In accordance with a first advantageous embodiment, the functions of the functional blocks also permit access to the application program executed on the embedded device. Firmware is present on the embedded device that acts as the operating system. The firmware can also provide a so-called “runtime” that is preferably real-time capable and executes an application program. The application program can, for example, include control commands for controlling an industrial plant and the like. The functions of the functional blocks can therefore relate both to the firmware and to the application program. Access to functions of the firmware and/or of the application program can thus take place by the authentication for different levels.

In accordance with a further advantageous embodiment, the authentication for different levels takes place by different keys. The security of the embedded device is additionally increased by the use of different keys.

The embedded device preferably uses a key-based cryptographic process for the authentication for a level. A random number is, for example, generated, wherein the key for the authentication for the respective level is generated by encrypting the random number by means of a public key and the embedded device decrypts the key by means of a private key and compares the result of the decryption with the random number. The encryption of the random number can be carried out by a user who has access to the embedded device.