A vehicle system comprising: a plurality of electronic control devices respectively coupled to a controller area network and configured to control each unit of a vehicle; and a management electronic control device configured to manage the plurality of electronic control devices, wherein when an encryption key used to verify a message is updated to another encryption key, the management electronic control device transmits a first message and a second message to the controller area network, the first message including a controller area network identifier, CAN-ID, that represents a destination of the first message, a unique identifier, UID, of the destination, and a slot where the encryption key is stored in a data field of the first message, the second message including the other encryption key, the CAN-ID that represents a destination of the second message, and a counter value for preventing a replay, and a destination electronic control device (102-A) of the plurality of electronic control devices is configured to: receive the first message and the second message, determine, when the destination electronic control device (102-A) confirms the CAN-ID of the first and second messages, whether the UID included in the first message matches with the UID allocated to the destination electronic control device (102-A), verify the counter value in the second message, and when the counter value is verified and it is determined that the UID included in the first message matches with the UID allocated to the destination electronic control device (102-A), update the encryption key to the other encryption key included in the second message. a plurality of electronic control devices respectively coupled to a controller area network and configured to control each unit of a vehicle; and a management electronic control device configured to manage the plurality of electronic control devices, wherein when an encryption key used to verify a message is updated to another encryption key, the management electronic control device transmits a first message and a second message to the controller area network, the first message including a controller area network identifier, CAN-ID, that represents a destination of the first message, a unique identifier, UID, of the destination, and a slot where the encryption key is stored in a data field of the first message, the second message including the other encryption key, the CAN-ID that represents a destination of the second message, and a counter value for preventing a replay, and a destination electronic control device (102-A) of the plurality of electronic control devices is configured to: receive the first message and the second message, determine, when the destination electronic control device (102-A) confirms the CAN-ID of the first and second messages, whether the UID included in the first message matches with the UID allocated to the destination electronic control device (102-A), verify the counter value in the second message, and when the counter value is verified and it is determined that the UID included in the first message matches with the UID allocated to the destination electronic control device (102-A), update the encryption key to the other encryption key included in the second message. receive the first message and the second message, determine, when the destination electronic control device (102-A) confirms the CAN-ID of the first and second messages, whether the UID included in the first message matches with the UID allocated to the destination electronic control device (102-A), verify the counter value in the second message, and when the counter value is verified and it is determined that the UID included in the first message matches with the UID allocated to the destination electronic control device (102-A), update the encryption key to the other encryption key included in the second message.