1. A method for marking a product, the method comprising: forming, on or in said product, a mark robust to copying, with a first resolution; forming, on or in said product, a mark sensitive to copying, with a second resolution higher than the first resolution; capturing an image of said mark robust to copying, said sensitive mark and another part of the product; and memorizing an item of information representing the image of said mark robust to copying, said sensitive mark and said other part of the product.