A system and method for securing communication across an in-vehicle bus, includes establishing a connection between a gateway in a vehicle and the in-vehicle bus; generating a session key at the gateway within the vehicle; transmitting a public key certificate and ephemeral key to the gateway and an electronic control unit of the vehicle; generating a shared secret at the gateway and the electronic control unit, respectively; encrypting the session key with the shared secret at the gateway; receiving the encrypted session key through the in-vehicle bus at the electronic control unit; and decrypting the encrypted session key based on the shared secret generated at the electronic control unit.