Method for operating an electronic data processing system and electronic data processing system

A method is disclosed for operating an electronic data processing system (10) operable under an operating system. The electronic data processing system has a boot system (13) for selectively loading an operating system from one of a plurality of storage media (12, 30). The boot system is accessible to an external user after the user executes an identification protocol with the boot system. The identification protocol is a challenge-response protocol based on a challenge generated by the boot system. More particularly, the challenge is randomly generated by the boot system and communicated to the user in an outgoing message and the user generates a response to the challenge as an incoming message to the boot system. A specific application is related to an electronic data processing system, and to a weighing scale (1), where the authentication system includes the electronic data processing system.