Abstract: The method comprises the steps: of applying the identifier (100?) on an object; of making a first digital image and, subsequently, a second digital image of the identifier; of deriving first and second digital keys from the first and second images, respectively; and of comparing the second digital key with the first digital key; wherein the identifier (100?) is made up of same-diameter microbeads (120) distributed in a random manner on the surface of the object, the microbeads being embedded in a layer (110?) of binder, and deriving the first digital key comprises the steps of applying elliptical regression to a distribution of points representative of the positions of the microbeads in the first image in order to define an ellipse, and of applying a change of reference frame consisting in expressing the positions of said points in a reference frame based on the ellipse.