The method for authenticating a code with geometric areas whose shapes and/or colors vary according to a message includes: a step (115) in which the code with variable geometric areas is generated, according to a message, to provide geometric areas; a step (120 to 130) in which a digital authentication code is generated to provide numeric values and a step (135) in which an image of the geometric code areas is formed, including a part of the digital authentication code in at least some of its geometric areas and/or in at least one space between geometric areas.