Three models within the Audo Max microcontrollers from Infineon have SHE (secure hardware extension). The 32bit microcontrollers are claimed to extend the tamper-proofing of ECUs (electronic control units) and protect against tuning, for example. Tamper-proofing and anti-theft protection for automotive control units have been confined to software or coupled with additional external hardware, meaning they could be circumvented. These monolithic microcontrollers are claimed to offer more that basic software protection because they integrate a secure keystore which cannot be read without access authorisation. The level of integration means that the communication does not run via interceptable external bus systems, as is the case when using external security chips. The SHE cryptographic module encrypts access codes with up to 128 bits. A complementary set of hardware functions prevent the application code from being illegitimately read and altered, or identify ECUs in the system network. Even if such an ECU were to be fitted in another, identical vehicle, its engine performance characteristics could not be changed: the cryptographic individual key of an ECU has to match all the cryptographic keys within the ECU network of a vehicle. That key is stored in the SHE. The keystore cannot be read by the diagnostic software and therefore the secret keys are protected particularly well from software attacks. Furthermore, SHE guards against any tampering even during boot-up: the secure boot feature ensures that only the original software is loaded during the boot process. Currently there are three devices, each with 4Mbyte flash memory but with different clock frequencies and packages. The TC1798 is a 300MHz microcontroller in a BGA-516; the TC1793 is a 270MHz device in a BGA-416 and the TC1791 is a 240MHz microcontroller in a BGA-292. Volume production has begun for the TC1793; with the TC1798 and TC1791 planned from Q1, 2012.
