Security module for a CAN node

A CAN node comprising:

• a CAN transceiver;
• the local controller;
• and
• a security module comprising:
• a receive data, RXD, input interface for receiving data from a CAN bus;
• a transmit data, TXD, output interface for transmitting data to the CAN bus;
• wherein the security module is configured to:
• receive a CAN frame from the CAN bus via the RXD input interface;
• compare an identifier of the received CAN frame with at least one identifier associated with a local controller;
• and
• upon detection of a match between the identifier of the received CAN frame and the at least one identifier associated with the local controller, output an error signal to the CAN bus via the TXD output interface by setting a predetermined plurality of consecutive bits in the CAN frame to a dominant value, wherein the predetermined plurality of consecutive bits identifies a security error to CAN nodes connected to the CAN bus and is at least 10 consecutive bits,
• wherein:
• the RXD input interface and TXD output interface of the security module are configured to communicate with the CAN bus via the CAN transceiver, and
• the security module is located on a data path between the CAN transceiver and the local controller.

A method for outputting an error signal to a controller area network, CAN, bus, the method comprising:

• receiving a CAN frame from the CAN bus;
• comparing an identifier of the received CAN frame with at least one identifier associated with a local controller;
• detecting a match between the identifier of the received CAN frame and the at least one identifier associated with the local controller;
• and
• outputting an error signal to the CAN bus by setting a predetermined plurality of consecutive bits in the CAN frame to a dominant value, wherein the predetermined plurality of consecutive bits identifies a security error to CAN nodes connected to the CAN bus and is at least 10 consecutive bits.