Abstract: A method of protecting an electronic device from unauthorized reprogramming, the electronic device comprising a data memory and a key memory, the method comprising loading into the key memory a predetermined public key of a cryptographic public key mechanism for verifying subsequent data items to be loaded into the data memory, the subsequent data items being signed with a corresponding private key; characterized in that the method further comprises setting a permanent identifier in the electronic device, the permanent identifier including an identifier identifying an entity authorized to reprogram the electronic device and an indicator identifying a selected one of a number of categories of public keys.

Abstract: Method of producing an electronic device comprising a data memory for storing data items and a key memory for storing at least one cryptographic key of a cryptographic public key mechanism. The method comprises the steps of loading a factory public key into the key memory; and loading factory software signed with a factory private key corresponding to the factory public key into the data memory. The method further comprises the steps of loading into the key memory a product public key different from the factory public key for verifying subsequent data items to be loaded into the data memory after delivering the electronic device to a customer the subsequent data items being signed with a corresponding product private key; and disabling the factory public key prior to delivering the electronic device to the customer.