1. A method of loading data into a data processing device, comprising the steps of: receiving a payload data item by the data processing device; performing a cryptographic authentication process to ensure the authenticity of the payload data item by calculating an audit hash value of at least the received data item; storing the authenticated received payload data item in the data processing device; and integrity protecting the stored payload data item, the integrity protecting comprising calculating a reference message authentication code value of a combined data item derived from at least the audit hash value and a random number or at least the audit hash value and a version control data item, wherein the calculating uses a secret key stored in the data processing device as an input.