A method of updating a data entry stored on a data storage unit, the data entry including data elements that are unique to the data storage unit and the data entry, may begin with generating, at the data storage unit, an update request that includes the data entry for transmission to an authority authorized to update the data entry. The authority then extracts extracting at the authority the unique data elements from the update request and verifies the authenticity of the data storage unit and data entry from the unique data elements. The authority then generates an updated data entry including a further data element unique to the updated data entry and derived from the updated data. The authority then transmits the updated data entry to the data storage unit. The method may then include storing the updated data entry on the data storage unit.