An analogical mark printed on a document that includes a distribution of dots defined by a digital file, having, as a result of unanticipated unknowns in printing, an unpredictable variation, dot by dot, of at least one geometric characteristic of the printed dots where dots of the distribution of dots have, in the digital file, at least one geometric characteristic that digitally varies among dots, the geometric amplitude of the digital variation having the order of magnitude of said unpredictable variation and being less than an average dimension of the dots of the distribution of dots.