The invention relates to a method for authentication of a piece of equipment by a communication system, comprising: a step for exchanging at least one data frame between a first piece of equipment and a second piece of equipment through a communication bus using a packet switching protocol, the data frame including a preamble and a message body, a step for searching in each exchanged data frame for the presence of a marker in the preamble, the marker being specific to the communication system, and only when the marker has been found by the second piece of equipment in a data frame, a step for authenticating the first piece of equipment.