1. A method for identifying/authenticating a person by means of an identification/authentication system comprising a capture device provided for capturing an image of a venous network of a finger of said person, a processing unit 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: a capture step during which the capture device captures an image of the venous network, a transmission step during which the capture device transmits the image of the venous network thus captured to the processing unit, a centring step during which the processing unit centres the image of the venous network with respect to a display window, a cutting step during which the processing unit cuts the image of the venous network thus centred into at least two bands parallel to the axis of the finger, a first extraction step during which the processing unit extracts a set of at least one topological characteristic of each band, a distance step during which the processing unit calculates, for each class, a distance between the set thus extracted and all the reference topological characteristics of said class, a classification step during which the processing unit allocates the image of the venous network to the class corresponding to the smallest distance, a comparison step during which the processing unit compares 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 a decision-taking step during which the processing unit takes a decision concerning the authenticity/identity of the person from the result of the comparison step.