A system includes a plurality of electronic control units (ECUs) and a shared high security module (sHSM) separate from and connected to the plurality of ECUs over one or more private networks. At least one of the ECUs, over at least one of the plurality of private networks, authenticates a session with the sHSM and requests servicing during the authenticated session. The servicing includes encryption, decryption, or authentication, of a message designated to be handled by the at least one ECU and included in the request for servicing. The sHSM receives the message, performs the requested servicing of the message using capabilities onboard the sHSM, and publishes a serviced version of the message to a designated controller area network bus.