Method For Operating A Tachograph And Tachograph

A method for operating a tachograph having an application controller and a security controller, wherein the application controller has an associated memory that stores a program executed by the application controller, and the security controller has an associated further memory that stores a further program executed by the security controller, wherein the application controller is connected to the security controller, the method comprising:

• providing an encrypted program code having at least one associated signature to the security controller;
• decrypting by the security controller the encrypted program code;
• verifying the decrypted program code using the at least one signature;
• detecting whether the decrypted program code is intended for at least one of the application controller and the security controller;
• replacing at least one of the program in the memory and the further program in the further memory with the decrypted program code based at least in part on the detection;
• and
• clearing at least one of the at least partly replaced program and the at least partly replaced further program for execution based at least in part on a result of the verification.

A tachograph comprising:

• an application controller connected to a security controller having an associated memory that stores a program that can be executed by the application controller;
• and
• the security controller having an associated further memory that stores a further program that can be executed by the security controller, the security controller configured to:
• decrypt an encrypted program code that has been made available to the security controller, the encrypted program code comprises at least one signature associated with the program code, and to verify it using the at least one signature;
• detect whether the decrypted program code is intended for at least one of the security controller and the application controller;
• at least partly replacing the further program in the further memory with the decrypted program code based at least in part on the detection;
• and
• clearing the at least partly replaced further program for at least one of execution and providing the application controller with the decrypted program code based at least in part on a result of verification;
• and
• the application controller is configured to:
• take the decrypted program code as a basis for at least partly replacing the program in the memory with the decrypted program code;
• and
• take the available result of the verification as a basis for clearing the at least partly replaced program in the memory for execution.