Abstract: This invention relates to a data system that anonymizes personalized event data, by receiving the personalized event data containing an encrypted personal identifier and determining whether an entry exists for the encrypted personal identifier in a key database. The encrypted personal identifier may be associated with a system identifier that uniquely identifies the encrypted personal identifier and is uniquely associated to one system identifier. If no entry is detected in the key database for the received encrypted personal identifier, then a new entry for the key database is generated in which the received encrypted personal identifier is uniquely associated to a new system identifier.