The invention proposes a method of inserting a message in a subset (VO) of digital data representing physical quantities, characterized in that it includes the steps of: estimating (E4) a capacity to receive a message for said subset, selecting (E5) a message with a size less than or equal to the estimated capacity, in a set of a messages, inserting (E6) the selected message in the said subset of digital data. The invention applies particularly to an object in a digital image.