1. A method for identifying/authenticating a person by an identification/authentication system comprising a capture device comprising a lens provided for capturing an image of a venous network of a finger of said person, a hardware processor, and a database containing reference venous network images partitioned by class according to topological characteristics and for each class a set of reference topological characteristics, the method comprising: capturing an image of the venous network, transmitting the image of the venous network thus captured to the hardware processor, centering the image of the venous network with respect to a display window, cuttings the image of the venous network thus centred into at least two bands parallel to the axis of the finger, extracting a set of at least one topological characteristic of each band, as a first extraction, calculating, for each class, a distance between the set thus extracted and all the reference topological characteristics of said class, allocating the image of the venous network to the class corresponding to the smallest distance, comparing the image of the venous network with each reference venous network image in the class to which the image of the venous network is thus allocated, and takinges a decision concerning the authenticity/identity of the person from the result of the comparison step.