Pseudonymisation (pseudo anonymisation) is the processing of personal
data in such a way that the data can no longer be related to the data
subject without the use of additional information. However, the
additional information must be kept separately and subject to technical
and organisational measures to ensure that data subjects remain
unidentifiable. As opposed to anonymisation, pseudonymisation is a
reversible process, which means that data subjects can be re-identified
if access to the additional information is enabled.