no longer governed by GDPR; consequently, Articles 17 & 20 are not applicable, and this does not constitute any conflict
  • if any personal data used as a source for the anonymized ones remain, they are subject to GDPR; data subjects can exercise their right to erasure and portability for these non-anonymized data
  • if the personal data used as a source for the anonymized ones are already erased (possibly in compliance to GDPR), then neither the right to erasure nor the right to portability are applicable any more, and this does not constitute any kind of conflict either.

Notice that the fact that ensuring effective anonymization is not as clear-cut as it may sound has also been legally recognized in the Opinion 05/2014 on Anonymisation Techniques of the Data Protection Working Party:

Thus, anonymisation should not be regarded as a one-off exercise and the attending risks should be reassessed regularly by data controllers.

  • $\begingroup$ Great answer. For me it's not clear how to handle data which cannot really anonymized. Think of pictures of faces e.g. or voice recordings. In these cases the data itself could potentially identify persons even if the related meta-data (name, e-mail, geo location, etc.) is anonymized. How should be this data be handled? $\endgroup$ – thinwybk Oct 13 '20 at 15:36
  • $\begingroup$ @thinwybk the issue is not straightforward, and arguably it cannot be resolved in a comment. I will also confess that I am by no means an expert on the subject; if you need to use such data for an application, I would strongly advise to consult an expert. $\endgroup$ – desertnaut Oct 13 '20 at 15:45

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