https://www.bleepingcomputer.com/news/security/bmw-fixes-sec...
I have written my own ECU flashing tool for Simos18 as well as a message injection system for the VW/Audi MQB platform (similar to the commercially available PolarFIS product). Really the only protection at all is that ECU flash files are encrypted in transit (on dealer DVDs) and over the wire, but with a fixed AES key and IV which is present in plaintext on the flash once the file is written. The CAN gateway messages are generally not encrypted, both over the infotainment CANbus and the powertrain CANbus.
Almost all cars are nearly completely insecure once you have interior physical access - which, IMO, is mostly OK as long as the bus wiring is in a reasonable location inaccessible to someone like a taxi passenger.
What is more interesting is the prevalence of head units with wireless or remote access - over 3G, Bluetooth, and WiFi. Compromising these hosts (and then finding a pivot or escalation between the infotainment bus and the powertrain bus via the gateway) is an interesting attack vector.
May be i was wrong, but there are nothing on the CAN bus in latest generations of Mercedes.
It does seem like most commodity FlexRay systems are still hackable although it's certainly harder than CAN where you can just attach a node and start spewing garbage from whichever address you'd like: https://brage.bibsys.no/xmlui/bitstream/handle/11250/2453093... (I'd expect all modern BMWs to be similar or identical to this MINI for cost reasons, although as evidenced I may be surprised!).
I still haven't found a robust use of end to end encryption anywhere in an automotive application - even the "most protected" routines like ECU flashing seem to be protected by weak XOR/known-secret seed/key security in tandem with symmetric cryptography using fixed key material.
Looks like it is AES-CBC with static IV, not very good, but not that bad. Still very very far from hackable. Even if you will be able to guess AES key (somehow) there are no way to hack asymmetric keys. Sure you can leak them during delivery of firmware, but i really feel that this is not the case for Mercedes. Also that's how they make money (and provide security) - lock down access to everything.
At AUTOSAR encryption docs there are RSA and ED25519, that is very good encryption obviously. (https://www.autosar.org/fileadmin/user_upload/standards/clas...)