I'm currently researching into CAN security for in-vehicle communication. I would like to know if anyone knows a reason why the CAN payloads of an ECU communication (between CAN nodes) should be encrypted when integrity, authenticity and protection against replay attacks are guaranteed.

In case of key exchange messages or other security protocol related messages that need protection against eavesdroppers encryption is undoubtedly necessary. Same goes for privacy critical data like GPS output.

However, I'm wondering why some researchers suggest encryption of any CAN payload. Is there anything useful an adversary could learn by sniffing CAN pakets which neither can be replayed nor manipulated?

  • Preventing spoofing was probably of a higher priority. Although full encryption would cut out the after market regarding 3rd party performance monitoring tools. So as a DRM maneuver it could be pretty effective. Pure profit motive. – infixed May 18 '16 at 16:57
  • I'm with you on that. DRM might be a motivation. At least for manufacturers. – enigma May 19 '16 at 7:04
  • Well, if you wanted to view the After-market equipment makers as business adversaries of the OEM, then that could fit your question. Although I don't know that most researchers would introspect deeply enough to consider that aspect. It's pretty outside the ivory tower. – infixed May 19 '16 at 13:44
  • 2
    how are "integrity, authenticity and protection against replay attacks" guaranteed in current CAN bus implementations? Or do you mean they will be in future? – Martin Thompson May 19 '16 at 14:28
  • @MartinThompson They will be, might be the better phrase. Most of the security protocol/mechanism proposals I found do guarantee them. Consequently, for the sake of clarity regarding my question, let's assume they are guaranteed. – enigma May 19 '16 at 14:49

I'd say CAN doesn't need encryption just like communications between CPUs and GPUs don't need it. It would add complexity, latency and more risk of failure in a critical system often used to control safety features. Physical security is already enough, as there is (or should be) no way for a remote attacker to access the CAN bus, and a local attacker with physical access may as well directly tamper with the ECU, completely bypassing the encryption.

What car manufacturers should work on instead is better segregation between different devices, possibly using separate firewalls to make sure devices can only send types of messages they are supposed to send.

  • 1
    There are a few flaws in this answer. Firstly, due to the numerous channels a modern car is and will be communicating with its environment (as mentioned above) there is a wide attack surface for remote attacks. Secondly, to tamper with the ECU is way harder than just connecting to the CAN bus. Thirdly, even though I agree with you on your comment about the segregation, I have to note: firewalls do not prevent, for example, eavesdropping or replay attacks. In addition, the fact that those systems are often used to control safety features encourages encryption, in my opinion. – enigma Oct 8 '16 at 18:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.