The invention relates to a method of authenticating a consumable or detachable element (20) of a continuous inkjet printer (CIJ), comprising: the generation, by the controller (3) of the printer, of a 1st item of random information and the dispatch thereof to an authentication circuit of the element; the encryption of the 1st item of random information by the authentication circuit of the element, a 1st encryption algorithm and a 1st secret key, thereby forming a 1st item of encrypted random information; the dispatch of said item of information to the controller of the printer; the encryption of the 1st item of random information by the controller of the printer, a 2nd encryption algorithm, and a 2nd- secret key, thereby forming a 2nd item of encrypted random information; and the comparison of the 1st item of encrypted random information with the 2nd encrypted item of random information, in order to authenticate, or not, the consumable element; if the consumable element is authenticated, at least one part of a 3rd key, termed the shared key, is dispatched by the consumable or detachable element (20) to the continuous inkjet printer.